Merge tag 'pstore-v5.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull pstore updates from Kees Cook:
"Fixes and new features for pstore.

This is a pretty big set of changes (relative to past pstore pulls),
but it has been in -next for a while. The biggest change here is the
ability to support a block device as a pstore backend, which has been
desired for a while. A lot of additional fixes and refactorings are
also included, mostly in support of the new features.

- refactor pstore locking for safer module unloading (Kees Cook)

- remove orphaned records from pstorefs when backend unloaded (Kees
Cook)

- refactor dump_oops parameter into max_reason (Pavel Tatashin)

- introduce pstore/zone for common code for contiguous storage
(WeiXiong Liao)

- introduce pstore/blk for block device backend (WeiXiong Liao)

- introduce mtd backend (WeiXiong Liao)"

* tag 'pstore-v5.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (35 commits)
mtd: Support kmsg dumper based on pstore/blk
pstore/blk: Introduce "best_effort" mode
pstore/blk: Support non-block storage devices
pstore/blk: Provide way to query pstore configuration
pstore/zone: Provide way to skip "broken" zone for MTD devices
Documentation: Add details for pstore/blk
pstore/zone,blk: Add ftrace frontend support
pstore/zone,blk: Add console frontend support
pstore/zone,blk: Add support for pmsg frontend
pstore/blk: Introduce backend for block devices
pstore/zone: Introduce common layer to manage storage zones
ramoops: Add "max-reason" optional field to ramoops DT node
pstore/ram: Introduce max_reason and convert dump_oops
pstore/platform: Pass max_reason to kmesg dump
printk: Introduce kmsg_dump_reason_str()
printk: honor the max_reason field in kmsg_dumper
printk: Collapse shutdown types into a single dump reason
pstore/ftrace: Provide ftrace log merging routine
pstore/ram: Refactor ftrace buffer merging
pstore/ram: Refactor DT size parsing
...

Documentation/admin-guide/pstore-blk.rst

···
+.. SPDX-License-Identifier: GPL-2.0
+
+pstore block oops/panic logger
+==============================
+
+Introduction
+------------
+
+pstore block (pstore/blk) is an oops/panic logger that writes its logs to a
+block device and non-block device before the system crashes. You can get
+these log files by mounting pstore filesystem like::
+
+    mount -t pstore pstore /sys/fs/pstore
+
+
+pstore block concepts
+---------------------
+
+pstore/blk provides efficient configuration method for pstore/blk, which
+divides all configurations into two parts, configurations for user and
+configurations for driver.
+
+Configurations for user determine how pstore/blk works, such as pmsg_size,
+kmsg_size and so on. All of them support both Kconfig and module parameters,
+but module parameters have priority over Kconfig.
+
+Configurations for driver are all about block device and non-block device,
+such as total_size of block device and read/write operations.
+
+Configurations for user
+-----------------------
+
+All of these configurations support both Kconfig and module parameters, but
+module parameters have priority over Kconfig.
+
+Here is an example for module parameters::
+
+        pstore_blk.blkdev=179:7 pstore_blk.kmsg_size=64
+
+The detail of each configurations may be of interest to you.
+
+blkdev
+~~~~~~
+
+The block device to use. Most of the time, it is a partition of block device.
+It's required for pstore/blk. It is also used for MTD device.
+
+It accepts the following variants for block device:
+
+1. <hex_major><hex_minor> device number in hexadecimal represents itself; no
+   leading 0x, for example b302.
+#. /dev/<disk_name> represents the device number of disk
+#. /dev/<disk_name><decimal> represents the device number of partition - device
+   number of disk plus the partition number
+#. /dev/<disk_name>p<decimal> - same as the above; this form is used when disk
+   name of partitioned disk ends with a digit.
+#. PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF represents the unique id of
+   a partition if the partition table provides it. The UUID may be either an
+   EFI/GPT UUID, or refer to an MSDOS partition using the format SSSSSSSS-PP,
+   where SSSSSSSS is a zero-filled hex representation of the 32-bit
+   "NT disk signature", and PP is a zero-filled hex representation of the
+   1-based partition number.
+#. PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation to a
+   partition with a known unique id.
+#. <major>:<minor> major and minor number of the device separated by a colon.
+
+It accepts the following variants for MTD device:
+
+1. <device name> MTD device name. "pstore" is recommended.
+#. <device number> MTD device number.
+
+kmsg_size
+~~~~~~~~~
+
+The chunk size in KB for oops/panic front-end. It **MUST** be a multiple of 4.
+It's optional if you do not care oops/panic log.
+
+There are multiple chunks for oops/panic front-end depending on the remaining
+space except other pstore front-ends.
+
+pstore/blk will log to oops/panic chunks one by one, and always overwrite the
+oldest chunk if there is no more free chunk.
+
+pmsg_size
+~~~~~~~~~
+
+The chunk size in KB for pmsg front-end. It **MUST** be a multiple of 4.
+It's optional if you do not care pmsg log.
+
+Unlike oops/panic front-end, there is only one chunk for pmsg front-end.
+
+Pmsg is a user space accessible pstore object. Writes to */dev/pmsg0* are
+appended to the chunk. On reboot the contents are available in
+*/sys/fs/pstore/pmsg-pstore-blk-0*.
+
+console_size
+~~~~~~~~~~~~
+
+The chunk size in KB for console front-end.  It **MUST** be a multiple of 4.
+It's optional if you do not care console log.
+
+Similar to pmsg front-end, there is only one chunk for console front-end.
+
+All log of console will be appended to the chunk. On reboot the contents are
+available in */sys/fs/pstore/console-pstore-blk-0*.
+
+ftrace_size
+~~~~~~~~~~~
+
+The chunk size in KB for ftrace front-end. It **MUST** be a multiple of 4.
+It's optional if you do not care console log.
+
+Similar to oops front-end, there are multiple chunks for ftrace front-end
+depending on the count of cpu processors. Each chunk size is equal to
+ftrace_size / processors_count.
+
+All log of ftrace will be appended to the chunk. On reboot the contents are
+combined and available in */sys/fs/pstore/ftrace-pstore-blk-0*.
+
+Persistent function tracing might be useful for debugging software or hardware
+related hangs. Here is an example of usage::
+
+ # mount -t pstore pstore /sys/fs/pstore
+ # mount -t debugfs debugfs /sys/kernel/debug/
+ # echo 1 > /sys/kernel/debug/pstore/record_ftrace
+ # reboot -f
+ [...]
+ # mount -t pstore pstore /sys/fs/pstore
+ # tail /sys/fs/pstore/ftrace-pstore-blk-0
+ CPU:0 ts:5914676 c0063828  c0063b94  call_cpuidle <- cpu_startup_entry+0x1b8/0x1e0
+ CPU:0 ts:5914678 c039ecdc  c006385c  cpuidle_enter_state <- call_cpuidle+0x44/0x48
+ CPU:0 ts:5914680 c039e9a0  c039ecf0  cpuidle_enter_freeze <- cpuidle_enter_state+0x304/0x314
+ CPU:0 ts:5914681 c0063870  c039ea30  sched_idle_set_state <- cpuidle_enter_state+0x44/0x314
+ CPU:1 ts:5916720 c0160f59  c015ee04  kernfs_unmap_bin_file <- __kernfs_remove+0x140/0x204
+ CPU:1 ts:5916721 c05ca625  c015ee0c  __mutex_lock_slowpath <- __kernfs_remove+0x148/0x204
+ CPU:1 ts:5916723 c05c813d  c05ca630  yield_to <- __mutex_lock_slowpath+0x314/0x358
+ CPU:1 ts:5916724 c05ca2d1  c05ca638  __ww_mutex_lock <- __mutex_lock_slowpath+0x31c/0x358
+
+max_reason
+~~~~~~~~~~
+
+Limiting which kinds of kmsg dumps are stored can be controlled via
+the ``max_reason`` value, as defined in include/linux/kmsg_dump.h's
+``enum kmsg_dump_reason``. For example, to store both Oopses and Panics,
+``max_reason`` should be set to 2 (KMSG_DUMP_OOPS), to store only Panics
+``max_reason`` should be set to 1 (KMSG_DUMP_PANIC). Setting this to 0
+(KMSG_DUMP_UNDEF), means the reason filtering will be controlled by the
+``printk.always_kmsg_dump`` boot param: if unset, it'll be KMSG_DUMP_OOPS,
+otherwise KMSG_DUMP_MAX.
+
+Configurations for driver
+-------------------------
+
+Only a block device driver cares about these configurations. A block device
+driver uses ``register_pstore_blk`` to register to pstore/blk.
+
+.. kernel-doc:: fs/pstore/blk.c
+   :identifiers: register_pstore_blk
+
+A non-block device driver uses ``register_pstore_device`` with
+``struct pstore_device_info`` to register to pstore/blk.
+
+.. kernel-doc:: fs/pstore/blk.c
+   :identifiers: register_pstore_device
+
+.. kernel-doc:: include/linux/pstore_blk.h
+   :identifiers: pstore_device_info
+
+Compression and header
+----------------------
+
+Block device is large enough for uncompressed oops data. Actually we do not
+recommend data compression because pstore/blk will insert some information into
+the first line of oops/panic data. For example::
+
+        Panic: Total 16 times
+
+It means that it's OOPS|Panic for the 16th time since the first booting.
+Sometimes the number of occurrences of oops|panic since the first booting is
+important to judge whether the system is stable.
+
+The following line is inserted by pstore filesystem. For example::
+
+        Oops#2 Part1
+
+It means that it's OOPS for the 2nd time on the last boot.
+
+Reading the data
+----------------
+
+The dump data can be read from the pstore filesystem. The format for these
+files is ``dmesg-pstore-blk-[N]`` for oops/panic front-end,
+``pmsg-pstore-blk-0`` for pmsg front-end and so on.  The timestamp of the
+dump file records the trigger time. To delete a stored record from block
+device, simply unlink the respective pstore file.
+
+Attentions in panic read/write APIs
+-----------------------------------
+
+If on panic, the kernel is not going to run for much longer, the tasks will not
+be scheduled and most kernel resources will be out of service. It
+looks like a single-threaded program running on a single-core computer.
+
+The following points require special attention for panic read/write APIs:
+
+1. Can **NOT** allocate any memory.
+   If you need memory, just allocate while the block driver is initializing
+   rather than waiting until the panic.
+#. Must be polled, **NOT** interrupt driven.
+   No task schedule any more. The block driver should delay to ensure the write
+   succeeds, but NOT sleep.
+#. Can **NOT** take any lock.
+   There is no other task, nor any shared resource; you are safe to break all
+   locks.
+#. Just use CPU to transfer.
+   Do not use DMA to transfer unless you are sure that DMA will not keep lock.
+#. Control registers directly.
+   Please control registers directly rather than use Linux kernel resources.
+   Do I/O map while initializing rather than wait until a panic occurs.
+#. Reset your block device and controller if necessary.
+   If you are not sure of the state of your block device and controller when
+   a panic occurs, you are safe to stop and reset them.
+
+pstore/blk supports psblk_blkdev_info(), which is defined in
+*linux/pstore_blk.h*, to get information of using block device, such as the
+device number, sector count and start sector of the whole disk.
+
+pstore block internals
+----------------------
+
+For developer reference, here are all the important structures and APIs:
+
+.. kernel-doc:: fs/pstore/zone.c
+   :internal:
+
+.. kernel-doc:: include/linux/pstore_zone.h
+   :internal:
+
+.. kernel-doc:: fs/pstore/blk.c
+   :export:
+
+.. kernel-doc:: include/linux/pstore_blk.h
+   :internal:

Documentation/admin-guide/ramoops.rst

···
 memory are implementation defined, and won't work on many ARMs such as omaps.
 
 The memory area is divided into ``record_size`` chunks (also rounded down to
-power of two) and each oops/panic writes a ``record_size`` chunk of
+power of two) and each kmesg dump writes a ``record_size`` chunk of
 information.
 
-Dumping both oopses and panics can be done by setting 1 in the ``dump_oops``
-variable while setting 0 in that variable dumps only the panics.
+Limiting which kinds of kmsg dumps are stored can be controlled via
+the ``max_reason`` value, as defined in include/linux/kmsg_dump.h's
+``enum kmsg_dump_reason``. For example, to store both Oopses and Panics,
+``max_reason`` should be set to 2 (KMSG_DUMP_OOPS), to store only Panics
+``max_reason`` should be set to 1 (KMSG_DUMP_PANIC). Setting this to 0
+(KMSG_DUMP_UNDEF), means the reason filtering will be controlled by the
+``printk.always_kmsg_dump`` boot param: if unset, it'll be KMSG_DUMP_OOPS,
+otherwise KMSG_DUMP_MAX.
 
 The module uses a counter to record multiple dumps but the counter gets reset
 on restart (i.e. new dumps after the restart will overwrite old ones).
···
         .mem_address            = <...>,
         .mem_type               = <...>,
         .record_size            = <...>,
-        .dump_oops              = <...>,
+        .max_reason             = <...>,
         .ecc                    = <...>,
   };
 

Documentation/devicetree/bindings/reserved-memory/ramoops.txt

···
 - ecc-size: enables ECC support and specifies ECC buffer size in bytes
   (defaults to 0: no ECC)
 
-- record-size: maximum size in bytes of each dump done on oops/panic
+- record-size: maximum size in bytes of each kmsg dump.
   (defaults to 0: disabled)
 
 - console-size: size in bytes of log buffer reserved for kernel messages
···
 - unbuffered: if present, use unbuffered mappings to map the reserved region
   (defaults to buffered mappings)
 
-- no-dump-oops: if present, only dump panics (defaults to panics and oops)
+- max-reason: if present, sets maximum type of kmsg dump reasons to store
+  (defaults to 2: log Oopses and Panics). This can be set to INT_MAX to
+  store all kmsg dumps. See include/linux/kmsg_dump.h KMSG_DUMP_* for other
+  kmsg dump reason values. Setting this to 0 (KMSG_DUMP_UNDEF), means the
+  reason filtering will be controlled by the printk.always_kmsg_dump boot
+  param: if unset, it will be KMSG_DUMP_OOPS, otherwise KMSG_DUMP_MAX.
+
+- no-dump-oops: deprecated, use max_reason instead. If present, and
+  max_reason is not specified, it is equivalent to max_reason = 1
+  (KMSG_DUMP_PANIC).
 
 - flags: if present, pass ramoops behavioral flags (defaults to 0,
   see include/linux/pstore_ram.h RAMOOPS_FLAG_* for flag values).

MAINTAINERS

···
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git for-next/pstore
 F:	Documentation/admin-guide/ramoops.rst
+F:	Documentation/admin-guide/pstore-blk.rst
 F:	Documentation/devicetree/bindings/reserved-memory/ramoops.txt
 F:	drivers/acpi/apei/erst.c
 F:	drivers/firmware/efi/efi-pstore.c

arch/powerpc/kernel/nvram_64.c

···
 	int rc = -1;
 
 	switch (reason) {
-	case KMSG_DUMP_RESTART:
-	case KMSG_DUMP_HALT:
-	case KMSG_DUMP_POWEROFF:
+	case KMSG_DUMP_SHUTDOWN:
 		/* These are almost always orderly shutdowns. */
 		return;
 	case KMSG_DUMP_OOPS:

drivers/mtd/Kconfig

···
 	  buffer in a flash partition where it can be read back at some
 	  later point.
 
+config MTD_PSTORE
+	tristate "Log panic/oops to an MTD buffer based on pstore"
+	depends on PSTORE_BLK
+	help
+	  This enables panic and oops messages to be logged to a circular
+	  buffer in a flash partition where it can be read back as files after
+	  mounting pstore filesystem.
+
+	  If unsure, say N.
+
 config MTD_SWAP
 	tristate "Swap on MTD device support"
 	depends on MTD && SWAP

drivers/mtd/Makefile

···
 obj-$(CONFIG_SSFDC)		+= ssfdc.o
 obj-$(CONFIG_SM_FTL)		+= sm_ftl.o
 obj-$(CONFIG_MTD_OOPS)		+= mtdoops.o
+obj-$(CONFIG_MTD_PSTORE)	+= mtdpstore.o
 obj-$(CONFIG_MTD_SWAP)		+= mtdswap.o
 
 nftl-objs		:= nftlcore.o nftlmount.o

drivers/mtd/mtdpstore.c

···
+// SPDX-License-Identifier: GPL-2.0
+
+#define dev_fmt(fmt) "mtdoops-pstore: " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/pstore_blk.h>
+#include <linux/mtd/mtd.h>
+#include <linux/bitops.h>
+
+static struct mtdpstore_context {
+	int index;
+	struct pstore_blk_config info;
+	struct pstore_device_info dev;
+	struct mtd_info *mtd;
+	unsigned long *rmmap;		/* removed bit map */
+	unsigned long *usedmap;		/* used bit map */
+	/*
+	 * used for panic write
+	 * As there are no block_isbad for panic case, we should keep this
+	 * status before panic to ensure panic_write not failed.
+	 */
+	unsigned long *badmap;		/* bad block bit map */
+} oops_cxt;
+
+static int mtdpstore_block_isbad(struct mtdpstore_context *cxt, loff_t off)
+{
+	int ret;
+	struct mtd_info *mtd = cxt->mtd;
+	u64 blknum;
+
+	off = ALIGN_DOWN(off, mtd->erasesize);
+	blknum = div_u64(off, mtd->erasesize);
+
+	if (test_bit(blknum, cxt->badmap))
+		return true;
+	ret = mtd_block_isbad(mtd, off);
+	if (ret < 0) {
+		dev_err(&mtd->dev, "mtd_block_isbad failed, aborting\n");
+		return ret;
+	} else if (ret > 0) {
+		set_bit(blknum, cxt->badmap);
+		return true;
+	}
+	return false;
+}
+
+static inline int mtdpstore_panic_block_isbad(struct mtdpstore_context *cxt,
+		loff_t off)
+{
+	struct mtd_info *mtd = cxt->mtd;
+	u64 blknum;
+
+	off = ALIGN_DOWN(off, mtd->erasesize);
+	blknum = div_u64(off, mtd->erasesize);
+	return test_bit(blknum, cxt->badmap);
+}
+
+static inline void mtdpstore_mark_used(struct mtdpstore_context *cxt,
+		loff_t off)
+{
+	struct mtd_info *mtd = cxt->mtd;
+	u64 zonenum = div_u64(off, cxt->info.kmsg_size);
+
+	dev_dbg(&mtd->dev, "mark zone %llu used\n", zonenum);
+	set_bit(zonenum, cxt->usedmap);
+}
+
+static inline void mtdpstore_mark_unused(struct mtdpstore_context *cxt,
+		loff_t off)
+{
+	struct mtd_info *mtd = cxt->mtd;
+	u64 zonenum = div_u64(off, cxt->info.kmsg_size);
+
+	dev_dbg(&mtd->dev, "mark zone %llu unused\n", zonenum);
+	clear_bit(zonenum, cxt->usedmap);
+}
+
+static inline void mtdpstore_block_mark_unused(struct mtdpstore_context *cxt,
+		loff_t off)
+{
+	struct mtd_info *mtd = cxt->mtd;
+	u32 zonecnt = mtd->erasesize / cxt->info.kmsg_size;
+	u64 zonenum;
+
+	off = ALIGN_DOWN(off, mtd->erasesize);
+	zonenum = div_u64(off, cxt->info.kmsg_size);
+	while (zonecnt > 0) {
+		dev_dbg(&mtd->dev, "mark zone %llu unused\n", zonenum);
+		clear_bit(zonenum, cxt->usedmap);
+		zonenum++;
+		zonecnt--;
+	}
+}
+
+static inline int mtdpstore_is_used(struct mtdpstore_context *cxt, loff_t off)
+{
+	u64 zonenum = div_u64(off, cxt->info.kmsg_size);
+	u64 blknum = div_u64(off, cxt->mtd->erasesize);
+
+	if (test_bit(blknum, cxt->badmap))
+		return true;
+	return test_bit(zonenum, cxt->usedmap);
+}
+
+static int mtdpstore_block_is_used(struct mtdpstore_context *cxt,
+		loff_t off)
+{
+	struct mtd_info *mtd = cxt->mtd;
+	u32 zonecnt = mtd->erasesize / cxt->info.kmsg_size;
+	u64 zonenum;
+
+	off = ALIGN_DOWN(off, mtd->erasesize);
+	zonenum = div_u64(off, cxt->info.kmsg_size);
+	while (zonecnt > 0) {
+		if (test_bit(zonenum, cxt->usedmap))
+			return true;
+		zonenum++;
+		zonecnt--;
+	}
+	return false;
+}
+
+static int mtdpstore_is_empty(struct mtdpstore_context *cxt, char *buf,
+		size_t size)
+{
+	struct mtd_info *mtd = cxt->mtd;
+	size_t sz;
+	int i;
+
+	sz = min_t(uint32_t, size, mtd->writesize / 4);
+	for (i = 0; i < sz; i++) {
+		if (buf[i] != (char)0xFF)
+			return false;
+	}
+	return true;
+}
+
+static void mtdpstore_mark_removed(struct mtdpstore_context *cxt, loff_t off)
+{
+	struct mtd_info *mtd = cxt->mtd;
+	u64 zonenum = div_u64(off, cxt->info.kmsg_size);
+
+	dev_dbg(&mtd->dev, "mark zone %llu removed\n", zonenum);
+	set_bit(zonenum, cxt->rmmap);
+}
+
+static void mtdpstore_block_clear_removed(struct mtdpstore_context *cxt,
+		loff_t off)
+{
+	struct mtd_info *mtd = cxt->mtd;
+	u32 zonecnt = mtd->erasesize / cxt->info.kmsg_size;
+	u64 zonenum;
+
+	off = ALIGN_DOWN(off, mtd->erasesize);
+	zonenum = div_u64(off, cxt->info.kmsg_size);
+	while (zonecnt > 0) {
+		clear_bit(zonenum, cxt->rmmap);
+		zonenum++;
+		zonecnt--;
+	}
+}
+
+static int mtdpstore_block_is_removed(struct mtdpstore_context *cxt,
+		loff_t off)
+{
+	struct mtd_info *mtd = cxt->mtd;
+	u32 zonecnt = mtd->erasesize / cxt->info.kmsg_size;
+	u64 zonenum;
+
+	off = ALIGN_DOWN(off, mtd->erasesize);
+	zonenum = div_u64(off, cxt->info.kmsg_size);
+	while (zonecnt > 0) {
+		if (test_bit(zonenum, cxt->rmmap))
+			return true;
+		zonenum++;
+		zonecnt--;
+	}
+	return false;
+}
+
+static int mtdpstore_erase_do(struct mtdpstore_context *cxt, loff_t off)
+{
+	struct mtd_info *mtd = cxt->mtd;
+	struct erase_info erase;
+	int ret;
+
+	off = ALIGN_DOWN(off, cxt->mtd->erasesize);
+	dev_dbg(&mtd->dev, "try to erase off 0x%llx\n", off);
+	erase.len = cxt->mtd->erasesize;
+	erase.addr = off;
+	ret = mtd_erase(cxt->mtd, &erase);
+	if (!ret)
+		mtdpstore_block_clear_removed(cxt, off);
+	else
+		dev_err(&mtd->dev, "erase of region [0x%llx, 0x%llx] on \"%s\" failed\n",
+		       (unsigned long long)erase.addr,
+		       (unsigned long long)erase.len, cxt->info.device);
+	return ret;
+}
+
+/*
+ * called while removing file
+ *
+ * Avoiding over erasing, do erase block only when the whole block is unused.
+ * If the block contains valid log, do erase lazily on flush_removed() when
+ * unregister.
+ */
+static ssize_t mtdpstore_erase(size_t size, loff_t off)
+{
+	struct mtdpstore_context *cxt = &oops_cxt;
+
+	if (mtdpstore_block_isbad(cxt, off))
+		return -EIO;
+
+	mtdpstore_mark_unused(cxt, off);
+
+	/* If the block still has valid data, mtdpstore do erase lazily */
+	if (likely(mtdpstore_block_is_used(cxt, off))) {
+		mtdpstore_mark_removed(cxt, off);
+		return 0;
+	}
+
+	/* all zones are unused, erase it */
+	return mtdpstore_erase_do(cxt, off);
+}
+
+/*
+ * What is security for mtdpstore?
+ * As there is no erase for panic case, we should ensure at least one zone
+ * is writable. Otherwise, panic write will fail.
+ * If zone is used, write operation will return -ENOMSG, which means that
+ * pstore/blk will try one by one until gets an empty zone. So, it is not
+ * needed to ensure the next zone is empty, but at least one.
+ */
+static int mtdpstore_security(struct mtdpstore_context *cxt, loff_t off)
+{
+	int ret = 0, i;
+	struct mtd_info *mtd = cxt->mtd;
+	u32 zonenum = (u32)div_u64(off, cxt->info.kmsg_size);
+	u32 zonecnt = (u32)div_u64(cxt->mtd->size, cxt->info.kmsg_size);
+	u32 blkcnt = (u32)div_u64(cxt->mtd->size, cxt->mtd->erasesize);
+	u32 erasesize = cxt->mtd->erasesize;
+
+	for (i = 0; i < zonecnt; i++) {
+		u32 num = (zonenum + i) % zonecnt;
+
+		/* found empty zone */
+		if (!test_bit(num, cxt->usedmap))
+			return 0;
+	}
+
+	/* If there is no any empty zone, we have no way but to do erase */
+	while (blkcnt--) {
+		div64_u64_rem(off + erasesize, cxt->mtd->size, (u64 *)&off);
+
+		if (mtdpstore_block_isbad(cxt, off))
+			continue;
+
+		ret = mtdpstore_erase_do(cxt, off);
+		if (!ret) {
+			mtdpstore_block_mark_unused(cxt, off);
+			break;
+		}
+	}
+
+	if (ret)
+		dev_err(&mtd->dev, "all blocks bad!\n");
+	dev_dbg(&mtd->dev, "end security\n");
+	return ret;
+}
+
+static ssize_t mtdpstore_write(const char *buf, size_t size, loff_t off)
+{
+	struct mtdpstore_context *cxt = &oops_cxt;
+	struct mtd_info *mtd = cxt->mtd;
+	size_t retlen;
+	int ret;
+
+	if (mtdpstore_block_isbad(cxt, off))
+		return -ENOMSG;
+
+	/* zone is used, please try next one */
+	if (mtdpstore_is_used(cxt, off))
+		return -ENOMSG;
+
+	dev_dbg(&mtd->dev, "try to write off 0x%llx size %zu\n", off, size);
+	ret = mtd_write(cxt->mtd, off, size, &retlen, (u_char *)buf);
+	if (ret < 0 || retlen != size) {
+		dev_err(&mtd->dev, "write failure at %lld (%zu of %zu written), err %d\n",
+				off, retlen, size, ret);
+		return -EIO;
+	}
+	mtdpstore_mark_used(cxt, off);
+
+	mtdpstore_security(cxt, off);
+	return retlen;
+}
+
+static inline bool mtdpstore_is_io_error(int ret)
+{
+	return ret < 0 && !mtd_is_bitflip(ret) && !mtd_is_eccerr(ret);
+}
+
+/*
+ * All zones will be read as pstore/blk will read zone one by one when do
+ * recover.
+ */
+static ssize_t mtdpstore_read(char *buf, size_t size, loff_t off)
+{
+	struct mtdpstore_context *cxt = &oops_cxt;
+	struct mtd_info *mtd = cxt->mtd;
+	size_t retlen, done;
+	int ret;
+
+	if (mtdpstore_block_isbad(cxt, off))
+		return -ENOMSG;
+
+	dev_dbg(&mtd->dev, "try to read off 0x%llx size %zu\n", off, size);
+	for (done = 0, retlen = 0; done < size; done += retlen) {
+		retlen = 0;
+
+		ret = mtd_read(cxt->mtd, off + done, size - done, &retlen,
+				(u_char *)buf + done);
+		if (mtdpstore_is_io_error(ret)) {
+			dev_err(&mtd->dev, "read failure at %lld (%zu of %zu read), err %d\n",
+					off + done, retlen, size - done, ret);
+			/* the zone may be broken, try next one */
+			return -ENOMSG;
+		}
+
+		/*
+		 * ECC error. The impact on log data is so small. Maybe we can
+		 * still read it and try to understand. So mtdpstore just hands
+		 * over what it gets and user can judge whether the data is
+		 * valid or not.
+		 */
+		if (mtd_is_eccerr(ret)) {
+			dev_err(&mtd->dev, "ecc error at %lld (%zu of %zu read), err %d\n",
+					off + done, retlen, size - done, ret);
+			/* driver may not set retlen when ecc error */
+			retlen = retlen == 0 ? size - done : retlen;
+		}
+	}
+
+	if (mtdpstore_is_empty(cxt, buf, size))
+		mtdpstore_mark_unused(cxt, off);
+	else
+		mtdpstore_mark_used(cxt, off);
+
+	mtdpstore_security(cxt, off);
+	return retlen;
+}
+
+static ssize_t mtdpstore_panic_write(const char *buf, size_t size, loff_t off)
+{
+	struct mtdpstore_context *cxt = &oops_cxt;
+	struct mtd_info *mtd = cxt->mtd;
+	size_t retlen;
+	int ret;
+
+	if (mtdpstore_panic_block_isbad(cxt, off))
+		return -ENOMSG;
+
+	/* zone is used, please try next one */
+	if (mtdpstore_is_used(cxt, off))
+		return -ENOMSG;
+
+	ret = mtd_panic_write(cxt->mtd, off, size, &retlen, (u_char *)buf);
+	if (ret < 0 || size != retlen) {
+		dev_err(&mtd->dev, "panic write failure at %lld (%zu of %zu read), err %d\n",
+				off, retlen, size, ret);
+		return -EIO;
+	}
+	mtdpstore_mark_used(cxt, off);
+
+	return retlen;
+}
+
+static void mtdpstore_notify_add(struct mtd_info *mtd)
+{
+	int ret;
+	struct mtdpstore_context *cxt = &oops_cxt;
+	struct pstore_blk_config *info = &cxt->info;
+	unsigned long longcnt;
+
+	if (!strcmp(mtd->name, info->device))
+		cxt->index = mtd->index;
+
+	if (mtd->index != cxt->index || cxt->index < 0)
+		return;
+
+	dev_dbg(&mtd->dev, "found matching MTD device %s\n", mtd->name);
+
+	if (mtd->size < info->kmsg_size * 2) {
+		dev_err(&mtd->dev, "MTD partition %d not big enough\n",
+				mtd->index);
+		return;
+	}
+	/*
+	 * kmsg_size must be aligned to 4096 Bytes, which is limited by
+	 * psblk. The default value of kmsg_size is 64KB. If kmsg_size
+	 * is larger than erasesize, some errors will occur since mtdpsotre
+	 * is designed on it.
+	 */
+	if (mtd->erasesize < info->kmsg_size) {
+		dev_err(&mtd->dev, "eraseblock size of MTD partition %d too small\n",
+				mtd->index);
+		return;
+	}
+	if (unlikely(info->kmsg_size % mtd->writesize)) {
+		dev_err(&mtd->dev, "record size %lu KB must align to write size %d KB\n",
+				info->kmsg_size / 1024,
+				mtd->writesize / 1024);
+		return;
+	}
+
+	longcnt = BITS_TO_LONGS(div_u64(mtd->size, info->kmsg_size));
+	cxt->rmmap = kcalloc(longcnt, sizeof(long), GFP_KERNEL);
+	cxt->usedmap = kcalloc(longcnt, sizeof(long), GFP_KERNEL);
+
+	longcnt = BITS_TO_LONGS(div_u64(mtd->size, mtd->erasesize));
+	cxt->badmap = kcalloc(longcnt, sizeof(long), GFP_KERNEL);
+
+	cxt->dev.total_size = mtd->size;
+	/* just support dmesg right now */
+	cxt->dev.flags = PSTORE_FLAGS_DMESG;
+	cxt->dev.read = mtdpstore_read;
+	cxt->dev.write = mtdpstore_write;
+	cxt->dev.erase = mtdpstore_erase;
+	cxt->dev.panic_write = mtdpstore_panic_write;
+
+	ret = register_pstore_device(&cxt->dev);
+	if (ret) {
+		dev_err(&mtd->dev, "mtd%d register to psblk failed\n",
+				mtd->index);
+		return;
+	}
+	cxt->mtd = mtd;
+	dev_info(&mtd->dev, "Attached to MTD device %d\n", mtd->index);
+}
+
+static int mtdpstore_flush_removed_do(struct mtdpstore_context *cxt,
+		loff_t off, size_t size)
+{
+	struct mtd_info *mtd = cxt->mtd;
+	u_char *buf;
+	int ret;
+	size_t retlen;
+	struct erase_info erase;
+
+	buf = kmalloc(mtd->erasesize, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	/* 1st. read to cache */
+	ret = mtd_read(mtd, off, mtd->erasesize, &retlen, buf);
+	if (mtdpstore_is_io_error(ret))
+		goto free;
+
+	/* 2nd. erase block */
+	erase.len = mtd->erasesize;
+	erase.addr = off;
+	ret = mtd_erase(mtd, &erase);
+	if (ret)
+		goto free;
+
+	/* 3rd. write back */
+	while (size) {
+		unsigned int zonesize = cxt->info.kmsg_size;
+
+		/* there is valid data on block, write back */
+		if (mtdpstore_is_used(cxt, off)) {
+			ret = mtd_write(mtd, off, zonesize, &retlen, buf);
+			if (ret)
+				dev_err(&mtd->dev, "write failure at %lld (%zu of %u written), err %d\n",
+						off, retlen, zonesize, ret);
+		}
+
+		off += zonesize;
+		size -= min_t(unsigned int, zonesize, size);
+	}
+
+free:
+	kfree(buf);
+	return ret;
+}
+
+/*
+ * What does mtdpstore_flush_removed() do?
+ * When user remove any log file on pstore filesystem, mtdpstore should do
+ * something to ensure log file removed. If the whole block is no longer used,
+ * it's nice to erase the block. However if the block still contains valid log,
+ * what mtdpstore can do is to erase and write the valid log back.
+ */
+static int mtdpstore_flush_removed(struct mtdpstore_context *cxt)
+{
+	struct mtd_info *mtd = cxt->mtd;
+	int ret;
+	loff_t off;
+	u32 blkcnt = (u32)div_u64(mtd->size, mtd->erasesize);
+
+	for (off = 0; blkcnt > 0; blkcnt--, off += mtd->erasesize) {
+		ret = mtdpstore_block_isbad(cxt, off);
+		if (ret)
+			continue;
+
+		ret = mtdpstore_block_is_removed(cxt, off);
+		if (!ret)
+			continue;
+
+		ret = mtdpstore_flush_removed_do(cxt, off, mtd->erasesize);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
+static void mtdpstore_notify_remove(struct mtd_info *mtd)
+{
+	struct mtdpstore_context *cxt = &oops_cxt;
+
+	if (mtd->index != cxt->index || cxt->index < 0)
+		return;
+
+	mtdpstore_flush_removed(cxt);
+
+	unregister_pstore_device(&cxt->dev);
+	kfree(cxt->badmap);
+	kfree(cxt->usedmap);
+	kfree(cxt->rmmap);
+	cxt->mtd = NULL;
+	cxt->index = -1;
+}
+
+static struct mtd_notifier mtdpstore_notifier = {
+	.add	= mtdpstore_notify_add,
+	.remove	= mtdpstore_notify_remove,
+};
+
+static int __init mtdpstore_init(void)
+{
+	int ret;
+	struct mtdpstore_context *cxt = &oops_cxt;
+	struct pstore_blk_config *info = &cxt->info;
+
+	ret = pstore_blk_get_config(info);
+	if (unlikely(ret))
+		return ret;
+
+	if (strlen(info->device) == 0) {
+		pr_err("mtd device must be supplied (device name is empty)\n");
+		return -EINVAL;
+	}
+	if (!info->kmsg_size) {
+		pr_err("no backend enabled (kmsg_size is 0)\n");
+		return -EINVAL;
+	}
+
+	/* Setup the MTD device to use */
+	ret = kstrtoint((char *)info->device, 0, &cxt->index);
+	if (ret)
+		cxt->index = -1;
+
+	register_mtd_user(&mtdpstore_notifier);
+	return 0;
+}
+module_init(mtdpstore_init);
+
+static void __exit mtdpstore_exit(void)
+{
+	unregister_mtd_user(&mtdpstore_notifier);
+}
+module_exit(mtdpstore_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("WeiXiong Liao <[e-mail]>");
+MODULE_DESCRIPTION("MTD backend for pstore/blk");

drivers/platform/chrome/chromeos_pstore.c

···
 	.record_size	= 0x40000,
 	.console_size	= 0x20000,
 	.ftrace_size	= 0x20000,
-	.dump_oops	= 1,
+	.max_reason	= KMSG_DUMP_OOPS,
 };
 
 static struct platform_device chromeos_ramoops = {

fs/pstore/Kconfig

···
 	  "ramoops.ko".
 
 	  For more information, see Documentation/admin-guide/ramoops.rst.
+
+config PSTORE_ZONE
+	tristate
+	depends on PSTORE
+	help
+	  The common layer for pstore/blk (and pstore/ram in the future)
+	  to manage storage in zones.
+
+config PSTORE_BLK
+	tristate "Log panic/oops to a block device"
+	depends on PSTORE
+	depends on BLOCK
+	select PSTORE_ZONE
+	default n
+	help
+	  This enables panic and oops message to be logged to a block dev
+	  where it can be read back at some later point.
+
+	  For more information, see Documentation/admin-guide/pstore-blk.rst
+
+	  If unsure, say N.
+
+config PSTORE_BLK_BLKDEV
+	string "block device identifier"
+	depends on PSTORE_BLK
+	default ""
+	help
+	  Which block device should be used for pstore/blk.
+
+	  It accepts the following variants:
+	  1) <hex_major><hex_minor> device number in hexadecimal representation,
+	     with no leading 0x, for example b302.
+	  2) /dev/<disk_name> represents the device name of disk
+	  3) /dev/<disk_name><decimal> represents the device name and number
+	     of partition - device number of disk plus the partition number
+	  4) /dev/<disk_name>p<decimal> - same as the above, this form is
+	     used when disk name of partitioned disk ends with a digit.
+	  5) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
+	     unique id of a partition if the partition table provides it.
+	     The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
+	     partition using the format SSSSSSSS-PP, where SSSSSSSS is a zero-
+	     filled hex representation of the 32-bit "NT disk signature", and PP
+	     is a zero-filled hex representation of the 1-based partition number.
+	  6) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation
+	     to a partition with a known unique id.
+	  7) <major>:<minor> major and minor number of the device separated by
+	     a colon.
+
+	  NOTE that, both Kconfig and module parameters can configure
+	  pstore/blk, but module parameters have priority over Kconfig.
+
+config PSTORE_BLK_KMSG_SIZE
+	int "Size in Kbytes of kmsg dump log to store"
+	depends on PSTORE_BLK
+	default 64
+	help
+	  This just sets size of kmsg dump (oops, panic, etc) log for
+	  pstore/blk. The size is in KB and must be a multiple of 4.
+
+	  NOTE that, both Kconfig and module parameters can configure
+	  pstore/blk, but module parameters have priority over Kconfig.
+
+config PSTORE_BLK_MAX_REASON
+	int "Maximum kmsg dump reason to store"
+	depends on PSTORE_BLK
+	default 2
+	help
+	  The maximum reason for kmsg dumps to store. The default is
+	  2 (KMSG_DUMP_OOPS), see include/linux/kmsg_dump.h's
+	  enum kmsg_dump_reason for more details.
+
+	  NOTE that, both Kconfig and module parameters can configure
+	  pstore/blk, but module parameters have priority over Kconfig.
+
+config PSTORE_BLK_PMSG_SIZE
+	int "Size in Kbytes of pmsg to store"
+	depends on PSTORE_BLK
+	depends on PSTORE_PMSG
+	default 64
+	help
+	  This just sets size of pmsg (pmsg_size) for pstore/blk. The size is
+	  in KB and must be a multiple of 4.
+
+	  NOTE that, both Kconfig and module parameters can configure
+	  pstore/blk, but module parameters have priority over Kconfig.
+
+config PSTORE_BLK_CONSOLE_SIZE
+	int "Size in Kbytes of console log to store"
+	depends on PSTORE_BLK
+	depends on PSTORE_CONSOLE
+	default 64
+	help
+	  This just sets size of console log (console_size) to store via
+	  pstore/blk. The size is in KB and must be a multiple of 4.
+
+	  NOTE that, both Kconfig and module parameters can configure
+	  pstore/blk, but module parameters have priority over Kconfig.
+
+config PSTORE_BLK_FTRACE_SIZE
+	int "Size in Kbytes of ftrace log to store"
+	depends on PSTORE_BLK
+	depends on PSTORE_FTRACE
+	default 64
+	help
+	  This just sets size of ftrace log (ftrace_size) for pstore/blk. The
+	  size is in KB and must be a multiple of 4.
+
+	  NOTE that, both Kconfig and module parameters can configure
+	  pstore/blk, but module parameters have priority over Kconfig.

fs/pstore/Makefile

···
 
 ramoops-objs += ram.o ram_core.o
 obj-$(CONFIG_PSTORE_RAM)	+= ramoops.o
+
+pstore_zone-objs += zone.o
+obj-$(CONFIG_PSTORE_ZONE)	+= pstore_zone.o
+
+pstore_blk-objs += blk.o
+obj-$(CONFIG_PSTORE_BLK)	+= pstore_blk.o

fs/pstore/blk.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implements pstore backend driver that write to block (or non-block) storage
+ * devices, using the pstore/zone API.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include "../../block/blk.h"
+#include <linux/blkdev.h>
+#include <linux/string.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/pstore_blk.h>
+#include <linux/mount.h>
+#include <linux/uio.h>
+
+static long kmsg_size = CONFIG_PSTORE_BLK_KMSG_SIZE;
+module_param(kmsg_size, long, 0400);
+MODULE_PARM_DESC(kmsg_size, "kmsg dump record size in kbytes");
+
+static int max_reason = CONFIG_PSTORE_BLK_MAX_REASON;
+module_param(max_reason, int, 0400);
+MODULE_PARM_DESC(max_reason,
+		 "maximum reason for kmsg dump (default 2: Oops and Panic)");
+
+#if IS_ENABLED(CONFIG_PSTORE_PMSG)
+static long pmsg_size = CONFIG_PSTORE_BLK_PMSG_SIZE;
+#else
+static long pmsg_size = -1;
+#endif
+module_param(pmsg_size, long, 0400);
+MODULE_PARM_DESC(pmsg_size, "pmsg size in kbytes");
+
+#if IS_ENABLED(CONFIG_PSTORE_CONSOLE)
+static long console_size = CONFIG_PSTORE_BLK_CONSOLE_SIZE;
+#else
+static long console_size = -1;
+#endif
+module_param(console_size, long, 0400);
+MODULE_PARM_DESC(console_size, "console size in kbytes");
+
+#if IS_ENABLED(CONFIG_PSTORE_FTRACE)
+static long ftrace_size = CONFIG_PSTORE_BLK_FTRACE_SIZE;
+#else
+static long ftrace_size = -1;
+#endif
+module_param(ftrace_size, long, 0400);
+MODULE_PARM_DESC(ftrace_size, "ftrace size in kbytes");
+
+static bool best_effort;
+module_param(best_effort, bool, 0400);
+MODULE_PARM_DESC(best_effort, "use best effort to write (i.e. do not require storage driver pstore support, default: off)");
+
+/*
+ * blkdev - the block device to use for pstore storage
+ *
+ * Usually, this will be a partition of a block device.
+ *
+ * blkdev accepts the following variants:
+ * 1) <hex_major><hex_minor> device number in hexadecimal representation,
+ *    with no leading 0x, for example b302.
+ * 2) /dev/<disk_name> represents the device number of disk
+ * 3) /dev/<disk_name><decimal> represents the device number
+ *    of partition - device number of disk plus the partition number
+ * 4) /dev/<disk_name>p<decimal> - same as the above, that form is
+ *    used when disk name of partitioned disk ends on a digit.
+ * 5) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
+ *    unique id of a partition if the partition table provides it.
+ *    The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
+ *    partition using the format SSSSSSSS-PP, where SSSSSSSS is a zero-
+ *    filled hex representation of the 32-bit "NT disk signature", and PP
+ *    is a zero-filled hex representation of the 1-based partition number.
+ * 6) PARTUUID=<UUID>/PARTNROFF=<int> to select a partition in relation to
+ *    a partition with a known unique id.
+ * 7) <major>:<minor> major and minor number of the device separated by
+ *    a colon.
+ */
+static char blkdev[80] = CONFIG_PSTORE_BLK_BLKDEV;
+module_param_string(blkdev, blkdev, 80, 0400);
+MODULE_PARM_DESC(blkdev, "block device for pstore storage");
+
+/*
+ * All globals must only be accessed under the pstore_blk_lock
+ * during the register/unregister functions.
+ */
+static DEFINE_MUTEX(pstore_blk_lock);
+static struct block_device *psblk_bdev;
+static struct pstore_zone_info *pstore_zone_info;
+static pstore_blk_panic_write_op blkdev_panic_write;
+
+struct bdev_info {
+	dev_t devt;
+	sector_t nr_sects;
+	sector_t start_sect;
+};
+
+#define check_size(name, alignsize) ({				\
+	long _##name_ = (name);					\
+	_##name_ = _##name_ <= 0 ? 0 : (_##name_ * 1024);	\
+	if (_##name_ & ((alignsize) - 1)) {			\
+		pr_info(#name " must align to %d\n",		\
+				(alignsize));			\
+		_##name_ = ALIGN(name, (alignsize));		\
+	}							\
+	_##name_;						\
+})
+
+static int __register_pstore_device(struct pstore_device_info *dev)
+{
+	int ret;
+
+	lockdep_assert_held(&pstore_blk_lock);
+
+	if (!dev || !dev->total_size || !dev->read || !dev->write)
+		return -EINVAL;
+
+	/* someone already registered before */
+	if (pstore_zone_info)
+		return -EBUSY;
+
+	pstore_zone_info = kzalloc(sizeof(struct pstore_zone_info), GFP_KERNEL);
+	if (!pstore_zone_info)
+		return -ENOMEM;
+
+	/* zero means not limit on which backends to attempt to store. */
+	if (!dev->flags)
+		dev->flags = UINT_MAX;
+
+#define verify_size(name, alignsize, enabled) {				\
+		long _##name_;						\
+		if (enabled)						\
+			_##name_ = check_size(name, alignsize);		\
+		else							\
+			_##name_ = 0;					\
+		name = _##name_ / 1024;					\
+		pstore_zone_info->name = _##name_;			\
+	}
+
+	verify_size(kmsg_size, 4096, dev->flags & PSTORE_FLAGS_DMESG);
+	verify_size(pmsg_size, 4096, dev->flags & PSTORE_FLAGS_PMSG);
+	verify_size(console_size, 4096, dev->flags & PSTORE_FLAGS_CONSOLE);
+	verify_size(ftrace_size, 4096, dev->flags & PSTORE_FLAGS_FTRACE);
+#undef verify_size
+
+	pstore_zone_info->total_size = dev->total_size;
+	pstore_zone_info->max_reason = max_reason;
+	pstore_zone_info->read = dev->read;
+	pstore_zone_info->write = dev->write;
+	pstore_zone_info->erase = dev->erase;
+	pstore_zone_info->panic_write = dev->panic_write;
+	pstore_zone_info->name = KBUILD_MODNAME;
+	pstore_zone_info->owner = THIS_MODULE;
+
+	ret = register_pstore_zone(pstore_zone_info);
+	if (ret) {
+		kfree(pstore_zone_info);
+		pstore_zone_info = NULL;
+	}
+	return ret;
+}
+/**
+ * register_pstore_device() - register non-block device to pstore/blk
+ *
+ * @dev: non-block device information
+ *
+ * Return:
+ * * 0		- OK
+ * * Others	- something error.
+ */
+int register_pstore_device(struct pstore_device_info *dev)
+{
+	int ret;
+
+	mutex_lock(&pstore_blk_lock);
+	ret = __register_pstore_device(dev);
+	mutex_unlock(&pstore_blk_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(register_pstore_device);
+
+static void __unregister_pstore_device(struct pstore_device_info *dev)
+{
+	lockdep_assert_held(&pstore_blk_lock);
+	if (pstore_zone_info && pstore_zone_info->read == dev->read) {
+		unregister_pstore_zone(pstore_zone_info);
+		kfree(pstore_zone_info);
+		pstore_zone_info = NULL;
+	}
+}
+
+/**
+ * unregister_pstore_device() - unregister non-block device from pstore/blk
+ *
+ * @dev: non-block device information
+ */
+void unregister_pstore_device(struct pstore_device_info *dev)
+{
+	mutex_lock(&pstore_blk_lock);
+	__unregister_pstore_device(dev);
+	mutex_unlock(&pstore_blk_lock);
+}
+EXPORT_SYMBOL_GPL(unregister_pstore_device);
+
+/**
+ * psblk_get_bdev() - open block device
+ *
+ * @holder:	Exclusive holder identifier
+ * @info:	Information about bdev to fill in
+ *
+ * Return: pointer to block device on success and others on error.
+ *
+ * On success, the returned block_device has reference count of one.
+ */
+static struct block_device *psblk_get_bdev(void *holder,
+					   struct bdev_info *info)
+{
+	struct block_device *bdev = ERR_PTR(-ENODEV);
+	fmode_t mode = FMODE_READ | FMODE_WRITE;
+	sector_t nr_sects;
+
+	lockdep_assert_held(&pstore_blk_lock);
+
+	if (pstore_zone_info)
+		return ERR_PTR(-EBUSY);
+
+	if (!blkdev[0])
+		return ERR_PTR(-ENODEV);
+
+	if (holder)
+		mode |= FMODE_EXCL;
+	bdev = blkdev_get_by_path(blkdev, mode, holder);
+	if (IS_ERR(bdev)) {
+		dev_t devt;
+
+		devt = name_to_dev_t(blkdev);
+		if (devt == 0)
+			return ERR_PTR(-ENODEV);
+		bdev = blkdev_get_by_dev(devt, mode, holder);
+		if (IS_ERR(bdev))
+			return bdev;
+	}
+
+	nr_sects = part_nr_sects_read(bdev->bd_part);
+	if (!nr_sects) {
+		pr_err("not enough space for '%s'\n", blkdev);
+		blkdev_put(bdev, mode);
+		return ERR_PTR(-ENOSPC);
+	}
+
+	if (info) {
+		info->devt = bdev->bd_dev;
+		info->nr_sects = nr_sects;
+		info->start_sect = get_start_sect(bdev);
+	}
+
+	return bdev;
+}
+
+static void psblk_put_bdev(struct block_device *bdev, void *holder)
+{
+	fmode_t mode = FMODE_READ | FMODE_WRITE;
+
+	lockdep_assert_held(&pstore_blk_lock);
+
+	if (!bdev)
+		return;
+
+	if (holder)
+		mode |= FMODE_EXCL;
+	blkdev_put(bdev, mode);
+}
+
+static ssize_t psblk_generic_blk_read(char *buf, size_t bytes, loff_t pos)
+{
+	struct block_device *bdev = psblk_bdev;
+	struct file file;
+	struct kiocb kiocb;
+	struct iov_iter iter;
+	struct kvec iov = {.iov_base = buf, .iov_len = bytes};
+
+	if (!bdev)
+		return -ENODEV;
+
+	memset(&file, 0, sizeof(struct file));
+	file.f_mapping = bdev->bd_inode->i_mapping;
+	file.f_flags = O_DSYNC | __O_SYNC | O_NOATIME;
+	file.f_inode = bdev->bd_inode;
+	file_ra_state_init(&file.f_ra, file.f_mapping);
+
+	init_sync_kiocb(&kiocb, &file);
+	kiocb.ki_pos = pos;
+	iov_iter_kvec(&iter, READ, &iov, 1, bytes);
+
+	return generic_file_read_iter(&kiocb, &iter);
+}
+
+static ssize_t psblk_generic_blk_write(const char *buf, size_t bytes,
+		loff_t pos)
+{
+	struct block_device *bdev = psblk_bdev;
+	struct iov_iter iter;
+	struct kiocb kiocb;
+	struct file file;
+	ssize_t ret;
+	struct kvec iov = {.iov_base = (void *)buf, .iov_len = bytes};
+
+	if (!bdev)
+		return -ENODEV;
+
+	/* Console/Ftrace backend may handle buffer until flush dirty zones */
+	if (in_interrupt() || irqs_disabled())
+		return -EBUSY;
+
+	memset(&file, 0, sizeof(struct file));
+	file.f_mapping = bdev->bd_inode->i_mapping;
+	file.f_flags = O_DSYNC | __O_SYNC | O_NOATIME;
+	file.f_inode = bdev->bd_inode;
+
+	init_sync_kiocb(&kiocb, &file);
+	kiocb.ki_pos = pos;
+	iov_iter_kvec(&iter, WRITE, &iov, 1, bytes);
+
+	inode_lock(bdev->bd_inode);
+	ret = generic_write_checks(&kiocb, &iter);
+	if (ret > 0)
+		ret = generic_perform_write(&file, &iter, pos);
+	inode_unlock(bdev->bd_inode);
+
+	if (likely(ret > 0)) {
+		const struct file_operations f_op = {.fsync = blkdev_fsync};
+
+		file.f_op = &f_op;
+		kiocb.ki_pos += ret;
+		ret = generic_write_sync(&kiocb, ret);
+	}
+	return ret;
+}
+
+static ssize_t psblk_blk_panic_write(const char *buf, size_t size,
+		loff_t off)
+{
+	int ret;
+
+	if (!blkdev_panic_write)
+		return -EOPNOTSUPP;
+
+	/* size and off must align to SECTOR_SIZE for block device */
+	ret = blkdev_panic_write(buf, off >> SECTOR_SHIFT,
+			size >> SECTOR_SHIFT);
+	/* try next zone */
+	if (ret == -ENOMSG)
+		return ret;
+	return ret ? -EIO : size;
+}
+
+static int __register_pstore_blk(struct pstore_blk_info *info)
+{
+	char bdev_name[BDEVNAME_SIZE];
+	struct block_device *bdev;
+	struct pstore_device_info dev;
+	struct bdev_info binfo;
+	void *holder = blkdev;
+	int ret = -ENODEV;
+
+	lockdep_assert_held(&pstore_blk_lock);
+
+	/* hold bdev exclusively */
+	memset(&binfo, 0, sizeof(binfo));
+	bdev = psblk_get_bdev(holder, &binfo);
+	if (IS_ERR(bdev)) {
+		pr_err("failed to open '%s'!\n", blkdev);
+		return PTR_ERR(bdev);
+	}
+
+	/* only allow driver matching the @blkdev */
+	if (!binfo.devt || (!best_effort &&
+			    MAJOR(binfo.devt) != info->major)) {
+		pr_debug("invalid major %u (expect %u)\n",
+				info->major, MAJOR(binfo.devt));
+		ret = -ENODEV;
+		goto err_put_bdev;
+	}
+
+	/* psblk_bdev must be assigned before register to pstore/blk */
+	psblk_bdev = bdev;
+	blkdev_panic_write = info->panic_write;
+
+	/* Copy back block device details. */
+	info->devt = binfo.devt;
+	info->nr_sects = binfo.nr_sects;
+	info->start_sect = binfo.start_sect;
+
+	memset(&dev, 0, sizeof(dev));
+	dev.total_size = info->nr_sects << SECTOR_SHIFT;
+	dev.flags = info->flags;
+	dev.read = psblk_generic_blk_read;
+	dev.write = psblk_generic_blk_write;
+	dev.erase = NULL;
+	dev.panic_write = info->panic_write ? psblk_blk_panic_write : NULL;
+
+	ret = __register_pstore_device(&dev);
+	if (ret)
+		goto err_put_bdev;
+
+	bdevname(bdev, bdev_name);
+	pr_info("attached %s%s\n", bdev_name,
+		info->panic_write ? "" : " (no dedicated panic_write!)");
+	return 0;
+
+err_put_bdev:
+	psblk_bdev = NULL;
+	blkdev_panic_write = NULL;
+	psblk_put_bdev(bdev, holder);
+	return ret;
+}
+
+/**
+ * register_pstore_blk() - register block device to pstore/blk
+ *
+ * @info: details on the desired block device interface
+ *
+ * Return:
+ * * 0		- OK
+ * * Others	- something error.
+ */
+int register_pstore_blk(struct pstore_blk_info *info)
+{
+	int ret;
+
+	mutex_lock(&pstore_blk_lock);
+	ret = __register_pstore_blk(info);
+	mutex_unlock(&pstore_blk_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(register_pstore_blk);
+
+static void __unregister_pstore_blk(unsigned int major)
+{
+	struct pstore_device_info dev = { .read = psblk_generic_blk_read };
+	void *holder = blkdev;
+
+	lockdep_assert_held(&pstore_blk_lock);
+	if (psblk_bdev && MAJOR(psblk_bdev->bd_dev) == major) {
+		__unregister_pstore_device(&dev);
+		psblk_put_bdev(psblk_bdev, holder);
+		blkdev_panic_write = NULL;
+		psblk_bdev = NULL;
+	}
+}
+
+/**
+ * unregister_pstore_blk() - unregister block device from pstore/blk
+ *
+ * @major: the major device number of device
+ */
+void unregister_pstore_blk(unsigned int major)
+{
+	mutex_lock(&pstore_blk_lock);
+	__unregister_pstore_blk(major);
+	mutex_unlock(&pstore_blk_lock);
+}
+EXPORT_SYMBOL_GPL(unregister_pstore_blk);
+
+/* get information of pstore/blk */
+int pstore_blk_get_config(struct pstore_blk_config *info)
+{
+	strncpy(info->device, blkdev, 80);
+	info->max_reason = max_reason;
+	info->kmsg_size = check_size(kmsg_size, 4096);
+	info->pmsg_size = check_size(pmsg_size, 4096);
+	info->ftrace_size = check_size(ftrace_size, 4096);
+	info->console_size = check_size(console_size, 4096);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pstore_blk_get_config);
+
+static int __init pstore_blk_init(void)
+{
+	struct pstore_blk_info info = { };
+	int ret = 0;
+
+	mutex_lock(&pstore_blk_lock);
+	if (!pstore_zone_info && best_effort && blkdev[0])
+		ret = __register_pstore_blk(&info);
+	mutex_unlock(&pstore_blk_lock);
+
+	return ret;
+}
+late_initcall(pstore_blk_init);
+
+static void __exit pstore_blk_exit(void)
+{
+	mutex_lock(&pstore_blk_lock);
+	if (psblk_bdev)
+		__unregister_pstore_blk(MAJOR(psblk_bdev->bd_dev));
+	else {
+		struct pstore_device_info dev = { };
+
+		if (pstore_zone_info)
+			dev.read = pstore_zone_info->read;
+		__unregister_pstore_device(&dev);
+	}
+	mutex_unlock(&pstore_blk_lock);
+}
+module_exit(pstore_blk_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("WeiXiong Liao <[e-mail]>");
+MODULE_AUTHOR("Kees Cook <[e-mail]>");
+MODULE_DESCRIPTION("pstore backend for block devices");

fs/pstore/ftrace.c

···
 #include <linux/debugfs.h>
 #include <linux/err.h>
 #include <linux/cache.h>
+#include <linux/slab.h>
 #include <asm/barrier.h>
 #include "internal.h"
 
···
 
 	debugfs_remove_recursive(pstore_ftrace_dir);
 }
+
+ssize_t pstore_ftrace_combine_log(char **dest_log, size_t *dest_log_size,
+				  const char *src_log, size_t src_log_size)
+{
+	size_t dest_size, src_size, total, dest_off, src_off;
+	size_t dest_idx = 0, src_idx = 0, merged_idx = 0;
+	void *merged_buf;
+	struct pstore_ftrace_record *drec, *srec, *mrec;
+	size_t record_size = sizeof(struct pstore_ftrace_record);
+
+	dest_off = *dest_log_size % record_size;
+	dest_size = *dest_log_size - dest_off;
+
+	src_off = src_log_size % record_size;
+	src_size = src_log_size - src_off;
+
+	total = dest_size + src_size;
+	merged_buf = kmalloc(total, GFP_KERNEL);
+	if (!merged_buf)
+		return -ENOMEM;
+
+	drec = (struct pstore_ftrace_record *)(*dest_log + dest_off);
+	srec = (struct pstore_ftrace_record *)(src_log + src_off);
+	mrec = (struct pstore_ftrace_record *)(merged_buf);
+
+	while (dest_size > 0 && src_size > 0) {
+		if (pstore_ftrace_read_timestamp(&drec[dest_idx]) <
+		    pstore_ftrace_read_timestamp(&srec[src_idx])) {
+			mrec[merged_idx++] = drec[dest_idx++];
+			dest_size -= record_size;
+		} else {
+			mrec[merged_idx++] = srec[src_idx++];
+			src_size -= record_size;
+		}
+	}
+
+	while (dest_size > 0) {
+		mrec[merged_idx++] = drec[dest_idx++];
+		dest_size -= record_size;
+	}
+
+	while (src_size > 0) {
+		mrec[merged_idx++] = srec[src_idx++];
+		src_size -= record_size;
+	}
+
+	kfree(*dest_log);
+	*dest_log = merged_buf;
+	*dest_log_size = total;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pstore_ftrace_combine_log);

fs/pstore/inode.c

···
 #include <linux/magic.h>
 #include <linux/pstore.h>
 #include <linux/slab.h>
-#include <linux/spinlock.h>
 #include <linux/uaccess.h>
 
 #include "internal.h"
 
 #define	PSTORE_NAMELEN	64
 
-static DEFINE_SPINLOCK(allpstore_lock);
-static LIST_HEAD(allpstore);
+static DEFINE_MUTEX(records_list_lock);
+static LIST_HEAD(records_list);
+
+static DEFINE_MUTEX(pstore_sb_lock);
+static struct super_block *pstore_sb;
 
 struct pstore_private {
 	struct list_head list;
+	struct dentry *dentry;
 	struct pstore_record *record;
 	size_t total_size;
 };
···
 {
 	struct pstore_private *p = d_inode(dentry)->i_private;
 	struct pstore_record *record = p->record;
+	int rc = 0;
 
 	if (!record->psi->erase)
 		return -EPERM;
+
+	/* Make sure we can't race while removing this file. */
+	mutex_lock(&records_list_lock);
+	if (!list_empty(&p->list))
+		list_del_init(&p->list);
+	else
+		rc = -ENOENT;
+	p->dentry = NULL;
+	mutex_unlock(&records_list_lock);
+	if (rc)
+		return rc;
 
 	mutex_lock(&record->psi->read_mutex);
 	record->psi->erase(record);
···
 static void pstore_evict_inode(struct inode *inode)
 {
 	struct pstore_private	*p = inode->i_private;
-	unsigned long		flags;
 
 	clear_inode(inode);
-	if (p) {
-		spin_lock_irqsave(&allpstore_lock, flags);
-		list_del(&p->list);
-		spin_unlock_irqrestore(&allpstore_lock, flags);
-		free_pstore_private(p);
-	}
+	free_pstore_private(p);
 }
 
 static const struct inode_operations pstore_dir_inode_operations = {
···
 	.show_options	= pstore_show_options,
 };
 
-static struct super_block *pstore_sb;
-
-bool pstore_is_mounted(void)
+static struct dentry *psinfo_lock_root(void)
 {
-	return pstore_sb != NULL;
+	struct dentry *root;
+
+	mutex_lock(&pstore_sb_lock);
+	/*
+	 * Having no backend is fine -- no records appear.
+	 * Not being mounted is fine -- nothing to do.
+	 */
+	if (!psinfo || !pstore_sb) {
+		mutex_unlock(&pstore_sb_lock);
+		return NULL;
+	}
+
+	root = pstore_sb->s_root;
+	inode_lock(d_inode(root));
+	mutex_unlock(&pstore_sb_lock);
+
+	return root;
+}
+
+int pstore_put_backend_records(struct pstore_info *psi)
+{
+	struct pstore_private *pos, *tmp;
+	struct dentry *root;
+	int rc = 0;
+
+	root = psinfo_lock_root();
+	if (!root)
+		return 0;
+
+	mutex_lock(&records_list_lock);
+	list_for_each_entry_safe(pos, tmp, &records_list, list) {
+		if (pos->record->psi == psi) {
+			list_del_init(&pos->list);
+			rc = simple_unlink(d_inode(root), pos->dentry);
+			if (WARN_ON(rc))
+				break;
+			d_drop(pos->dentry);
+			dput(pos->dentry);
+			pos->dentry = NULL;
+		}
+	}
+	mutex_unlock(&records_list_lock);
+
+	inode_unlock(d_inode(root));
+
+	return rc;
 }
 
 /*
···
 	int			rc = 0;
 	char			name[PSTORE_NAMELEN];
 	struct pstore_private	*private, *pos;
-	unsigned long		flags;
 	size_t			size = record->size + record->ecc_notice_size;
 
-	WARN_ON(!inode_is_locked(d_inode(root)));
+	if (WARN_ON(!inode_is_locked(d_inode(root))))
+		return -EINVAL;
 
-	spin_lock_irqsave(&allpstore_lock, flags);
-	list_for_each_entry(pos, &allpstore, list) {
+	rc = -EEXIST;
+	/* Skip records that are already present in the filesystem. */
+	mutex_lock(&records_list_lock);
+	list_for_each_entry(pos, &records_list, list) {
 		if (pos->record->type == record->type &&
 		    pos->record->id == record->id &&
-		    pos->record->psi == record->psi) {
-			rc = -EEXIST;
-			break;
-		}
+		    pos->record->psi == record->psi)
+			goto fail;
 	}
-	spin_unlock_irqrestore(&allpstore_lock, flags);
-	if (rc)
-		return rc;
 
 	rc = -ENOMEM;
 	inode = pstore_get_inode(root->d_sb);
···
 	if (!dentry)
 		goto fail_private;
 
+	private->dentry = dentry;
 	private->record = record;
 	inode->i_size = private->total_size = size;
 	inode->i_private = private;
···
 
 	d_add(dentry, inode);
 
-	spin_lock_irqsave(&allpstore_lock, flags);
-	list_add(&private->list, &allpstore);
-	spin_unlock_irqrestore(&allpstore_lock, flags);
+	list_add(&private->list, &records_list);
+	mutex_unlock(&records_list_lock);
 
 	return 0;
 
···
 	free_pstore_private(private);
 fail_inode:
 	iput(inode);
-
 fail:
+	mutex_unlock(&records_list_lock);
 	return rc;
 }
 
···
  */
 void pstore_get_records(int quiet)
 {
-	struct pstore_info *psi = psinfo;
 	struct dentry *root;
 
-	if (!psi || !pstore_sb)
+	root = psinfo_lock_root();
+	if (!root)
 		return;
 
-	root = pstore_sb->s_root;
-
-	inode_lock(d_inode(root));
-	pstore_get_backend_records(psi, root, quiet);
+	pstore_get_backend_records(psinfo, root, quiet);
 	inode_unlock(d_inode(root));
 }
 
 static int pstore_fill_super(struct super_block *sb, void *data, int silent)
 {
 	struct inode *inode;
-
-	pstore_sb = sb;
 
 	sb->s_maxbytes		= MAX_LFS_FILESIZE;
 	sb->s_blocksize		= PAGE_SIZE;
···
 	if (!sb->s_root)
 		return -ENOMEM;
 
+	mutex_lock(&pstore_sb_lock);
+	pstore_sb = sb;
+	mutex_unlock(&pstore_sb_lock);
+
 	pstore_get_records(0);
 
 	return 0;
···
 
 static void pstore_kill_sb(struct super_block *sb)
 {
+	mutex_lock(&pstore_sb_lock);
+	WARN_ON(pstore_sb != sb);
+
 	kill_litter_super(sb);
 	pstore_sb = NULL;
+
+	mutex_lock(&records_list_lock);
+	INIT_LIST_HEAD(&records_list);
+	mutex_unlock(&records_list_lock);
+
+	mutex_unlock(&pstore_sb_lock);
 }
 
 static struct file_system_type pstore_fs_type = {

fs/pstore/internal.h

···
 #ifdef CONFIG_PSTORE_FTRACE
 extern void pstore_register_ftrace(void);
 extern void pstore_unregister_ftrace(void);
+ssize_t pstore_ftrace_combine_log(char **dest_log, size_t *dest_log_size,
+				  const char *src_log, size_t src_log_size);
 #else
 static inline void pstore_register_ftrace(void) {}
 static inline void pstore_unregister_ftrace(void) {}
+static inline ssize_t
+pstore_ftrace_combine_log(char **dest_log, size_t *dest_log_size,
+			  const char *src_log, size_t src_log_size)
+{
+	*dest_log_size = 0;
+	return 0;
+}
 #endif
 
 #ifdef CONFIG_PSTORE_PMSG
···
 extern void	pstore_get_records(int);
 extern void	pstore_get_backend_records(struct pstore_info *psi,
 					   struct dentry *root, int quiet);
+extern int	pstore_put_backend_records(struct pstore_info *psi);
 extern int	pstore_mkfile(struct dentry *root,
 			      struct pstore_record *record);
-extern bool	pstore_is_mounted(void);
 extern void	pstore_record_init(struct pstore_record *record,
 				   struct pstore_info *psi);
 

fs/pstore/platform.c

···
 module_param_named(update_ms, pstore_update_ms, int, 0600);
 MODULE_PARM_DESC(update_ms, "milliseconds before pstore updates its content "
 		 "(default is -1, which means runtime updates are disabled; "
-		 "enabling this option is not safe, it may lead to further "
+		 "enabling this option may not be safe; it may lead to further "
 		 "corruption on Oopses)");
 
 /* Names should be in the same order as the enum pstore_type_id */
···
 static DECLARE_WORK(pstore_work, pstore_dowork);
 
 /*
- * pstore_lock just protects "psinfo" during
- * calls to pstore_register()
+ * psinfo_lock protects "psinfo" during calls to
+ * pstore_register(), pstore_unregister(), and
+ * the filesystem mount/unmount routines.
  */
-static DEFINE_SPINLOCK(pstore_lock);
+static DEFINE_MUTEX(psinfo_lock);
 struct pstore_info *psinfo;
 
 static char *backend;
+module_param(backend, charp, 0444);
+MODULE_PARM_DESC(backend, "specific backend to use");
+
 static char *compress =
 #ifdef CONFIG_PSTORE_COMPRESS_DEFAULT
 		CONFIG_PSTORE_COMPRESS_DEFAULT;
 #else
 		NULL;
 #endif
+module_param(compress, charp, 0444);
+MODULE_PARM_DESC(compress, "compression to use");
 
 /* Compression parameters */
 static struct crypto_comp *tfm;
···
 }
 EXPORT_SYMBOL_GPL(pstore_name_to_type);
 
-static const char *get_reason_str(enum kmsg_dump_reason reason)
+static void pstore_timer_kick(void)
 {
-	switch (reason) {
-	case KMSG_DUMP_PANIC:
-		return "Panic";
-	case KMSG_DUMP_OOPS:
-		return "Oops";
-	case KMSG_DUMP_EMERG:
-		return "Emergency";
-	case KMSG_DUMP_RESTART:
-		return "Restart";
-	case KMSG_DUMP_HALT:
-		return "Halt";
-	case KMSG_DUMP_POWEROFF:
-		return "Poweroff";
-	default:
-		return "Unknown";
-	}
+	if (pstore_update_ms < 0)
+		return;
+
+	mod_timer(&pstore_timer, jiffies + msecs_to_jiffies(pstore_update_ms));
 }
 
 /*
···
 	unsigned int	part = 1;
 	int		ret;
 
-	why = get_reason_str(reason);
+	why = kmsg_dump_reason_str(reason);
 
 	if (down_trylock(&psinfo->buf_lock)) {
 		/* Failed to acquire lock: give up if we cannot wait. */
···
 		}
 
 		ret = psinfo->write(&record);
-		if (ret == 0 && reason == KMSG_DUMP_OOPS && pstore_is_mounted())
+		if (ret == 0 && reason == KMSG_DUMP_OOPS) {
 			pstore_new_entry = 1;
+			pstore_timer_kick();
+		}
 
 		total += record.size;
 		part++;
···
 }
 
 static struct console pstore_console = {
-	.name	= "pstore",
 	.write	= pstore_console_write,
-	.flags	= CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME,
 	.index	= -1,
 };
 
 static void pstore_register_console(void)
 {
+	/* Show which backend is going to get console writes. */
+	strscpy(pstore_console.name, psinfo->name,
+		sizeof(pstore_console.name));
+	/*
+	 * Always initialize flags here since prior unregister_console()
+	 * calls may have changed settings (specifically CON_ENABLED).
+	 */
+	pstore_console.flags = CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME;
 	register_console(&pstore_console);
 }
 
···
  */
 int pstore_register(struct pstore_info *psi)
 {
-	struct module *owner = psi->owner;
-
 	if (backend && strcmp(backend, psi->name)) {
 		pr_warn("ignoring unexpected backend '%s'\n", psi->name);
 		return -EPERM;
···
 		return -EINVAL;
 	}
 
-	spin_lock(&pstore_lock);
+	mutex_lock(&psinfo_lock);
 	if (psinfo) {
 		pr_warn("backend '%s' already loaded: ignoring '%s'\n",
 			psinfo->name, psi->name);
-		spin_unlock(&pstore_lock);
+		mutex_unlock(&psinfo_lock);
 		return -EBUSY;
 	}
 
···
 	psinfo = psi;
 	mutex_init(&psinfo->read_mutex);
 	sema_init(&psinfo->buf_lock, 1);
-	spin_unlock(&pstore_lock);
-
-	if (owner && !try_module_get(owner)) {
-		psinfo = NULL;
-		return -EINVAL;
-	}
 
 	if (psi->flags & PSTORE_FLAGS_DMESG)
 		allocate_buf_for_compression();
 
-	if (pstore_is_mounted())
-		pstore_get_records(0);
+	pstore_get_records(0);
 
-	if (psi->flags & PSTORE_FLAGS_DMESG)
+	if (psi->flags & PSTORE_FLAGS_DMESG) {
+		pstore_dumper.max_reason = psinfo->max_reason;
 		pstore_register_kmsg();
+	}
 	if (psi->flags & PSTORE_FLAGS_CONSOLE)
 		pstore_register_console();
 	if (psi->flags & PSTORE_FLAGS_FTRACE)
···
 		pstore_register_pmsg();
 
 	/* Start watching for new records, if desired. */
-	if (pstore_update_ms >= 0) {
-		pstore_timer.expires = jiffies +
-			msecs_to_jiffies(pstore_update_ms);
-		add_timer(&pstore_timer);
-	}
+	pstore_timer_kick();
 
 	/*
 	 * Update the module parameter backend, so it is visible
 	 * through /sys/module/pstore/parameters/backend
 	 */
-	backend = psi->name;
+	backend = kstrdup(psi->name, GFP_KERNEL);
 
 	pr_info("Registered %s as persistent store backend\n", psi->name);
 
-	module_put(owner);
-
+	mutex_unlock(&psinfo_lock);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(pstore_register);
 
 void pstore_unregister(struct pstore_info *psi)
 {
-	/* Stop timer and make sure all work has finished. */
-	pstore_update_ms = -1;
-	del_timer_sync(&pstore_timer);
-	flush_work(&pstore_work);
+	/* It's okay to unregister nothing. */
+	if (!psi)
+		return;
 
+	mutex_lock(&psinfo_lock);
+
+	/* Only one backend can be registered at a time. */
+	if (WARN_ON(psi != psinfo)) {
+		mutex_unlock(&psinfo_lock);
+		return;
+	}
+
+	/* Unregister all callbacks. */
 	if (psi->flags & PSTORE_FLAGS_PMSG)
 		pstore_unregister_pmsg();
 	if (psi->flags & PSTORE_FLAGS_FTRACE)
···
 	if (psi->flags & PSTORE_FLAGS_DMESG)
 		pstore_unregister_kmsg();
 
+	/* Stop timer and make sure all work has finished. */
+	del_timer_sync(&pstore_timer);
+	flush_work(&pstore_work);
+
+	/* Remove all backend records from filesystem tree. */
+	pstore_put_backend_records(psi);
+
 	free_buf_for_compression();
 
 	psinfo = NULL;
+	kfree(backend);
 	backend = NULL;
+	mutex_unlock(&psinfo_lock);
 }
 EXPORT_SYMBOL_GPL(pstore_unregister);
 
···
 		schedule_work(&pstore_work);
 	}
 
-	if (pstore_update_ms >= 0)
-		mod_timer(&pstore_timer,
-			  jiffies + msecs_to_jiffies(pstore_update_ms));
+	pstore_timer_kick();
 }
 
 static void __init pstore_choose_compression(void)
···
 	pstore_exit_fs();
 }
 module_exit(pstore_exit)
-
-module_param(compress, charp, 0444);
-MODULE_PARM_DESC(compress, "Pstore compression to use");
-
-module_param(backend, charp, 0444);
-MODULE_PARM_DESC(backend, "Pstore backend to use");
 
 MODULE_AUTHOR("Tony Luck <[e-mail]>");
 MODULE_LICENSE("GPL");

fs/pstore/ram.c

···
 #include <linux/pstore_ram.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
+#include "internal.h"
 
 #define RAMOOPS_KERNMSG_HDR "===="
 #define MIN_MEM_SIZE 4096UL
···
 		"size of reserved RAM used to store oops/panic logs");
 
 static unsigned int mem_type;
-module_param(mem_type, uint, 0600);
+module_param(mem_type, uint, 0400);
 MODULE_PARM_DESC(mem_type,
 		"set to 1 to try to use unbuffered memory (default 0)");
 
-static int dump_oops = 1;
-module_param(dump_oops, int, 0600);
-MODULE_PARM_DESC(dump_oops,
-		"set to 1 to dump oopses, 0 to only dump panics (default 1)");
+static int ramoops_max_reason = -1;
+module_param_named(max_reason, ramoops_max_reason, int, 0400);
+MODULE_PARM_DESC(max_reason,
+		 "maximum reason for kmsg dump (default 2: Oops and Panic) ");
 
 static int ramoops_ecc;
-module_param_named(ecc, ramoops_ecc, int, 0600);
+module_param_named(ecc, ramoops_ecc, int, 0400);
 MODULE_PARM_DESC(ramoops_ecc,
 		"if non-zero, the option enables ECC support and specifies "
 		"ECC buffer size in bytes (1 is a special value, means 16 "
 		"bytes ECC)");
+
+static int ramoops_dump_oops = -1;
+module_param_named(dump_oops, ramoops_dump_oops, int, 0400);
+MODULE_PARM_DESC(dump_oops,
+		 "(deprecated: use max_reason instead) set to 1 to dump oopses & panics, 0 to only dump panics");
 
 struct ramoops_context {
 	struct persistent_ram_zone **dprzs;	/* Oops dump zones */
···
 	size_t console_size;
 	size_t ftrace_size;
 	size_t pmsg_size;
-	int dump_oops;
 	u32 flags;
 	struct persistent_ram_ecc_info ecc_info;
 	unsigned int max_dump_cnt;
···
 			   persistent_ram_ecc_string(prz, NULL, 0));
 }
 
-static ssize_t ftrace_log_combine(struct persistent_ram_zone *dest,
-				  struct persistent_ram_zone *src)
-{
-	size_t dest_size, src_size, total, dest_off, src_off;
-	size_t dest_idx = 0, src_idx = 0, merged_idx = 0;
-	void *merged_buf;
-	struct pstore_ftrace_record *drec, *srec, *mrec;
-	size_t record_size = sizeof(struct pstore_ftrace_record);
-
-	dest_off = dest->old_log_size % record_size;
-	dest_size = dest->old_log_size - dest_off;
-
-	src_off = src->old_log_size % record_size;
-	src_size = src->old_log_size - src_off;
-
-	total = dest_size + src_size;
-	merged_buf = kmalloc(total, GFP_KERNEL);
-	if (!merged_buf)
-		return -ENOMEM;
-
-	drec = (struct pstore_ftrace_record *)(dest->old_log + dest_off);
-	srec = (struct pstore_ftrace_record *)(src->old_log + src_off);
-	mrec = (struct pstore_ftrace_record *)(merged_buf);
-
-	while (dest_size > 0 && src_size > 0) {
-		if (pstore_ftrace_read_timestamp(&drec[dest_idx]) <
-		    pstore_ftrace_read_timestamp(&srec[src_idx])) {
-			mrec[merged_idx++] = drec[dest_idx++];
-			dest_size -= record_size;
-		} else {
-			mrec[merged_idx++] = srec[src_idx++];
-			src_size -= record_size;
-		}
-	}
-
-	while (dest_size > 0) {
-		mrec[merged_idx++] = drec[dest_idx++];
-		dest_size -= record_size;
-	}
-
-	while (src_size > 0) {
-		mrec[merged_idx++] = srec[src_idx++];
-		src_size -= record_size;
-	}
-
-	kfree(dest->old_log);
-	dest->old_log = merged_buf;
-	dest->old_log_size = total;
-
-	return 0;
-}
-
 static ssize_t ramoops_pstore_read(struct pstore_record *record)
 {
 	ssize_t size = 0;
···
 				tmp_prz->corrected_bytes +=
 						prz_next->corrected_bytes;
 				tmp_prz->bad_blocks += prz_next->bad_blocks;
-				size = ftrace_log_combine(tmp_prz, prz_next);
+
+				size = pstore_ftrace_combine_log(
+						&tmp_prz->old_log,
+						&tmp_prz->old_log_size,
+						prz_next->old_log,
+						prz_next->old_log_size);
 				if (size)
 					goto out;
 			}
···
 		return -EINVAL;
 
 	/*
-	 * Out of the various dmesg dump types, ramoops is currently designed
-	 * to only store crash logs, rather than storing general kernel logs.
+	 * We could filter on record->reason here if we wanted to (which
+	 * would duplicate what happened before the "max_reason" setting
+	 * was added), but that would defeat the purpose of a system
+	 * changing printk.always_kmsg_dump, so instead log everything that
+	 * the kmsg dumper sends us, since it should be doing the filtering
+	 * based on the combination of printk.always_kmsg_dump and our
+	 * requested "max_reason".
 	 */
-	if (record->reason != KMSG_DUMP_OOPS &&
-	    record->reason != KMSG_DUMP_PANIC)
-		return -EINVAL;
-
-	/* Skip Oopes when configured to do so. */
-	if (record->reason == KMSG_DUMP_OOPS && !cxt->dump_oops)
-		return -EINVAL;
 
 	/*
 	 * Explicitly only take the first part of any new crash.
···
 	return 0;
 }
 
-static int ramoops_parse_dt_size(struct platform_device *pdev,
-				 const char *propname, u32 *value)
+/* Read a u32 from a dt property and make sure it's safe for an int. */
+static int ramoops_parse_dt_u32(struct platform_device *pdev,
+				const char *propname,
+				u32 default_value, u32 *value)
 {
 	u32 val32 = 0;
 	int ret;
 
 	ret = of_property_read_u32(pdev->dev.of_node, propname, &val32);
-	if (ret < 0 && ret != -EINVAL) {
+	if (ret == -EINVAL) {
+		/* field is missing, use default value. */
+		val32 = default_value;
+	} else if (ret < 0) {
 		dev_err(&pdev->dev, "failed to parse property %s: %d\n",
 			propname, ret);
 		return ret;
 	}
 
+	/* Sanity check our results. */
 	if (val32 > INT_MAX) {
 		dev_err(&pdev->dev, "%s %u > INT_MAX\n", propname, val32);
 		return -EOVERFLOW;
···
 	pdata->mem_size = resource_size(res);
 	pdata->mem_address = res->start;
 	pdata->mem_type = of_property_read_bool(of_node, "unbuffered");
-	pdata->dump_oops = !of_property_read_bool(of_node, "no-dump-oops");
+	/*
+	 * Setting "no-dump-oops" is deprecated and will be ignored if
+	 * "max_reason" is also specified.
+	 */
+	if (of_property_read_bool(of_node, "no-dump-oops"))
+		pdata->max_reason = KMSG_DUMP_PANIC;
+	else
+		pdata->max_reason = KMSG_DUMP_OOPS;
 
-#define parse_size(name, field) {					\
-		ret = ramoops_parse_dt_size(pdev, name, &value);	\
+#define parse_u32(name, field, default_value) {				\
+		ret = ramoops_parse_dt_u32(pdev, name, default_value,	\
+					    &value);			\
 		if (ret < 0)						\
 			return ret;					\
 		field = value;						\
 	}
 
-	parse_size("record-size", pdata->record_size);
-	parse_size("console-size", pdata->console_size);
-	parse_size("ftrace-size", pdata->ftrace_size);
-	parse_size("pmsg-size", pdata->pmsg_size);
-	parse_size("ecc-size", pdata->ecc_info.ecc_size);
-	parse_size("flags", pdata->flags);
+	parse_u32("record-size", pdata->record_size, 0);
+	parse_u32("console-size", pdata->console_size, 0);
+	parse_u32("ftrace-size", pdata->ftrace_size, 0);
+	parse_u32("pmsg-size", pdata->pmsg_size, 0);
+	parse_u32("ecc-size", pdata->ecc_info.ecc_size, 0);
+	parse_u32("flags", pdata->flags, 0);
+	parse_u32("max-reason", pdata->max_reason, pdata->max_reason);
 
-#undef parse_size
+#undef parse_u32
 
 	/*
 	 * Some old Chromebooks relied on the kernel setting the
···
 	cxt->console_size = pdata->console_size;
 	cxt->ftrace_size = pdata->ftrace_size;
 	cxt->pmsg_size = pdata->pmsg_size;
-	cxt->dump_oops = pdata->dump_oops;
 	cxt->flags = pdata->flags;
 	cxt->ecc_info = pdata->ecc_info;
 
···
 	 * the single region size is how to check.
 	 */
 	cxt->pstore.flags = 0;
-	if (cxt->max_dump_cnt)
+	if (cxt->max_dump_cnt) {
 		cxt->pstore.flags |= PSTORE_FLAGS_DMESG;
+		cxt->pstore.max_reason = pdata->max_reason;
+	}
 	if (cxt->console_size)
 		cxt->pstore.flags |= PSTORE_FLAGS_CONSOLE;
 	if (cxt->max_ftrace_cnt)
···
 	mem_size = pdata->mem_size;
 	mem_address = pdata->mem_address;
 	record_size = pdata->record_size;
-	dump_oops = pdata->dump_oops;
+	ramoops_max_reason = pdata->max_reason;
 	ramoops_console_size = pdata->console_size;
 	ramoops_pmsg_size = pdata->pmsg_size;
 	ramoops_ftrace_size = pdata->ftrace_size;
···
 	pdata.console_size = ramoops_console_size;
 	pdata.ftrace_size = ramoops_ftrace_size;
 	pdata.pmsg_size = ramoops_pmsg_size;
-	pdata.dump_oops = dump_oops;
+	/* If "max_reason" is set, its value has priority over "dump_oops". */
+	if (ramoops_max_reason >= 0)
+		pdata.max_reason = ramoops_max_reason;
+	/* Otherwise, if "dump_oops" is set, parse it into "max_reason". */
+	else if (ramoops_dump_oops != -1)
+		pdata.max_reason = ramoops_dump_oops ? KMSG_DUMP_OOPS
+						     : KMSG_DUMP_PANIC;
+	/* And if neither are explicitly set, use the default. */
+	else
+		pdata.max_reason = KMSG_DUMP_OOPS;
 	pdata.flags = RAMOOPS_FLAG_FTRACE_PER_CPU;
 
 	/*

fs/pstore/zone.c

···
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Provide a pstore intermediate backend, organized into kernel memory
+ * allocated zones that are then mapped and flushed into a single
+ * contiguous region on a storage backend of some kind (block, mtd, etc).
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/mount.h>
+#include <linux/printk.h>
+#include <linux/fs.h>
+#include <linux/pstore_zone.h>
+#include <linux/kdev_t.h>
+#include <linux/device.h>
+#include <linux/namei.h>
+#include <linux/fcntl.h>
+#include <linux/uio.h>
+#include <linux/writeback.h>
+#include "internal.h"
+
+/**
+ * struct psz_head - header of zone to flush to storage
+ *
+ * @sig: signature to indicate header (PSZ_SIG xor PSZONE-type value)
+ * @datalen: length of data in @data
+ * @start: offset into @data where the beginning of the stored bytes begin
+ * @data: zone data.
+ */
+struct psz_buffer {
+#define PSZ_SIG (0x43474244) /* DBGC */
+	uint32_t sig;
+	atomic_t datalen;
+	atomic_t start;
+	uint8_t data[];
+};
+
+/**
+ * struct psz_kmsg_header - kmsg dump-specific header to flush to storage
+ *
+ * @magic: magic num for kmsg dump header
+ * @time: kmsg dump trigger time
+ * @compressed: whether conpressed
+ * @counter: kmsg dump counter
+ * @reason: the kmsg dump reason (e.g. oops, panic, etc)
+ * @data: pointer to log data
+ *
+ * This is a sub-header for a kmsg dump, trailing after &psz_buffer.
+ */
+struct psz_kmsg_header {
+#define PSTORE_KMSG_HEADER_MAGIC 0x4dfc3ae5 /* Just a random number */
+	uint32_t magic;
+	struct timespec64 time;
+	bool compressed;
+	uint32_t counter;
+	enum kmsg_dump_reason reason;
+	uint8_t data[];
+};
+
+/**
+ * struct pstore_zone - single stored buffer
+ *
+ * @off: zone offset of storage
+ * @type: front-end type for this zone
+ * @name: front-end name for this zone
+ * @buffer: pointer to data buffer managed by this zone
+ * @oldbuf: pointer to old data buffer
+ * @buffer_size: bytes in @buffer->data
+ * @should_recover: whether this zone should recover from storage
+ * @dirty: whether the data in @buffer dirty
+ *
+ * zone structure in memory.
+ */
+struct pstore_zone {
+	loff_t off;
+	const char *name;
+	enum pstore_type_id type;
+
+	struct psz_buffer *buffer;
+	struct psz_buffer *oldbuf;
+	size_t buffer_size;
+	bool should_recover;
+	atomic_t dirty;
+};
+
+/**
+ * struct psz_context - all about running state of pstore/zone
+ *
+ * @kpszs: kmsg dump storage zones
+ * @ppsz: pmsg storage zone
+ * @cpsz: console storage zone
+ * @fpszs: ftrace storage zones
+ * @kmsg_max_cnt: max count of @kpszs
+ * @kmsg_read_cnt: counter of total read kmsg dumps
+ * @kmsg_write_cnt: counter of total kmsg dump writes
+ * @pmsg_read_cnt: counter of total read pmsg zone
+ * @console_read_cnt: counter of total read console zone
+ * @ftrace_max_cnt: max count of @fpszs
+ * @ftrace_read_cnt: counter of max read ftrace zone
+ * @oops_counter: counter of oops dumps
+ * @panic_counter: counter of panic dumps
+ * @recovered: whether finished recovering data from storage
+ * @on_panic: whether panic is happening
+ * @pstore_zone_info_lock: lock to @pstore_zone_info
+ * @pstore_zone_info: information from backend
+ * @pstore: structure for pstore
+ */
+struct psz_context {
+	struct pstore_zone **kpszs;
+	struct pstore_zone *ppsz;
+	struct pstore_zone *cpsz;
+	struct pstore_zone **fpszs;
+	unsigned int kmsg_max_cnt;
+	unsigned int kmsg_read_cnt;
+	unsigned int kmsg_write_cnt;
+	unsigned int pmsg_read_cnt;
+	unsigned int console_read_cnt;
+	unsigned int ftrace_max_cnt;
+	unsigned int ftrace_read_cnt;
+	/*
+	 * These counters should be calculated during recovery.
+	 * It records the oops/panic times after crashes rather than boots.
+	 */
+	unsigned int oops_counter;
+	unsigned int panic_counter;
+	atomic_t recovered;
+	atomic_t on_panic;
+
+	/*
+	 * pstore_zone_info_lock protects this entire structure during calls
+	 * to register_pstore_zone()/unregister_pstore_zone().
+	 */
+	struct mutex pstore_zone_info_lock;
+	struct pstore_zone_info *pstore_zone_info;
+	struct pstore_info pstore;
+};
+static struct psz_context pstore_zone_cxt;
+
+static void psz_flush_all_dirty_zones(struct work_struct *);
+static DECLARE_DELAYED_WORK(psz_cleaner, psz_flush_all_dirty_zones);
+
+/**
+ * enum psz_flush_mode - flush mode for psz_zone_write()
+ *
+ * @FLUSH_NONE: do not flush to storage but update data on memory
+ * @FLUSH_PART: just flush part of data including meta data to storage
+ * @FLUSH_META: just flush meta data of zone to storage
+ * @FLUSH_ALL: flush all of zone
+ */
+enum psz_flush_mode {
+	FLUSH_NONE = 0,
+	FLUSH_PART,
+	FLUSH_META,
+	FLUSH_ALL,
+};
+
+static inline int buffer_datalen(struct pstore_zone *zone)
+{
+	return atomic_read(&zone->buffer->datalen);
+}
+
+static inline int buffer_start(struct pstore_zone *zone)
+{
+	return atomic_read(&zone->buffer->start);
+}
+
+static inline bool is_on_panic(void)
+{
+	return atomic_read(&pstore_zone_cxt.on_panic);
+}
+
+static ssize_t psz_zone_read_buffer(struct pstore_zone *zone, char *buf,
+		size_t len, unsigned long off)
+{
+	if (!buf || !zone || !zone->buffer)
+		return -EINVAL;
+	if (off > zone->buffer_size)
+		return -EINVAL;
+	len = min_t(size_t, len, zone->buffer_size - off);
+	memcpy(buf, zone->buffer->data + off, len);
+	return len;
+}
+
+static int psz_zone_read_oldbuf(struct pstore_zone *zone, char *buf,
+		size_t len, unsigned long off)
+{
+	if (!buf || !zone || !zone->oldbuf)
+		return -EINVAL;
+	if (off > zone->buffer_size)
+		return -EINVAL;
+	len = min_t(size_t, len, zone->buffer_size - off);
+	memcpy(buf, zone->oldbuf->data + off, len);
+	return 0;
+}
+
+static int psz_zone_write(struct pstore_zone *zone,
+		enum psz_flush_mode flush_mode, const char *buf,
+		size_t len, unsigned long off)
+{
+	struct pstore_zone_info *info = pstore_zone_cxt.pstore_zone_info;
+	ssize_t wcnt = 0;
+	ssize_t (*writeop)(const char *buf, size_t bytes, loff_t pos);
+	size_t wlen;
+
+	if (off > zone->buffer_size)
+		return -EINVAL;
+
+	wlen = min_t(size_t, len, zone->buffer_size - off);
+	if (buf && wlen) {
+		memcpy(zone->buffer->data + off, buf, wlen);
+		atomic_set(&zone->buffer->datalen, wlen + off);
+	}
+
+	/* avoid to damage old records */
+	if (!is_on_panic() && !atomic_read(&pstore_zone_cxt.recovered))
+		goto dirty;
+
+	writeop = is_on_panic() ? info->panic_write : info->write;
+	if (!writeop)
+		goto dirty;
+
+	switch (flush_mode) {
+	case FLUSH_NONE:
+		if (unlikely(buf && wlen))
+			goto dirty;
+		return 0;
+	case FLUSH_PART:
+		wcnt = writeop((const char *)zone->buffer->data + off, wlen,
+				zone->off + sizeof(*zone->buffer) + off);
+		if (wcnt != wlen)
+			goto dirty;
+		fallthrough;
+	case FLUSH_META:
+		wlen = sizeof(struct psz_buffer);
+		wcnt = writeop((const char *)zone->buffer, wlen, zone->off);
+		if (wcnt != wlen)
+			goto dirty;
+		break;
+	case FLUSH_ALL:
+		wlen = zone->buffer_size + sizeof(*zone->buffer);
+		wcnt = writeop((const char *)zone->buffer, wlen, zone->off);
+		if (wcnt != wlen)
+			goto dirty;
+		break;
+	}
+
+	return 0;
+dirty:
+	/* no need to mark dirty if going to try next zone */
+	if (wcnt == -ENOMSG)
+		return -ENOMSG;
+	atomic_set(&zone->dirty, true);
+	/* flush dirty zones nicely */
+	if (wcnt == -EBUSY && !is_on_panic())
+		schedule_delayed_work(&psz_cleaner, msecs_to_jiffies(500));
+	return -EBUSY;
+}
+
+static int psz_flush_dirty_zone(struct pstore_zone *zone)
+{
+	int ret;
+
+	if (unlikely(!zone))
+		return -EINVAL;
+
+	if (unlikely(!atomic_read(&pstore_zone_cxt.recovered)))
+		return -EBUSY;
+
+	if (!atomic_xchg(&zone->dirty, false))
+		return 0;
+
+	ret = psz_zone_write(zone, FLUSH_ALL, NULL, 0, 0);
+	if (ret)
+		atomic_set(&zone->dirty, true);
+	return ret;
+}
+
+static int psz_flush_dirty_zones(struct pstore_zone **zones, unsigned int cnt)
+{
+	int i, ret;
+	struct pstore_zone *zone;
+
+	if (!zones)
+		return -EINVAL;
+
+	for (i = 0; i < cnt; i++) {
+		zone = zones[i];
+		if (!zone)
+			return -EINVAL;
+		ret = psz_flush_dirty_zone(zone);
+		if (ret)
+			return ret;
+	}
+	return 0;
+}
+
+static int psz_move_zone(struct pstore_zone *old, struct pstore_zone *new)
+{
+	const char *data = (const char *)old->buffer->data;
+	int ret;
+
+	ret = psz_zone_write(new, FLUSH_ALL, data, buffer_datalen(old), 0);
+	if (ret) {
+		atomic_set(&new->buffer->datalen, 0);
+		atomic_set(&new->dirty, false);
+		return ret;
+	}
+	atomic_set(&old->buffer->datalen, 0);
+	return 0;
+}
+
+static void psz_flush_all_dirty_zones(struct work_struct *work)
+{
+	struct psz_context *cxt = &pstore_zone_cxt;
+	int ret = 0;
+
+	if (cxt->ppsz)
+		ret |= psz_flush_dirty_zone(cxt->ppsz);
+	if (cxt->cpsz)
+		ret |= psz_flush_dirty_zone(cxt->cpsz);
+	if (cxt->kpszs)
+		ret |= psz_flush_dirty_zones(cxt->kpszs, cxt->kmsg_max_cnt);
+	if (cxt->fpszs)
+		ret |= psz_flush_dirty_zones(cxt->fpszs, cxt->ftrace_max_cnt);
+	if (ret && cxt->pstore_zone_info)
+		schedule_delayed_work(&psz_cleaner, msecs_to_jiffies(1000));
+}
+
+static int psz_kmsg_recover_data(struct psz_context *cxt)
+{
+	struct pstore_zone_info *info = cxt->pstore_zone_info;
+	struct pstore_zone *zone = NULL;
+	struct psz_buffer *buf;
+	unsigned long i;
+	ssize_t rcnt;
+
+	if (!info->read)
+		return -EINVAL;
+
+	for (i = 0; i < cxt->kmsg_max_cnt; i++) {
+		zone = cxt->kpszs[i];
+		if (unlikely(!zone))
+			return -EINVAL;
+		if (atomic_read(&zone->dirty)) {
+			unsigned int wcnt = cxt->kmsg_write_cnt;
+			struct pstore_zone *new = cxt->kpszs[wcnt];
+			int ret;
+
+			ret = psz_move_zone(zone, new);
+			if (ret) {
+				pr_err("move zone from %lu to %d failed\n",
+						i, wcnt);
+				return ret;
+			}
+			cxt->kmsg_write_cnt = (wcnt + 1) % cxt->kmsg_max_cnt;
+		}
+		if (!zone->should_recover)
+			continue;
+		buf = zone->buffer;
+		rcnt = info->read((char *)buf, zone->buffer_size + sizeof(*buf),
+				zone->off);
+		if (rcnt != zone->buffer_size + sizeof(*buf))
+			return (int)rcnt < 0 ? (int)rcnt : -EIO;
+	}
+	return 0;
+}
+
+static int psz_kmsg_recover_meta(struct psz_context *cxt)
+{
+	struct pstore_zone_info *info = cxt->pstore_zone_info;
+	struct pstore_zone *zone;
+	size_t rcnt, len;
+	struct psz_buffer *buf;
+	struct psz_kmsg_header *hdr;
+	struct timespec64 time = { };
+	unsigned long i;
+	/*
+	 * Recover may on panic, we can't allocate any memory by kmalloc.
+	 * So, we use local array instead.
+	 */
+	char buffer_header[sizeof(*buf) + sizeof(*hdr)] = {0};
+
+	if (!info->read)
+		return -EINVAL;
+
+	len = sizeof(*buf) + sizeof(*hdr);
+	buf = (struct psz_buffer *)buffer_header;
+	for (i = 0; i < cxt->kmsg_max_cnt; i++) {
+		zone = cxt->kpszs[i];
+		if (unlikely(!zone))
+			return -EINVAL;
+
+		rcnt = info->read((char *)buf, len, zone->off);
+		if (rcnt == -ENOMSG) {
+			pr_debug("%s with id %lu may be broken, skip\n",
+					zone->name, i);
+			continue;
+		} else if (rcnt != len) {
+			pr_err("read %s with id %lu failed\n", zone->name, i);
+			return (int)rcnt < 0 ? (int)rcnt : -EIO;
+		}
+
+		if (buf->sig != zone->buffer->sig) {
+			pr_debug("no valid data in kmsg dump zone %lu\n", i);
+			continue;
+		}
+
+		if (zone->buffer_size < atomic_read(&buf->datalen)) {
+			pr_info("found overtop zone: %s: id %lu, off %lld, size %zu\n",
+					zone->name, i, zone->off,
+					zone->buffer_size);
+			continue;
+		}
+
+		hdr = (struct psz_kmsg_header *)buf->data;
+		if (hdr->magic != PSTORE_KMSG_HEADER_MAGIC) {
+			pr_info("found invalid zone: %s: id %lu, off %lld, size %zu\n",
+					zone->name, i, zone->off,
+					zone->buffer_size);
+			continue;
+		}
+
+		/*
+		 * we get the newest zone, and the next one must be the oldest
+		 * or unused zone, because we do write one by one like a circle.
+		 */
+		if (hdr->time.tv_sec >= time.tv_sec) {
+			time.tv_sec = hdr->time.tv_sec;
+			cxt->kmsg_write_cnt = (i + 1) % cxt->kmsg_max_cnt;
+		}
+
+		if (hdr->reason == KMSG_DUMP_OOPS)
+			cxt->oops_counter =
+				max(cxt->oops_counter, hdr->counter);
+		else if (hdr->reason == KMSG_DUMP_PANIC)
+			cxt->panic_counter =
+				max(cxt->panic_counter, hdr->counter);
+
+		if (!atomic_read(&buf->datalen)) {
+			pr_debug("found erased zone: %s: id %lu, off %lld, size %zu, datalen %d\n",
+					zone->name, i, zone->off,
+					zone->buffer_size,
+					atomic_read(&buf->datalen));
+			continue;
+		}
+
+		if (!is_on_panic())
+			zone->should_recover = true;
+		pr_debug("found nice zone: %s: id %lu, off %lld, size %zu, datalen %d\n",
+				zone->name, i, zone->off,
+				zone->buffer_size, atomic_read(&buf->datalen));
+	}
+
+	return 0;
+}
+
+static int psz_kmsg_recover(struct psz_context *cxt)
+{
+	int ret;
+
+	if (!cxt->kpszs)
+		return 0;
+
+	ret = psz_kmsg_recover_meta(cxt);
+	if (ret)
+		goto recover_fail;
+
+	ret = psz_kmsg_recover_data(cxt);
+	if (ret)
+		goto recover_fail;
+
+	return 0;
+recover_fail:
+	pr_debug("psz_recover_kmsg failed\n");
+	return ret;
+}
+
+static int psz_recover_zone(struct psz_context *cxt, struct pstore_zone *zone)
+{
+	struct pstore_zone_info *info = cxt->pstore_zone_info;
+	struct psz_buffer *oldbuf, tmpbuf;
+	int ret = 0;
+	char *buf;
+	ssize_t rcnt, len, start, off;
+
+	if (!zone || zone->oldbuf)
+		return 0;
+
+	if (is_on_panic()) {
+		/* save data as much as possible */
+		psz_flush_dirty_zone(zone);
+		return 0;
+	}
+
+	if (unlikely(!info->read))
+		return -EINVAL;
+
+	len = sizeof(struct psz_buffer);
+	rcnt = info->read((char *)&tmpbuf, len, zone->off);
+	if (rcnt != len) {
+		pr_debug("read zone %s failed\n", zone->name);
+		return (int)rcnt < 0 ? (int)rcnt : -EIO;
+	}
+
+	if (tmpbuf.sig != zone->buffer->sig) {
+		pr_debug("no valid data in zone %s\n", zone->name);
+		return 0;
+	}
+
+	if (zone->buffer_size < atomic_read(&tmpbuf.datalen) ||
+		zone->buffer_size < atomic_read(&tmpbuf.start)) {
+		pr_info("found overtop zone: %s: off %lld, size %zu\n",
+				zone->name, zone->off, zone->buffer_size);
+		/* just keep going */
+		return 0;
+	}
+
+	if (!atomic_read(&tmpbuf.datalen)) {
+		pr_debug("found erased zone: %s: off %lld, size %zu, datalen %d\n",
+				zone->name, zone->off, zone->buffer_size,
+				atomic_read(&tmpbuf.datalen));
+		return 0;
+	}
+
+	pr_debug("found nice zone: %s: off %lld, size %zu, datalen %d\n",
+			zone->name, zone->off, zone->buffer_size,
+			atomic_read(&tmpbuf.datalen));
+
+	len = atomic_read(&tmpbuf.datalen) + sizeof(*oldbuf);
+	oldbuf = kzalloc(len, GFP_KERNEL);
+	if (!oldbuf)
+		return -ENOMEM;
+
+	memcpy(oldbuf, &tmpbuf, sizeof(*oldbuf));
+	buf = (char *)oldbuf + sizeof(*oldbuf);
+	len = atomic_read(&oldbuf->datalen);
+	start = atomic_read(&oldbuf->start);
+	off = zone->off + sizeof(*oldbuf);
+
+	/* get part of data */
+	rcnt = info->read(buf, len - start, off + start);
+	if (rcnt != len - start) {
+		pr_err("read zone %s failed\n", zone->name);
+		ret = (int)rcnt < 0 ? (int)rcnt : -EIO;
+		goto free_oldbuf;
+	}
+
+	/* get the rest of data */
+	rcnt = info->read(buf + len - start, start, off);
+	if (rcnt != start) {
+		pr_err("read zone %s failed\n", zone->name);
+		ret = (int)rcnt < 0 ? (int)rcnt : -EIO;
+		goto free_oldbuf;
+	}
+
+	zone->oldbuf = oldbuf;
+	psz_flush_dirty_zone(zone);
+	return 0;
+
+free_oldbuf:
+	kfree(oldbuf);
+	return ret;
+}
+
+static int psz_recover_zones(struct psz_context *cxt,
+		struct pstore_zone **zones, unsigned int cnt)
+{
+	int ret;
+	unsigned int i;
+	struct pstore_zone *zone;
+
+	if (!zones)
+		return 0;
+
+	for (i = 0; i < cnt; i++) {
+		zone = zones[i];
+		if (unlikely(!zone))
+			continue;
+		ret = psz_recover_zone(cxt, zone);
+		if (ret)
+			goto recover_fail;
+	}
+
+	return 0;
+recover_fail:
+	pr_debug("recover %s[%u] failed\n", zone->name, i);
+	return ret;
+}
+
+/**
+ * psz_recovery() - recover data from storage
+ * @cxt: the context of pstore/zone
+ *
+ * recovery means reading data back from storage after rebooting
+ *
+ * Return: 0 on success, others on failure.
+ */
+static inline int psz_recovery(struct psz_context *cxt)
+{
+	int ret;
+
+	if (atomic_read(&cxt->recovered))
+		return 0;
+
+	ret = psz_kmsg_recover(cxt);
+	if (ret)
+		goto out;
+
+	ret = psz_recover_zone(cxt, cxt->ppsz);
+	if (ret)
+		goto out;
+
+	ret = psz_recover_zone(cxt, cxt->cpsz);
+	if (ret)
+		goto out;
+
+	ret = psz_recover_zones(cxt, cxt->fpszs, cxt->ftrace_max_cnt);
+
+out:
+	if (unlikely(ret))
+		pr_err("recover failed\n");
+	else {
+		pr_debug("recover end!\n");
+		atomic_set(&cxt->recovered, 1);
+	}
+	return ret;
+}
+
+static int psz_pstore_open(struct pstore_info *psi)
+{
+	struct psz_context *cxt = psi->data;
+
+	cxt->kmsg_read_cnt = 0;
+	cxt->pmsg_read_cnt = 0;
+	cxt->console_read_cnt = 0;
+	cxt->ftrace_read_cnt = 0;
+	return 0;
+}
+
+static inline bool psz_old_ok(struct pstore_zone *zone)
+{
+	if (zone && zone->oldbuf && atomic_read(&zone->oldbuf->datalen))
+		return true;
+	return false;
+}
+
+static inline bool psz_ok(struct pstore_zone *zone)
+{
+	if (zone && zone->buffer && buffer_datalen(zone))
+		return true;
+	return false;
+}
+
+static inline int psz_kmsg_erase(struct psz_context *cxt,
+		struct pstore_zone *zone, struct pstore_record *record)
+{
+	struct psz_buffer *buffer = zone->buffer;
+	struct psz_kmsg_header *hdr =
+		(struct psz_kmsg_header *)buffer->data;
+	size_t size;
+
+	if (unlikely(!psz_ok(zone)))
+		return 0;
+
+	/* this zone is already updated, no need to erase */
+	if (record->count != hdr->counter)
+		return 0;
+
+	size = buffer_datalen(zone) + sizeof(*zone->buffer);
+	atomic_set(&zone->buffer->datalen, 0);
+	if (cxt->pstore_zone_info->erase)
+		return cxt->pstore_zone_info->erase(size, zone->off);
+	else
+		return psz_zone_write(zone, FLUSH_META, NULL, 0, 0);
+}
+
+static inline int psz_record_erase(struct psz_context *cxt,
+		struct pstore_zone *zone)
+{
+	if (unlikely(!psz_old_ok(zone)))
+		return 0;
+
+	kfree(zone->oldbuf);
+	zone->oldbuf = NULL;
+	/*
+	 * if there are new data in zone buffer, that means the old data
+	 * are already invalid. It is no need to flush 0 (erase) to
+	 * block device.
+	 */
+	if (!buffer_datalen(zone))
+		return psz_zone_write(zone, FLUSH_META, NULL, 0, 0);
+	psz_flush_dirty_zone(zone);
+	return 0;
+}
+
+static int psz_pstore_erase(struct pstore_record *record)
+{
+	struct psz_context *cxt = record->psi->data;
+
+	switch (record->type) {
+	case PSTORE_TYPE_DMESG:
+		if (record->id >= cxt->kmsg_max_cnt)
+			return -EINVAL;
+		return psz_kmsg_erase(cxt, cxt->kpszs[record->id], record);
+	case PSTORE_TYPE_PMSG:
+		return psz_record_erase(cxt, cxt->ppsz);
+	case PSTORE_TYPE_CONSOLE:
+		return psz_record_erase(cxt, cxt->cpsz);
+	case PSTORE_TYPE_FTRACE:
+		if (record->id >= cxt->ftrace_max_cnt)
+			return -EINVAL;
+		return psz_record_erase(cxt, cxt->fpszs[record->id]);
+	default: return -EINVAL;
+	}
+}
+
+static void psz_write_kmsg_hdr(struct pstore_zone *zone,
+		struct pstore_record *record)
+{
+	struct psz_context *cxt = record->psi->data;
+	struct psz_buffer *buffer = zone->buffer;
+	struct psz_kmsg_header *hdr =
+		(struct psz_kmsg_header *)buffer->data;
+
+	hdr->magic = PSTORE_KMSG_HEADER_MAGIC;
+	hdr->compressed = record->compressed;
+	hdr->time.tv_sec = record->time.tv_sec;
+	hdr->time.tv_nsec = record->time.tv_nsec;
+	hdr->reason = record->reason;
+	if (hdr->reason == KMSG_DUMP_OOPS)
+		hdr->counter = ++cxt->oops_counter;
+	else if (hdr->reason == KMSG_DUMP_PANIC)
+		hdr->counter = ++cxt->panic_counter;
+	else
+		hdr->counter = 0;
+}
+
+/*
+ * In case zone is broken, which may occur to MTD device, we try each zones,
+ * start at cxt->kmsg_write_cnt.
+ */
+static inline int notrace psz_kmsg_write_record(struct psz_context *cxt,
+		struct pstore_record *record)
+{
+	size_t size, hlen;
+	struct pstore_zone *zone;
+	unsigned int i;
+
+	for (i = 0; i < cxt->kmsg_max_cnt; i++) {
+		unsigned int zonenum, len;
+		int ret;
+
+		zonenum = (cxt->kmsg_write_cnt + i) % cxt->kmsg_max_cnt;
+		zone = cxt->kpszs[zonenum];
+		if (unlikely(!zone))
+			return -ENOSPC;
+
+		/* avoid destroying old data, allocate a new one */
+		len = zone->buffer_size + sizeof(*zone->buffer);
+		zone->oldbuf = zone->buffer;
+		zone->buffer = kzalloc(len, GFP_KERNEL);
+		if (!zone->buffer) {
+			zone->buffer = zone->oldbuf;
+			return -ENOMEM;
+		}
+		zone->buffer->sig = zone->oldbuf->sig;
+
+		pr_debug("write %s to zone id %d\n", zone->name, zonenum);
+		psz_write_kmsg_hdr(zone, record);
+		hlen = sizeof(struct psz_kmsg_header);
+		size = min_t(size_t, record->size, zone->buffer_size - hlen);
+		ret = psz_zone_write(zone, FLUSH_ALL, record->buf, size, hlen);
+		if (likely(!ret || ret != -ENOMSG)) {
+			cxt->kmsg_write_cnt = zonenum + 1;
+			cxt->kmsg_write_cnt %= cxt->kmsg_max_cnt;
+			/* no need to try next zone, free last zone buffer */
+			kfree(zone->oldbuf);
+			zone->oldbuf = NULL;
+			return ret;
+		}
+
+		pr_debug("zone %u may be broken, try next dmesg zone\n",
+				zonenum);
+		kfree(zone->buffer);
+		zone->buffer = zone->oldbuf;
+		zone->oldbuf = NULL;
+	}
+
+	return -EBUSY;
+}
+
+static int notrace psz_kmsg_write(struct psz_context *cxt,
+		struct pstore_record *record)
+{
+	int ret;
+
+	/*
+	 * Explicitly only take the first part of any new crash.
+	 * If our buffer is larger than kmsg_bytes, this can never happen,
+	 * and if our buffer is smaller than kmsg_bytes, we don't want the
+	 * report split across multiple records.
+	 */
+	if (record->part != 1)
+		return -ENOSPC;
+
+	if (!cxt->kpszs)
+		return -ENOSPC;
+
+	ret = psz_kmsg_write_record(cxt, record);
+	if (!ret && is_on_panic()) {
+		/* ensure all data are flushed to storage when panic */
+		pr_debug("try to flush other dirty zones\n");
+		psz_flush_all_dirty_zones(NULL);
+	}
+
+	/* always return 0 as we had handled it on buffer */
+	return 0;
+}
+
+static int notrace psz_record_write(struct pstore_zone *zone,
+		struct pstore_record *record)
+{
+	size_t start, rem;
+	bool is_full_data = false;
+	char *buf;
+	int cnt;
+
+	if (!zone || !record)
+		return -ENOSPC;
+
+	if (atomic_read(&zone->buffer->datalen) >= zone->buffer_size)
+		is_full_data = true;
+
+	cnt = record->size;
+	buf = record->buf;
+	if (unlikely(cnt > zone->buffer_size)) {
+		buf += cnt - zone->buffer_size;
+		cnt = zone->buffer_size;
+	}
+
+	start = buffer_start(zone);
+	rem = zone->buffer_size - start;
+	if (unlikely(rem < cnt)) {
+		psz_zone_write(zone, FLUSH_PART, buf, rem, start);
+		buf += rem;
+		cnt -= rem;
+		start = 0;
+		is_full_data = true;
+	}
+
+	atomic_set(&zone->buffer->start, cnt + start);
+	psz_zone_write(zone, FLUSH_PART, buf, cnt, start);
+
+	/**
+	 * psz_zone_write will set datalen as start + cnt.
+	 * It work if actual data length lesser than buffer size.
+	 * If data length greater than buffer size, pmsg will rewrite to
+	 * beginning of zone, which make buffer->datalen wrongly.
+	 * So we should reset datalen as buffer size once actual data length
+	 * greater than buffer size.
+	 */
+	if (is_full_data) {
+		atomic_set(&zone->buffer->datalen, zone->buffer_size);
+		psz_zone_write(zone, FLUSH_META, NULL, 0, 0);
+	}
+	return 0;
+}
+
+static int notrace psz_pstore_write(struct pstore_record *record)
+{
+	struct psz_context *cxt = record->psi->data;
+
+	if (record->type == PSTORE_TYPE_DMESG &&
+			record->reason == KMSG_DUMP_PANIC)
+		atomic_set(&cxt->on_panic, 1);
+
+	/*
+	 * if on panic, do not write except panic records
+	 * Fix case that panic_write prints log which wakes up console backend.
+	 */
+	if (is_on_panic() && record->type != PSTORE_TYPE_DMESG)
+		return -EBUSY;
+
+	switch (record->type) {
+	case PSTORE_TYPE_DMESG:
+		return psz_kmsg_write(cxt, record);
+	case PSTORE_TYPE_CONSOLE:
+		return psz_record_write(cxt->cpsz, record);
+	case PSTORE_TYPE_PMSG:
+		return psz_record_write(cxt->ppsz, record);
+	case PSTORE_TYPE_FTRACE: {
+		int zonenum = smp_processor_id();
+
+		if (!cxt->fpszs)
+			return -ENOSPC;
+		return psz_record_write(cxt->fpszs[zonenum], record);
+	}
+	default:
+		return -EINVAL;
+	}
+}
+
+static struct pstore_zone *psz_read_next_zone(struct psz_context *cxt)
+{
+	struct pstore_zone *zone = NULL;
+
+	while (cxt->kmsg_read_cnt < cxt->kmsg_max_cnt) {
+		zone = cxt->kpszs[cxt->kmsg_read_cnt++];
+		if (psz_ok(zone))
+			return zone;
+	}
+
+	if (cxt->ftrace_read_cnt < cxt->ftrace_max_cnt)
+		/*
+		 * No need psz_old_ok(). Let psz_ftrace_read() do so for
+		 * combination. psz_ftrace_read() should traverse over
+		 * all zones in case of some zone without data.
+		 */
+		return cxt->fpszs[cxt->ftrace_read_cnt++];
+
+	if (cxt->pmsg_read_cnt == 0) {
+		cxt->pmsg_read_cnt++;
+		zone = cxt->ppsz;
+		if (psz_old_ok(zone))
+			return zone;
+	}
+
+	if (cxt->console_read_cnt == 0) {
+		cxt->console_read_cnt++;
+		zone = cxt->cpsz;
+		if (psz_old_ok(zone))
+			return zone;
+	}
+
+	return NULL;
+}
+
+static int psz_kmsg_read_hdr(struct pstore_zone *zone,
+		struct pstore_record *record)
+{
+	struct psz_buffer *buffer = zone->buffer;
+	struct psz_kmsg_header *hdr =
+		(struct psz_kmsg_header *)buffer->data;
+
+	if (hdr->magic != PSTORE_KMSG_HEADER_MAGIC)
+		return -EINVAL;
+	record->compressed = hdr->compressed;
+	record->time.tv_sec = hdr->time.tv_sec;
+	record->time.tv_nsec = hdr->time.tv_nsec;
+	record->reason = hdr->reason;
+	record->count = hdr->counter;
+	return 0;
+}
+
+static ssize_t psz_kmsg_read(struct pstore_zone *zone,
+		struct pstore_record *record)
+{
+	ssize_t size, hlen = 0;
+
+	size = buffer_datalen(zone);
+	/* Clear and skip this kmsg dump record if it has no valid header */
+	if (psz_kmsg_read_hdr(zone, record)) {
+		atomic_set(&zone->buffer->datalen, 0);
+		atomic_set(&zone->dirty, 0);
+		return -ENOMSG;
+	}
+	size -= sizeof(struct psz_kmsg_header);
+
+	if (!record->compressed) {
+		char *buf = kasprintf(GFP_KERNEL, "%s: Total %d times\n",
+				      kmsg_dump_reason_str(record->reason),
+				      record->count);
+		hlen = strlen(buf);
+		record->buf = krealloc(buf, hlen + size, GFP_KERNEL);
+		if (!record->buf) {
+			kfree(buf);
+			return -ENOMEM;
+		}
+	} else {
+		record->buf = kmalloc(size, GFP_KERNEL);
+		if (!record->buf)
+			return -ENOMEM;
+	}
+
+	size = psz_zone_read_buffer(zone, record->buf + hlen, size,
+			sizeof(struct psz_kmsg_header));
+	if (unlikely(size < 0)) {
+		kfree(record->buf);
+		return -ENOMSG;
+	}
+
+	return size + hlen;
+}
+
+/* try to combine all ftrace zones */
+static ssize_t psz_ftrace_read(struct pstore_zone *zone,
+		struct pstore_record *record)
+{
+	struct psz_context *cxt;
+	struct psz_buffer *buf;
+	int ret;
+
+	if (!zone || !record)
+		return -ENOSPC;
+
+	if (!psz_old_ok(zone))
+		goto out;
+
+	buf = (struct psz_buffer *)zone->oldbuf;
+	if (!buf)
+		return -ENOMSG;
+
+	ret = pstore_ftrace_combine_log(&record->buf, &record->size,
+			(char *)buf->data, atomic_read(&buf->datalen));
+	if (unlikely(ret))
+		return ret;
+
+out:
+	cxt = record->psi->data;
+	if (cxt->ftrace_read_cnt < cxt->ftrace_max_cnt)
+		/* then, read next ftrace zone */
+		return -ENOMSG;
+	record->id = 0;
+	return record->size ? record->size : -ENOMSG;
+}
+
+static ssize_t psz_record_read(struct pstore_zone *zone,
+		struct pstore_record *record)
+{
+	size_t len;
+	struct psz_buffer *buf;
+
+	if (!zone || !record)
+		return -ENOSPC;
+
+	buf = (struct psz_buffer *)zone->oldbuf;
+	if (!buf)
+		return -ENOMSG;
+
+	len = atomic_read(&buf->datalen);
+	record->buf = kmalloc(len, GFP_KERNEL);
+	if (!record->buf)
+		return -ENOMEM;
+
+	if (unlikely(psz_zone_read_oldbuf(zone, record->buf, len, 0))) {
+		kfree(record->buf);
+		return -ENOMSG;
+	}
+
+	return len;
+}
+
+static ssize_t psz_pstore_read(struct pstore_record *record)
+{
+	struct psz_context *cxt = record->psi->data;
+	ssize_t (*readop)(struct pstore_zone *zone,
+			struct pstore_record *record);
+	struct pstore_zone *zone;
+	ssize_t ret;
+
+	/* before read, we must recover from storage */
+	ret = psz_recovery(cxt);
+	if (ret)
+		return ret;
+
+next_zone:
+	zone = psz_read_next_zone(cxt);
+	if (!zone)
+		return 0;
+
+	record->type = zone->type;
+	switch (record->type) {
+	case PSTORE_TYPE_DMESG:
+		readop = psz_kmsg_read;
+		record->id = cxt->kmsg_read_cnt - 1;
+		break;
+	case PSTORE_TYPE_FTRACE:
+		readop = psz_ftrace_read;
+		break;
+	case PSTORE_TYPE_CONSOLE:
+		fallthrough;
+	case PSTORE_TYPE_PMSG:
+		readop = psz_record_read;
+		break;
+	default:
+		goto next_zone;
+	}
+
+	ret = readop(zone, record);
+	if (ret == -ENOMSG)
+		goto next_zone;
+	return ret;
+}
+
+static struct psz_context pstore_zone_cxt = {
+	.pstore_zone_info_lock =
+		__MUTEX_INITIALIZER(pstore_zone_cxt.pstore_zone_info_lock),
+	.recovered = ATOMIC_INIT(0),
+	.on_panic = ATOMIC_INIT(0),
+	.pstore = {
+		.owner = THIS_MODULE,
+		.open = psz_pstore_open,
+		.read = psz_pstore_read,
+		.write = psz_pstore_write,
+		.erase = psz_pstore_erase,
+	},
+};
+
+static void psz_free_zone(struct pstore_zone **pszone)
+{
+	struct pstore_zone *zone = *pszone;
+
+	if (!zone)
+		return;
+
+	kfree(zone->buffer);
+	kfree(zone);
+	*pszone = NULL;
+}
+
+static void psz_free_zones(struct pstore_zone ***pszones, unsigned int *cnt)
+{
+	struct pstore_zone **zones = *pszones;
+
+	if (!zones)
+		return;
+
+	while (*cnt > 0) {
+		(*cnt)--;
+		psz_free_zone(&(zones[*cnt]));
+	}
+	kfree(zones);
+	*pszones = NULL;
+}
+
+static void psz_free_all_zones(struct psz_context *cxt)
+{
+	if (cxt->kpszs)
+		psz_free_zones(&cxt->kpszs, &cxt->kmsg_max_cnt);
+	if (cxt->ppsz)
+		psz_free_zone(&cxt->ppsz);
+	if (cxt->cpsz)
+		psz_free_zone(&cxt->cpsz);
+	if (cxt->fpszs)
+		psz_free_zones(&cxt->fpszs, &cxt->ftrace_max_cnt);
+}
+
+static struct pstore_zone *psz_init_zone(enum pstore_type_id type,
+		loff_t *off, size_t size)
+{
+	struct pstore_zone_info *info = pstore_zone_cxt.pstore_zone_info;
+	struct pstore_zone *zone;
+	const char *name = pstore_type_to_name(type);
+
+	if (!size)
+		return NULL;
+
+	if (*off + size > info->total_size) {
+		pr_err("no room for %s (0x%zx@0x%llx over 0x%lx)\n",
+			name, size, *off, info->total_size);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	zone = kzalloc(sizeof(struct pstore_zone), GFP_KERNEL);
+	if (!zone)
+		return ERR_PTR(-ENOMEM);
+
+	zone->buffer = kmalloc(size, GFP_KERNEL);
+	if (!zone->buffer) {
+		kfree(zone);
+		return ERR_PTR(-ENOMEM);
+	}
+	memset(zone->buffer, 0xFF, size);
+	zone->off = *off;
+	zone->name = name;
+	zone->type = type;
+	zone->buffer_size = size - sizeof(struct psz_buffer);
+	zone->buffer->sig = type ^ PSZ_SIG;
+	zone->oldbuf = NULL;
+	atomic_set(&zone->dirty, 0);
+	atomic_set(&zone->buffer->datalen, 0);
+	atomic_set(&zone->buffer->start, 0);
+
+	*off += size;
+
+	pr_debug("pszone %s: off 0x%llx, %zu header, %zu data\n", zone->name,
+			zone->off, sizeof(*zone->buffer), zone->buffer_size);
+	return zone;
+}
+
+static struct pstore_zone **psz_init_zones(enum pstore_type_id type,
+	loff_t *off, size_t total_size, ssize_t record_size,
+	unsigned int *cnt)
+{
+	struct pstore_zone_info *info = pstore_zone_cxt.pstore_zone_info;
+	struct pstore_zone **zones, *zone;
+	const char *name = pstore_type_to_name(type);
+	int c, i;
+
+	*cnt = 0;
+	if (!total_size || !record_size)
+		return NULL;
+
+	if (*off + total_size > info->total_size) {
+		pr_err("no room for zones %s (0x%zx@0x%llx over 0x%lx)\n",
+			name, total_size, *off, info->total_size);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	c = total_size / record_size;
+	zones = kcalloc(c, sizeof(*zones), GFP_KERNEL);
+	if (!zones) {
+		pr_err("allocate for zones %s failed\n", name);
+		return ERR_PTR(-ENOMEM);
+	}
+	memset(zones, 0, c * sizeof(*zones));
+
+	for (i = 0; i < c; i++) {
+		zone = psz_init_zone(type, off, record_size);
+		if (!zone || IS_ERR(zone)) {
+			pr_err("initialize zones %s failed\n", name);
+			psz_free_zones(&zones, &i);
+			return (void *)zone;
+		}
+		zones[i] = zone;
+	}
+
+	*cnt = c;
+	return zones;
+}
+
+static int psz_alloc_zones(struct psz_context *cxt)
+{
+	struct pstore_zone_info *info = cxt->pstore_zone_info;
+	loff_t off = 0;
+	int err;
+	size_t off_size = 0;
+
+	off_size += info->pmsg_size;
+	cxt->ppsz = psz_init_zone(PSTORE_TYPE_PMSG, &off, info->pmsg_size);
+	if (IS_ERR(cxt->ppsz)) {
+		err = PTR_ERR(cxt->ppsz);
+		cxt->ppsz = NULL;
+		goto free_out;
+	}
+
+	off_size += info->console_size;
+	cxt->cpsz = psz_init_zone(PSTORE_TYPE_CONSOLE, &off,
+			info->console_size);
+	if (IS_ERR(cxt->cpsz)) {
+		err = PTR_ERR(cxt->cpsz);
+		cxt->cpsz = NULL;
+		goto free_out;
+	}
+
+	off_size += info->ftrace_size;
+	cxt->fpszs = psz_init_zones(PSTORE_TYPE_FTRACE, &off,
+			info->ftrace_size,
+			info->ftrace_size / nr_cpu_ids,
+			&cxt->ftrace_max_cnt);
+	if (IS_ERR(cxt->fpszs)) {
+		err = PTR_ERR(cxt->fpszs);
+		cxt->fpszs = NULL;
+		goto free_out;
+	}
+
+	cxt->kpszs = psz_init_zones(PSTORE_TYPE_DMESG, &off,
+			info->total_size - off_size,
+			info->kmsg_size, &cxt->kmsg_max_cnt);
+	if (IS_ERR(cxt->kpszs)) {
+		err = PTR_ERR(cxt->kpszs);
+		cxt->kpszs = NULL;
+		goto free_out;
+	}
+
+	return 0;
+free_out:
+	psz_free_all_zones(cxt);
+	return err;
+}
+
+/**
+ * register_pstore_zone() - register to pstore/zone
+ *
+ * @info: back-end driver information. See &struct pstore_zone_info.
+ *
+ * Only one back-end at one time.
+ *
+ * Return: 0 on success, others on failure.
+ */
+int register_pstore_zone(struct pstore_zone_info *info)
+{
+	int err = -EINVAL;
+	struct psz_context *cxt = &pstore_zone_cxt;
+
+	if (info->total_size < 4096) {
+		pr_warn("total_size must be >= 4096\n");
+		return -EINVAL;
+	}
+
+	if (!info->kmsg_size && !info->pmsg_size && !info->console_size &&
+	    !info->ftrace_size) {
+		pr_warn("at least one record size must be non-zero\n");
+		return -EINVAL;
+	}
+
+	if (!info->name || !info->name[0])
+		return -EINVAL;
+
+#define check_size(name, size) {					\
+		if (info->name > 0 && info->name < (size)) {		\
+			pr_err(#name " must be over %d\n", (size));	\
+			return -EINVAL;					\
+		}							\
+		if (info->name & (size - 1)) {				\
+			pr_err(#name " must be a multiple of %d\n",	\
+					(size));			\
+			return -EINVAL;					\
+		}							\
+	}
+
+	check_size(total_size, 4096);
+	check_size(kmsg_size, SECTOR_SIZE);
+	check_size(pmsg_size, SECTOR_SIZE);
+	check_size(console_size, SECTOR_SIZE);
+	check_size(ftrace_size, SECTOR_SIZE);
+
+#undef check_size
+
+	/*
+	 * the @read and @write must be applied.
+	 * if no @read, pstore may mount failed.
+	 * if no @write, pstore do not support to remove record file.
+	 */
+	if (!info->read || !info->write) {
+		pr_err("no valid general read/write interface\n");
+		return -EINVAL;
+	}
+
+	mutex_lock(&cxt->pstore_zone_info_lock);
+	if (cxt->pstore_zone_info) {
+		pr_warn("'%s' already loaded: ignoring '%s'\n",
+				cxt->pstore_zone_info->name, info->name);
+		mutex_unlock(&cxt->pstore_zone_info_lock);
+		return -EBUSY;
+	}
+	cxt->pstore_zone_info = info;
+
+	pr_debug("register %s with properties:\n", info->name);
+	pr_debug("\ttotal size : %ld Bytes\n", info->total_size);
+	pr_debug("\tkmsg size : %ld Bytes\n", info->kmsg_size);
+	pr_debug("\tpmsg size : %ld Bytes\n", info->pmsg_size);
+	pr_debug("\tconsole size : %ld Bytes\n", info->console_size);
+	pr_debug("\tftrace size : %ld Bytes\n", info->ftrace_size);
+
+	err = psz_alloc_zones(cxt);
+	if (err) {
+		pr_err("alloc zones failed\n");
+		goto fail_out;
+	}
+
+	if (info->kmsg_size) {
+		cxt->pstore.bufsize = cxt->kpszs[0]->buffer_size -
+			sizeof(struct psz_kmsg_header);
+		cxt->pstore.buf = kzalloc(cxt->pstore.bufsize, GFP_KERNEL);
+		if (!cxt->pstore.buf) {
+			err = -ENOMEM;
+			goto fail_free;
+		}
+	}
+	cxt->pstore.data = cxt;
+
+	pr_info("registered %s as backend for", info->name);
+	cxt->pstore.max_reason = info->max_reason;
+	cxt->pstore.name = info->name;
+	if (info->kmsg_size) {
+		cxt->pstore.flags |= PSTORE_FLAGS_DMESG;
+		pr_cont(" kmsg(%s",
+			kmsg_dump_reason_str(cxt->pstore.max_reason));
+		if (cxt->pstore_zone_info->panic_write)
+			pr_cont(",panic_write");
+		pr_cont(")");
+	}
+	if (info->pmsg_size) {
+		cxt->pstore.flags |= PSTORE_FLAGS_PMSG;
+		pr_cont(" pmsg");
+	}
+	if (info->console_size) {
+		cxt->pstore.flags |= PSTORE_FLAGS_CONSOLE;
+		pr_cont(" console");
+	}
+	if (info->ftrace_size) {
+		cxt->pstore.flags |= PSTORE_FLAGS_FTRACE;
+		pr_cont(" ftrace");
+	}
+	pr_cont("\n");
+
+	err = pstore_register(&cxt->pstore);
+	if (err) {
+		pr_err("registering with pstore failed\n");
+		goto fail_free;
+	}
+	mutex_unlock(&pstore_zone_cxt.pstore_zone_info_lock);
+
+	return 0;
+
+fail_free:
+	kfree(cxt->pstore.buf);
+	cxt->pstore.buf = NULL;
+	cxt->pstore.bufsize = 0;
+	psz_free_all_zones(cxt);
+fail_out:
+	pstore_zone_cxt.pstore_zone_info = NULL;
+	mutex_unlock(&pstore_zone_cxt.pstore_zone_info_lock);
+	return err;
+}
+EXPORT_SYMBOL_GPL(register_pstore_zone);
+
+/**
+ * unregister_pstore_zone() - unregister to pstore/zone
+ *
+ * @info: back-end driver information. See struct pstore_zone_info.
+ */
+void unregister_pstore_zone(struct pstore_zone_info *info)
+{
+	struct psz_context *cxt = &pstore_zone_cxt;
+
+	mutex_lock(&cxt->pstore_zone_info_lock);
+	if (!cxt->pstore_zone_info) {
+		mutex_unlock(&cxt->pstore_zone_info_lock);
+		return;
+	}
+
+	/* Stop incoming writes from pstore. */
+	pstore_unregister(&cxt->pstore);
+
+	/* Flush any pending writes. */
+	psz_flush_all_dirty_zones(NULL);
+	flush_delayed_work(&psz_cleaner);
+
+	/* Clean up allocations. */
+	kfree(cxt->pstore.buf);
+	cxt->pstore.buf = NULL;
+	cxt->pstore.bufsize = 0;
+	cxt->pstore_zone_info = NULL;
+
+	psz_free_all_zones(cxt);
+
+	/* Clear counters and zone state. */
+	cxt->oops_counter = 0;
+	cxt->panic_counter = 0;
+	atomic_set(&cxt->recovered, 0);
+	atomic_set(&cxt->on_panic, 0);
+
+	mutex_unlock(&cxt->pstore_zone_info_lock);
+}
+EXPORT_SYMBOL_GPL(unregister_pstore_zone);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("WeiXiong Liao <[e-mail]>");
+MODULE_AUTHOR("Kees Cook <[e-mail]>");
+MODULE_DESCRIPTION("Storage Manager for pstore/blk");

include/linux/kmsg_dump.h

···
 	KMSG_DUMP_PANIC,
 	KMSG_DUMP_OOPS,
 	KMSG_DUMP_EMERG,
-	KMSG_DUMP_RESTART,
-	KMSG_DUMP_HALT,
-	KMSG_DUMP_POWEROFF,
+	KMSG_DUMP_SHUTDOWN,
+	KMSG_DUMP_MAX
 };
 
 /**
···
 int kmsg_dump_register(struct kmsg_dumper *dumper);
 
 int kmsg_dump_unregister(struct kmsg_dumper *dumper);
+
+const char *kmsg_dump_reason_str(enum kmsg_dump_reason reason);
 #else
 static inline void kmsg_dump(enum kmsg_dump_reason reason)
 {
···
 static inline int kmsg_dump_unregister(struct kmsg_dumper *dumper)
 {
 	return -EINVAL;
+}
+
+static inline const char *kmsg_dump_reason_str(enum kmsg_dump_reason reason)
+{
+	return "Disabled";
 }
 #endif
 

include/linux/pstore.h

···
  *
  * @read_mutex:	serializes @open, @read, @close, and @erase callbacks
  * @flags:	bitfield of frontends the backend can accept writes for
+ * @max_reason:	Used when PSTORE_FLAGS_DMESG is set. Contains the
+ *		kmsg_dump_reason enum value. KMSG_DUMP_UNDEF means
+ *		"use existing kmsg_dump() filtering, based on the
+ *		printk.always_kmsg_dump boot param" (which is either
+ *		KMSG_DUMP_OOPS when false, or KMSG_DUMP_MAX when
+ *		true); see printk.always_kmsg_dump for more details.
  * @data:	backend-private pointer passed back during callbacks
  *
  * Callbacks:
···
  */
 struct pstore_info {
 	struct module	*owner;
-	char		*name;
+	const char	*name;
 
 	struct semaphore buf_lock;
 	char		*buf;
···
 	struct mutex	read_mutex;
 
 	int		flags;
+	int		max_reason;
 	void		*data;
 
 	int		(*open)(struct pstore_info *psi);

include/linux/pstore_blk.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __PSTORE_BLK_H_
+#define __PSTORE_BLK_H_
+
+#include <linux/types.h>
+#include <linux/pstore.h>
+#include <linux/pstore_zone.h>
+
+/**
+ * typedef pstore_blk_panic_write_op - panic write operation to block device
+ *
+ * @buf: the data to write
+ * @start_sect: start sector to block device
+ * @sects: sectors count on buf
+ *
+ * Return: On success, zero should be returned. Others excluding -ENOMSG
+ * mean error. -ENOMSG means to try next zone.
+ *
+ * Panic write to block device must be aligned to SECTOR_SIZE.
+ */
+typedef int (*pstore_blk_panic_write_op)(const char *buf, sector_t start_sect,
+		sector_t sects);
+
+/**
+ * struct pstore_blk_info - pstore/blk registration details
+ *
+ * @major:	Which major device number to support with pstore/blk
+ * @flags:	The supported PSTORE_FLAGS_* from linux/pstore.h.
+ * @panic_write:The write operation only used for the panic case.
+ *		This can be NULL, but is recommended to avoid losing
+ *		crash data if the kernel's IO path or work queues are
+ *		broken during a panic.
+ * @devt:	The dev_t that pstore/blk has attached to.
+ * @nr_sects:	Number of sectors on @devt.
+ * @start_sect:	Starting sector on @devt.
+ */
+struct pstore_blk_info {
+	unsigned int major;
+	unsigned int flags;
+	pstore_blk_panic_write_op panic_write;
+
+	/* Filled in by pstore/blk after registration. */
+	dev_t devt;
+	sector_t nr_sects;
+	sector_t start_sect;
+};
+
+int  register_pstore_blk(struct pstore_blk_info *info);
+void unregister_pstore_blk(unsigned int major);
+
+/**
+ * struct pstore_device_info - back-end pstore/blk driver structure.
+ *
+ * @total_size: The total size in bytes pstore/blk can use. It must be greater
+ *		than 4096 and be multiple of 4096.
+ * @flags:	Refer to macro starting with PSTORE_FLAGS defined in
+ *		linux/pstore.h. It means what front-ends this device support.
+ *		Zero means all backends for compatible.
+ * @read:	The general read operation. Both of the function parameters
+ *		@size and @offset are relative value to bock device (not the
+ *		whole disk).
+ *		On success, the number of bytes should be returned, others
+ *		means error.
+ * @write:	The same as @read, but the following error number:
+ *		-EBUSY means try to write again later.
+ *		-ENOMSG means to try next zone.
+ * @erase:	The general erase operation for device with special removing
+ *		job. Both of the function parameters @size and @offset are
+ *		relative value to storage.
+ *		Return 0 on success and others on failure.
+ * @panic_write:The write operation only used for panic case. It's optional
+ *		if you do not care panic log. The parameters are relative
+ *		value to storage.
+ *		On success, the number of bytes should be returned, others
+ *		excluding -ENOMSG mean error. -ENOMSG means to try next zone.
+ */
+struct pstore_device_info {
+	unsigned long total_size;
+	unsigned int flags;
+	pstore_zone_read_op read;
+	pstore_zone_write_op write;
+	pstore_zone_erase_op erase;
+	pstore_zone_write_op panic_write;
+};
+
+int  register_pstore_device(struct pstore_device_info *dev);
+void unregister_pstore_device(struct pstore_device_info *dev);
+
+/**
+ * struct pstore_blk_config - the pstore_blk backend configuration
+ *
+ * @device:		Name of the desired block device
+ * @max_reason:		Maximum kmsg dump reason to store to block device
+ * @kmsg_size:		Total size of for kmsg dumps
+ * @pmsg_size:		Total size of the pmsg storage area
+ * @console_size:	Total size of the console storage area
+ * @ftrace_size:	Total size for ftrace logging data (for all CPUs)
+ */
+struct pstore_blk_config {
+	char device[80];
+	enum kmsg_dump_reason max_reason;
+	unsigned long kmsg_size;
+	unsigned long pmsg_size;
+	unsigned long console_size;
+	unsigned long ftrace_size;
+};
+
+/**
+ * pstore_blk_get_config - get a copy of the pstore_blk backend configuration
+ *
+ * @info:	The sturct pstore_blk_config to be filled in
+ *
+ * Failure returns negative error code, and success returns 0.
+ */
+int pstore_blk_get_config(struct pstore_blk_config *info);
+
+#endif

include/linux/pstore_ram.h

···
 	unsigned long	console_size;
 	unsigned long	ftrace_size;
 	unsigned long	pmsg_size;
-	int		dump_oops;
+	int		max_reason;
 	u32		flags;
 	struct persistent_ram_ecc_info ecc_info;
 };

include/linux/pstore_zone.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __PSTORE_ZONE_H_
+#define __PSTORE_ZONE_H_
+
+#include <linux/types.h>
+
+typedef ssize_t (*pstore_zone_read_op)(char *, size_t, loff_t);
+typedef ssize_t (*pstore_zone_write_op)(const char *, size_t, loff_t);
+typedef ssize_t (*pstore_zone_erase_op)(size_t, loff_t);
+/**
+ * struct pstore_zone_info - pstore/zone back-end driver structure
+ *
+ * @owner:	Module which is responsible for this back-end driver.
+ * @name:	Name of the back-end driver.
+ * @total_size: The total size in bytes pstore/zone can use. It must be greater
+ *		than 4096 and be multiple of 4096.
+ * @kmsg_size:	The size of oops/panic zone. Zero means disabled, otherwise,
+ *		it must be multiple of SECTOR_SIZE(512 Bytes).
+ * @max_reason: Maximum kmsg dump reason to store.
+ * @pmsg_size:	The size of pmsg zone which is the same as @kmsg_size.
+ * @console_size:The size of console zone which is the same as @kmsg_size.
+ * @ftrace_size:The size of ftrace zone which is the same as @kmsg_size.
+ * @read:	The general read operation. Both of the function parameters
+ *		@size and @offset are relative value to storage.
+ *		On success, the number of bytes should be returned, others
+ *		mean error.
+ * @write:	The same as @read, but the following error number:
+ *		-EBUSY means try to write again later.
+ *		-ENOMSG means to try next zone.
+ * @erase:	The general erase operation for device with special removing
+ *		job. Both of the function parameters @size and @offset are
+ *		relative value to storage.
+ *		Return 0 on success and others on failure.
+ * @panic_write:The write operation only used for panic case. It's optional
+ *		if you do not care panic log. The parameters are relative
+ *		value to storage.
+ *		On success, the number of bytes should be returned, others
+ *		excluding -ENOMSG mean error. -ENOMSG means to try next zone.
+ */
+struct pstore_zone_info {
+	struct module *owner;
+	const char *name;
+
+	unsigned long total_size;
+	unsigned long kmsg_size;
+	int max_reason;
+	unsigned long pmsg_size;
+	unsigned long console_size;
+	unsigned long ftrace_size;
+	pstore_zone_read_op read;
+	pstore_zone_write_op write;
+	pstore_zone_erase_op erase;
+	pstore_zone_write_op panic_write;
+};
+
+extern int register_pstore_zone(struct pstore_zone_info *info);
+extern void unregister_pstore_zone(struct pstore_zone_info *info);
+
+#endif

kernel/printk/printk.c

···
 static bool always_kmsg_dump;
 module_param_named(always_kmsg_dump, always_kmsg_dump, bool, S_IRUGO | S_IWUSR);
 
+const char *kmsg_dump_reason_str(enum kmsg_dump_reason reason)
+{
+	switch (reason) {
+	case KMSG_DUMP_PANIC:
+		return "Panic";
+	case KMSG_DUMP_OOPS:
+		return "Oops";
+	case KMSG_DUMP_EMERG:
+		return "Emergency";
+	case KMSG_DUMP_SHUTDOWN:
+		return "Shutdown";
+	default:
+		return "Unknown";
+	}
+}
+EXPORT_SYMBOL_GPL(kmsg_dump_reason_str);
+
 /**
  * kmsg_dump - dump kernel log to kernel message dumpers.
  * @reason: the reason (oops, panic etc) for dumping
···
 	struct kmsg_dumper *dumper;
 	unsigned long flags;
 
-	if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
-		return;
-
 	rcu_read_lock();
 	list_for_each_entry_rcu(dumper, &dump_list, list) {
-		if (dumper->max_reason && reason > dumper->max_reason)
+		enum kmsg_dump_reason max_reason = dumper->max_reason;
+
+		/*
+		 * If client has not provided a specific max_reason, default
+		 * to KMSG_DUMP_OOPS, unless always_kmsg_dump was set.
+		 */
+		if (max_reason == KMSG_DUMP_UNDEF) {
+			max_reason = always_kmsg_dump ? KMSG_DUMP_MAX :
+							KMSG_DUMP_OOPS;
+		}
+		if (reason > max_reason)
 			continue;
 
 		/* initialize iterator with data about the stored records */

kernel/reboot.c

···
 		pr_emerg("Restarting system\n");
 	else
 		pr_emerg("Restarting system with command '%s'\n", cmd);
-	kmsg_dump(KMSG_DUMP_RESTART);
+	kmsg_dump(KMSG_DUMP_SHUTDOWN);
 	machine_restart(cmd);
 }
 EXPORT_SYMBOL_GPL(kernel_restart);
···
 	migrate_to_reboot_cpu();
 	syscore_shutdown();
 	pr_emerg("System halted\n");
-	kmsg_dump(KMSG_DUMP_HALT);
+	kmsg_dump(KMSG_DUMP_SHUTDOWN);
 	machine_halt();
 }
 EXPORT_SYMBOL_GPL(kernel_halt);
···
 	migrate_to_reboot_cpu();
 	syscore_shutdown();
 	pr_emerg("Power down\n");
-	kmsg_dump(KMSG_DUMP_POWEROFF);
+	kmsg_dump(KMSG_DUMP_SHUTDOWN);
 	machine_power_off();
 }
 EXPORT_SYMBOL_GPL(kernel_power_off);

tools/testing/selftests/pstore/pstore_tests

···
 . ./common_tests
 
 prlog -n "Checking pstore console is registered ... "
-dmesg | grep -q "console \[pstore"
+dmesg | grep -Eq "console \[(pstore|${backend})"
 show_result $?
 
 prlog -n "Checking /dev/pmsg0 exists ... "