tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
zram: deprecate zram attrs sysfs nodes
Add Documentation/ABI/obsolete/sysfs-block-zram file and list obsolete and
deprecated attributes there. The patch also adds additional information
to zram documentation and describes the basic strategy:
- the existing RW nodes will be downgraded to WO nodes (in 4.11)
- deprecated RO sysfs nodes will eventually be removed (in 4.11)
Users will be additionally notified about deprecated attr usage by
pr_warn_once() (added to every deprecated attr _show()), as suggested by
Minchan Kim.
User space is advised to use zram<id>/stat, zram<id>/io_stat and
zram<id>/mm_stat files.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
authored by
Sergey Senozhatsky
and committed by
Linus Torvalds
8f7d282c
4f2109f6
+150
+119
Documentation/ABI/obsolete/sysfs-block-zram
+119
Documentation/ABI/obsolete/sysfs-block-zram
···
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What: /sys/block/zram<id>/num_reads
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Date: August 2015
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Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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Description:
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The num_reads file is read-only and specifies the number of
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reads (failed or successful) done on this device.
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Now accessible via zram<id>/stat node.
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What: /sys/block/zram<id>/num_writes
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Date: August 2015
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Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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Description:
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The num_writes file is read-only and specifies the number of
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writes (failed or successful) done on this device.
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Now accessible via zram<id>/stat node.
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What: /sys/block/zram<id>/invalid_io
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Date: August 2015
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Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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Description:
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The invalid_io file is read-only and specifies the number of
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non-page-size-aligned I/O requests issued to this device.
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Now accessible via zram<id>/io_stat node.
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What: /sys/block/zram<id>/failed_reads
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Date: August 2015
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Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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Description:
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The failed_reads file is read-only and specifies the number of
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failed reads happened on this device.
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Now accessible via zram<id>/io_stat node.
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What: /sys/block/zram<id>/failed_writes
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Date: August 2015
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Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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Description:
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The failed_writes file is read-only and specifies the number of
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failed writes happened on this device.
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Now accessible via zram<id>/io_stat node.
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What: /sys/block/zram<id>/notify_free
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Date: August 2015
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Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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Description:
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The notify_free file is read-only. Depending on device usage
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scenario it may account a) the number of pages freed because
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of swap slot free notifications or b) the number of pages freed
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because of REQ_DISCARD requests sent by bio. The former ones
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are sent to a swap block device when a swap slot is freed, which
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implies that this disk is being used as a swap disk. The latter
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ones are sent by filesystem mounted with discard option,
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whenever some data blocks are getting discarded.
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Now accessible via zram<id>/io_stat node.
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What: /sys/block/zram<id>/zero_pages
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Date: August 2015
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Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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Description:
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The zero_pages file is read-only and specifies number of zero
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filled pages written to this disk. No memory is allocated for
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such pages.
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Now accessible via zram<id>/mm_stat node.
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What: /sys/block/zram<id>/orig_data_size
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Date: August 2015
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Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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Description:
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The orig_data_size file is read-only and specifies uncompressed
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size of data stored in this disk. This excludes zero-filled
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pages (zero_pages) since no memory is allocated for them.
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Unit: bytes
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Now accessible via zram<id>/mm_stat node.
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What: /sys/block/zram<id>/compr_data_size
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Date: August 2015
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Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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Description:
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The compr_data_size file is read-only and specifies compressed
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size of data stored in this disk. So, compression ratio can be
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calculated using orig_data_size and this statistic.
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Unit: bytes
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Now accessible via zram<id>/mm_stat node.
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What: /sys/block/zram<id>/mem_used_total
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Date: August 2015
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Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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Description:
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The mem_used_total file is read-only and specifies the amount
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of memory, including allocator fragmentation and metadata
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overhead, allocated for this disk. So, allocator space
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efficiency can be calculated using compr_data_size and this
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statistic.
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Unit: bytes
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Now accessible via zram<id>/mm_stat node.
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What: /sys/block/zram<id>/mem_used_max
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Date: August 2015
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Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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Description:
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The mem_used_max file is read/write and specifies the amount
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of maximum memory zram have consumed to store compressed data.
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For resetting the value, you should write "0". Otherwise,
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you could see -EINVAL.
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Unit: bytes
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Downgraded to write-only node: so it's possible to set new
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value only; its current value is stored in zram<id>/mm_stat
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node.
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What: /sys/block/zram<id>/mem_limit
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Date: August 2015
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Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
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Description:
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The mem_limit file is read/write and specifies the maximum
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amount of memory ZRAM can use to store the compressed data.
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The limit could be changed in run time and "0" means disable
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the limit. No limit is the initial state. Unit: bytes
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Downgraded to write-only node: so it's possible to set new
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value only; its current value is stored in zram<id>/mm_stat
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node.
+16
Documentation/blockdev/zram.txt
+16
Documentation/blockdev/zram.txt
···
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num_migrated RO the number of objects migrated migrated by compaction
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WARNING
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=======
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per-stat sysfs attributes are considered to be deprecated.
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The basic strategy is:
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-- the existing RW nodes will be downgraded to WO nodes (in linux 4.11)
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-- deprecated RO sysfs nodes will eventually be removed (in linux 4.11)
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The list of deprecated attributes can be found here:
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Documentation/ABI/obsolete/sysfs-block-zram
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Basically, every attribute that has its own read accessible sysfs node
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(e.g. num_reads) *AND* is accessible via one of the stat files (zram<id>/stat
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or zram<id>/io_stat or zram<id>/mm_stat) is considered to be deprecated.
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User space is advised to use the following files to read the device statistics.
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File /sys/block/zram<id>/stat
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Represents block layer statistics. Read Documentation/block/stat.txt for
+15
drivers/block/zram/zram_drv.c
+15
drivers/block/zram/zram_drv.c
···
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/* Module params (documentation at end) */
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static unsigned int num_devices = 1;
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static inline void deprecated_attr_warn(const char *name)
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{
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pr_warn_once("%d (%s) Attribute %s (and others) will be removed. %s\n",
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task_pid_nr(current),
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current->comm,
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name,
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"See zram documentation.");
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}
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#define ZRAM_ATTR_RO(name) \
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static ssize_t name##_show(struct device *d, \
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struct device_attribute *attr, char *b) \
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{ \
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struct zram *zram = dev_to_zram(d); \
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\
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deprecated_attr_warn(__stringify(name)); \
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return scnprintf(b, PAGE_SIZE, "%llu\n", \
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(u64)atomic64_read(&zram->stats.name)); \
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} \
···
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{
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struct zram *zram = dev_to_zram(dev);
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deprecated_attr_warn("orig_data_size");
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return scnprintf(buf, PAGE_SIZE, "%llu\n",
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(u64)(atomic64_read(&zram->stats.pages_stored)) << PAGE_SHIFT);
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}
···
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u64 val = 0;
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struct zram *zram = dev_to_zram(dev);
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deprecated_attr_warn("mem_used_total");
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down_read(&zram->init_lock);
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if (init_done(zram)) {
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struct zram_meta *meta = zram->meta;
···
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u64 val;
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struct zram *zram = dev_to_zram(dev);
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deprecated_attr_warn("mem_limit");
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down_read(&zram->init_lock);
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val = zram->limit_pages;
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up_read(&zram->init_lock);
···
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u64 val = 0;
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struct zram *zram = dev_to_zram(dev);
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deprecated_attr_warn("mem_used_max");
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down_read(&zram->init_lock);
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if (init_done(zram))
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val = atomic_long_read(&zram->stats.max_used_pages);