tjh.dev
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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Logical block size has type unsigned short. That means that it can be at
most 32768. However, there are architectures that can run with 64k pages
(for example arm64) and on these architectures, it may be possible to
create block devices with 64k block size.
For exmaple (run this on an architecture with 64k pages):
Mount will fail with this error because it tries to read the superblock using 2-sector
access:
device-mapper: writecache: I/O is not aligned, sector 2, size 1024, block size 65536
EXT4-fs (dm-0): unable to read superblock
This patch changes the logical block size from unsigned short to unsigned
int to avoid the overflow.
Cc: stable@vger.kernel.org
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
null_zone_write() only allows writing empty and implicitly opened zones.
Writing to closed and explicitly opened zones must also be allowed and
the zone condition must be transitioned to implicit open if the zone
is not explicitly opened already.
Fixes: da644b2cc1a4 ("null_blk: add zone open, close, and finish support")
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Commit 429120f3df2d starts to take account of segment's start dma address
when computing max segment size, and data type of 'unsigned long'
is used to do that. However, the segment mask may be 0xffffffff, so
the figured out segment size may be overflowed in case of zero physical
address on 32bit arch.
Fix the issue by returning queue_max_segment_size() directly when that
happens.
Fixes: 429120f3df2d ("block: fix splitting segments on boundary masks")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Cc: Christoph Hellwig <hch@lst.de>
Tested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
The existing implementation for the get_feature admin-cmd does not
use per-feature data len. This patch introduces a new helper function
nvmet_feat_data_len(), which is used to calculate per feature data len.
Right now we only set data len for fid 0x81 (NVME_FEAT_HOST_ID).
Fixes: commit e9061c397839 ("nvmet: Remove the data_len field from the nvmet_req struct")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Amit Engel <amit.engel@dell.com>
[endiness, naming, and kernel style fixes]
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Decode interrupted command and not ready namespace nvme status codes to
BLK_STS_TARGET. These are not generic IO errors and should use a non-path
specific error so that it can use the non-failover retry path.
Reported-by: John Meneghini <John.Meneghini@netapp.com>
Cc: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Commit 85a8ce62c2ea ("block: add bio_truncate to fix guard_bio_eod")
adds bio_truncate() for handling bio EOD. However, bio_truncate()
doesn't use the passed 'op' parameter from guard_bio_eod's callers.
So bio_trunacate() may retrieve wrong 'op', and zering pages may
not be done for READ bio.
Fixes this issue by moving guard_bio_eod() after bio_set_op_attrs()
in submit_bh_wbc() so that bio_truncate() can always retrieve correct
op info.
Meantime remove the 'op' parameter from guard_bio_eod() because it isn't
used any more.
Cc: Carlos Maiolino <cmaiolino@redhat.com>
Cc: linux-fsdevel@vger.kernel.org
Fixes: 85a8ce62c2ea ("block: add bio_truncate to fix guard_bio_eod")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Fold in kerneldoc and bio_op() change.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
After commit 85a8ce62c2ea ("block: add bio_truncate to fix guard_bio_eod")
this function is unused, remove it.
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
In order to match ZBC defined behavior, closing an empty zone must
result in the "empty" zone condition instead of the "closed" condition.
Fixes: da644b2cc1a4 ("null_blk: add zone open, close, and finish support")
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We ran into a problem with a mpt3sas based controller, where we would
see random (and hard to reproduce) file corruption). The issue seemed
specific to this controller, but wasn't specific to the file system.
After a lot of debugging, we find out that it's caused by segments
spanning a 4G memory boundary. This shouldn't happen, as the default
setting for segment boundary masks is 4G.
Turns out there are two issues in get_max_segment_size():
1) The default segment boundary mask is bypassed
2) The segment start address isn't taken into account when checking
segment boundary limit
Fix these two issues by removing the bypass of the segment boundary
check even if the mask is set to the default value, and taking into
account the actual start address of the request when checking if a
segment needs splitting.
Cc: stable@vger.kernel.org # v5.1+
Reviewed-by: Chris Mason <clm@fb.com>
Tested-by: Chris Mason <clm@fb.com>
Fixes: dcebd755926b ("block: use bio_for_each_bvec() to compute multi-page bvec count")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Dropped const on the page pointer, ppc page_to_phys() doesn't mark the
page as const...
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Some filesystem, such as vfat, may send bio which crosses device boundary,
and the worse thing is that the IO request starting within device boundaries
can contain more than one segment past EOD.
Commit dce30ca9e3b6 ("fs: fix guard_bio_eod to check for real EOD errors")
tries to fix this issue by returning -EIO for this situation. However,
this way lets fs user code lose chance to handle -EIO, then sync_inodes_sb()
may hang for ever.
Also the current truncating on last segment is dangerous by updating the
last bvec, given bvec table becomes not immutable any more, and fs bio
users may not retrieve the truncated pages via bio_for_each_segment_all() in
its .end_io callback.
Fixes this issue by supporting multi-segment truncating. And the
approach is simpler:
- just update bio size since block layer can make correct bvec with
the updated bio size. Then bvec table becomes really immutable.
- zero all truncated segments for read bio
Cc: Carlos Maiolino <cmaiolino@redhat.com>
Cc: linux-fsdevel@vger.kernel.org
Fixed-by: dce30ca9e3b6 ("fs: fix guard_bio_eod to check for real EOD errors")
Reported-by: syzbot+2b9e54155c8c25d8d165@syzkaller.appspotmail.com
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
These were added to blkdev_ioctl() in linux-5.5 but not
blkdev_compat_ioctl, so add them now.
Cc: <stable@vger.kernel.org> # v4.4+
Fixes: bbd3e064362e ("block: add an API for Persistent Reservations")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fold in followup patch from Arnd with missing pr.h header include.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
These were added to blkdev_ioctl() in linux-5.5 but not
blkdev_compat_ioctl, so add them now.
Fixes: e876df1fe0ad ("block: add zone open, close and finish ioctl support")
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
These were added to blkdev_ioctl() in v4.20 but not blkdev_compat_ioctl,
so add them now.
Cc: <stable@vger.kernel.org> # v4.20+
Fixes: 72cd87576d1d ("block: Introduce BLKGETZONESZ ioctl")
Fixes: 65e4e3eee83d ("block: Introduce BLKGETNRZONES ioctl")
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
These were added to blkdev_ioctl() but not blkdev_compat_ioctl,
so add them now.
Cc: <stable@vger.kernel.org> # v4.10+
Fixes: 3ed05a987e0f ("blk-zoned: implement ioctls")
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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