linux.git/drivers/block/loop.c, branch v6.6.131

loop: Avoid updating block size under exclusive owner

2025-10-02T11:42:54+00:00

commit 7e49538288e523427beedd26993d446afef1a6fb upstream.

Syzbot came up with a reproducer where a loop device block size is
changed underneath a mounted filesystem. This causes a mismatch between
the block device block size and the block size stored in the superblock
causing confusion in various places such as fs/buffer.c. The particular
issue triggered by syzbot was a warning in __getblk_slow() due to
requested buffer size not matching block device block size.

Fix the problem by getting exclusive hold of the loop device to change
its block size. This fails if somebody (such as filesystem) has already
an exclusive ownership of the block device and thus prevents modifying
the loop device under some exclusive owner which doesn't expect it.

Reported-by: syzbot+01ef7a8da81a975e1ccd@syzkaller.appspotmail.com
Signed-off-by: Jan Kara 
Tested-by: syzbot+01ef7a8da81a975e1ccd@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/20250711163202.19623-2-jack@suse.cz
Signed-off-by: Jens Axboe 
Signed-off-by: Zheng Qixing 
Signed-off-by: Greg Kroah-Hartman

Revert "loop: Avoid updating block size under exclusive owner"

2025-09-25T09:00:10+00:00

Revert commit ce8da5d13d8c2a7b30b2fb376a22e8eb1a70b8bb which is commit
7e49538288e523427beedd26993d446afef1a6fb upstream.

This reverts commit ce8da5d13d8c ("loop: Avoid updating block size under
exclusive owner") for the 6.6 kernel, because if the LTP ioctl_loop06 test is
run with this patch in place, the test will fail, it leaves the host unable to
kexec into the kernel again (hangs forever) and "losetup -a" will hang on
attempting to access the /dev/loopN device that the test has set up.

The patch doesn't need to be reverted from 6.12, as it works fine there.

Cc: stable@vger.kernel.org # 6.6.x
Signed-off-by: Eric Hagberg 
Signed-off-by: Greg Kroah-Hartman

loop: Avoid updating block size under exclusive owner

2025-08-28T14:28:15+00:00

[ Upstream commit 7e49538288e523427beedd26993d446afef1a6fb ]

Syzbot came up with a reproducer where a loop device block size is
changed underneath a mounted filesystem. This causes a mismatch between
the block device block size and the block size stored in the superblock
causing confusion in various places such as fs/buffer.c. The particular
issue triggered by syzbot was a warning in __getblk_slow() due to
requested buffer size not matching block device block size.

Fix the problem by getting exclusive hold of the loop device to change
its block size. This fails if somebody (such as filesystem) has already
an exclusive ownership of the block device and thus prevents modifying
the loop device under some exclusive owner which doesn't expect it.

Reported-by: syzbot+01ef7a8da81a975e1ccd@syzkaller.appspotmail.com
Signed-off-by: Jan Kara 
Tested-by: syzbot+01ef7a8da81a975e1ccd@syzkaller.appspotmail.com
Link: https://lore.kernel.org/r/20250711163202.19623-2-jack@suse.cz
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

loop: aio inherit the ioprio of original request

2025-05-02T05:51:01+00:00

[ Upstream commit 1fdb8188c3d505452b40cdb365b1bb32be533a8e ]

Set cmd->iocb.ki_ioprio to the ioprio of loop device's request.
The purpose is to inherit the original request ioprio in the aio
flow.

Signed-off-by: Yunlong Xing 
Signed-off-by: Zhiguo Niu 
Reviewed-by: Christoph Hellwig 
Link: https://lore.kernel.org/r/20250414030159.501180-1-yunlong.xing@unisoc.com
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

loop: LOOP_SET_FD: send uevents for partitions

2025-04-25T08:45:48+00:00

commit 0dba7a05b9e47d8b546399117b0ddf2426dc6042 upstream.

Remove the suppression of the uevents before scanning for partitions.
The partitions inherit their suppression settings from their parent device,
which lead to the uevents being dropped.

This is similar to the same changes for LOOP_CONFIGURE done in
commit bb430b694226 ("loop: LOOP_CONFIGURE: send uevents for partitions").

Fixes: 498ef5c777d9 ("loop: suppress uevents while reconfiguring the device")
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Weißschuh 
Reviewed-by: Jan Kara 
Link: https://lore.kernel.org/r/20250415-loop-uevent-changed-v3-1-60ff69ac6088@linutronix.de
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

loop: properly send KOBJ_CHANGED uevent for disk device

2025-04-25T08:45:48+00:00

commit e7bc0010ceb403d025100698586c8e760921d471 upstream.

The original commit message and the wording "uncork" in the code comment
indicate that it is expected that the suppressed event instances are
automatically sent after unsuppressing.
This is not the case, instead they are discarded.
In effect this means that no "changed" events are emitted on the device
itself by default.
While each discovered partition does trigger a changed event on the
device, devices without partitions don't have any event emitted.

This makes udev miss the device creation and prompted workarounds in
userspace. See the linked util-linux/losetup bug.

Explicitly emit the events and drop the confusingly worded comments.

Link: https://github.com/util-linux/util-linux/issues/2434
Fixes: 498ef5c777d9 ("loop: suppress uevents while reconfiguring the device")
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Weißschuh 
Link: https://lore.kernel.org/r/20250415-loop-uevent-changed-v2-1-0c4e6a923b2a@linutronix.de
Signed-off-by: Jens Axboe 
Signed-off-by: Greg Kroah-Hartman

loop: don't set QUEUE_FLAG_NOMERGES

2024-10-10T09:57:18+00:00

[ Upstream commit 667ea36378cf7f669044b27871c496e1559c872a ]

QUEUE_FLAG_NOMERGES isn't really a driver interface, but a user tunable.
There also isn't any good reason to set it in the loop driver.

The original commit adding it (5b5e20f421c0b6d "block: loop: set
QUEUE_FLAG_NOMERGES for request queue of loop") claims that "It doesn't
make sense to enable merge because the I/O submitted to backing file is
handled page by page."  which of course isn't true for multi-page bvec
now, and it never has been for direct I/O, for which commit 40326d8a33d
("block/loop: allow request merge for directio mode") alredy disabled
the nomerges flag.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Bart Van Assche 
Link: https://lore.kernel.org/r/20240627124926.512662-2-hch@lst.de
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

loop: fix the the direct I/O support check when used on top of block devices

2024-01-25T23:36:00+00:00

[ Upstream commit baa7d536077dcdfe2b70c476a8873d1745d3de0f ]

__loop_update_dio only checks the alignment requirement for block backed
file systems, but misses them for the case where the loop device is
created directly on top of another block device.  Due to this creating
a loop device with default option plus the direct I/O flag on a > 512 byte
sector size file system will lead to incorrect I/O being submitted to the
lower block device and a lot of error from the lock layer.  This can
be seen with xfstests generic/563.

Fix the code in __loop_update_dio by factoring the alignment check into
a helper, and calling that also for the struct block_device of a block
device inode.

Also remove the TODO comment talking about dynamically switching between
buffered and direct I/O, which is a would be a recipe for horrible
performance and occasional data loss.

Fixes: 2e5ab5f379f9 ("block: loop: prepare for supporing direct IO")
Signed-off-by: Christoph Hellwig 
Reviewed-by: Ming Lei 
Link: https://lore.kernel.org/r/20240117175901.871796-1-hch@lst.de
Signed-off-by: Jens Axboe 
Signed-off-by: Sasha Levin

Merge tag 'v6.6-vfs.super' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

2023-08-28T18:04:18+00:00

Pull superblock updates from Christian Brauner:
"This contains the super rework that was ready for this cycle. The
first part changes the order of how we open block devices and allocate
superblocks, contains various cleanups, simplifications, and a new
mechanism to wait on superblock state changes.

This unblocks work to ultimately limit the number of writers to a
block device. Jan has already scheduled follow-up work that will be
ready for v6.7 and allows us to restrict the number of writers to a
given block device. That series builds on this work right here.

The second part contains filesystem freezing updates.

Overview:

The generic superblock changes are rougly organized as follows
(ignoring additional minor cleanups):

(1) Removal of the bd_super member from struct block_device.

This was a very odd back pointer to struct super_block with
unclear rules. For all relevant places we have other means to get
the same information so just get rid of this.

(2) Simplify rules for superblock cleanup.

Roughly, everything that is allocated during fs_context
initialization and that's stored in fs_context->s_fs_info needs
to be cleaned up by the fs_context->free() implementation before
the superblock allocation function has been called successfully.

After sget_fc() returned fs_context->s_fs_info has been
transferred to sb->s_fs_info at which point sb->kill_sb() if
fully responsible for cleanup. Adhering to these rules means that
cleanup of sb->s_fs_info in fill_super() is to be avoided as it's
brittle and inconsistent.

Cleanup shouldn't be duplicated between sb->put_super() as
sb->put_super() is only called if sb->s_root has been set aka
when the filesystem has been successfully born (SB_BORN). That
complexity should be avoided.

This also means that block devices are to be closed in
sb->kill_sb() instead of sb->put_super(). More details in the
lower section.

(3) Make it possible to lookup or create a superblock before opening
block devices

There's a subtle dependency on (2) as some filesystems did rely
on fill_super() to be called in order to correctly clean up
sb->s_fs_info. All these filesystems have been fixed.

(4) Switch most filesystem to follow the same logic as the generic
mount code now does as outlined in (3).

(5) Use the superblock as the holder of the block device. We can now
easily go back from block device to owning superblock.

(6) Export and extend the generic fs_holder_ops and use them as
holder ops everywhere and remove the filesystem specific holder
ops.

(7) Call from the block layer up into the filesystem layer when the
block device is removed, allowing to shut down the filesystem
without risk of deadlocks.

(8) Get rid of get_super().

We can now easily go back from the block device to owning
superblock and can call up from the block layer into the
filesystem layer when the device is removed. So no need to wade
through all registered superblock to find the owning superblock
anymore"

Link: https://lore.kernel.org/lkml/20230824-prall-intakt-95dbffdee4a0@brauner/

* tag 'v6.6-vfs.super' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (47 commits)
super: use higher-level helper for {freeze,thaw}
super: wait until we passed kill super
super: wait for nascent superblocks
super: make locking naming consistent
super: use locking helpers
fs: simplify invalidate_inodes
fs: remove get_super
block: call into the file system for ioctl BLKFLSBUF
block: call into the file system for bdev_mark_dead
block: consolidate __invalidate_device and fsync_bdev
block: drop the "busy inodes on changed media" log message
dasd: also call __invalidate_device when setting the device offline
amiflop: don't call fsync_bdev in FDFMTBEG
floppy: call disk_force_media_change when changing the format
block: simplify the disk_force_media_change interface
nbd: call blk_mark_disk_dead in nbd_clear_sock_ioctl
xfs use fs_holder_ops for the log and RT devices
xfs: drop s_umount over opening the log and RT devices
ext4: use fs_holder_ops for the log device
ext4: drop s_umount over opening the log device
...

block: simplify the disk_force_media_change interface

2023-08-21T12:35:30+00:00

Hard code the events to DISK_EVENT_MEDIA_CHANGE as that is the only
useful use case, and drop the superfluous return value.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Josef Bacik 
Message-Id: <20230811100828.1897174-9-hch@lst.de>
Signed-off-by: Christian Brauner