dm-bufio: fix sched in atomic context

In the Linux kernel, the following vulnerability has been resolved:

dm-bufio: fix sched in atomic context

If "try_verify_in_tasklet" is set for dm-verity, DM_BUFIO_CLIENT_NO_SLEEP

is enabled for dm-bufio. However, when bufio tries to evict buffers, there

is a chance to trigger scheduling in spin_lock_bh, the following warning

is hit:

BUG: sleeping function called from invalid context at drivers/md/dm-bufio.c:2745

in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 123, name: kworker/2:2

preempt_count: 201, expected: 0

RCU nest depth: 0, expected: 0

4 locks held by kworker/2:2/123:

#0: ffff88800a2d1548 ((wq_completion)dm_bufio_cache){....}-{0:0}, at: process_one_work+0xe46/0x1970

#1: ffffc90000d97d20 ((work_completion)(&dm_bufio_replacement_work)){....}-{0:0}, at: process_one_work+0x763/0x1970

#2: ffffffff8555b528 (dm_bufio_clients_lock){....}-{3:3}, at: do_global_cleanup+0x1ce/0x710

#3: ffff88801d5820b8 (&c->spinlock){....}-{2:2}, at: do_global_cleanup+0x2a5/0x710

Preemption disabled at:

[<0000000000000000>] 0x0

CPU: 2 UID: 0 PID: 123 Comm: kworker/2:2 Not tainted 6.16.0-rc3-g90548c634bd0 #305 PREEMPT(voluntary)

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014

Workqueue: dm_bufio_cache do_global_cleanup

Call Trace:

<TASK>

dump_stack_lvl+0x53/0x70

__might_resched+0x360/0x4e0

do_global_cleanup+0x2f5/0x710

process_one_work+0x7db/0x1970

worker_thread+0x518/0xea0

kthread+0x359/0x690

ret_from_fork+0xf3/0x1b0

ret_from_fork_asm+0x1a/0x30

</TASK>

That can be reproduced by:

veritysetup format --data-block-size=4096 --hash-block-size=4096 /dev/vda /dev/vdb

SIZE=$(blockdev --getsz /dev/vda)

dmsetup create myverity -r --table "0 $SIZE verity 1 /dev/vda /dev/vdb 4096 4096 <data_blocks> 1 sha256 <root_hash> <salt> 1 try_verify_in_tasklet"

mount /dev/dm-0 /mnt -o ro

echo 102400 > /sys/module/dm_bufio/parameters/max_cache_size_bytes

[read files in /mnt]