dm-bufio: fix no-sleep mode

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commit 2a695062a5 upstream.

dm-bufio has a no-sleep mode. When activated (with the
DM_BUFIO_CLIENT_NO_SLEEP flag), the bufio client is read-only and we
could call dm_bufio_get from tasklets. This is used by dm-verity.

Unfortunately, commit 450e8dee51 ("dm bufio: improve concurrent IO
performance") broke this and the kernel would warn that cache_get()
was calling down_read() from no-sleeping context. The bug can be
reproduced by using "veritysetup open" with the "--use-tasklets"
flag.

This commit fixes dm-bufio, so that the tasklet mode works again, by
expanding use of the 'no_sleep_enabled' static_key to conditionally
use either a rw_semaphore or rwlock_t (which are colocated in the
buffer_tree structure using a union).

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org	# v6.4
Fixes: 450e8dee51 ("dm bufio: improve concurrent IO performance")
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Mikulas Patocka 2023-11-17 18:36:34 +01:00 • committed by Greg Kroah-Hartman

parent 4aa9db1eab

commit 5be21d6543

1 changed files with 62 additions and 25 deletions

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drivers/md/dm-bufio.c

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