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dm: fix race in dm_start_io_acct

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After commit 82f6cdcc36 ("dm: switch dm_io booleans over to proper
flags") dm_start_io_acct stopped atomically checking and setting
was_accounted, which turned into the DM_IO_ACCOUNTED flag. This opened
the possibility for a race where IO accounting is started twice for
duplicate bios. To remove the race, check the flag while holding the
io->lock.

Fixes: 82f6cdcc36 ("dm: switch dm_io booleans over to proper flags")
Cc: stable@vger.kernel.org
Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
This commit is contained in:
Benjamin Marzinski 2022-06-14 11:10:28 -05:00 committed by Mike Snitzer
parent b13baccc38
commit 10eb3a0d51
1 changed files with 4 additions and 0 deletions
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4
drivers/md/dm.c
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@ -555,6 +555,10 @@ static void dm_start_io_acct(struct dm_io *io, struct bio *clone)
unsigned long flags;
/* Can afford locking given DM_TIO_IS_DUPLICATE_BIO */
spin_lock_irqsave(&io->lock, flags);
if (dm_io_flagged(io, DM_IO_ACCOUNTED)) {
spin_unlock_irqrestore(&io->lock, flags);
return;
}
dm_io_set_flag(io, DM_IO_ACCOUNTED);
spin_unlock_irqrestore(&io->lock, flags);
}