Commit 10eb3a0d authored by Benjamin Marzinski's avatar Benjamin Marzinski Committed by Mike Snitzer
Browse files

dm: fix race in dm_start_io_acct 



After commit 82f6cdcc ("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: 82f6cdcc ("dm: switch dm_io booleans over to proper flags")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarBenjamin Marzinski <bmarzins@redhat.com>
Signed-off-by: default avatarMike Snitzer <snitzer@kernel.org>
parent b13baccc

drivers/md/dm.c

+4 −0
Original line number Diff line number Diff line
@@ -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);

	}