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dm: dec_pending needs locking to save error value 

Multiple instances of dec_pending() can run concurrently so a lock is
needed when it saves the first error code.

I have never experienced actual problem without locking and just found
this during code inspection while implementing the barrier support
patch for request-based dm.

This patch adds the locking.
I've done compile, boot and basic I/O testings.

Cc: stable@kernel.org
Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
This commit is contained in:
Kiyoshi Ueda 2009-10-16 23:18:15 +01:00 committed by Alasdair G Kergon
parent 03022c54b9
commit f88fb98118
1 changed files with 8 additions and 2 deletions
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10
drivers/md/dm.c
View File

@ -47,6 +47,7 @@ struct dm_io {
atomic_t io_count;
struct bio *bio;
unsigned long start_time;
spinlock_t endio_lock;
};
/*
@ -578,8 +579,12 @@ static void dec_pending(struct dm_io *io, int error)
struct mapped_device *md = io->md;
/* Push-back supersedes any I/O errors */
if (error && !(io->error > 0 && __noflush_suspending(md)))
io->error = error;
if (unlikely(error)) {
spin_lock_irqsave(&io->endio_lock, flags);
if (!(io->error > 0 && __noflush_suspending(md)))
io->error = error;
spin_unlock_irqrestore(&io->endio_lock, flags);
}
if (atomic_dec_and_test(&io->io_count)) {
if (io->error == DM_ENDIO_REQUEUE) {
@ -1226,6 +1231,7 @@ static void __split_and_process_bio(struct mapped_device *md, struct bio *bio)
atomic_set(&ci.io->io_count, 1);
ci.io->bio = bio;
ci.io->md = md;
spin_lock_init(&ci.io->endio_lock);
ci.sector = bio->bi_sector;
ci.sector_count = bio_sectors(bio);
if (unlikely(bio_empty_barrier(bio)))