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>
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index c5f9918..724efc6 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -47,6 +47,7 @@
atomic_t io_count;
struct bio *bio;
unsigned long start_time;
+ spinlock_t endio_lock;
};
/*
@@ -578,8 +579,12 @@
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 @@
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)))