md/raid10: decrement correct pending counter when writing to replacement.

When a write to a replacement device completes, we carefully
and correctly found the rdev that the write actually went to
and the blithely called rdev_dec_pending on the primary rdev,
even if this write was to the replacement.

This means that any writes to an array while a replacement
was ongoing would cause the nr_pending count for the primary
device to go negative, so it could never be removed.

This bug has been present since replacement was introduced in
3.3, so it is suitable for any -stable kernel since then.

Reported-by: "George Spelvin" <linux@horizon.com>
Cc: stable@vger.kernel.org
Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index ad032518fdc00981b344dc5c1c98880defd79095..0d5d0ff2c0f7beb47a02bd4692273b31369b2bc5 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -499,7 +499,7 @@ static void raid10_end_write_request(struct bio *bio, int error)
         */
        one_write_done(r10_bio);
        if (dec_rdev)
-               rdev_dec_pending(conf->mirrors[dev].rdev, conf->mddev);
+               rdev_dec_pending(rdev, conf->mddev);
 }
 
 /*