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authorNeilBrown <neilb@suse.de>2010-08-07 21:17:00 +1000
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-13 13:30:49 -0700
commitf986737b930114d41549f405a4efdeb13002db70 (patch)
tree83f6948f73504719914ac24cd01324a458562fb9
parent8fa8b10c9dc5729d3af41babae879b48ab4ee095 (diff)
downloadlinux-2.6.34-ux500-f986737b930114d41549f405a4efdeb13002db70.tar.gz
md/raid10: fix deadlock with unaligned read during resync
commit 51e9ac77035a3dfcb6fc0a88a0d80b6f99b5edb1 upstream. If the 'bio_split' path in raid10-read is used while resync/recovery is happening it is possible to deadlock. Fix this be elevating ->nr_waiting for the duration of both parts of the split request. This fixes a bug that has been present since 2.6.22 but has only started manifesting recently for unknown reasons. It is suitable for and -stable since then. Reported-by: Justin Bronder <jsbronder@gentoo.org> Tested-by: Justin Bronder <jsbronder@gentoo.org> Signed-off-by: NeilBrown <neilb@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
-rw-r--r--drivers/md/raid10.c18
1 files changed, 18 insertions, 0 deletions
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 42e64e4e5e2..d1d68912634 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -825,11 +825,29 @@ static int make_request(mddev_t *mddev, struct bio * bio)
*/
bp = bio_split(bio,
chunk_sects - (bio->bi_sector & (chunk_sects - 1)) );
+
+ /* Each of these 'make_request' calls will call 'wait_barrier'.
+ * If the first succeeds but the second blocks due to the resync
+ * thread raising the barrier, we will deadlock because the
+ * IO to the underlying device will be queued in generic_make_request
+ * and will never complete, so will never reduce nr_pending.
+ * So increment nr_waiting here so no new raise_barriers will
+ * succeed, and so the second wait_barrier cannot block.
+ */
+ spin_lock_irq(&conf->resync_lock);
+ conf->nr_waiting++;
+ spin_unlock_irq(&conf->resync_lock);
+
if (make_request(mddev, &bp->bio1))
generic_make_request(&bp->bio1);
if (make_request(mddev, &bp->bio2))
generic_make_request(&bp->bio2);
+ spin_lock_irq(&conf->resync_lock);
+ conf->nr_waiting--;
+ wake_up(&conf->wait_barrier);
+ spin_unlock_irq(&conf->resync_lock);
+
bio_pair_release(bp);
return 0;
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