md/raid1{,0}: fix deadlock in bitmap_unplug.

If the raid1 or raid10 unplug function gets called
from a make_request function (which is very possible) when
there are bios on the current->bio_list list, then it will not
be able to successfully call bitmap_unplug() and it could
need to submit more bios and wait for them to complete.
But they won't complete while current->bio_list is non-empty.

So detect that case and handle the unplugging off to another thread
just like we already do when called from within the scheduler.

RAID1 version of bug was introduced in 3.6, so that part of fix is
suitable for 3.6.y.  RAID10 part won't apply.

Cc: stable@vger.kernel.org
Reported-by: Torsten Kaiser <just.for.lkml@googlemail.com>
Reported-by: Peter Maloney <peter.maloney@brockmann-consult.de>
Signed-off-by: NeilBrown <neilb@suse.de>

2 files changed, 2 insertions, 2 deletions

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 636bae0405e8..a0f73092176e 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -963,7 +963,7 @@ static void raid1_unplug(struct blk_plug_cb *cb, bool from_schedule)
         struct r1conf *conf = mddev->private;
         struct bio *bio;
 
-        if (from_schedule) {
+        if (from_schedule || current->bio_list) {
                 spin_lock_irq(&conf->device_lock);
                 bio_list_merge(&conf->pending_bio_list, &plug->pending);
                 conf->pending_count += plug->pending_cnt;
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 0d5d0ff2c0f7..c9acbd717131 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -1069,7 +1069,7 @@ static void raid10_unplug(struct blk_plug_cb *cb, bool from_schedule)
         struct r10conf *conf = mddev->private;
         struct bio *bio;
 
-        if (from_schedule) {
+        if (from_schedule || current->bio_list) {
                 spin_lock_irq(&conf->device_lock);
                 bio_list_merge(&conf->pending_bio_list, &plug->pending);
                 conf->pending_count += plug->pending_cnt;