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

commit 874807a83139abc094f939e93623c5623573d543 upstream.

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.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 05bb49e13648267d21a02efb698db165d0180026..7077dcf471858fe2c8d08c9a2353aa645f345789 100644 (file)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -958,7 +958,7 @@ 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;