blk: Ensure users for current->bio_list can see the full list.

commit f5fe1b51905df7cfe4fdfd85c5fb7bc5b71a094f upstream.

Commit 79bd99596b73 ("blk: improve order of bio handling in generic_make_request()")
changed current->bio_list so that it did not contain *all* of the
queued bios, but only those submitted by the currently running
make_request_fn.

There are two places which walk the list and requeue selected bios,
and others that check if the list is empty.  These are no longer
correct.

So redefine current->bio_list to point to an array of two lists, which
contain all queued bios, and adjust various code to test or walk both
lists.

Signed-off-by: NeilBrown <neilb@suse.com>
Fixes: 79bd99596b73 ("blk: improve order of bio handling in generic_make_request()")
Signed-off-by: Jens Axboe <axboe@fb.com>
Cc: Jack Wang <jinpu.wang@profitbricks.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 18 insertions, 14 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 628ba001bb3c..e66f4040d84b 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -986,26 +986,29 @@ static void flush_current_bio_list(struct blk_plug_cb *cb, bool from_schedule)
         struct dm_offload *o = container_of(cb, struct dm_offload, cb);
         struct bio_list list;
         struct bio *bio;
+        int i;
 
         INIT_LIST_HEAD(&o->cb.list);
 
         if (unlikely(!current->bio_list))
                 return;
 
-        list = *current->bio_list;
-        bio_list_init(current->bio_list);
-
-        while ((bio = bio_list_pop(&list))) {
-                struct bio_set *bs = bio->bi_pool;
-                if (unlikely(!bs) || bs == fs_bio_set) {
-                        bio_list_add(current->bio_list, bio);
-                        continue;
+        for (i = 0; i < 2; i++) {
+                list = current->bio_list[i];
+                bio_list_init(&current->bio_list[i]);
+
+                while ((bio = bio_list_pop(&list))) {
+                        struct bio_set *bs = bio->bi_pool;
+                        if (unlikely(!bs) || bs == fs_bio_set) {
+                                bio_list_add(&current->bio_list[i], bio);
+                                continue;
+                        }
+
+                        spin_lock(&bs->rescue_lock);
+                        bio_list_add(&bs->rescue_list, bio);
+                        queue_work(bs->rescue_workqueue, &bs->rescue_work);
+                        spin_unlock(&bs->rescue_lock);
                 }
-
-                spin_lock(&bs->rescue_lock);
-                bio_list_add(&bs->rescue_list, bio);
-                queue_work(bs->rescue_workqueue, &bs->rescue_work);
-                spin_unlock(&bs->rescue_lock);
         }
 }
 
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 55b5e0e77b17..4c4aab02e311 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -941,7 +941,8 @@ static void wait_barrier(struct r10conf *conf)
                                     !conf->barrier ||
                                     (atomic_read(&conf->nr_pending) &&
                                      current->bio_list &&
-                                     !bio_list_empty(current->bio_list)),
+                                     (!bio_list_empty(&current->bio_list[0]) ||
+                                      !bio_list_empty(&current->bio_list[1]))),
                                     conf->resync_lock);
                 conf->nr_waiting--;
                 if (!conf->nr_waiting)