dm: requeue IO if mapping table not yet available

Update both bio-based and request-based DM to requeue IO if the
mapping table not available.

This race of IO being submitted before the DM device ready is so
narrow, yet possible for initial table load given that the DM device's
request_queue is created prior, that it best to requeue IO to handle
this unlikely case.

Reported-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c
index 6948d5db909253f6ae76bff21631b6f6ecb3a345..3dd040a56318e48fa6b53858f2a51da40d47468a 100644 (file)
--- a/drivers/md/dm-rq.c
+++ b/drivers/md/dm-rq.c
@@ -491,8 +491,13 @@ static blk_status_t dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
 
        if (unlikely(!ti)) {
                int srcu_idx;
-               struct dm_table *map = dm_get_live_table(md, &srcu_idx);
+               struct dm_table *map;
 
+               map = dm_get_live_table(md, &srcu_idx);
+               if (unlikely(!map)) {
+                       dm_put_live_table(md, srcu_idx);
+                       return BLK_STS_RESOURCE;
+               }
                ti = dm_table_find_target(map, 0);
                dm_put_live_table(md, srcu_idx);
        }

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index ba1068f4cb526731340c6a11d10a62c961cd8cd5..3640ef4bf327623e6a154a5408939d4e1c328ba7 100644 (file)
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1533,15 +1533,10 @@ static void dm_submit_bio(struct bio *bio)
        struct dm_table *map;
 
        map = dm_get_live_table(md, &srcu_idx);
-       if (unlikely(!map)) {
-               DMERR_LIMIT("%s: mapping table unavailable, erroring io",
-                           dm_device_name(md));
-               bio_io_error(bio);
-               goto out;
-       }
 
-       /* If suspended, queue this IO for later */
-       if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags))) {
+       /* If suspended, or map not yet available, queue this IO for later */
+       if (unlikely(test_bit(DMF_BLOCK_IO_FOR_SUSPEND, &md->flags)) ||
+           unlikely(!map)) {
                if (bio->bi_opf & REQ_NOWAIT)
                        bio_wouldblock_error(bio);
                else if (bio->bi_opf & REQ_RAHEAD)