Merge tag 'for-5.9/dm-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper fixes from Mike Snitzer:

 - DM core fix for incorrect double bio splitting. Keep "fixing" this
   because past attempts didn't fully appreciate the liability relative
   to recursive bio splitting. This fix limits DM's bio splitting to a
   single method and does _not_ use blk_queue_split() for normal IO.

 - DM crypt Documentation updates for features added during 5.9 merge.

* tag 'for-5.9/dm-fixes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
  dm crypt: document encrypted keyring key option
  dm crypt: document new no_workqueue flags
  dm: fix comment in dm_process_bio()
  dm: fix bio splitting and its bio completion order for regular IO

1 files changed, 5 insertions, 22 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 4a40df8af7d3..6ed05ca65a0f 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1724,23 +1724,6 @@ out:
 	return ret;
 }
 
-static void dm_queue_split(struct mapped_device *md, struct dm_target *ti, struct bio **bio)
-{
-	unsigned len, sector_count;
-
-	sector_count = bio_sectors(*bio);
-	len = min_t(sector_t, max_io_len((*bio)->bi_iter.bi_sector, ti), sector_count);
-
-	if (sector_count > len) {
-		struct bio *split = bio_split(*bio, len, GFP_NOIO, &md->queue->bio_split);
-
-		bio_chain(split, *bio);
-		trace_block_split(md->queue, split, (*bio)->bi_iter.bi_sector);
-		submit_bio_noacct(*bio);
-		*bio = split;
-	}
-}
-
 static blk_qc_t dm_process_bio(struct mapped_device *md,
 			       struct dm_table *map, struct bio *bio)
 {
@@ -1761,21 +1744,21 @@ static blk_qc_t dm_process_bio(struct mapped_device *md,
 	}
 
 	/*
-	 * If in ->queue_bio we need to use blk_queue_split(), otherwise
+	 * If in ->submit_bio we need to use blk_queue_split(), otherwise
 	 * queue_limits for abnormal requests (e.g. discard, writesame, etc)
 	 * won't be imposed.
+	 * If called from dm_wq_work() for deferred bio processing, bio
+	 * was already handled by following code with previous ->submit_bio.
 	 */
 	if (current->bio_list) {
 		if (is_abnormal_io(bio))
 			blk_queue_split(&bio);
-		else
-			dm_queue_split(md, ti, &bio);
+		/* regular IO is split by __split_and_process_bio */
 	}
 
 	if (dm_get_md_type(md) == DM_TYPE_NVME_BIO_BASED)
 		return __process_bio(md, map, bio, ti);
-	else
-		return __split_and_process_bio(md, map, bio);
+	return __split_and_process_bio(md, map, bio);
 }
 
 static blk_qc_t dm_submit_bio(struct bio *bio)