Merge tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper update from Mike Snitzer:

 - a couple small cleanups in dm-cache, dm-verity, persistent-data's
   dm-btree, and DM core.

 - a 4.1-stable fix for dm-cache that fixes the leaking of deferred bio
   prison cells

 - a 4.2-stable fix that adds feature reporting for the dm-stats
   features added in 4.2

 - improve DM-snapshot to not invalidate the on-disk snapshot if
   snapshot device write overflow occurs; but a write overflow triggered
   through the origin device will still invalidate the snapshot.

 - optimize DM-thinp's async discard submission a bit now that late bio
   splitting has been included in block core.

 - switch DM-cache's SMQ policy lock from using a mutex to a spinlock;
   improves performance on very low latency devices (eg. NVMe SSD).

 - document DM RAID 4/5/6's discard support

[ I did not pull the slab changes, which weren't appropriate for this
  tree, and weren't obviously the right thing to do anyway.  At the very
  least they need some discussion and explanation before getting merged.

  Because not pulling the actual tagged commit but doing a partial pull
  instead, this merge commit thus also obviously is missing the git
  signature from the original tag ]

* tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
  dm cache: fix use after freeing migrations
  dm cache: small cleanups related to deferred prison cell cleanup
  dm cache: fix leaking of deferred bio prison cells
  dm raid: document RAID 4/5/6 discard support
  dm stats: report precise_timestamps and histogram in @stats_list output
  dm thin: optimize async discard submission
  dm snapshot: don't invalidate on-disk image on snapshot write overflow
  dm: remove unlikely() before IS_ERR()
  dm: do not override error code returned from dm_get_device()
  dm: test return value for DM_MAPIO_SUBMITTED
  dm verity: remove unused mempool
  dm cache: move wake_waker() from free_migrations() to where it is needed
  dm btree remove: remove unused function get_nr_entries()
  dm btree: remove unused "dm_block_t root" parameter in btree_split_sibling()
  dm cache policy smq: change the mutex to a spinlock

1 files changed, 16 insertions, 4 deletions

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index d10b6876018e..c0bcd6516dfe 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -63,6 +63,13 @@ struct dm_snapshot {
 	 */
 	int valid;
 
+	/*
+	 * The snapshot overflowed because of a write to the snapshot device.
+	 * We don't have to invalidate the snapshot in this case, but we need
+	 * to prevent further writes.
+	 */
+	int snapshot_overflowed;
+
 	/* Origin writes don't trigger exceptions until this is set */
 	int active;
 
@@ -1152,6 +1159,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
 	s->ti = ti;
 	s->valid = 1;
+	s->snapshot_overflowed = 0;
 	s->active = 0;
 	atomic_set(&s->pending_exceptions_count, 0);
 	s->exception_start_sequence = 0;
@@ -1301,6 +1309,7 @@ static void __handover_exceptions(struct dm_snapshot *snap_src,
 
 	snap_dest->ti->max_io_len = snap_dest->store->chunk_size;
 	snap_dest->valid = snap_src->valid;
+	snap_dest->snapshot_overflowed = snap_src->snapshot_overflowed;
 
 	/*
 	 * Set source invalid to ensure it receives no further I/O.
@@ -1691,7 +1700,7 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio)
 	 * to copy an exception */
 	down_write(&s->lock);
 
-	if (!s->valid) {
+	if (!s->valid || (unlikely(s->snapshot_overflowed) && bio_rw(bio) == WRITE)) {
 		r = -EIO;
 		goto out_unlock;
 	}
@@ -1715,7 +1724,7 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio)
 			pe = alloc_pending_exception(s);
 			down_write(&s->lock);
 
-			if (!s->valid) {
+			if (!s->valid || s->snapshot_overflowed) {
 				free_pending_exception(pe);
 				r = -EIO;
 				goto out_unlock;
@@ -1730,7 +1739,8 @@ static int snapshot_map(struct dm_target *ti, struct bio *bio)
 
 			pe = __find_pending_exception(s, pe, chunk);
 			if (!pe) {
-				__invalidate_snapshot(s, -ENOMEM);
+				s->snapshot_overflowed = 1;
+				DMERR("Snapshot overflowed: Unable to allocate exception.");
 				r = -EIO;
 				goto out_unlock;
 			}
@@ -1990,6 +2000,8 @@ static void snapshot_status(struct dm_target *ti, status_type_t type,
 			DMEMIT("Invalid");
 		else if (snap->merge_failed)
 			DMEMIT("Merge failed");
+		else if (snap->snapshot_overflowed)
+			DMEMIT("Overflow");
 		else {
 			if (snap->store->type->usage) {
 				sector_t total_sectors, sectors_allocated,
@@ -2353,7 +2365,7 @@ static struct target_type origin_target = {
 
 static struct target_type snapshot_target = {
 	.name    = "snapshot",
-	.version = {1, 13, 0},
+	.version = {1, 14, 0},
 	.module  = THIS_MODULE,
 	.ctr     = snapshot_ctr,
 	.dtr     = snapshot_dtr,