Merge tag 'for-5.3/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper updates from Mike Snitzer:

 - Add encrypted byte-offset initialization vector (eboiv) to DM crypt.

 - Add optional discard features to DM snapshot which allow freeing
   space from a DM device whose free space was exhausted.

 - Various small improvements to use struct_size() and kzalloc().

 - Fix to check if DM thin metadata is in fail_io mode before attempting
   to update the superblock to set the needs_check flag. Otherwise the
   DM thin-pool can hang.

 - Fix DM bufio shrinker's potential for ABBA recursion deadlock with DM
   thin provisioning on loop usecase.

* tag 'for-5.3/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm:
  dm bufio: fix deadlock with loop device
  dm snapshot: add optional discard support features
  dm crypt: implement eboiv - encrypted byte-offset initialization vector
  dm crypt: remove obsolete comment about plumb IV
  dm crypt: wipe private IV struct after key invalid flag is set
  dm integrity: use kzalloc() instead of kmalloc() + memset()
  dm: update stale comment in end_clone_bio()
  dm log writes: fix incorrect comment about the logged sequence example
  dm log writes: use struct_size() to calculate size of pending_block
  dm crypt: use struct_size() when allocating encryption context
  dm integrity: always set version on superblock update
  dm thin metadata: check if in fail_io mode when setting needs_check

1 files changed, 17 insertions, 1 deletions

diff --git a/Documentation/device-mapper/snapshot.rst b/Documentation/device-mapper/snapshot.rst
index 4c53304e72f1..ccdd8b587a74 100644
--- a/Documentation/device-mapper/snapshot.rst
+++ b/Documentation/device-mapper/snapshot.rst
@@ -32,6 +32,7 @@ its visible content unchanged, at least until the <COW device> fills up.
 
 
 -  snapshot <origin> <COW device> <persistent?> <chunksize>
+   [<# feature args> [<arg>]*]
 
 A snapshot of the <origin> block device is created. Changed chunks of
 <chunksize> sectors will be stored on the <COW device>.  Writes will
@@ -54,8 +55,23 @@ When loading or unloading the snapshot target, the corresponding
 snapshot-origin or snapshot-merge target must be suspended. A failure to
 suspend the origin target could result in data corruption.
 
+Optional features:
 
-* snapshot-merge <origin> <COW device> <persistent> <chunksize>
+   discard_zeroes_cow - a discard issued to the snapshot device that
+   maps to entire chunks to will zero the corresponding exception(s) in
+   the snapshot's exception store.
+
+   discard_passdown_origin - a discard to the snapshot device is passed
+   down to the snapshot-origin's underlying device.  This doesn't cause
+   copy-out to the snapshot exception store because the snapshot-origin
+   target is bypassed.
+
+   The discard_passdown_origin feature depends on the discard_zeroes_cow
+   feature being enabled.
+
+
+-  snapshot-merge <origin> <COW device> <persistent> <chunksize>
+   [<# feature args> [<arg>]*]
 
 takes the same table arguments as the snapshot target except it only
 works with persistent snapshots.  This target assumes the role of the