Merge tag 'for-5.14/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm

Pull device mapper updates from Mike Snitzer:

 - Various DM persistent-data library improvements and fixes that
   benefit both the DM thinp and cache targets.

 - A few small DM kcopyd efficiency improvements.

 - Significant zoned related block core, DM core and DM zoned target
   changes that culminate with adding zoned append emulation (which is
   required to properly fix DM crypt's zoned support).

 - Various DM writecache target changes that improve efficiency. Adds an
   optional "metadata_only" feature that only promotes bios flagged with
   REQ_META. But the most significant improvement is writecache's
   ability to pause writeback, for a confiurable time, if/when the
   working set is larger than the cache (and the cache is full) -- this
   ensures performance is no worse than the slower origin device.

* tag 'for-5.14/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (35 commits)
  dm writecache: make writeback pause configurable
  dm writecache: pause writeback if cache full and origin being written directly
  dm io tracker: factor out IO tracker
  dm btree remove: assign new_root only when removal succeeds
  dm zone: fix dm_revalidate_zones() memory allocation
  dm ps io affinity: remove redundant continue statement
  dm writecache: add optional "metadata_only" parameter
  dm writecache: add "cleaner" and "max_age" to Documentation
  dm writecache: write at least 4k when committing
  dm writecache: flush origin device when writing and cache is full
  dm writecache: have ssd writeback wait if the kcopyd workqueue is busy
  dm writecache: use list_move instead of list_del/list_add in writecache_writeback()
  dm writecache: commit just one block, not a full page
  dm writecache: remove unused gfp_t argument from wc_add_block()
  dm crypt: Fix zoned block device support
  dm: introduce zone append emulation
  dm: rearrange core declarations for extended use from dm-zone.c
  block: introduce BIO_ZONE_WRITE_LOCKED bio flag
  block: introduce bio zone helpers
  block: improve handling of all zones reset operation
  ...

1 files changed, 23 insertions, 2 deletions

diff --git a/Documentation/admin-guide/device-mapper/writecache.rst b/Documentation/admin-guide/device-mapper/writecache.rst
index dce0184e07ca..65427d8dfca6 100644
--- a/Documentation/admin-guide/device-mapper/writecache.rst
+++ b/Documentation/admin-guide/device-mapper/writecache.rst
@@ -12,7 +12,6 @@ first sector should contain valid superblock from previous invocation.
 Constructor parameters:
 
 1. type of the cache device - "p" or "s"
-
 	- p - persistent memory
 	- s - SSD
 2. the underlying device that will be cached
@@ -21,7 +20,6 @@ Constructor parameters:
    size)
 5. the number of optional parameters (the parameters with an argument
    count as two)
-
 	start_sector n		(default: 0)
 		offset from the start of cache device in 512-byte sectors
 	high_watermark n	(default: 50)
@@ -53,6 +51,27 @@ Constructor parameters:
 
 		- some underlying devices perform better with fua, some
 		  with nofua. The user should test it
+	cleaner
+		when this option is activated (either in the constructor
+		arguments or by a message), the cache will not promote
+		new writes (however, writes to already cached blocks are
+		promoted, to avoid data corruption due to misordered
+		writes) and it will gradually writeback any cached
+		data. The userspace can then monitor the cleaning
+		process with "dmsetup status". When the number of cached
+		blocks drops to zero, userspace can unload the
+		dm-writecache target and replace it with dm-linear or
+		other targets.
+	max_age n
+		specifies the maximum age of a block in milliseconds. If
+		a block is stored in the cache for too long, it will be
+		written to the underlying device and cleaned up.
+	metadata_only
+		only metadata is promoted to the cache. This option
+		improves performance for heavier REQ_META workloads.
+	pause_writeback n	(default: 3000)
+		pause writeback if there was some write I/O redirected to
+		the origin volume in the last n milliseconds
 
 Status:
 1. error indicator - 0 if there was no error, otherwise error number
@@ -77,3 +96,5 @@ Messages:
 		5. resume the device, so that it will use the linear
 		   target
 		6. the cache device is now inactive and it can be deleted
+	cleaner
+		See above "cleaner" constructor documentation.