linux-toradex.git/Documentation/device-mapper, branch v4.20-rc6

Merge tag 'docs-4.20' of git://git.lwn.net/linux

2018-10-24T17:01:11+00:00

Pull documentation updates from Jonathan Corbet:
 "This is a fairly typical cycle for documentation. There's some welcome
  readability improvements for the formatted output, some LICENSES
  updates including the addition of the ISC license, the removal of the
  unloved and unmaintained 00-INDEX files, the deprecated APIs document
  from Kees, more MM docs from Mike Rapoport, and the usual pile of typo
  fixes and corrections"

* tag 'docs-4.20' of git://git.lwn.net/linux: (41 commits)
  docs: Fix typos in histogram.rst
  docs: Introduce deprecated APIs list
  kernel-doc: fix declaration type determination
  doc: fix a typo in adding-syscalls.rst
  docs/admin-guide: memory-hotplug: remove table of contents
  doc: printk-formats: Remove bogus kobject references for device nodes
  Documentation: preempt-locking: Use better example
  dm flakey: Document "error_writes" feature
  docs/completion.txt: Fix a couple of punctuation nits
  LICENSES: Add ISC license text
  LICENSES: Add note to CDDL-1.0 license that it should not be used
  docs/core-api: memory-hotplug: add some details about locking internals
  docs/core-api: rename memory-hotplug-notifier to memory-hotplug
  docs: improve readability for people with poorer eyesight
  yama: clarify ptrace_scope=2 in Yama documentation
  docs/vm: split memory hotplug notifier description to Documentation/core-api
  docs: move memory hotplug description into admin-guide/mm
  doc: Fix acronym "FEKEK" in ecryptfs
  docs: fix some broken documentation references
  iommu: Fix passthrough option documentation
  ...

dm flakey: Document "error_writes" feature

2018-10-12T17:31:39+00:00

Commit ef548c551e72 ("dm flakey: introduce "error_writes" feature")
added the ability to dm flakey to error out writes in contrast to
silently dropping it with 'drop_writes'. Unfortunately this feature
is not currently documented and one has to be either familiar with the
source code of dm flakey or check out xfstests sources to know of
this parameter. So document it.

Signed-off-by: Nikolay Borisov 
Signed-off-by: Jonathan Corbet

block: Finish renaming REQ_DISCARD into REQ_OP_DISCARD

2018-10-03T22:12:28+00:00

Some time ago REQ_DISCARD was renamed into REQ_OP_DISCARD. Some comments
and documentation files were not updated however. Update these comments
and documentation files. See also commit 4e1b2d52a80d ("block, fs,
drivers: remove REQ_OP compat defs and related code").

Signed-off-by: Bart Van Assche 
Cc: Mike Christie 
Cc: Martin K. Petersen 
Cc: Philipp Reisner 
Cc: Lars Ellenberg 
Signed-off-by: Jens Axboe

dm raid: bump target version, update comments and documentation

2018-09-06T21:07:58+00:00

Bump target version to reflect the documented fixes are available.
Also fix some code comments (typos and clarity).

Signed-off-by: Heinz Mauelshagen 
Signed-off-by: Mike Snitzer

dm thin: include metadata_low_watermark threshold in pool status

2018-07-30T15:49:08+00:00

The metadata low watermark threshold is set by the kernel.  But the
kernel depends on userspace to extend the thinpool metadata device when
the threshold is crossed.

Since the metadata low watermark threshold is not visible to userspace,
upon receiving an event, userspace cannot tell that the kernel wants the
metadata device extended, instead of some other eventing condition.
Making it visible (but not settable) enables userspace to affirmatively
know the kernel is asking for a metadata device extension, by comparing
metadata_low_watermark against nr_free_blocks_metadata, also reported in
status.

Current solutions like dmeventd have their own thresholds for extending
the data and metadata devices, and both devices are checked against
their thresholds on each event.  This lessens the value of the kernel-set
threshold, since userspace will either extend the metadata device sooner,
when receiving another event; or will receive the metadata lowater event
and do nothing, if dmeventd's threshold is less than the kernel's.
(This second case is dangerous. The metadata lowater event will not be
re-sent, so no further event will be generated before the metadata
device is out if space, unless some other event causes userspace to
recheck its thresholds.)

Signed-off-by: Andy Grover 
Signed-off-by: Mike Snitzer

dm integrity: recalculate checksums on creation

2018-07-27T19:24:27+00:00

When using external metadata device and internal hash, recalculate the
checksums when the device is created - so that dm-integrity doesn't
have to overwrite the device.  The superblock stores the last position
when the recalculation ended, so that it is properly restarted.

Integrity tags that haven't been recalculated yet are ignored.

Also bump the target version.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer

dm delay: add flush as a third class of IO

2018-07-27T19:24:19+00:00

Add a new class for dm-delay that delays flush requests.  Previously,
flushes were delayed as writes, but it caused problems if the user
needed to create a device with one or a few slow sectors for the purpose
of testing - all flushes would be forwarded to this device and delayed,
and that skews the test results.  Fix this by allowing to select 0 delay
for flushes.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer

dm thin: update stale "Status" Documentation

2018-07-27T19:24:03+00:00

Documentation/device-mapper-/thin-provisioning.txt's "Status" section no
longer reflected the current fitness level of DM thin-provisioning.
That is, DM thinp is no longer "EXPERIMENTAL".  It has since seen
considerable improvement, has been fairly widely deployed and has
performed in a robust manner.

Update Documentation to dispel concern raised by potential DM thinp
users.

Reported-by: Drew Hastings 
Signed-off-by: Mike Snitzer

dm writecache: support optional offset for start of device

2018-07-02T20:14:02+00:00

Add an optional parameter "start_sector" to allow the start of the
device to be offset by the specified number of 512-byte sectors.  The
sectors below this offset are not used by the writecache device and are
left to be used for disk labels and/or userspace metadata (e.g. lvm).

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer

dm: add writecache target

2018-06-08T15:59:51+00:00

The writecache target caches writes on persistent memory or SSD.
It is intended for databases or other programs that need extremely low
commit latency.

The writecache target doesn't cache reads because reads are supposed to
be cached in page cache in normal RAM.

If persistent memory isn't available this target can still be used in
SSD mode.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Colin Ian King  # fix missing goto
Signed-off-by: Ross Zwisler  # fix compilation issue with !DAX
Signed-off-by: Dan Carpenter  # use msecs_to_jiffies
Acked-by: Dan Williams  # reworks to unify ARM and x86 flushing
Signed-off-by: Mike Snitzer