linux/Documentation/device-mapper, branch v5.2

dm integrity: add a bitmap mode

2019-05-08T17:41:58Z

Introduce an alternate mode of operation where dm-integrity uses a bitmap instead of a journal. If a bit in the bitmap is 1, the corresponding region's data and integrity tags are not synchronized - if the machine crashes, the unsynchronized regions will be recalculated. The bitmap mode is faster than the journal mode, because we don't have to write the data twice, but it is also less reliable, because if data corruption happens when the machine crashes, it may not be detected. Benchmark results for an SSD connected to a SATA300 port, when doing large linear writes with dd: buffered I/O: raw device throughput - 245MB/s dm-integrity with journaling - 120MB/s dm-integrity with bitmap - 238MB/s direct I/O with 1MB block size: raw device throughput - 248MB/s dm-integrity with journaling - 123MB/s dm-integrity with bitmap - 223MB/s For more info see dm-integrity in Documentation/device-mapper/ Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm integrity: update documentation

2019-05-07T20:05:10Z

Update documentation with the "meta_device" parameter and flags. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm: add dust target

2019-04-30T20:37:19Z

Add the dm-dust target, which simulates the behavior of bad sectors at arbitrary locations, and the ability to enable the emulation of the read failures at an arbitrary time. This target behaves similarly to a linear target. At a given time, the user can send a message to the target to start failing read requests on specific blocks. When the failure behavior is enabled, reads of blocks configured "bad" will fail with EIO. Writes of blocks configured "bad" will result in the following: 1. Remove the block from the "bad block list". 2. Successfully complete the write. After this point, the block will successfully contain the written data, and will service reads and writes normally. This emulates the behavior of a "remapped sector" on a hard disk drive. dm-dust provides logging of which blocks have been added or removed to the "bad block list", as well as logging when a block has been removed from the bad block list. These messages can be used alongside the messages from the driver using a dm-dust device to analyze the driver's behavior when a read fails at a given time. (This logging can be reduced via a "quiet" mode, if desired.) NOTE: If the block size is larger than 512 bytes, only the first sector of each "dust block" is detected. Placing a limiting layer above a dust target, to limit the minimum I/O size to the dust block size, will ensure proper emulation of the given large block size. Signed-off-by: Bryan Gurney Co-developed-by: Joe Shimkus Co-developed-by: John Dorminy Co-developed-by: John Pittman Co-developed-by: Thomas Jaskiewicz Signed-off-by: Mike Snitzer

dm cache: add support for discard passdown to the origin device

2019-03-05T19:53:52Z

DM cache now defaults to passing discards down to the origin device. User may disable this using the "no_discard_passdown" feature when creating the cache device. If the cache's underlying origin device doesn't support discards then passdown is disabled (with warning). Similarly, if the underlying origin device's max_discard_sectors is less than a cache block discard passdown will be disabled (this is required because sizing of the cache internal discard bitset depends on it). Signed-off-by: Mike Snitzer

dm: add support to directly boot to a mapped device

2019-03-05T19:53:50Z

Add a "create" module parameter, which allows device-mapper targets to be configured at boot time. This enables early use of DM targets in the boot process (as the root device or otherwise) without the need of an initramfs. The syntax used in the boot param is based on the concise format from the dmsetup tool to follow the rule of least surprise: dmsetup table --concise /dev/mapper/lroot Which is: dm-mod.create=,,,,[,

+][;,,,,

+]+] Where, ::= The device name. ::= xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx | "" ::= The device minor number | "" ::= "ro" | "rw"

::= ::= "verity" | "linear" | ... For example, the following could be added in the boot parameters: dm-mod.create="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0 Only the targets that were tested are allowed and the ones that don't change any block device when the device is create as read-only. For example, mirror and cache targets are not allowed. The rationale behind this is that if the user makes a mistake, choosing the wrong device to be the mirror or the cache can corrupt data. The only targets initially allowed are: * crypt * delay * linear * snapshot-origin * striped * verity Co-developed-by: Will Drewry Co-developed-by: Kees Cook Co-developed-by: Enric Balletbo i Serra Signed-off-by: Helen Koike Reviewed-by: Kees Cook Signed-off-by: Mike Snitzer

Documentation: Use "while" instead of "whilst"

2018-11-20T16:30:43Z

Whilst making an unrelated change to some Documentation, Linus sayeth: | Afaik, even in Britain, "whilst" is unusual and considered more | formal, and "while" is the common word. | | [...] | | Can we just admit that we work with computers, and we don't need to | use þe eald Englisc spelling of words that most of the world never | uses? dictionary.com refers to the word as "Chiefly British", which is probably an undesirable attribute for technical documentation. Replace all occurrences under Documentation/ with "while". Cc: David Howells Cc: Liam Girdwood Cc: Chris Wilson Cc: Michael Halcrow Cc: Jonathan Corbet Reported-by: Linus Torvalds Signed-off-by: Will Deacon Signed-off-by: Jonathan Corbet

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

2018-10-24T17:01:11Z

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

2018-10-12T17:31:39Z

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

2018-10-03T22:12:28Z

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

2018-09-06T21:07:58Z

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