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author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-06-05 15:45:03 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-06-05 15:45:03 -0700 |
commit | b25c6644bfd3affd7d0127ce95c5c96c155a7515 (patch) | |
tree | 9ef9c0fe74a08b7baf3a3c3753368b0f481b581f /Documentation/admin-guide/device-mapper/dm-ebs.rst | |
parent | 818dbde78e0f4f11c9f804c36913a7ccfc2e87ad (diff) | |
parent | 64611a15ca9da91ff532982429c44686f4593b5f (diff) |
Merge tag 'for-5.8/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper updates from Mike Snitzer:
- The largest change for this cycle is the DM zoned target's metadata
version 2 feature that adds support for pairing regular block devices
with a zoned device to ease the performance impact associated with
finite random zones of zoned device.
The changes came in three batches: the first prepared for and then
added the ability to pair a single regular block device, the second
was a batch of fixes to improve zoned's reclaim heuristic, and the
third removed the limitation of only adding a single additional
regular block device to allow many devices.
Testing has shown linear scaling as more devices are added.
- Add new emulated block size (ebs) target that emulates a smaller
logical_block_size than a block device supports
The primary use-case is to emulate "512e" devices that have 512 byte
logical_block_size and 4KB physical_block_size. This is useful to
some legacy applications that otherwise wouldn't be able to be used
on 4K devices because they depend on issuing IO in 512 byte
granularity.
- Add discard interfaces to DM bufio. First consumer of the interface
is the dm-ebs target that makes heavy use of dm-bufio.
- Fix DM crypt's block queue_limits stacking to not truncate
logic_block_size.
- Add Documentation for DM integrity's status line.
- Switch DMDEBUG from a compile time config option to instead use
dynamic debug via pr_debug.
- Fix DM multipath target's hueristic for how it manages
"queue_if_no_path" state internally.
DM multipath now avoids disabling "queue_if_no_path" unless it is
actually needed (e.g. in response to configure timeout or explicit
"fail_if_no_path" message).
This fixes reports of spurious -EIO being reported back to userspace
application during fault tolerance testing with an NVMe backend.
Added various dynamic DMDEBUG messages to assist with debugging
queue_if_no_path in the future.
- Add a new DM multipath "Historical Service Time" Path Selector.
- Fix DM multipath's dm_blk_ioctl() to switch paths on IO error.
- Improve DM writecache target performance by using explicit cache
flushing for target's single-threaded usecase and a small cleanup to
remove unnecessary test in persistent_memory_claim.
- Other small cleanups in DM core, dm-persistent-data, and DM
integrity.
* tag 'for-5.8/dm-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (62 commits)
dm crypt: avoid truncating the logical block size
dm mpath: add DM device name to Failing/Reinstating path log messages
dm mpath: enhance queue_if_no_path debugging
dm mpath: restrict queue_if_no_path state machine
dm mpath: simplify __must_push_back
dm zoned: check superblock location
dm zoned: prefer full zones for reclaim
dm zoned: select reclaim zone based on device index
dm zoned: allocate zone by device index
dm zoned: support arbitrary number of devices
dm zoned: move random and sequential zones into struct dmz_dev
dm zoned: per-device reclaim
dm zoned: add metadata pointer to struct dmz_dev
dm zoned: add device pointer to struct dm_zone
dm zoned: allocate temporary superblock for tertiary devices
dm zoned: convert to xarray
dm zoned: add a 'reserved' zone flag
dm zoned: improve logging messages for reclaim
dm zoned: avoid unnecessary device recalulation for secondary superblock
dm zoned: add debugging message for reading superblocks
...
Diffstat (limited to 'Documentation/admin-guide/device-mapper/dm-ebs.rst')
-rw-r--r-- | Documentation/admin-guide/device-mapper/dm-ebs.rst | 51 |
1 files changed, 51 insertions, 0 deletions
diff --git a/Documentation/admin-guide/device-mapper/dm-ebs.rst b/Documentation/admin-guide/device-mapper/dm-ebs.rst new file mode 100644 index 000000000000..534fa38e8862 --- /dev/null +++ b/Documentation/admin-guide/device-mapper/dm-ebs.rst @@ -0,0 +1,51 @@ +====== +dm-ebs +====== + + +This target is similar to the linear target except that it emulates +a smaller logical block size on a device with a larger logical block +size. Its main purpose is to provide emulation of 512 byte sectors on +devices that do not provide this emulation (i.e. 4K native disks). + +Supported emulated logical block sizes 512, 1024, 2048 and 4096. + +Underlying block size can be set to > 4K to test buffering larger units. + + +Table parameters +---------------- + <dev path> <offset> <emulated sectors> [<underlying sectors>] + +Mandatory parameters: + + <dev path>: + Full pathname to the underlying block-device, + or a "major:minor" device-number. + <offset>: + Starting sector within the device; + has to be a multiple of <emulated sectors>. + <emulated sectors>: + Number of sectors defining the logical block size to be emulated; + 1, 2, 4, 8 sectors of 512 bytes supported. + +Optional parameter: + + <underyling sectors>: + Number of sectors defining the logical block size of <dev path>. + 2^N supported, e.g. 8 = emulate 8 sectors of 512 bytes = 4KiB. + If not provided, the logical block size of <dev path> will be used. + + +Examples: + +Emulate 1 sector = 512 bytes logical block size on /dev/sda starting at +offset 1024 sectors with underlying devices block size automatically set: + +ebs /dev/sda 1024 1 + +Emulate 2 sector = 1KiB logical block size on /dev/sda starting at +offset 128 sectors, enforce 2KiB underlying device block size. +This presumes 2KiB logical blocksize on /dev/sda or less to work: + +ebs /dev/sda 128 2 4 |