diff options
author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-06-05 15:45:03 -0700 |
---|---|---|
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-zoned.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-zoned.rst')
-rw-r--r-- | Documentation/admin-guide/device-mapper/dm-zoned.rst | 62 |
1 files changed, 55 insertions, 7 deletions
diff --git a/Documentation/admin-guide/device-mapper/dm-zoned.rst b/Documentation/admin-guide/device-mapper/dm-zoned.rst index 07f56ebc1730..553752ea2521 100644 --- a/Documentation/admin-guide/device-mapper/dm-zoned.rst +++ b/Documentation/admin-guide/device-mapper/dm-zoned.rst @@ -37,9 +37,13 @@ Algorithm dm-zoned implements an on-disk buffering scheme to handle non-sequential write accesses to the sequential zones of a zoned block device. Conventional zones are used for caching as well as for storing internal -metadata. +metadata. It can also use a regular block device together with the zoned +block device; in that case the regular block device will be split logically +in zones with the same size as the zoned block device. These zones will be +placed in front of the zones from the zoned block device and will be handled +just like conventional zones. -The zones of the device are separated into 2 types: +The zones of the device(s) are separated into 2 types: 1) Metadata zones: these are conventional zones used to store metadata. Metadata zones are not reported as useable capacity to the user. @@ -127,6 +131,13 @@ resumed. Flushing metadata thus only temporarily delays write and discard requests. Read requests can be processed concurrently while metadata flush is being executed. +If a regular device is used in conjunction with the zoned block device, +a third set of metadata (without the zone bitmaps) is written to the +start of the zoned block device. This metadata has a generation counter of +'0' and will never be updated during normal operation; it just serves for +identification purposes. The first and second copy of the metadata +are located at the start of the regular block device. + Usage ===== @@ -138,9 +149,46 @@ Ex:: dmzadm --format /dev/sdxx -For a formatted device, the target can be created normally with the -dmsetup utility. The only parameter that dm-zoned requires is the -underlying zoned block device name. Ex:: - echo "0 `blockdev --getsize ${dev}` zoned ${dev}" | \ - dmsetup create dmz-`basename ${dev}` +If two drives are to be used, both devices must be specified, with the +regular block device as the first device. + +Ex:: + + dmzadm --format /dev/sdxx /dev/sdyy + + +Fomatted device(s) can be started with the dmzadm utility, too.: + +Ex:: + + dmzadm --start /dev/sdxx /dev/sdyy + + +Information about the internal layout and current usage of the zones can +be obtained with the 'status' callback from dmsetup: + +Ex:: + + dmsetup status /dev/dm-X + +will return a line + + 0 <size> zoned <nr_zones> zones <nr_unmap_rnd>/<nr_rnd> random <nr_unmap_seq>/<nr_seq> sequential + +where <nr_zones> is the total number of zones, <nr_unmap_rnd> is the number +of unmapped (ie free) random zones, <nr_rnd> the total number of zones, +<nr_unmap_seq> the number of unmapped sequential zones, and <nr_seq> the +total number of sequential zones. + +Normally the reclaim process will be started once there are less than 50 +percent free random zones. In order to start the reclaim process manually +even before reaching this threshold the 'dmsetup message' function can be +used: + +Ex:: + + dmsetup message /dev/dm-X 0 reclaim + +will start the reclaim process and random zones will be moved to sequential +zones. |