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authorLinus Torvalds <torvalds@linux-foundation.org>2020-06-05 15:45:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-05 15:45:03 -0700
commitb25c6644bfd3affd7d0127ce95c5c96c155a7515 (patch)
tree9ef9c0fe74a08b7baf3a3c3753368b0f481b581f /Documentation
parent818dbde78e0f4f11c9f804c36913a7ccfc2e87ad (diff)
parent64611a15ca9da91ff532982429c44686f4593b5f (diff)
downloadlinux-b25c6644bfd3affd7d0127ce95c5c96c155a7515.tar.bz2
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')
-rw-r--r--Documentation/admin-guide/device-mapper/dm-ebs.rst51
-rw-r--r--Documentation/admin-guide/device-mapper/dm-integrity.rst8
-rw-r--r--Documentation/admin-guide/device-mapper/dm-zoned.rst62
3 files changed, 114 insertions, 7 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
diff --git a/Documentation/admin-guide/device-mapper/dm-integrity.rst b/Documentation/admin-guide/device-mapper/dm-integrity.rst
index 8439d2ae689b..9edd45593abd 100644
--- a/Documentation/admin-guide/device-mapper/dm-integrity.rst
+++ b/Documentation/admin-guide/device-mapper/dm-integrity.rst
@@ -193,6 +193,14 @@ should not be changed when reloading the target because the layout of disk
data depend on them and the reloaded target would be non-functional.
+Status line:
+
+1. the number of integrity mismatches
+2. provided data sectors - that is the number of sectors that the user
+ could use
+3. the current recalculating position (or '-' if we didn't recalculate)
+
+
The layout of the formatted block device:
* reserved sectors
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.