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2018-01-30dm cache: Documentation: update default migration_throttling valueJohn Pittman1-1/+1
In commit f8350daf7af0 ("dm cache: tune migration throttling") the value for DEFAULT_MIGRATION_THRESHOLD was decreased from 204800 to 2048. Edit device-mapper/cache.txt to reflect the correct default value for migration_threshold. Signed-off-by: John Pittman <jpittman@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2018-01-17dm cache: be consistent in specifying sectors and SI units in cache.txtmulhern1-2/+2
Signed-off-by: mulhern <amulhern@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2018-01-17dm cache: delete obsoleted paragraph in cache.txtmulhern1-5/+0
The 'mq' policy is no longer the default policy, and the default policy, 'smq', does not store hit counts. Signed-off-by: mulhern <amulhern@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2017-03-19Documentation: device-mapper: cache.txt: Fix typossayli karnik1-1/+1
Fix a spelling error (hexidecimal->hexadecimal). Signed-off-by: sayli karnik <karniksayli1995@gmail.com> Signed-off-by: Jonathan Corbet <corbet@lwn.net>
2017-02-16dm cache metadata: add "metadata2" featureJoe Thornber1-0/+4
If "metadata2" is provided as a table argument when creating/loading a cache target a more compact metadata format, with separate dirty bits, is used. "metadata2" improves speed of shutting down a cache target. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2015-07-16dm cache: display 'needs_check' in status if it is setMike Snitzer1-0/+6
There is currently no way to see that the needs_check flag has been set in the metadata. Display 'needs_check' in the cache status if it is set in the cache metadata. Also, update cache documentation. Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2015-06-11dm cache: add fail io mode and needs_check flagJoe Thornber1-2/+7
If a cache metadata operation fails (e.g. transaction commit) the cache's metadata device will abort the current transaction, set a new needs_check flag, and the cache will transition to "read-only" mode. If aborting the transaction or setting the needs_check flag fails the cache will transition to "fail-io" mode. Once needs_check is set the cache device will not be allowed to activate. Activation requires write access to metadata. Future work is needed to add proper support for running the cache in read-only mode. Once in fail-io mode the cache will report a status of "Fail". Also, add commit() wrapper that will disallow commits if in read_only or fail mode. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2014-03-05dm thin: ensure user takes action to validate data and metadata consistencyMike Snitzer1-6/+5
If a thin metadata operation fails the current transaction will abort, whereby causing potential for IO layers up the stack (e.g. filesystems) to have data loss. As such, set THIN_METADATA_NEEDS_CHECK_FLAG in the thin metadata's superblock which: 1) requires the user verify the thin metadata is consistent (e.g. use thin_check, etc) 2) suggests the user verify the thin data is consistent (e.g. use fsck) The only way to clear the superblock's THIN_METADATA_NEEDS_CHECK_FLAG is to run thin_repair. On metadata operation failure: abort current metadata transaction, set pool in read-only mode, and now set the needs_check flag. As part of this change, constraints are introduced or relaxed: * don't allow a pool to transition to write mode if needs_check is set * don't allow data or metadata space to be resized if needs_check is set * if a thin pool's metadata space is exhausted: the kernel will now force the user to take the pool offline for repair before the kernel will allow the metadata space to be extended. Also, update Documentation to include information about when the thin provisioning target commits metadata, how it handles metadata failures and running out of space. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Joe Thornber <ejt@redhat.com>
2014-01-16dm cache: add policy name to status outputMike Snitzer1-1/+2
The cache's policy may have been established using the "default" alias, which is currently the "mq" policy but the default policy may change in the future. It is useful to know exactly which policy is being used. Add a 'real' member to the dm_cache_policy_type structure and have the "default" dm_cache_policy_type point to the real "mq" dm_cache_policy_type. Update dm_cache_policy_get_name() to check if real is set, if so report the name of the real policy (not the alias). Requested-by: Jonathan Brassow <jbrassow@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2014-01-10dm cache: add block sizes and total cache blocks to status outputMike Snitzer1-22/+28
Improve cache_status to emit: <metadata block size> <#used metadata blocks>/<#total metadata blocks> <cache block size> <#used cache blocks>/<#total cache blocks> ... Adding the block sizes allows for easier calculation of the overall size of both the metadata and cache devices. Adding <#total cache blocks> provides useful context for how much of the cache is used. Unfortunately these additions to the status will require updates to users' scripts that monitor the cache status. But these changes help provide more comprehensive information about the cache device and will simplify tools that are being developed to manage dm-cache devices -- because they won't need to issue 3 operations to cobble together the information that we can easily provide via a single status ioctl. While updating the status documentation in cache.txt spaces were tabify'd. Requested-by: Jonathan Brassow <jbrassow@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Acked-by: Joe Thornber <ejt@redhat.com>
2013-12-10dm cache: update Documentation for invalidate_cblocks's range syntaxMike Snitzer1-4/+6
The cache target's invalidate_cblocks message allows cache block (cblock) ranges to be expressed with: <cblock start>-<cblock end> The range's <cblock end> value is "one past the end", so the range includes <cblock start> through <cblock end>-1. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Acked-by: Joe Thornber <ejt@redhat.com>
2013-11-12dm cache: resolve small nits and improve DocumentationMike Snitzer1-10/+32
Document passthrough mode, cache shrinking, and cache invalidation. Also, use strcasecmp() and hlist_unhashed(). Reported-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2013-11-11dm cache: add cache block invalidation supportJoe Thornber1-1/+11
Cache block invalidation is removing an entry from the cache without writing it back. Cache blocks can be invalidated via the 'invalidate_cblocks' message, which takes an arbitrary number of cblock ranges: invalidate_cblocks [<cblock>|<cblock begin>-<cblock end>]* E.g. dmsetup message my_cache 0 invalidate_cblocks 2345 3456-4567 5678-6789 Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2013-11-11dm cache: add passthrough modeJoe Thornber1-3/+16
"Passthrough" is a dm-cache operating mode (like writethrough or writeback) which is intended to be used when the cache contents are not known to be coherent with the origin device. It behaves as follows: * All reads are served from the origin device (all reads miss the cache) * All writes are forwarded to the origin device; additionally, write hits cause cache block invalidates This mode decouples cache coherency checks from cache device creation, largely to avoid having to perform coherency checks while booting. Boot scripts can create cache devices in passthrough mode and put them into service (mount cached filesystems, for example) without having to worry about coherency. Coherency that exists is maintained, although the cache will gradually cool as writes take place. Later, applications can perform coherency checks, the nature of which will depend on the type of the underlying storage. If coherency can be verified, the cache device can be transitioned to writethrough or writeback mode while still warm; otherwise, the cache contents can be discarded prior to transitioning to the desired operating mode. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com> Signed-off-by: Morgan Mears <Morgan.Mears@netapp.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2013-08-23dm cache: add data block size limits to code and DocumentationMike Snitzer1-1/+2
Place upper bound on the cache's data block size (1GB). Inform users that the data block size can't be any arbitrary number, i.e. its value must be between 32KB and 1GB. Also, it should be a multiple of 32KB. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Acked-by: Joe Thornber <ejt@redhat.com>
2013-08-23dm cache: document metadata device is exclussive to a cacheMike Snitzer1-1/+2
A cache's metadata device may not be shared by multiple cache devices. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Acked-by: Joe Thornber <ejt@redhat.com>
2013-05-28doc: fix misspellings with 'codespell' toolAnatol Pomozov1-1/+1
Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
2013-03-01dm: add cache targetJoe Thornber1-0/+243
Add a target that allows a fast device such as an SSD to be used as a cache for a slower device such as a disk. A plug-in architecture was chosen so that the decisions about which data to migrate and when are delegated to interchangeable tunable policy modules. The first general purpose module we have developed, called "mq" (multiqueue), follows in the next patch. Other modules are under development. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Heinz Mauelshagen <mauelshagen@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
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