summaryrefslogtreecommitdiffstats
path: root/drivers/md/dm-thin-metadata.c (follow)
Commit message (Collapse)AuthorAgeFilesLines
* dm persistent data: eliminate unnecessary return valuesMikulas Patocka2015-11-011-4/+12
| | | | | | | | | | | dm_bm_unlock and dm_tm_unlock return an integer value but the returned value is always 0. The calling code sometimes checks the return value and sometimes doesn't. Eliminate these unnecessary return values and also the checks for them. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
* dm thin metadata: delete btrees when releasing metadata snapshotJoe Thornber2015-08-121-2/+2
| | | | | | | | | The device details and mapping trees were just being decremented before. Now btree_del() is called to do a deep delete. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org
* dm thin metadata: fix a race when entering fail modeJoe Thornber2015-06-111-3/+4
| | | | | | | | | In dm_thin_find_block() the ->fail_io flag was checked outside the metadata device's root_lock, causing dm_thin_find_block() to race with the setting of this flag. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
* dm thin metadata: add dm_thin_remove_range()Joe Thornber2015-06-111-0/+54
| | | | | | | Removes a range of blocks from the btree. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
* dm thin metadata: add dm_thin_find_mapped_range()Joe Thornber2015-06-111-0/+57
| | | | | | | | Retrieve the next run of contiguously mapped blocks. Useful for working out where to break up IO. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
* dm thin metadata: remove in-core 'read_only' flagMike Snitzer2015-05-291-5/+1
| | | | | | | Leverage the block manager's read_only flag instead of duplicating it; access with new dm_bm_is_read_only() method. Signed-off-by: Mike Snitzer <snitzer@redhat.com>
* dm thin metadata: remove unused dm_pool_get_data_block_size()Rickard Strandqvist2015-02-091-9/+0
| | | | | | | | | | | The thin-pool target doesn't display the data block size as part of its table status, unlike the dm-cache target, so there is no need for dm_pool_get_data_block_size(). This was found using cppcheck. Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
* dm thin: prefetch missing metadata pagesJoe Thornber2014-11-101-0/+5
| | | | | | | | Prefetch metadata at the start of the worker thread and then again every 128th bio processed from the deferred list. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
* dm thin metadata: change dm_thin_find_block to allow blocking, but not ↵Joe Thornber2014-11-101-17/+13
| | | | | | | | | issuing, IO This change is a prerequisite for allowing metadata to be prefetched. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
* dm thin metadata: do not allow the data block size to changeMike Snitzer2014-07-151-0/+9
| | | | | | | | | | | | | | | | | | | | | | | | | The block size for the thin-pool's data device must remained fixed for the life of the thin-pool. Disallow any attempt to change the thin-pool's data block size. It should be noted that attempting to change the data block size via thin-pool table reload will be ignored as a side-effect of the thin-pool handover that the thin-pool target does during thin-pool table reload. Here is an example outcome of attempting to load a thin-pool table that reduced the thin-pool's data block size from 1024K to 512K. Before: kernel: device-mapper: thin: 253:4: growing the data device from 204800 to 409600 blocks After: kernel: device-mapper: thin metadata: changing the data block size (from 2048 to 1024) is not supported kernel: device-mapper: table: 253:4: thin-pool: Error creating metadata object kernel: device-mapper: ioctl: error adding target to table Signed-off-by: Mike Snitzer <snitzer@redhat.com> Acked-by: Joe Thornber <ejt@redhat.com> Cc: stable@vger.kernel.org
* dm: take care to copy the space map roots before locking the superblockJoe Thornber2014-03-271-33/+47
| | | | | | | | | | | | In theory copying the space map root can fail, but in practice it never does because we're careful to check what size buffer is needed. But make certain we're able to copy the space map roots before locking the superblock. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org # drop dm-era and dm-cache changes as needed
* dm thin: ensure user takes action to validate data and metadata consistencyMike Snitzer2014-03-051-1/+36
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 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>
* dm thin: allow metadata space larger than supported to go unusedMike Snitzer2014-02-271-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It was always intended that a user could provide a thin metadata device that is larger than the max supported by the on-disk format. The extra space would just go unused. Unfortunately that never worked. If the user attempted to use a larger metadata device on creation they would get an error like the following: device-mapper: space map common: space map too large device-mapper: transaction manager: couldn't create metadata space map device-mapper: thin metadata: tm_create_with_sm failed device-mapper: table: 252:17: thin-pool: Error creating metadata object device-mapper: ioctl: error adding target to table Fix this by allowing the initial metadata space map creation to cap its size at the max number of blocks supported (DM_SM_METADATA_MAX_BLOCKS). get_metadata_dev_size() must also impose DM_SM_METADATA_MAX_BLOCKS (via THIN_METADATA_MAX_SECTORS), otherwise extending metadata would cap at THIN_METADATA_MAX_SECTORS_WARNING (which is larger than supported). Also, the calculation for THIN_METADATA_MAX_SECTORS didn't account for the sizeof the disk_bitmap_header. So the supported maximum metadata size is a bit smaller (reduced from 33423360 to 33292800 sectors). Lastly, remove the "excess space will not be used" warning message from get_metadata_dev_size(); it resulted in printing the warning multiple times. Factor out warn_if_metadata_device_too_big(), call it from pool_ctr() and maybe_resize_metadata_dev(). Signed-off-by: Mike Snitzer <snitzer@redhat.com> Acked-by: Joe Thornber <ejt@redhat.com>
* dm thin: avoid metadata commit if a pool's thin devices haven't changedMike Snitzer2014-02-171-0/+17
| | | | | | | | | | | | | | Commit 905e51b ("dm thin: commit outstanding data every second") introduced a periodic commit. This commit occurs regardless of whether any thin devices have made changes. Fix the periodic commit to check if any of a pool's thin devices have changed using dm_pool_changed_this_transaction(). Reported-by: Alexander Larsson <alexl@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Acked-by: Joe Thornber <ejt@redhat.com> Cc: stable@vger.kernel.org
* dm thin: fix discard support to a previously shared blockJoe Thornber2014-01-071-0/+20
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If a snapshot is created and later deleted the origin dm_thin_device's snapshotted_time will have been updated to reflect the snapshot's creation time. The 'shared' flag in the dm_thin_lookup_result struct returned from dm_thin_find_block() is an approximation based on snapshotted_time -- this is done to avoid 0(n), or worse, time complexity. In this case, the shared flag would be true. But because the 'shared' flag reflects an approximation a block can be incorrectly assumed to be shared (e.g. false positive for 'shared' because the snapshot no longer exists). This could result in discards issued to a thin device not being passed down to the pool's underlying data device. To fix this we double check that a thin block is really still in-use after a mapping is removed using dm_pool_block_is_used(). If the reference count for a block is now zero the discard is allowed to be passed down. Also add a 'definitely_not_shared' member to the dm_thin_new_mapping structure -- reflects that the 'shared' flag in the response from dm_thin_find_block() can only be held as definitive if false is returned. Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1043527 Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org
* dm thin: allow pool in read-only mode to transition to read-write modeJoe Thornber2013-12-101-0/+8
| | | | | | | | | | | | A thin-pool may be in read-only mode because the pool's data or metadata space was exhausted. To allow for recovery, by adding more space to the pool, we must allow a pool to transition from PM_READ_ONLY to PM_WRITE mode. Otherwise, running out of space will render the pool permanently read-only. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org
* dm thin: generate event when metadata threshold passedJoe Thornber2013-05-101-0/+14
| | | | | | | | | | | Generate a dm event when the amount of remaining thin pool metadata space falls below a certain level. The threshold is taken to be a quarter of the size of the metadata device with a minimum threshold of 4MB. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin: detect metadata device resizingJoe Thornber2013-05-101-0/+12
| | | | | | | | | | | Allow the dm thin pool metadata device to be extended. Whenever a pool is resumed, detect whether the size of the metadata device has increased, and if so, extend the metadata to use the new space. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin: refactor data dev resizeJoe Thornber2013-05-101-5/+5
| | | | | | | | Refactor device size functions in preparation for similar metadata device resizing functions. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm persistent data: set some btree fn parms constMike Snitzer2013-03-011-6/+6
| | | | | | | Mark some constant parameters constant in some dm-btree functions. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm persistent data: fix nested btree deletionJoe Thornber2012-12-211-1/+1
| | | | | | | | | | | When deleting nested btrees, the code forgets to delete the innermost btree. The thin-metadata code serendipitously compensates for this by claiming there is one extra layer in the tree. This patch corrects both problems. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: introduce dm_pool_abort_metadataJoe Thornber2012-07-271-61/+146
| | | | | | | | | | | | | | | | Introduce dm_pool_abort_metadata to abort the current metadata transaction. Generally this will only be called when bad things are happening and dm-thin is trying to roll back to a good state for read-only mode. It's complicated by the fact that the metadata device may have failed completely causing the abort to be unable to read the old transaction. In this case the metadata object is placed in a 'fail' mode and everything fails apart from destroying it. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: introduce dm_pool_metadata_set_read_onlyJoe Thornber2012-07-271-4/+16
| | | | | | | | | Introduce dm_pool_metadata_set_read_only to put the underlying block manager into read-only mode. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: add dm_thin_changed_this_transactionJoe Thornber2012-07-271-3/+13
| | | | | | | | | | Introduce dm_thin_changed_this_transaction to dm-thin-metadata to publish a useful bit of information we're already tracking. This will help dm thin decide when to commit. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: add format option to dm_pool_metadata_openJoe Thornber2012-07-271-8/+9
| | | | | | | | | Add a parameter to dm_pool_metadata_open to indicate whether or not an unformatted metadata area should be formatted. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: tidy up open and format error pathsJoe Thornber2012-07-271-22/+21
| | | | | | | | Tidy up error path in __open_metadata and __format_metadata in dm-thin-metadata. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: only check incompat features on openMike Snitzer2012-07-271-26/+36
| | | | | | | | | Factor out __check_incompat_features and only call it once when we open the metadata device rather than at the beginning of every transaction. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: remove duplicate pmd initialisationJoe Thornber2012-07-271-5/+0
| | | | | | | | | | | | Remove some duplicate initialisation of struct dm_pool_metadata. These pmd fields are initialised by both: __format_metadata's calls to dm_btree_empty __write_initial_superblock + __begin_transaction Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: remove create parameter from __create_persistent_data_objectsJoe Thornber2012-07-271-10/+7
| | | | | | | | Remove 'create' parameter from __create_persistent_data_objects() in dm-thin-metadata. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: move __superblock_all_zeroes to __open_or_format_metadataJoe Thornber2012-07-271-9/+9
| | | | | | | | | | Move the check for __superblock_all_zeroes from __create_persistent_data_objects() down to __open_or_format_metadata in dm-thin-metadata. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: remove nr_blocks arg from __create_persistent_data_objectsJoe Thornber2012-07-271-7/+7
| | | | | | | | | Remove nr_blocks arg from __create_persistent_data_objects in dm-thin-metadata. It was always passed as zero. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: split __open or format metadataJoe Thornber2012-07-271-50/+74
| | | | | | | | | Split __open_or_format_metadata into __format_metadata and __open_metadata in dm-thin-metadata. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: use struct dm_pool_metadata members in ↵Joe Thornber2012-07-271-23/+17
| | | | | | | | | | | __open_or_format_metadata Clean up __open_or_format_metadata in dm-thin-metadata by using struct dm_pool_metadata members to replace local variables. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: zero unused superblock uuidJoe Thornber2012-07-271-0/+1
| | | | | | | | Zero the unused uuid when initialising the metadata superblock. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: lift __begin_transaction out of __write_initial_superblockJoe Thornber2012-07-271-13/+6
| | | | | | | | | Lift the call to __begin_transaction out of __write_initial_superblock in dm-thin-metadata. Called higher up the call chain now. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: move dm_commit_pool_metadata into __write_initial_superblockJoe Thornber2012-07-271-6/+38
| | | | | | | | Move dm_commit_pool_metadata inline into __write_initial_superblock in dm-thin-metadata. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: factor out __write_initial_superblockJoe Thornber2012-07-271-51/+58
| | | | | | | | | Factor out __write_initial_superblock and also pull some other initial creation code out of dm_pool_metadata_open. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: lift some initialisation out of __open_or_format_metadataJoe Thornber2012-07-271-4/+4
| | | | | | | | Lift some initialisation out of __open_or_format_metadata in dm-thin-metadata. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: factor __destroy_persistent_data out of dm_pool_metadata_closeJoe Thornber2012-07-271-5/+10
| | | | | | | | Factor __destroy_persistent_data_objects out of dm_pool_metadata_close. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: move bm creation code into create_persistent_data_objectsJoe Thornber2012-07-271-24/+32
| | | | | | | | | Move block manager creation and the check for unformatted metadata into __create_persistent_data_objects(). Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: rename init_pmd to __create_persistent_data_objectsJoe Thornber2012-07-271-4/+4
| | | | | | | | Rename init_pmd to __create_persistent_data_objects in dm-thin-metadata. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: wrap superblock lockingJoe Thornber2012-07-271-21/+20
| | | | | | | | | Introduce wrappers to handle write locking the superblock appropriately. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm persistent data: tidy transaction manager creation fnsJoe Thornber2012-07-271-15/+27
| | | | | | | | | | | | | Tidy the transaction manager creation functions. They no longer lock the superblock. Superblock locking is pulled out to the caller. Also export dm_bm_write_lock_zero. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: stop tracking need for commitJoe Thornber2012-07-271-38/+2
| | | | | | | | | | | | | | Remove an optimisation that tracks whether or not a thin metadata commit is needed. If dm_pool_commit_metadata() is called and no changes have been made to the metadata then this optimisation avoided writing to disk. Removing because we're going to do something better later. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm persistent data: create new dm_block_manager structJoe Thornber2012-07-271-3/+3
| | | | | | | | | | | | | | | This patch introduces a separate struct for the block_manager. It also uses IS_ERR to check the return value of dm_bufio_client_create instead of testing incorrectly for NULL. Prior to this patch a struct dm_block_manager was really an alias for a struct dm_bufio_client. We want to add some functionality to the block manager that will require extra fields, so this one to one mapping is no longer valid. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: factor __setup_btree_details out of init_pmdJoe Thornber2012-07-271-35/+39
| | | | | | | | Factor __setup_btree_details out of init_pmd in dm-thin-metadata. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: introduce THIN_MAX_CONCURRENT_LOCKSJoe Thornber2012-07-271-6/+8
| | | | | | | | | Introduce THIN_MAX_CONCURRENT_LOCKS into dm-thin-metadata to give a name to an otherwise "magic" number. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin metadata: remove pointless label from __commit_transactionJoe Thornber2012-07-271-8/+7
| | | | | | | | | Remove the pointless label 'out' from __commit_transaction in dm-thin-metadata.c Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin: clean up compiler warningMike Snitzer2012-07-271-1/+1
| | | | | | | | | Clean up "warning: dubious: !x & y". Also make it clear that __snapshotted_since() returns a bool and that dm_thin_lookup_result's 'shared' member is a flag. Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
* dm thin: provide userspace access to pool metadataJoe Thornber2012-06-031-6/+130
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch implements two new messages that can be sent to the thin pool target allowing it to take a snapshot of the _metadata_. This, read-only snapshot can be accessed by userland, concurrently with the live target. Only one metadata snapshot can be held at a time. The pool's status line will give the block location for the current msnap. Since version 0.1.5 of the userland thin provisioning tools, the thin_dump program displays the msnap as follows: thin_dump -m <msnap root> <metadata dev> Available here: https://github.com/jthornber/thin-provisioning-tools Now that userland can access the metadata we can do various things that have traditionally been kernel side tasks: i) Incremental backups. By using metadata snapshots we can work out what blocks have changed over time. Combined with data snapshots we can ensure the data doesn't change while we back it up. A short proof of concept script can be found here: https://github.com/jthornber/thinp-test-suite/blob/master/incremental_backup_example.rb ii) Migration of thin devices from one pool to another. iii) Merging snapshots back into an external origin. iv) Asyncronous replication. Signed-off-by: Joe Thornber <ejt@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-22 17:43:03 +0100