kernel.git/Documentation/device-mapper/dm-raid.txt, branch linux-4.19.y

dm raid: bump target version, update comments and documentation

2018-09-06T21:07:58Z

Bump target version to reflect the documented fixes are available. Also fix some code comments (typos and clarity). Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

dm raid: stop keeping raid set frozen altogether

2017-12-13T16:52:02Z

In order to avoid redoing synchronization/recovery/reshape partially, the raid set got frozen until after all passed in table line flags had been cleared. The related table reload sequence had to be precisely followed, or reshaping may lead to data corruption caused by the active mapping carrying on with a reshape when the inactive mapping already had retrieved a stale reshape position. Harden by retrieving the actual resync/recovery/reshape position during resume whilst the active table is suspended thus avoiding to keep the raid set frozen altogether. This prevents superfluous redoing of an already resynchronized or recovered segment and, most importantly, potential for redoing of an already reshaped segment causing data corruption. Fixes: d39f0010e ("dm raid: fix raid_resume() to keep raid set frozen as needed") Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

dm raid: bump target version to reflect numerous fixes

2017-12-08T15:59:58Z

Also update Documentation accordingly. Signed-off-by: Mike Snitzer

dm raid: fix incorrect status output at the end of a "recover" process

2017-10-05T20:21:30Z

There are three important fields that indicate the overall health and status of an array: dev_health, sync_ratio, and sync_action. They tell us the condition of the devices in the array, and the degree to which the array is synchronized. This commit fixes a condition that is reported incorrectly. When a member of the array is being rebuilt or a new device is added, the "recover" process is used to synchronize it with the rest of the array. When the process is complete, but the sync thread hasn't yet been reaped, it is possible for the state of MD to be: mddev->recovery = [ MD_RECOVERY_RUNNING MD_RECOVERY_RECOVER MD_RECOVERY_DONE ] curr_resync_completed = (but not MaxSector) and all rdevs to be In_sync. This causes the 'array_in_sync' output parameter that is passed to rs_get_progress() to be computed incorrectly and reported as 'false' -- or not in-sync. This in turn causes the dev_health status characters to be reported as all 'a', rather than the proper 'A'. This can cause erroneous output for several seconds at a time when tools will want to be checking the condition due to events that are raised at the end of a sync process. Fix this by properly calculating the 'array_in_sync' return parameter in rs_get_progress(). Also, remove an unnecessary intermediate 'recovery_cp' variable in rs_get_progress(). Signed-off-by: Jonathan Brassow Signed-off-by: Mike Snitzer

dm raid: bump target version

2017-07-25T18:54:20Z

Bumo dm-raid target version to 1.12.1 to reflect that commit cc27b0c78c ("md: fix deadlock between mddev_suspend() and md_write_start()") is available. This version change allows userspace to detect that MD fix is available. Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

dm raid: add raid4/5/6 journal write-back support via journal_mode option

2017-03-27T16:08:07Z

Commit 63c32ed4afc ("dm raid: add raid4/5/6 journaling support") added journal support to close the raid4/5/6 "write hole" -- in terms of writethrough caching. Introduce a "journal_mode" feature and use the new r5c_journal_mode_set() API to add support for switching the journal device's cache mode between write-through (the current default) and write-back. NOTE: If the journal device is not layered on resilent storage and it fails, write-through mode will cause the "write hole" to reoccur. But if the journal fails while in write-back mode it will cause data loss for any dirty cache entries unless resilent storage is used for the journal. Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

dm raid: fix table line argument order in status

2017-03-27T15:45:26Z

Commit 3a1c1ef2f ("dm raid: enhance status interface and fixup takeover/raid0") added new table line arguments and introduced an ordering flaw. The sequence of the raid10_copies and raid10_format raid parameters got reversed which causes lvm2 userspace to fail by falsely assuming a changed table line. Sequence those 2 parameters as before so that old lvm2 can function properly with new kernels by adjusting the table line output as documented in Documentation/device-mapper/dm-raid.txt. Also, add missing version 1.10.1 highlight to the documention. Fixes: 3a1c1ef2f ("dm raid: enhance status interface and fixup takeover/raid0") Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

scripts/spelling.txt: add "explictely" pattern and fix typo instances

2017-02-28T02:43:47Z

Fix typos and add the following to the scripts/spelling.txt: explictely||explicitly Link: http://lkml.kernel.org/r/1481573103-11329-25-git-send-email-yamada.masahiro@socionext.com Signed-off-by: Masahiro Yamada Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

dm raid: add raid4/5/6 journaling support

2017-01-25T11:49:06Z

Add md raid4/5/6 journaling support (upstream commit bac624f3f86a started the implementation) which closes the write hole (i.e. non-atomic updates to stripes) using a dedicated journal device. Background: raid4/5/6 stripes hold N data payloads per stripe plus one parity raid4/5 or two raid6 P/Q syndrome payloads in an in-memory stripe cache. Parity or P/Q syndromes used to recover any data payloads in case of a disk failure are calculated from the N data payloads and need to be updated on the different component devices of the raid device. Those are non-atomic, persistent updates. Hence a crash can cause failure to update all stripe payloads persistently and thus cause data loss during stripe recovery. This problem gets addressed by writing whole stripe cache entries (together with journal metadata) to a persistent journal entry on a dedicated journal device. Only if that journal entry is written successfully, the stripe cache entry is updated on the component devices of the raid device (i.e. writethrough type). In case of a crash, the entry can be recovered from the journal and be written again thus ensuring consistent stripe payload suitable to data recovery. Future dependencies: once writeback caching being worked on to compensate for the throughput implictions involved with writethrough overhead is supported with journaling in upstream, an additional patch based on this one will support it in dm-raid. Journal resilience related remarks: because stripes are recovered from the journal in case of a crash, the journal device better be resilient. Resilience becomes mandatory with future writeback support, because loosing the working set in the log means data loss as oposed to writethrough, were the loss of the journal device 'only' reintroduces the write hole. Fix comment on data offsets in parse_dev_params() and initialize new_data_offset as well. Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer

dm raid: fix transient device failure processing

2017-01-25T11:49:06Z

This fix addresses the following 3 failure scenarios: 1) If a (transiently) inaccessible metadata device is being passed into the constructor (e.g. a device tuple '254:4 254:5'), it is processed as if '- -' was given. This erroneously results in a status table line containing '- -', which mistakenly differs from what has been passed in. As a result, userspace libdevmapper puts the device tuple seperate from the RAID device thus not processing the dependencies properly. 2) False health status char 'A' instead of 'D' is emitted on the status status info line for the meta/data device tuple in this metadata device failure case. 3) If the metadata device is accessible when passed into the constructor but the data device (partially) isn't, that leg may be set faulty by the raid personality on access to the (partially) unavailable leg. Restore tried in a second raid device resume on such failed leg (status char 'D') fails after the (partial) leg returned. Fixes for aforementioned failure scenarios: - don't release passed in devices in the constructor thus allowing the status table line to e.g. contain '254:4 254:5' rather than '- -' - emit device status char 'D' rather than 'A' for the device tuple with the failed metadata device on the status info line - when attempting to restore faulty devices in a second resume, allow the device hot remove function to succeed by setting the device to not in-sync In case userspace intentionally passes '- -' into the constructor to avoid that device tuple (e.g. to split off a raid1 leg temporarily for later re-addition), the status table line will correctly show '- -' and the status info line will provide a '-' device health character for the non-defined device tuple. Signed-off-by: Heinz Mauelshagen Signed-off-by: Mike Snitzer