Heinz Mauelshagen 63c32ed4af dm raid: add raid4/5/6 journaling support ... Add md raid4/5/6 journaling support (upstream commit bac624f3f8 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 <heinzm@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>		2017-01-25 12:49:06 +01:00
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cache-policies.txt	dm cache: update cache-policies.txt now that mq is an alias for smq	2016-05-05 15:25:53 -04:00
cache.txt	dm cache: display 'needs_check' in status if it is set	2015-07-16 10:23:50 -04:00
delay.txt	Documentation/device-mapper: s/getsize/getsz/	2016-12-14 10:54:27 +01:00
dm-crypt.txt	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial	2016-12-14 11:12:25 -08:00
dm-flakey.txt	block: rename bio bi_rw to bi_opf	2016-08-07 14:41:02 -06:00
dm-io.txt
dm-log.txt	dm log userspace: fix comment hyphens	2011-10-31 20:21:22 +00:00
dm-queue-length.txt
dm-raid.txt	dm raid: add raid4/5/6 journaling support	2017-01-25 12:49:06 +01:00
dm-service-time.txt	Fix common misspellings	2011-03-31 11:26:23 -03:00
dm-uevent.txt
era.txt	dm: add era target	2014-03-27 16:56:23 -04:00
kcopyd.txt
linear.txt	Documentation/device-mapper: s/getsize/getsz/	2016-12-14 10:54:27 +01:00
log-writes.txt	block, drivers, fs: rename REQ_FLUSH to REQ_PREFLUSH	2016-06-07 13:41:38 -06:00
persistent-data.txt	Documentation: Fix multiple typo in Documentation	2012-03-07 16:08:24 +01:00
snapshot.txt	dm snapshot: add new persistent store option to support overflow	2015-10-09 16:57:03 -04:00
statistics.txt	dm stats: fix spelling mistake in Documentation	2016-05-05 15:25:54 -04:00
striped.txt	Documentation/device-mapper: s/getsize/getsz/	2016-12-14 10:54:27 +01:00
switch.txt	Documentation/device-mapper: s/getsize/getsz/	2016-12-14 10:54:27 +01:00
thin-provisioning.txt	dm thin: display 'needs_check' in status if it is set	2015-07-16 10:23:50 -04:00
verity.txt	dm verity: add ignore_zero_blocks feature	2015-12-10 10:39:03 -05:00
zero.txt