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Mike Snitzer 586b286b11 dm crypt: constrain crypt device's max_segment_size to PAGE_SIZE 
Setting the dm-crypt device's max_segment_size to PAGE_SIZE is an
unfortunate constraint that is required to avoid the potential for
exceeding dm-crypt's underlying device's max_segments limits -- due to
crypt_alloc_buffer() possibly allocating pages for the encryption bio
that are not as physically contiguous as the original bio.

It is interesting to note that this problem was already fixed back in
2007 via commit 91e106259 ("dm crypt: use bio_add_page").  But Linux 4.0
commit cf2f1abfb ("dm crypt: don't allocate pages for a partial
request") regressed dm-crypt back to _not_ using bio_add_page().  But
given dm-crypt's cpu parallelization changes all depend on commit
cf2f1abfb's abandoning of the more complex io fragments processing that
dm-crypt previously had we cannot easily go back to using
bio_add_page().

So all said the cleanest way to resolve this issue is to fix dm-crypt to
properly constrain the original bios entering dm-crypt so the encryption
bios that dm-crypt generates from the original bios are always
compatible with the underlying device's max_segments queue limits.

It should be noted that technically Linux 4.3 does _not_ need this fix
because of the block core's new late bio-splitting capability.  But, it
is reasoned, there is little to be gained by having the block core split
the encrypted bio that is composed of PAGE_SIZE segments.  That said, in
the future we may revert this change.

Fixes: cf2f1abfb ("dm crypt: don't allocate pages for a partial request")
Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=104421
Suggested-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Cc: stable@vger.kernel.org # 4.0+
 		2015-09-14 12:04:24 -04:00
..
bcache bcache: remove driver private bio splitting code 2015-08-13 12:31:40 -06:00
persistent-data dm: remove unlikely() before IS_ERR() 2015-08-12 11:32:21 -04:00
Kconfig SCSI misc on 20150911 2015-09-11 18:15:18 -07:00
Makefile dm cache: add stochastic-multi-queue (smq) policy 2015-06-11 17:12:59 -04:00
bitmap.c Some md fixes for 4.2 2015-07-25 11:24:58 -07:00
bitmap.h md-cluster: re-add capabilities 2015-04-22 07:59:39 +10:00
dm-bio-prison.c block: add a bi_error field to struct bio 2015-07-29 08:55:15 -06:00
dm-bio-prison.h dm bio prison: add dm_cell_promote_or_release() 2015-05-29 14:19:06 -04:00
dm-bio-record.h dm: Refactor for new bio cloning/splitting 2013-11-23 22:33:55 -08:00
dm-bufio.c block: add a bi_error field to struct bio 2015-07-29 08:55:15 -06:00
dm-bufio.h dm snapshot: use dm-bufio prefetch 2014-01-14 23:23:03 -05:00
dm-builtin.c dm sysfs: fix a module unload race 2014-01-14 23:23:04 -05:00
dm-cache-block-types.h dm cache: revert "remove remainder of distinct discard block size" 2014-11-10 15:25:30 -05:00
dm-cache-metadata.c dm cache: add fail io mode and needs_check flag 2015-06-11 17:13:00 -04:00
dm-cache-metadata.h dm cache: add fail io mode and needs_check flag 2015-06-11 17:13:00 -04:00
dm-cache-policy-cleaner.c dm cache: pass a new 'critical' flag to the policies when requesting writeback work 2015-05-29 14:19:04 -04:00
dm-cache-policy-internal.h dm cache: age and write back cache entries even without active IO 2015-06-11 17:13:01 -04:00
dm-cache-policy-mq.c dm cache policy smq: move 'dm-cache-default' module alias to SMQ 2015-08-12 11:27:29 -04:00
dm-cache-policy-smq.c dm cache policy smq: change the mutex to a spinlock 2015-08-12 11:32:19 -04:00
dm-cache-policy.c dm cache: add policy name to status output 2014-01-16 13:44:11 -05:00
dm-cache-policy.h dm cache: age and write back cache entries even without active IO 2015-06-11 17:13:01 -04:00
dm-cache-target.c Merge tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm 2015-09-02 16:35:26 -07:00
dm-crypt.c dm crypt: constrain crypt device's max_segment_size to PAGE_SIZE 2015-09-14 12:04:24 -04:00
dm-delay.c dm: do not override error code returned from dm_get_device() 2015-08-12 11:32:21 -04:00
dm-era-target.c block: kill merge_bvec_fn() completely 2015-08-13 12:31:57 -06:00
dm-exception-store.c dm: replace simple_strtoul 2012-07-27 15:07:59 +01:00
dm-exception-store.h
…
dm-flakey.c Merge tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm 2015-09-02 16:35:26 -07:00
dm-io.c block: remove bio_get_nr_vecs() 2015-08-13 12:32:04 -06:00
dm-ioctl.c char: make misc_deregister a void function 2015-08-05 10:35:49 -07:00
dm-kcopyd.c dm: stop using WQ_NON_REENTRANT 2013-08-23 09:02:13 -04:00
dm-linear.c Merge tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm 2015-09-02 16:35:26 -07:00
dm-log-userspace-base.c dm log userspace base: fix compile warning 2015-04-15 12:10:20 -04:00
dm-log-userspace-transfer.c dm log userspace transfer: match wait_for_completion_timeout return type 2015-04-15 12:10:20 -04:00
dm-log-userspace-transfer.h
…
dm-log-writes.c Merge tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm 2015-09-02 16:35:26 -07:00
dm-log.c dm: use memweight() 2012-07-30 17:25:16 -07:00
dm-mpath.c dm-mpath, scsi_dh: request scsi_dh modules in scsi_dh, not dm-mpath 2015-08-28 13:14:55 -07:00
dm-mpath.h
…
dm-path-selector.c
…
dm-path-selector.h
…
dm-queue-length.c
…
dm-raid.c block: kill merge_bvec_fn() completely 2015-08-13 12:31:57 -06:00
dm-raid1.c Merge tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm 2015-09-02 16:35:26 -07:00
dm-region-hash.c block: Abstract out bvec iterator 2013-11-23 22:33:47 -08:00
dm-round-robin.c
…
dm-service-time.c
…
dm-snap-persistent.c dm: remove unlikely() before IS_ERR() 2015-08-12 11:32:21 -04:00
dm-snap-transient.c
…
dm-snap.c Merge tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm 2015-09-02 16:35:26 -07:00
dm-stats.c dm stats: report precise_timestamps and histogram in @stats_list output 2015-08-18 17:20:03 -04:00
dm-stats.h dm stats: support precise timestamps 2015-06-17 12:40:40 -04:00
dm-stripe.c Merge tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm 2015-09-02 16:35:26 -07:00
dm-switch.c dm switch: efficiently support repetitive patterns 2014-08-01 12:30:37 -04:00
dm-sysfs.c dm: add 'use_blk_mq' module param and expose in per-device ro sysfs attr 2015-04-15 12:10:17 -04:00
dm-table.c block: Replace SG_GAPS with new queue limits mask 2015-08-19 14:26:02 -07:00
dm-target.c dm: allocate requests in target when stacking on blk-mq devices 2015-02-09 13:06:47 -05:00
dm-thin-metadata.c dm thin metadata: delete btrees when releasing metadata snapshot 2015-08-12 10:42:51 -04:00
dm-thin-metadata.h dm thin metadata: add dm_thin_remove_range() 2015-06-11 17:13:04 -04:00
dm-thin.c dm thin: disable discard support for thin devices if pool's is disabled 2015-09-13 21:32:10 -04:00
dm-uevent.c
…
dm-uevent.h
…
dm-verity.c Merge tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm 2015-09-02 16:35:26 -07:00
dm-zero.c block: add a bi_error field to struct bio 2015-07-29 08:55:15 -06:00
dm.c Merge tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm 2015-09-02 16:35:26 -07:00
dm.h block: kill merge_bvec_fn() completely 2015-08-13 12:31:57 -06:00
faulty.c block: add a bi_error field to struct bio 2015-07-29 08:55:15 -06:00
linear.c block: kill merge_bvec_fn() completely 2015-08-13 12:31:57 -06:00
linear.h
…
md-cluster.c md-cluster: remove inappropriate try_module_get from join() 2015-08-31 19:43:17 +02:00
md-cluster.h Fix read-balancing during node failure 2015-07-24 13:37:59 +10:00
md.c Merge linux-block/for-4.3/core into md/for-linux 2015-09-05 11:08:32 +02:00
md.h block: kill merge_bvec_fn() completely 2015-08-13 12:31:57 -06:00
multipath.c block: kill merge_bvec_fn() completely 2015-08-13 12:31:57 -06:00
multipath.h
…
raid0.c Merge linux-block/for-4.3/core into md/for-linux 2015-09-05 11:08:32 +02:00
raid0.h block: kill merge_bvec_fn() completely 2015-08-13 12:31:57 -06:00
raid1.c Merge linux-block/for-4.3/core into md/for-linux 2015-09-05 11:08:32 +02:00
raid1.h md/raid1: ensure device failure recorded before write request returns. 2015-08-31 19:43:23 +02:00
raid5.c Merge linux-block/for-4.3/core into md/for-linux 2015-09-05 11:08:32 +02:00
raid5.h md/raid5: ensure device failure recorded before write request returns. 2015-08-31 19:43:59 +02:00
raid10.c Merge linux-block/for-4.3/core into md/for-linux 2015-09-05 11:08:32 +02:00
raid10.h md/raid10: ensure device failure recorded before write request returns. 2015-08-31 19:43:45 +02:00