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linux/drivers/md
Kiyoshi Ueda ecdb2e257a dm table: remove dm_get from dm_table_get_md
Remove the dm_get() in dm_table_get_md() because dm_table_get_md() could
be called from presuspend/postsuspend, which are called while
mapped_device is in DMF_FREEING state, where dm_get() is not allowed.

Justification for that is the lifetime of both objects: As far as the
current dm design/implementation, mapped_device is never freed while
targets are doing something, because dm core waits for targets to become
quiet in dm_put() using presuspend/postsuspend.  So targets should be
able to touch mapped_device without holding reference count of the
mapped_device, and we should allow targets to touch mapped_device even
if it is in DMF_FREEING state.

Backgrounds:
I'm trying to remove the multipath internal queue, since dm core now has
a generic queue for request-based dm.  In the patch-set, the multipath
target wants to request dm core to start/stop queue.  One of such
start/stop requests can happen during postsuspend() while the target
waits for pg-init to complete, because the target stops queue when
starting pg-init and tries to restart it when completing pg-init.  Since
queue belongs to mapped_device, it involves calling dm_table_get_md()
and dm_put().  On the other hand, postsuspend() is called in dm_put()
for mapped_device which is in DMF_FREEING state, and that triggers
BUG_ON(DMF_FREEING) in the 2nd dm_put().

I had tried to solve this problem by changing only multipath not to
touch mapped_device which is in DMF_FREEING state, but I couldn't and I
came up with a question why we need dm_get() in dm_table_get_md().

Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2010-03-06 02:29:52 +00:00
..
raid6test md: drivers/md/unroll.pl replaced with awk analog 2009-10-16 16:25:19 +11:00
.gitignore
bitmap.c md/bitmap: update dirty flag when bitmap bits are explicitly set. 2009-12-14 12:51:41 +11:00
bitmap.h md: Support write-intent bitmaps with externally managed metadata. 2009-12-14 12:51:41 +11:00
dm-bio-record.h
dm-crypt.c dm crypt: add plain64 iv 2009-12-10 23:52:25 +00:00
dm-delay.c dm table: pass correct dev area size to device_area_is_valid 2009-07-23 20:30:42 +01:00
dm-exception-store.c dm snapshot: move cow ref from exception store to snap core 2009-12-10 23:52:12 +00:00
dm-exception-store.h dm snapshot: add merging 2009-12-10 23:52:32 +00:00
dm-io.c dm io: handle empty barriers 2009-12-10 23:52:22 +00:00
dm-ioctl.c dm: rename dm_suspended to dm_suspended_md 2009-12-10 23:52:26 +00:00
dm-kcopyd.c dm kcopyd: accept zero size jobs 2009-12-10 23:52:13 +00:00
dm-linear.c dm table: pass correct dev area size to device_area_is_valid 2009-07-23 20:30:42 +01:00
dm-log-userspace-base.c dm log: userspace fix incorrect luid cast in userspace_ctr 2009-10-16 23:18:15 +01:00
dm-log-userspace-transfer.c dm log: userspace fix overhead_size calcuations 2010-02-16 18:42:53 +00:00
dm-log-userspace-transfer.h dm log: userspace add luid to distinguish between concurrent log instances 2009-09-04 20:40:34 +01:00
dm-log.c dm raid1: report flush errors separately in status 2009-12-10 23:52:02 +00:00
dm-mpath.c dm mpath: skip activate_path for failed paths 2010-03-06 02:29:49 +00:00
dm-mpath.h
dm-path-selector.c
dm-path-selector.h dm mpath: add start_io and nr_bytes to path selectors 2009-06-22 10:12:27 +01:00
dm-queue-length.c dm mpath: add queue length load balancer 2009-06-22 10:12:27 +01:00
dm-raid1.c dm raid1: fail writes if errors are not handled and log fails 2010-02-16 18:42:55 +00:00
dm-region-hash.c dm raid1: fix null pointer dereference in suspend 2010-02-16 18:42:58 +00:00
dm-round-robin.c dm mpath: add start_io and nr_bytes to path selectors 2009-06-22 10:12:27 +01:00
dm-service-time.c dm mpath: add service time load balancer 2009-06-22 10:12:28 +01:00
dm-snap-persistent.c dm snapshot: persistent annotate work_queue as on stack 2010-02-16 18:42:51 +00:00
dm-snap-transient.c dm snapshot: move cow ref from exception store to snap core 2009-12-10 23:52:12 +00:00
dm-snap.c dm snapshot: use merge origin if snapshot invalid 2009-12-10 23:52:36 +00:00
dm-stripe.c dm stripe: avoid divide by zero with invalid stripe count 2010-02-16 18:42:47 +00:00
dm-sysfs.c dm: sysfs revert add empty release function to avoid debug warning 2010-02-16 18:43:04 +00:00
dm-table.c dm table: remove dm_get from dm_table_get_md 2010-03-06 02:29:52 +00:00
dm-target.c
dm-uevent.c dm table: remove dm_get from dm_table_get_md 2010-03-06 02:29:52 +00:00
dm-uevent.h
dm-zero.c
dm.c dm table: remove dm_get from dm_table_get_md 2010-03-06 02:29:52 +00:00
dm.h dm: rename dm_suspended to dm_suspended_md 2009-12-10 23:52:26 +00:00
faulty.c md: add MODULE_DESCRIPTION for all md related modules. 2009-12-14 12:51:41 +11:00
Kconfig md: revise Kconfig help for MD_MULTIPATH 2009-12-14 12:51:41 +11:00
linear.c block: Rename blk_queue_max_sectors to blk_queue_max_hw_sectors 2010-02-26 13:58:08 +01:00
linear.h md/linear: use call_rcu to free obsolete 'conf' structures. 2009-06-18 08:49:42 +10:00
Makefile md: drivers/md/unroll.pl replaced with awk analog 2009-10-16 16:25:19 +11:00
md.c md: fix some lockdep issues between md and sysfs. 2010-02-10 11:26:09 +11:00
md.h raid: improve MD/raid10 handling of correctable read errors. 2009-12-14 12:51:41 +11:00
mktables.c
multipath.c block: Rename blk_queue_max_sectors to blk_queue_max_hw_sectors 2010-02-26 13:58:08 +01:00
multipath.h md: remove mddev_to_conf "helper" macro 2009-06-16 16:54:21 +10:00
raid0.c block: Rename blk_queue_max_sectors to blk_queue_max_hw_sectors 2010-02-26 13:58:08 +01:00
raid0.h md: remove mddev_to_conf "helper" macro 2009-06-16 16:54:21 +10:00
raid1.c block: Rename blk_queue_max_sectors to blk_queue_max_hw_sectors 2010-02-26 13:58:08 +01:00
raid1.h md/raid1: add takeover support for raid5->raid1 2009-12-14 12:51:41 +11:00
raid5.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu 2010-03-03 07:34:18 -08:00
raid5.h percpu: add __percpu sparse annotations to what's left 2010-02-17 11:17:38 +09:00
raid6algos.c md: add MODULE_DESCRIPTION for all md related modules. 2009-12-14 12:51:41 +11:00
raid6altivec.uc md: drivers/md/unroll.pl replaced with awk analog 2009-10-16 16:25:19 +11:00
raid6int.uc md: drivers/md/unroll.pl replaced with awk analog 2009-10-16 16:25:19 +11:00
raid6mmx.c
raid6recov.c
raid6sse1.c
raid6sse2.c
raid6x86.h
raid10.c block: Rename blk_queue_max_sectors to blk_queue_max_hw_sectors 2010-02-26 13:58:08 +01:00
raid10.h md: remove mddev_to_conf "helper" macro 2009-06-16 16:54:21 +10:00
unroll.awk md: drivers/md/unroll.pl replaced with awk analog 2009-10-16 16:25:19 +11:00