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Oleg Nesterov 4d4ef86d44 md/raid5: Fix CPU hotplug callback registration 
commit 789b5e0315 upstream.

Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	register_cpu_notifier(&foobar_cpu_notifier);

	put_online_cpus();

This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).

Interestingly, the raid5 code can actually prevent double initialization and
hence can use the following simplified form of callback registration:

	register_cpu_notifier(&foobar_cpu_notifier);

	get_online_cpus();

	for_each_online_cpu(cpu)
		init_cpu(cpu);

	put_online_cpus();

A hotplug operation that occurs between registering the notifier and calling
get_online_cpus(), won't disrupt anything, because the code takes care to
perform the memory allocations only once.

So reorganize the code in raid5 this way to fix the deadlock with callback
registration.

Cc: linux-raid@vger.kernel.org
Fixes: 36d1c6476b
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
[Srivatsa: Fixed the unregister_cpu_notifier() deadlock, added the
free_scratch_buffer() helper to condense code further and wrote the changelog.]
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-02-22 12:41:29 -08:00
..
bcache bcache: Data corruption fix 2014-02-06 11:08:16 -08:00
persistent-data dm space map metadata: fix bug in resizing of thin metadata 2014-02-13 13:48:01 -08:00
bitmap.c md: use set_bit_le and clear_bit_le 2013-04-24 11:42:41 +10:00
bitmap.h md/bitmap: record the space available for the bitmap in the superblock. 2012-05-22 13:55:34 +10:00
dm-bio-prison.c dm: add cache target 2013-03-01 22:45:51 +00:00
dm-bio-prison.h dm: add cache target 2013-03-01 22:45:51 +00:00
dm-bio-record.h
dm-bufio.c dm bufio: initialize read-only module parameters 2013-12-20 07:45:10 -08:00
dm-bufio.h dm bufio: prefetch 2012-03-28 18:41:29 +01:00
dm-builtin.c dm sysfs: fix a module unload race 2014-02-13 13:48:02 -08:00
dm-cache-block-types.h dm: add cache target 2013-03-01 22:45:51 +00:00
dm-cache-metadata.c dm cache: replace memcpy with struct assignment 2013-05-10 14:37:18 +01:00
dm-cache-metadata.h dm cache: policy ignore hints if generated by different version 2013-03-20 17:21:28 +00:00
dm-cache-policy-cleaner.c dm cache: policy change version from string to integer set 2013-03-20 17:21:27 +00:00
dm-cache-policy-internal.h dm cache: policy change version from string to integer set 2013-03-20 17:21:27 +00:00
dm-cache-policy-mq.c dm cache: policy change version from string to integer set 2013-03-20 17:21:27 +00:00
dm-cache-policy.c dm cache: policy change version from string to integer set 2013-03-20 17:21:27 +00:00
dm-cache-policy.h dm cache policy: fix description of lookup fn 2013-05-10 14:37:17 +01:00
dm-cache-target.c dm cache: fix a race condition between queuing new migrations and quiescing for a shutdown 2013-12-04 10:56:43 -08:00
dm-crypt.c block: Convert some code to bio_for_each_segment_all() 2013-03-23 14:26:30 -07:00
dm-delay.c dm delay: fix a possible deadlock due to shared workqueue 2013-12-20 07:45:11 -08:00
dm-exception-store.c dm: replace simple_strtoul 2012-07-27 15:07:59 +01:00
dm-exception-store.h
dm-flakey.c dm: rename request variables to bios 2013-03-01 22:45:47 +00:00
dm-io.c dm kcopyd: add WRITE SAME support to dm_kcopyd_zero 2012-12-21 20:23:37 +00:00
dm-ioctl.c dm ioctl: set noio flag to avoid __vmalloc deadlock 2013-08-04 16:51:02 +08:00
dm-kcopyd.c dm kcopyd: introduce configurable throttling 2013-03-01 22:45:49 +00:00
dm-linear.c dm: rename request variables to bios 2013-03-01 22:45:47 +00:00
dm-log-userspace-base.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
dm-log-userspace-transfer.c connector/userns: replace netlink uses of cap_raised() with capable() 2012-05-10 23:21:39 -04:00
dm-log-userspace-transfer.h
dm-log.c dm: use memweight() 2012-07-30 17:25:16 -07:00
dm-mpath.c dm mpath: fix race condition between multipath_dtr and pg_init_done 2013-12-04 10:56:41 -08:00
dm-mpath.h
dm-path-selector.c md: Add module.h to all files using it implicitly 2011-10-31 19:31:18 -04:00
dm-path-selector.h
dm-queue-length.c dm: reject trailing characters in sccanf input 2012-03-28 18:41:26 +01:00
dm-raid.c dm-raid: silence compiler warning on rebuilds_per_group. 2013-10-05 07:13:11 -07:00
dm-raid1.c block: Use bio_sectors() more consistently 2013-03-23 14:15:30 -07:00
dm-region-hash.c dm raid1: fix crash with mirror recovery and discard 2012-07-20 14:25:03 +01:00
dm-round-robin.c dm: reject trailing characters in sccanf input 2012-03-28 18:41:26 +01:00
dm-service-time.c dm: reject trailing characters in sccanf input 2012-03-28 18:41:26 +01:00
dm-snap-persistent.c dm snapshot: fix data corruption 2013-11-04 04:31:06 -08:00
dm-snap-transient.c md: Add in export.h for files using EXPORT_SYMBOL 2011-10-31 19:31:19 -04:00
dm-snap.c dm snapshot: avoid snapshot space leak on crash 2013-12-20 07:45:10 -08:00
dm-stripe.c dm stripe: fix regression in stripe_width calculation 2013-05-10 14:37:14 +01:00
dm-sysfs.c dm sysfs: fix a module unload race 2014-02-13 13:48:02 -08:00
dm-table.c dm table: fail dm_table_create on dm_round_up overflow 2013-12-20 07:45:11 -08:00
dm-target.c dm: rename request variables to bios 2013-03-01 22:45:47 +00:00
dm-thin-metadata.c dm thin: fix discard support to a previously shared block 2014-02-13 13:48:01 -08:00
dm-thin-metadata.h dm thin: fix discard support to a previously shared block 2014-02-13 13:48:01 -08:00
dm-thin.c dm thin: initialize dm_thin_new_mapping returned by get_next_mapping 2014-02-13 13:48:01 -08:00
dm-uevent.c md: Add in export.h for files using EXPORT_SYMBOL 2011-10-31 19:31:19 -04:00
dm-uevent.h
dm-verity.c dm verity: fix inability to use a few specific devices sizes 2013-08-04 16:51:02 +08:00
dm-zero.c dm: rename request variables to bios 2013-03-01 22:45:47 +00:00
dm.c dm sysfs: fix a module unload race 2014-02-13 13:48:02 -08:00
dm.h dm sysfs: fix a module unload race 2014-02-13 13:48:02 -08:00
faulty.c block: Add bio_end_sector() 2013-03-23 14:15:29 -07:00
Kconfig dm sysfs: fix a module unload race 2014-02-13 13:48:02 -08:00
linear.c block: Add bio_end_sector() 2013-03-23 14:15:29 -07:00
linear.h md/linear: typedef removal: linear_conf_t -> struct linear_conf 2011-10-11 16:48:54 +11:00
Makefile dm sysfs: fix a module unload race 2014-02-13 13:48:02 -08:00
md.c md: fix problem when adding device to read-only array with bitmap. 2014-01-25 08:27:12 -08:00
md.h md: fix problem when adding device to read-only array with bitmap. 2014-01-25 08:27:12 -08:00
multipath.c MD: change the parameter of md thread 2012-10-11 13:34:00 +11:00
multipath.h md/multipath: typedef removal: multipath_conf_t -> struct mpconf 2011-10-11 16:48:57 +11:00
raid0.c block: Change bio_split() to respect the current value of bi_idx 2013-03-23 14:15:30 -07:00
raid0.h md: add proper merge_bvec handling to RAID0 and Linear. 2012-03-19 12:46:39 +11:00
raid1.c md/raid1: restore ability for check and repair to fix read errors. 2014-02-22 12:41:29 -08:00
raid1.h md/raid1: prevent merging too large request 2012-07-31 10:03:53 +10:00
raid5.c md/raid5: Fix CPU hotplug callback registration 2014-02-22 12:41:29 -08:00
raid5.h md/raid5: fix interaction of 'replace' and 'recovery'. 2013-08-04 16:50:54 +08:00
raid10.c md/raid10: fix two bugs in handling of known-bad-blocks. 2014-01-25 08:27:12 -08:00
raid10.h MD RAID10: Improve redundancy for 'far' and 'offset' algorithms (part 1) 2013-02-26 11:55:30 +11:00