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Tejun Heo eb7d8c07f9 cfq: fix cfqg ref handling when BLK_CGROUP && !CFQ_GROUP_IOSCHED 
When BLK_CGROUP is enabled but CFQ_GROUP_IOSCHED is, cfq ends up
calling blkg_get/put() on dummy cfqg leading to the following crash.

  BUG: unable to handle kernel NULL pointer dereference at 00000000000000b0
  IP: [<ffffffff813d44d8>] cfq_init_queue+0x258/0x430
  PGD 0
  Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
  CPU 0
  Modules linked in:

  Pid: 1, comm: swapper/0 Not tainted 3.3.0-rc6-work+ #125 Bochs Bochs
  RIP: 0010:[<ffffffff813d44d8>]  [<ffffffff813d44d8>] cfq_init_queue+0x258/0x430
  RSP: 0018:ffff88001f9dfd80  EFLAGS: 00010046
  RAX: ffff88001aefbbf0 RBX: ffff88001aeedbf0 RCX: 0000000000000100
  RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff820ffd40
  RBP: ffff88001f9dfdd0 R08: 0000000000000000 R09: 0000000000000001
  R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
  R13: 0000000000000009 R14: ffff88001aefbc30 R15: 0000000000000003
  FS:  0000000000000000(0000) GS:ffff88001fc00000(0000) knlGS:0000000000000000
  CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
  CR2: 00000000000000b0 CR3: 000000000206f000 CR4: 00000000000006f0
  DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
  Process swapper/0 (pid: 1, threadinfo ffff88001f9de000, task ffff88001f9dc040)
  Stack:
   ffff88001aeedbf0 ffff88001aefbdb0 ffff88001aef1548 ffff88001aefbbf0
   ffff88001f9dfdd0 ffff88001aef1548 ffffffff820d6320 ffffffff8165ce30
   ffffffff82c555e0 ffff88001aeebbf0 ffff88001f9dfe00 ffffffff813b0507
  Call Trace:
   [<ffffffff813b0507>] elevator_init+0xd7/0x140
   [<ffffffff813b83d5>] blk_init_allocated_queue+0x125/0x150
   [<ffffffff813b94d3>] blk_init_queue_node+0x43/0x80
   [<ffffffff813b9523>] blk_init_queue+0x13/0x20
   [<ffffffff821aec00>] floppy_init+0x82/0xec7
   [<ffffffff810001d2>] do_one_initcall+0x42/0x170
   [<ffffffff821835fc>] kernel_init+0xcb/0x14f
   [<ffffffff81b40b24>] kernel_thread_helper+0x4/0x10
  Code: 00 e8 1d 9e 76 00 48 8b 43 48 48 85 c0 48 89 83 28 03 00 00 74 07 4c 8b a0 10 ff ff ff 8b 15 b0 2e d0 00 85 d2 0f 85 49 01 00 00 <41> 8b 84 24 b0 00 00 00 85 c0 0f 8e 8c 01 00 00 83 e8 01 85 c0
  RIP  [<ffffffff813d44d8>] cfq_init_queue+0x258/0x430

Because cfq's blkcg support has a on/off switch, CFQ_GROUP_IOSCHED,
separate from BLK_CGROUP, blkg access through cfqg needs to be
conditioned on it.

* Make blkg_to_cfqg() and cfqg_to_blkg() conditioned on
  CFQ_GROUP_IOSCHED.  If disabled, they always return %NULL.

* Introduce cfqg_get() and cfqg_put() conditioned on
  CFQ_GROUP_IOSCHED.  If disabled, they are noops.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2012-03-23 14:02:53 +01:00
..
partitions separate partition format handling from generic code 2012-01-03 22:54:06 -05:00
blk-cgroup.c block: remove ioc_*_changed() 2012-03-20 12:47:48 +01:00
blk-cgroup.h blkcg: add blkcg->id 2012-03-20 12:47:47 +01:00
blk-core.c block: implement bio_associate_current() 2012-03-06 21:27:24 +01:00
blk-exec.c block: add missing blk_queue_dead() checks 2011-12-14 00:33:37 +01:00
blk-flush.c blk-flush: move the queue kick into 2011-10-24 16:24:31 +02:00
blk-integrity.c block: add export.h to files using EXPORT_SYMBOL/THIS_MODULE macros 2011-10-31 19:31:12 -04:00
blk-ioc.c block: remove ioc_*_changed() 2012-03-20 12:47:48 +01:00
blk-iopoll.c tree-wide: fix assorted typos all over the place 2009-12-04 15:39:55 +01:00
blk-lib.c block: fix patch import error in max_discard_sectors check 2011-07-23 20:34:59 +02:00
blk-map.c block: re-use existing 'reading' variable instead of checking direction again 2011-12-21 15:27:24 +01:00
blk-merge.c block: separate out blk_rq_merge_ok() and blk_try_merge() from elevator functions 2012-02-08 09:19:38 +01:00
blk-settings.c block: Introduce blk_set_stacking_limits function 2012-01-11 16:27:11 +01:00
blk-softirq.c block: Don't check QUEUE_FLAG_SAME_COMP in __blk_complete_request 2011-09-14 09:31:01 +02:00
blk-sysfs.c blkcg: unify blkg's for blkcg policies 2012-03-06 21:27:23 +01:00
blk-tag.c block: fix blk_queue_end_tag() 2011-12-29 09:16:28 +01:00
blk-throttle.c block: make blk-throttle preserve the issuing task on delayed bios 2012-03-06 21:27:24 +01:00
blk-timeout.c fault-injection: add ability to export fault_attr in arbitrary directory 2011-08-03 14:25:20 -10:00
blk.h block: interface update for ioc/icq creation functions 2012-03-06 21:27:24 +01:00
bsg-lib.c block: Change module.h -> export.h in bsg-lib.c 2011-10-31 19:31:13 -04:00
bsg.c bsg: fix sysfs link remove warning 2012-02-08 20:02:03 +01:00
cfq-iosched.c cfq: fix cfqg ref handling when BLK_CGROUP && !CFQ_GROUP_IOSCHED 2012-03-23 14:02:53 +01:00
cfq.h blkcg: use double locking instead of RCU for blkg synchronization 2012-03-06 21:27:24 +01:00
compat_ioctl.c block: Add BLKROTATIONAL ioctl 2012-01-11 16:29:31 +01:00
deadline-iosched.c elevator: make elevator_init_fn() return 0/-errno 2012-03-06 21:27:21 +01:00
elevator.c block: implement bio_associate_current() 2012-03-06 21:27:24 +01:00
genhd.c Block: use a freezable workqueue for disk-event polling 2012-03-02 10:51:00 +01:00
ioctl.c Merge branch 'for-3.3/core' of git://git.kernel.dk/linux-block 2012-01-15 12:24:45 -08:00
Kconfig move fs/partitions to block/ 2012-01-03 22:54:06 -05:00
Kconfig.iosched blkcg: make CONFIG_BLK_CGROUP bool 2012-03-06 21:27:21 +01:00
Makefile separate partition format handling from generic code 2012-01-03 22:54:06 -05:00
noop-iosched.c elevator: make elevator_init_fn() return 0/-errno 2012-03-06 21:27:21 +01:00
partition-generic.c block: Fix NULL pointer dereference in sd_revalidate_disk 2012-03-02 10:38:33 +01:00
scsi_ioctl.c block: fail SCSI passthrough ioctls on partition devices 2012-01-14 15:07:24 -08:00