• Tejun Heo's avatar
    block: blkcg_policy_cfq shouldn't be used if !CONFIG_CFQ_GROUP_IOSCHED · ffea73fc
    Tejun Heo authored
    cfq may be built w/ or w/o blkcg support depending on
    CONFIG_CFQ_CGROUP_IOSCHED.  If blkcg support is disabled, most of
    related code is ifdef'd out but some part is left dangling -
    blkcg_policy_cfq is left zero-filled and blkcg_policy_[un]register()
    calls are made on it.
    Feeding zero filled policy to blkcg_policy_register() is incorrect and
    triggers the following WARN_ON() if CONFIG_BLK_CGROUP &&
     ------------[ cut here ]------------
     WARNING: at block/blk-cgroup.c:867
     Modules linked in:
     Modules linked in:
     CPU: 3 Not tainted 3.4.0-09547-gfb21affa #1
     Process swapper/0 (pid: 1, task: 000000003ff80000, ksp: 000000003ff7f8b8)
     Krnl PSW : 0704100180000000 00000000003d76ca (blkcg_policy_register+0xca/0xe0)
    	    R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:0 CC:1 PM:0 EA:3
     Krnl GPRS: 0000000000000000 00000000014b85ec 00000000014b85b0 0000000000000000
    	    000000000096fb60 0000000000000000 00000000009a8e78 0000000000000048
    	    000000000099c070 0000000000b6f000 0000000000000000 000000000099c0b8
    	    00000000014b85b0 0000000000667580 000000003ff7fd98 000000003ff7fd70
     Krnl Code: 00000000003d76be: a7280001           lhi     %r2,1
    	    00000000003d76c2: a7f4ffdf           brc     15,3d7680
    	   #00000000003d76c6: a7f40001           brc     15,3d76c8
    	   >00000000003d76ca: a7c8ffea           lhi     %r12,-22
    	    00000000003d76ce: a7f4ffce           brc     15,3d766a
    	    00000000003d76d2: a7f40001           brc     15,3d76d4
    	    00000000003d76d6: a7c80000           lhi     %r12,0
    	    00000000003d76da: a7f4ffc2           brc     15,3d765e
     Call Trace:
     ([<0000000000b6f000>] initcall_debug+0x0/0x4)
      [<0000000000989e8a>] cfq_init+0x62/0xd4
      [<00000000001000ba>] do_one_initcall+0x3a/0x170
      [<000000000096fb60>] kernel_init+0x214/0x2bc
      [<0000000000623202>] kernel_thread_starter+0x6/0xc
      [<00000000006231fc>] kernel_thread_starter+0x0/0xc
     no locks held by swapper/0/1.
     Last Breaking-Event-Address:
      [<00000000003d76c6>] blkcg_policy_register+0xc6/0xe0
     ---[ end trace b8ef4903fcbf9dd3 ]---
    This patch fixes the problem by ensuring all blkcg support code is
    * blkcg_policy_cfq declaration and blkg_to_cfqg() definition are moved
      inside the first CONFIG_CFQ_GROUP_IOSCHED block.  __maybe_unused is
      dropped from blkcg_policy_cfq decl.
    * blkcg_deactivate_poilcy() invocation is moved inside ifdef.  This
      also makes the activation logic match cfq_init_queue().
    * All blkcg_policy_[un]register() invocations are moved inside ifdef.
    Signed-off-by: default avatarTejun Heo <tj@kernel.org>
    Reported-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
    LKML-Reference: <20120601112954.GC3535@osiris.boeblingen.de.ibm.com>
    Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
cfq-iosched.c 108 KB