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SubjectRe: [PATCH 2/2] block: blkcg_policy_cfq shouldn't be used if !CONFIG_CFQ_GROUP_IOSCHED
On 06/04/2012 06:31 AM, Tejun Heo wrote:
> 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 &&
> !CONFIG_CFQ_GROUP_IOSCHED.
>
> ------------[ cut here ]------------
> WARNING: at block/blk-cgroup.c:867
> Modules linked in:
> Modules linked in:
> CPU: 3 Not tainted 3.4.0-09547-gfb21aff #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
> inside CONFIG_CFQ_GROUP_IOSCHED.
>
> * 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: Tejun Heo <tj@kernel.org>
> Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
> LKML-Reference: <20120601112954.GC3535@osiris.boeblingen.de.ibm.com>

Thanks Tejun, applied this one and 1/2 as well as a standalone bug fix.

--
Jens Axboe



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