Re: [PATCH v3 0/7] Fix potential kernel panic when increase hardware queue

From: Weiping Zhang <zwp10758@gmail.com>
To: Jens Axboe <axboe@kernel.dk>,
	Bart Van Assche <bvanassche@acm.org>,
	linux-block@vger.kernel.org
Subject: Re: [PATCH v3 0/7] Fix potential kernel panic when increase hardware queue
Date: Wed, 8 Apr 2020 20:25:31 +0800	[thread overview]
Message-ID: <CAA70yB7mNEt+H5xd+hpeRDLXDi+V+Qmuvuy27wJ63dtmcKDpzQ@mail.gmail.com> (raw)
In-Reply-To: <cover.1586199103.git.zhangweiping@didiglobal.com>

Weiping Zhang <zhangweiping@didiglobal.com> 于2020年4月7日周二 上午3:36写道：
>
> Hi,
>
> This series do some improvement base on V2, and also fix two memleaks.
> And V2 import a regression for blktest/block/test/029, this test case
> will increase and decrease hardware queue count quickly.
>
>
> Memleak 1:
>
> __blk_mq_alloc_rq_maps
>         __blk_mq_alloc_rq_map
>
> if fail
>         blk_mq_free_rq_map
>
> Actually, __blk_mq_alloc_rq_map alloc both map and request, here
> also need free request.
>
> Memleak 2:
> When driver decrease hardware queue, set->nr_hw_queues will be changed
> firstly in blk_mq_realloc_tag_set_tags or __blk_mq_update_nr_hw_queues,
> then blk_mq_realloc_hw_ctxs and blk_mq_map_swqueue, even
> blk_mq_free_tag_set have no chance to free these hardware queue resource,
> because they iterate hardware queue by
> for (i = 0; i < set->nr_hw_queues; i++).
>
> Patch1~3: rename some function name, no function change.
> Patch4: fix first memleak.
> Patch5: fix prev_nr_hw_queues issue, need be saved before change.
> Patch6: alloc map and request to fix potential kernel panic.
>
Update patch description:
Patch1~3: rename some function name, no function change.
Patch4: fix first memleak.
Patch5: fix prev_nr_hw_queues issue, need be saved before change.
Patch6: add nr_allocated_map_rqs to struct blk_mq_tag_set to record how
may rq and maps were allocated for this tag set, and also fix memleak2.

Patch7: fix kernel panic when update hardware queue count > cpu count,
when use multiple maps. Patch7's commit message has more detail information
about this issue.

>
> Changes since V2:
>  * rename some functions name and fix memleak when free map and requests
>  * Not free new allocated map and request, they will be relased when tagset gone
>
> Changes since V1:
>  * Add fix for potential kernel panic when increase hardware queue
>
> Weiping Zhang (7):
>   block: rename __blk_mq_alloc_rq_map
>   block: rename __blk_mq_alloc_rq_maps
>   block: rename blk_mq_alloc_rq_maps
>   block: free both map and request
>   block: save previous hardware queue count before udpate
>   block: refactor __blk_mq_alloc_rq_map_and_requests
>   block: alloc map and request for new hardware queue
>
>  block/blk-mq.c         | 49 ++++++++++++++++++++++++++++++------------
>  include/linux/blk-mq.h |  1 +
>  2 files changed, 36 insertions(+), 14 deletions(-)
>
> --
> 2.18.1
>