Re: [PATCH 0/2] block: fixes for always associate blkg

[Jens Axboe]

On 10/20/18 12:56 PM, Dennis Zhou wrote:
> Hi everyone,
> 
> It was reported in [1] that blk_get_rl() cleanup patch was causing a
> null pointer dereference. After some back and forth debugging with
> Valdis, it turns out I wasn't properly handling association with
> recursive calls to make_request().
> 
> Another issue was identified with the blk_get_rl() update as it is
> possible under certain circumstances that a blkg cannot be allocated
> when called in blk_get_rl(). This could result in the blkcg_root being
> returned. However, the blkcg_root is a special case where all blkgs
> share the request_queue's request_list.
> 
> The original series can be found at [2].
> 
> [1] https://lore.kernel.org/lkml/13987.1539646128@xxxxxxxxxxxxxxxxxxxxxxx/
> [2] https://lore.kernel.org/lkml/20180911184137.35897-1-dennisszhou@xxxxxxxxx/
> 
> This patchset contains the following 2 patches:
>   0001-blkcg-fix-edge-case-for-blk_get_rl-under-memory-pres.patch
>   0002-blkcg-reassociate-bios-when-make_request-is-called-r.patch
> 
> 0001 addresses an edge case where a blkg cannot be created and can
> possibly return a blkg associated with the blkcg_root. 0002 fixes the
> stale association when make_request() is called recursively.

Thanks Dennis, applied.

-- 
Jens Axboe