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Subject: Re: [PATCH block/for-linus] blkcg: Fix ->pd_alloc_fn() being called
 with the wrong blkcg on policy activation
To:     Tejun Heo <tj@kernel.org>
Cc:     linux-block@vger.kernel.org, newella@fb.com, kernel-team@fb.com,
        linux-kernel@vger.kernel.org
References: <20191014185027.GH18794@devbig004.ftw2.facebook.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <ee958749-62af-2393-d1e5-5bc4fc3eb146@kernel.dk>
Date:   Mon, 14 Oct 2019 13:55:32 -0600
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On 10/14/19 12:50 PM, Tejun Heo wrote:
> cf09a8ee19ad ("blkcg: pass @q and @blkcg into
> blkcg_pol_alloc_pd_fn()") added @blkcg to ->pd_alloc_fn(); however,
> blkcg_activate_policy() ends up using pd's allocated for the root
> blkcg for all preallocations, so ->pd_init_fn() for non-root blkcgs
> can be passed in pd's which are allocated for the root blkcg.
> 
> For blk-iocost, this means that ->pd_init_fn() can write beyond the
> end of the allocated object as it determines the length of the flex
> array at the end based on the blkcg's nesting level.

Applied, thanks.

-- 
Jens Axboe