linux-kernel - Re: [PATCH] blkcg: add rcu lock to bio_clone_blkg

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Message-ID: <f1dacd9e-7c3d-44e5-aff1-923d9e7a374c@kernel.dk>
Date:   Fri, 21 Dec 2018 08:26:02 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Dennis Zhou <dennis@...nel.org>
Cc:     kernel-team@...com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] blkcg: add rcu lock to bio_clone_blkg_association()

On 12/21/18 7:54 AM, Dennis Zhou wrote:
> I cleaned up blkg_tryget_closest() to require rcu_read_lock() earlier.
> However, this was a subtle case too which clearly was too subtle for me.
> The idea was the src bio should be holding a ref to the blkg so rcu
> wasn't technically needed. If it doesn't hold a ref, it should be %NULL
> and the blkg->parent pointers are unused.
> 
> This adds the appropriate read lock in bio_clone_blkg_association().

Shall I just fold this with the previous? I staged it in a
later-in-merge-cycle branch, so that's not an issue to amend.

-- 
Jens Axboe