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

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Message-ID: <20181221170243.GA17140@dennisz-mbp>
Date:   Fri, 21 Dec 2018 11:02:43 -0600
From:   Dennis Zhou <dennis@...nel.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Dennis Zhou <dennis@...nel.org>, 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 Fri, Dec 21, 2018 at 08:26:02AM -0700, Jens Axboe wrote:
> 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.
> 

Yeah that would be great!

Thanks,
Dennis