linux-kernel - Re: [PATCH 05/15] blkcg: update blkg_lookup

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Message-ID: <20180831230902.GC1488037@devbig004.ftw2.facebook.com>
Date:   Fri, 31 Aug 2018 16:09:02 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Dennis Zhou <dennisszhou@...il.com>
Cc:     Jens Axboe <axboe@...nel.dk>, Johannes Weiner <hannes@...xchg.org>,
        Josef Bacik <josef@...icpanda.com>, kernel-team@...com,
        linux-block@...r.kernel.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/15] blkcg: update blkg_lookup_create to do locking

On Thu, Aug 30, 2018 at 09:53:46PM -0400, Dennis Zhou wrote:
> From: "Dennis Zhou (Facebook)" <dennisszhou@...il.com>
> 
> To know when to create a blkg, the general pattern is to do a
> blkg_lookup and if that fails, lock and then do a lookup again and if
> that fails finally create. It doesn't make much sense for everyone who
> wants to do creation to write this themselves.
> 
> This changes blkg_lookup_create to do locking and implement this
> pattern. The old blkg_lookup_create is renamed to __blkg_lookup_create.
> If a call site wants to do its own error handling or already owns the
> queue lock, they can use __blkg_lookup_create.
> 
> Signed-off-by: Dennis Zhou <dennisszhou@...il.com>

It looks a bit weird w/o actual users, might be worthwhile to mention
that future patches will add users.

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun