linux-kernel - Re: [PATCH 5/5] block: revert back to synchronous request

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Date:   Tue, 14 Apr 2020 23:46:44 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     Christoph Hellwig <hch@...radead.org>, axboe@...nel.dk,
        viro@...iv.linux.org.uk, bvanassche@....org,
        gregkh@...uxfoundation.org, rostedt@...dmis.org, mingo@...hat.com,
        jack@...e.cz, ming.lei@...hat.com, nstange@...e.de,
        akpm@...ux-foundation.org, mhocko@...e.com, yukuai3@...wei.com,
        linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Omar Sandoval <osandov@...com>,
        Hannes Reinecke <hare@...e.com>,
        Michal Hocko <mhocko@...nel.org>
Subject: Re: [PATCH 5/5] block: revert back to synchronous request_queue
 removal

On Tue, Apr 14, 2020 at 08:58:52PM +0000, Luis Chamberlain wrote:
> > I think this needs a WARN_ON thrown in to enforece the calling context.
> 
> I considered adding a might_sleep() but upon review with Bart, he noted
> that this function already has a mutex_lock(), and if you look under the
> hood of mutex_lock(), it has a might_sleep() at the very top. The
> warning then is implicit.

It might just be a personal preference, but I think the documentation
value of a WARN_ON_ONCE or might_sleep with a comment at the top of
the function is much higher than a blurb in a long kerneldoc text and
a later mutex_lock.