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

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Message-ID: <20200415132019.GW11244@42.do-not-panic.com>
Date:   Wed, 15 Apr 2020 13:20:19 +0000
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     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 11:46:44PM -0700, Christoph Hellwig wrote:
> 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.

Well I'm a fan of making this explicit, so sure will just sprinkle a
might_sleep(), even though we have a mutex_lock().

  Luis