From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from verein.lst.de ([213.95.11.211]:37070 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726643AbeHHMKs (ORCPT ); Wed, 8 Aug 2018 08:10:48 -0400 Date: Wed, 8 Aug 2018 11:57:19 +0200 From: Christoph Hellwig To: Andrew Morton Cc: Christoph Hellwig , viro@zeniv.linux.org.uk, Avi Kivity , Linus Torvalds , linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/4] aio: allow direct aio poll comletions for keyed wakeups Message-ID: <20180808095719.GA20653@lst.de> References: <20180806083058.14724-1-hch@lst.de> <20180806083058.14724-5-hch@lst.de> <20180806152705.37809e16c02543cc24626607@linux-foundation.org> <20180807072555.GA678@lst.de> <20180807090441.67f7e281f502ce448de849c1@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180807090441.67f7e281f502ce448de849c1@linux-foundation.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Tue, Aug 07, 2018 at 09:04:41AM -0700, Andrew Morton wrote: > > Because it is faster obviously. I can update the comment. > > I meant the comment could explain why it's a trylock instead of a > spin_lock(). We could something like this the patch below. Al, do you want me to resend or can you just fold it in? diff --git a/fs/aio.c b/fs/aio.c index 5943098a87c6..84df2c2bf80b 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1684,7 +1684,8 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, /* * Try to complete the iocb inline if we can to avoid a costly - * context switch. + * context switch. As the waitqueue lock nests inside the ctx + * lock we can only do that if we can get it without waiting. */ if (spin_trylock(&iocb->ki_ctx->ctx_lock)) { list_del(&iocb->ki_list);