From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([198.137.202.133]:51316 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935921AbeEYIcM (ORCPT ); Fri, 25 May 2018 04:32:12 -0400 Date: Fri, 25 May 2018 01:32:11 -0700 From: Christoph Hellwig To: Jens Axboe Cc: linux-fsdevel@vger.kernel.org, viro@zeniv.linux.org.uk, akpm@linux-foundation.org Subject: Re: [PATCHSET 0/3] Submit ->readpages() IO as read-ahead Message-ID: <20180525083211.GA25442@infradead.org> References: <1527177774-21414-1-git-send-email-axboe@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1527177774-21414-1-git-send-email-axboe@kernel.dk> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Thu, May 24, 2018 at 10:02:51AM -0600, Jens Axboe wrote: > The only caller of ->readpages() is from read-ahead, yet we don't > submit IO flagged with REQ_RAHEAD. This means we don't see it in > blktrace, for instance, which is a shame. We already make assumptions > about ->readpages() just being for read-ahead in the mpage > implementation, using readahead_gfp_mask(mapping) as out GFP mask of > choice. > > This small series fixes up mpage_readpages() to submit with > REQ_RAHEAD, which takes care of file systems using mpage_readpages(). > The last two fixup ext4 and btrfs. What are the benefits? Any setup where this buys us anything? Any setup where this actually regressed because drivers/hardware are doing stupid things with REQ_RAHEAD?