From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id p94D2Dnt042837 for ; Tue, 4 Oct 2011 08:02:15 -0500 Received: from bombadil.infradead.org (localhost [127.0.0.1]) by cuda.sgi.com (Spam Firewall) with ESMTP id 557BB4D1972 for ; Tue, 4 Oct 2011 06:02:10 -0700 (PDT) Received: from bombadil.infradead.org (173-166-109-252-newengland.hfc.comcastbusiness.net [173.166.109.252]) by cuda.sgi.com with ESMTP id 3HgBihncslKBh5b3 for ; Tue, 04 Oct 2011 06:02:10 -0700 (PDT) Date: Tue, 4 Oct 2011 09:02:08 -0400 From: Christoph Hellwig Subject: Re: SEEK_DATA/SEEK_HOLE support Message-ID: <20111004130208.GA19263@infradead.org> References: <4E887D7F.2010306@oracle.com> <20111002154259.GA14543@infradead.org> <4E888C0D.9060701@oracle.com> <20111002175902.GA9420@infradead.org> <4E89343B.4030007@oracle.com> <20111003234305.GM3159@dastard> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20111003234305.GM3159@dastard> List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Dave Chinner Cc: Christoph Hellwig , Jeff Liu , xfs@oss.sgi.com On Tue, Oct 04, 2011 at 10:43:05AM +1100, Dave Chinner wrote: > The lookup is pretty simple - if there's cached data over the > unwritten range, then I'm considering it a data range. If there's no > cached data over the unwritten extent, it's a hole. That makes the > lookup simply a case of finding the first cached page in the > unwritten extent. > > It'll end up reading something like this: > > iomap = offset_to_extent(offset); > first_index = extent_to_page_index(iomap); > > nr_found = pagevec_lookup(&pvec, inode->i_mapping, first_index, 1); > if (!nr_found) > break; > > offset = page->index << PAGECACHE_SHIFT; > pagevec_release(&pvec); > > /* If we fell off the end of the extent lookup next extent */ > if (offset >= end_of_extent(iomap)) { > offset = end_of_extent(iomap); > goto next_extent; > } > > All the extent manipulations are pretty filesystem specific, so > there's not much that can be extracted into generic helper, I > think... Actually pretty similar code will work just fine if you passt the start + len of the extents in (which we got from looking it up fs-specificly): Note that we have to look for both dirty and writeback pages to make it safe. _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs