From mboxrd@z Thu Jan 1 00:00:00 1970 From: OGAWA Hirofumi Subject: Re: [PATCH 0/7] Discard requests, v2 Date: Wed, 13 Aug 2008 05:11:15 +0900 Message-ID: <87abfi804c.fsf@devron.myhome.or.jp> References: <1218299181.26926.88.camel@pmac.infradead.org> <20080812091446.GF20055@kernel.dk> <87ljz280x7.fsf@devron.myhome.or.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Woodhouse , Andrew Morton , Ric Wheeler , linux-fsdevel@vger.kernel.org, gilad@codefidence.com, matthew@wil.cx To: Jens Axboe Return-path: Received: from mail.parknet.ad.jp ([210.171.162.6]:49653 "EHLO mail.officemail.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752457AbYHLULT (ORCPT ); Tue, 12 Aug 2008 16:11:19 -0400 In-Reply-To: <87ljz280x7.fsf@devron.myhome.or.jp> (OGAWA Hirofumi's message of "Wed, 13 Aug 2008 04:53:56 +0900") Sender: linux-fsdevel-owner@vger.kernel.org List-ID: OGAWA Hirofumi writes: > Jens Axboe writes: > >> But we don't already have this problem, that is the point. For page >> cache writes, the page cache nicely solves this issue for us - a write >> that comes in later gets to wait on the page lock before proceeding. So >> at least it's ordered. For O_DIRECT, the issuer is on his own. >> >> I think this is a serious problem and that we must ensure that an >> overlapping write doesn't pass a previously issued discard request. So >> in that sense, discards must be considered soft barriers. > > Um.., if blocks used by data (page cache) is reused as directory (meta > data), it can happen? Ugh, sorry, can't happen. forget it. FWIW, it would happen, if someone directly access to device mounted by fs, it can.. But it's user's fault already. -- OGAWA Hirofumi