From: Linus Torvalds Subject: Re: [RFC][PATCH] ext3: don't read inode block if the buffer has a write error Date: Mon, 23 Jun 2008 20:01:46 -0700 (PDT) Message-ID: References: <485F8822.5030205@hitachi.com> <200806232146.28379.nickpiggin@yahoo.com.au> <20080623191733.52c3491c.akpm@linux-foundation.org> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: Nick Piggin , Hidehiro Kawai , sct@redhat.com, adilger@sun.com, linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org, jack@suse.cz, sugita , Satoshi OSHIMA To: Andrew Morton Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:51693 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752374AbYFXDCg (ORCPT ); Mon, 23 Jun 2008 23:02:36 -0400 In-Reply-To: <20080623191733.52c3491c.akpm@linux-foundation.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, 23 Jun 2008, Andrew Morton wrote: > > I don't know why it was done like this, or if anybody actually tested > > any of it, but AFAIKS the best way to fix this is to simply not > > clear any uptodate bits upon write errors. > > There's a plausible-sounding reason for this behaviour which I forgot > about three years ago. Maybe Linus remembers? We have to drop the data at _some_ point. Maybe some errors are transient, but a whole lot aren't. Jank out your USB memory stick, and those writes will continue fail. So you can't just keep things dirty - and that also implies that the buffer sure as heck isn't up-to-date either. Yes, we could haev a "retry once or twice", but quite frankly, that has always been left to the low-level driver. By the time the buffer cache or page cache sees the error, it should be considered more than "transient", and the data in memory is simply not _useful_ any more. So clearing the uptodate bit seems to be the logical thing to do. But on the other hand, it's probably not helping much either, so I don't personally care if we keep it "uptodate" - as long as the dirty bit doesn't get set, and as long as there is *some* way to get rid of the bad buffer later. Linus