From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965402AbXCLJWm (ORCPT ); Mon, 12 Mar 2007 05:22:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965419AbXCLJWm (ORCPT ); Mon, 12 Mar 2007 05:22:42 -0400 Received: from mailhub.sw.ru ([195.214.233.200]:21808 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965402AbXCLJWl (ORCPT ); Mon, 12 Mar 2007 05:22:41 -0400 To: Nick Piggin Cc: Dmitriy Monakhov , linux-kernel@vger.kernel.org, Andrew Morton , devel@openvz.org Subject: Re: [PATCH 2/2] mm: incorrect direct io error handling (v6) References: <877itmrizx.fsf@sw.ru> <20070312082028.GA28546@wotan.suse.de> <871wjurgcd.fsf@sw.ru> <20070312090917.GD28546@wotan.suse.de> From: Dmitriy Monakhov Date: Mon, 12 Mar 2007 12:23:00 +0300 In-Reply-To: <20070312090917.GD28546@wotan.suse.de> (Nick Piggin's message of "Mon, 12 Mar 2007 10:09:17 +0100") Message-ID: <87tzwqq0i3.fsf@sw.ru> User-Agent: Gnus/5.1008 (Gnus v5.10.8) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Nick Piggin writes: > On Mon, Mar 12, 2007 at 11:55:30AM +0300, Dmitriy Monakhov wrote: >> Nick Piggin writes: >> >> > On Mon, Mar 12, 2007 at 10:58:10AM +0300, Dmitriy Monakhov wrote: > >> >> @@ -2240,6 +2241,29 @@ ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, >> >> mutex_lock(&inode->i_mutex); >> >> ret = __generic_file_aio_write_nolock(iocb, iov, nr_segs, >> >> &iocb->ki_pos); >> >> + /* >> >> + * If __generic_file_aio_write_nolock has failed. >> >> + * This may happen because of: >> >> + * 1) Bad segment found (failed before actual write attempt) >> >> + * 2) Segments are good, but actual write operation failed >> >> + * and may have instantiated a few blocks outside i_size. >> >> + * a) in case of buffered write these blocks was already >> >> + * trimmed by generic_file_buffered_write() >> >> + * b) in case of O_DIRECT these blocks weren't trimmed yet. >> >> + * >> >> + * In case of (2b) these blocks have to be trimmed off again. >> >> + */ >> >> + if (unlikely( ret < 0 && file->f_flags & O_DIRECT)) { >> >> + unsigned long nr_segs_avail = nr_segs; >> >> + size_t count = 0; >> >> + if (!generic_segment_checks(iov, &nr_segs_avail, &count, >> >> + VERIFY_READ)) { >> >> + /*It is (2b) case, because segments are good*/ >> >> + loff_t isize = i_size_read(inode); >> >> + if (pos + count > isize) >> >> + vmtruncate(inode, isize); >> >> + } >> >> + } >> > >> > OK, but wouldn't this be better to be done in the actual direct IO >> > functions themselves? Thus you could be sure that you have the 2b case, >> > and the code would be less fragile to something changing? >> Ohh, We can't just call vmtruncate() after generic_file_direct_write() >> failure while __generic_file_aio_write_nolock() becase where is no guarantee >> what i_mutex held. In fact all existing fs always invoke >> __generic_file_aio_write_nolock() with i_mutex held in case of S_ISREG files, >> but this was't explicitly demanded and documented. I've proposed to do it in >> previous versions of this patch, because it this just document current state >> of affairs, but David Chinner wasn't agree with it. > > It seemed like it was documented in the comments that you altered in this > patch... > > How would such a filesystem that did not hold i_mutex propose to fix the > problem? > > The burden should be on those filesystems that might not want to hold > i_mutex here, to solve the problem nicely, rather than generic code to take > this ugly code. Ok then what do you think about this version http://lkml.org/lkml/2006/12/18/103 witch was posted almost month ago :) > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/