Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932082AbWLLGhT (ORCPT ); Tue, 12 Dec 2006 01:37:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932081AbWLLGhT (ORCPT ); Tue, 12 Dec 2006 01:37:19 -0500 Received: from smtp.osdl.org ([65.172.181.25]:49499 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932080AbWLLGhR (ORCPT ); Tue, 12 Dec 2006 01:37:17 -0500 Date: Mon, 11 Dec 2006 22:36:30 -0800 From: Andrew Morton To: Dmitriy Monakhov Cc: Dmitriy Monakhov , linux-kernel@vger.kernel.org, Linux Memory Management , , xfs@oss.sgi.com Subject: Re: [PATCH] incorrect error handling inside generic_file_direct_write Message-Id: <20061211223630.a96ef156.akpm@osdl.org> In-Reply-To: <87lkld31vd.fsf@sw.ru> References: <87k60y1rq4.fsf@sw.ru> <20061211124052.144e69a0.akpm@osdl.org> <87lkld31vd.fsf@sw.ru> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2150 Lines: 61 On Tue, 12 Dec 2006 12:22:14 +0300 Dmitriy Monakhov wrote: > >> @@ -2041,6 +2041,14 @@ generic_file_direct_write(struct kiocb * > >> mark_inode_dirty(inode); > >> } > >> *ppos = end; > >> + } else if (written < 0) { > >> + loff_t isize = i_size_read(inode); > >> + /* > >> + * generic_file_direct_IO() may have instantiated a few blocks > >> + * outside i_size. Trim these off again. > >> + */ > >> + if (pos + count > isize) > >> + vmtruncate(inode, isize); > >> } > >> > > > > XFS (at least) can call generic_file_direct_write() with i_mutex not held. > How could it be ? > > from mm/filemap.c:2046 generic_file_direct_write() comment right after > place where i want to add vmtruncate() > /* > * Sync the fs metadata but not the minor inode changes and > * of course not the data as we did direct DMA for the IO. > * i_mutex is held, which protects generic_osync_inode() from > * livelocking. > */ > > > And vmtruncate() expects i_mutex to be held. > generic_file_direct_IO must called under i_mutex too > from mm/filemap.c:2388 > /* > * Called under i_mutex for writes to S_ISREG files. Returns -EIO if something > * went wrong during pagecache shootdown. > */ > static ssize_t > generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, yup, the comments are wrong. > This means XFS generic_file_direct_write() call generic_file_direct_IO() without > i_mutex held too? Think so. XFS uses blockdev_direct_IO_own_locking(). We'd need to check with the XFS guys regarding its precise operation and what needs to be done here. > > > > I guess a suitable solution would be to push this problem back up to the > > callers: let them decide whether to run vmtruncate() and if so, to ensure > > that i_mutex is held. > > > > The existence of generic_file_aio_write_nolock() makes that rather messy > > though. - 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/