Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932788Ab0D3RJy (ORCPT ); Fri, 30 Apr 2010 13:09:54 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:53812 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932747Ab0D3RJV (ORCPT ); Fri, 30 Apr 2010 13:09:21 -0400 Date: Thu, 29 Apr 2010 14:39:31 -0700 From: Andrew Morton To: Dave Chinner Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, xfs@oss.sgi.com, "Aneesh Kumar K.V" , "Theodore Ts'o" Subject: Re: [PATCH 3/4] writeback: pay attention to wbc->nr_to_write in write_cache_pages Message-Id: <20100429143931.331c2bab.akpm@linux-foundation.org> In-Reply-To: <1271731314-5893-4-git-send-email-david@fromorbit.com> References: <1271731314-5893-1-git-send-email-david@fromorbit.com> <1271731314-5893-4-git-send-email-david@fromorbit.com> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.9; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1425 Lines: 41 On Tue, 20 Apr 2010 12:41:53 +1000 Dave Chinner wrote: > If a filesystem writes more than one page in ->writepage, write_cache_pages > fails to notice this and continues to attempt writeback when wbc->nr_to_write > has gone negative - this trace was captured from XFS: > > > wbc_writeback_start: towrt=1024 > wbc_writepage: towrt=1024 > wbc_writepage: towrt=0 > wbc_writepage: towrt=-1 > wbc_writepage: towrt=-5 > wbc_writepage: towrt=-21 > wbc_writepage: towrt=-85 > Bug. AFAIT it's a regression introduced by : commit 17bc6c30cf6bfffd816bdc53682dd46fc34a2cf4 : Author: Aneesh Kumar K.V : AuthorDate: Thu Oct 16 10:09:17 2008 -0400 : Commit: Theodore Ts'o : CommitDate: Thu Oct 16 10:09:17 2008 -0400 : : vfs: Add no_nrwrite_index_update writeback control flag I suggest that what you do here is remove the local `nr_to_write' from write_cache_pages() and go back to directly using wbc->nr_to_write within the loop. And thus we restore the convention that if the fs writes back more than a single page, it subtracts (nr_written - 1) from wbc->nr_to_write. -- 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/