From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762976AbZAWBa4 (ORCPT ); Thu, 22 Jan 2009 20:30:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756380AbZAWBP6 (ORCPT ); Thu, 22 Jan 2009 20:15:58 -0500 Received: from kroah.org ([198.145.64.141]:50767 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1760255AbZAWBPM (ORCPT ); Thu, 22 Jan 2009 20:15:12 -0500 Date: Thu, 22 Jan 2009 17:12:44 -0800 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , Chuck Ebbert , Domenico Andreoli , Willy Tarreau , Rodrigo Rubira Branco , Jake Edge , Eugene Teo , torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Nick Piggin , Chris Mason , Dave Chinner Subject: [patch 34/46] mm: write_cache_pages cyclic fix Message-ID: <20090123011244.GI19756@kroah.com> References: <20090123010651.683741823@mini.kroah.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline; filename="mm-write_cache_pages-cyclic-fix.patch" In-Reply-To: <20090123011110.GA19756@kroah.com> User-Agent: Mutt/1.5.16 (2007-06-09) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.28-stable review patch. If anyone has any objections, please let us know. ------------------ From: Nick Piggin commit 31a12666d8f0c22235297e1c1575f82061480029 upstream. In write_cache_pages, scanned == 1 is supposed to mean that cyclic writeback has circled through zero, thus we should not circle again. However it gets set to 1 after the first successful pagevec lookup. This leads to cases where not enough data gets written. Counterexample: file with first 10 pages dirty, writeback_index == 5, nr_to_write == 10. Then the 5 last pages will be found, and scanned will be set to 1, after writing those out, we will not cycle back to get the first 5. Rework this logic, now we'll always cycle unless we started off from index 0. When cycling, only write out as far as 1 page before the start page from the first cycle (so we don't write parts of the file twice). Signed-off-by: Nick Piggin Cc: Chris Mason Cc: Dave Chinner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/page-writeback.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -868,9 +868,10 @@ int write_cache_pages(struct address_spa int done = 0; struct pagevec pvec; int nr_pages; + pgoff_t uninitialized_var(writeback_index); pgoff_t index; pgoff_t end; /* Inclusive */ - int scanned = 0; + int cycled; int range_whole = 0; long nr_to_write = wbc->nr_to_write; @@ -881,14 +882,19 @@ int write_cache_pages(struct address_spa pagevec_init(&pvec, 0); if (wbc->range_cyclic) { - index = mapping->writeback_index; /* Start from prev offset */ + writeback_index = mapping->writeback_index; /* prev offset */ + index = writeback_index; + if (index == 0) + cycled = 1; + else + cycled = 0; end = -1; } else { index = wbc->range_start >> PAGE_CACHE_SHIFT; end = wbc->range_end >> PAGE_CACHE_SHIFT; if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) range_whole = 1; - scanned = 1; + cycled = 1; /* ignore range_cyclic tests */ } retry: while (!done && (index <= end) && @@ -897,7 +903,6 @@ retry: min(end - index, (pgoff_t)PAGEVEC_SIZE-1) + 1))) { unsigned i; - scanned = 1; for (i = 0; i < nr_pages; i++) { struct page *page = pvec.pages[i]; @@ -915,7 +920,11 @@ retry: continue; } - if (!wbc->range_cyclic && page->index > end) { + if (page->index > end) { + /* + * can't be range_cyclic (1st pass) because + * end == -1 in that case. + */ done = 1; unlock_page(page); continue; @@ -946,13 +955,15 @@ retry: pagevec_release(&pvec); cond_resched(); } - if (!scanned && !done) { + if (!cycled) { /* + * range_cyclic: * We hit the last page and there is more work to be done: wrap * back to the start of the file */ - scanned = 1; + cycled = 1; index = 0; + end = writeback_index - 1; goto retry; } if (!wbc->no_nrwrite_index_update) {