>From wfg@mail.ustc.edu.cn Tue Oct 23 11:48:28 2007 Received: from pentafluge.infradead.org (pentafluge.infradead.org [213.146.154.40]) (using TLSv1 with cipher EDH-RSA-DES-CBC3-SHA (168/168 bits)) (No client certificate requested) by gateway.programming.kicks-ass.net (Postfix) with ESMTP id 5420413CA5F for ; Tue, 23 Oct 2007 11:48:28 +0200 (CEST) Received: from smtp.ustc.edu.cn ([202.38.64.16] helo=ustc.edu.cn) by pentafluge.infradead.org with smtp (Exim 4.63 #1 (Red Hat Linux)) id 1IkEc4-0004P7-J7 for peterz@infradead.org; Tue, 23 Oct 2007 08:55:50 +0100 Received: (eyou send program); Tue, 23 Oct 2007 15:55:19 +0800 Message-ID: <393126119.26275@ustc.edu.cn> X-EYOUMAIL-SMTPAUTH: wfg@mail.ustc.edu.cn Received: from unknown (HELO localhost) (211.86.144.46) by 202.38.64.8 with SMTP; Tue, 23 Oct 2007 15:55:19 +0800 Received: from wfg by localhost with local (Exim 4.67) (envelope-from ) id 1IkEba-0001sv-5B; Tue, 23 Oct 2007 15:55:14 +0800 Date: Tue, 23 Oct 2007 15:55:14 +0800 From: Fengguang Wu To: Maxim Levitsky Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, Fengguang Wu , Andrew Morton Subject: [PATCH] reiserfs: don't drop PG_dirty when releasing sub-page-sized dirty file References: <200710220822.52370.maximlevitsky@gmail.com> <200710221258.11384.maximlevitsky@gmail.com> <393051953.24752@ustc.edu.cn> <200710221421.21439.maximlevitsky@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200710221421.21439.maximlevitsky@gmail.com> X-GPG-Fingerprint: 53D2 DDCE AB5C 8DC6 188B 1CB1 F766 DA34 8D8B 1C6D User-Agent: Mutt/1.5.16 (2007-06-11) X-Bad-Reply: References and In-Reply-To but no 'Re:' in Subject. X-Spam-Checker-Version: SpamAssassin 3.0.3-gr0 (2005-04-27) on server X-Spam-Level: X-Spam-Status: No, score=-1.3 required=5.0 tests=AWL,BAYES_00, MSGID_FROM_MTA_HEADER,RCVD_BY_IP,TW_FC,TW_JL autolearn=no version=3.0.3-gr0 X-Evolution-Source: imap://peter%40programming.kicks-ass.net@programming.kicks-ass.net/ Content-Transfer-Encoding: 8bit This is not a new problem in 2.6.23-git17. 2.6.22/2.6.23 is buggy in the same way. Reiserfs could leave newly created sub-page-size files in dirty state for ever. They cannot be synced to disk by pdflush routines or explicit `sync' commands. Only `umount' can do the trick. The direct cause is: the dirty page's PG_dirty is wrongly _cleared_. Call trace: [] cancel_dirty_page+0xd0/0xf0 [] :reiserfs:reiserfs_cut_from_item+0x660/0x710 [] :reiserfs:reiserfs_do_truncate+0x271/0x530 [] :reiserfs:reiserfs_truncate_file+0xfd/0x3b0 [] :reiserfs:reiserfs_file_release+0x1e0/0x340 [] __fput+0xcc/0x1b0 [] fput+0x16/0x20 [] filp_close+0x56/0x90 [] sys_close+0xad/0x110 [] system_call+0x7e/0x83 Fix the bug by removing the cancel_dirty_page() call. Tests show that it causes no bad behaviors on various write sizes. === for the patient === Here are more detailed demonstrations of the problem. 1) the page has both PG_dirty(D)/PAGECACHE_TAG_DIRTY(d) after being written to; and then only PAGECACHE_TAG_DIRTY(d) remains after the file is closed. ------------------------------ screen 0 ------------------------------ [T0] root /home/wfg# cat > /test/tiny [T1] hi [T2] root /home/wfg# ------------------------------ screen 1 ------------------------------ [T1] root /home/wfg# echo /test/tiny > /proc/filecache [T1] root /home/wfg# cat /proc/filecache # file /test/tiny # flags R:referenced A:active M:mmap U:uptodate D:dirty W:writeback O:owner B:buffer d:dirty w:writeback # idx len state refcnt 0 1 ___UD__Bd_ 2 [T2] root /home/wfg# cat /proc/filecache # file /test/tiny # flags R:referenced A:active M:mmap U:uptodate D:dirty W:writeback O:owner B:buffer d:dirty w:writeback # idx len state refcnt 0 1 ___U___Bd_ 2 2) note the non-zero 'cancelled_write_bytes' after /tmp/hi is copied. ------------------------------ screen 0 ------------------------------ [T0] root /home/wfg# echo hi > /tmp/hi [T1] root /home/wfg# cp /tmp/hi /dev/stdin /test [T2] hi [T3] root /home/wfg# ------------------------------ screen 1 ------------------------------ [T1] root /proc/4397# cd /proc/`pidof cp` [T1] root /proc/4713# cat io rchar: 8396 wchar: 3 syscr: 20 syscw: 1 read_bytes: 0 write_bytes: 20480 cancelled_write_bytes: 4096 [T2] root /proc/4713# cat io rchar: 8399 wchar: 6 syscr: 21 syscw: 2 read_bytes: 0 write_bytes: 24576 cancelled_write_bytes: 4096 //Question: the 'write_bytes' is a bit more than expected ;-) Cc: Maxim Levitsky Cc: Peter Zijlstra Signed-off-by: Fengguang Wu --- fs/reiserfs/stree.c | 3 --- 1 file changed, 3 deletions(-) --- linux-2.6.24-git17.orig/fs/reiserfs/stree.c +++ linux-2.6.24-git17/fs/reiserfs/stree.c @@ -1458,9 +1458,6 @@ static void unmap_buffers(struct page *p } bh = next; } while (bh != head); - if (PAGE_SIZE == bh->b_size) { - cancel_dirty_page(page, PAGE_CACHE_SIZE); - } } } }