Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753224AbaKAWso (ORCPT ); Sat, 1 Nov 2014 18:48:44 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:60215 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751696AbaKAWjb (ORCPT ); Sat, 1 Nov 2014 18:39:31 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Andreas Rohner" , "Linus Torvalds" , "Ryusuke Konishi" Date: Sat, 01 Nov 2014 22:28:03 +0000 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 072/102] nilfs2: fix data loss with mmap() In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.249 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.64-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Andreas Rohner commit 56d7acc792c0d98f38f22058671ee715ff197023 upstream. This bug leads to reproducible silent data loss, despite the use of msync(), sync() and a clean unmount of the file system. It is easily reproducible with the following script: ----------------[BEGIN SCRIPT]-------------------- mkfs.nilfs2 -f /dev/sdb mount /dev/sdb /mnt dd if=/dev/zero bs=1M count=30 of=/mnt/testfile umount /mnt mount /dev/sdb /mnt CHECKSUM_BEFORE="$(md5sum /mnt/testfile)" /root/mmaptest/mmaptest /mnt/testfile 30 10 5 sync CHECKSUM_AFTER="$(md5sum /mnt/testfile)" umount /mnt mount /dev/sdb /mnt CHECKSUM_AFTER_REMOUNT="$(md5sum /mnt/testfile)" umount /mnt echo "BEFORE MMAP:\t$CHECKSUM_BEFORE" echo "AFTER MMAP:\t$CHECKSUM_AFTER" echo "AFTER REMOUNT:\t$CHECKSUM_AFTER_REMOUNT" ----------------[END SCRIPT]-------------------- The mmaptest tool looks something like this (very simplified, with error checking removed): ----------------[BEGIN mmaptest]-------------------- data = mmap(NULL, file_size - file_offset, PROT_READ | PROT_WRITE, MAP_SHARED, fd, file_offset); for (i = 0; i < write_count; ++i) { memcpy(data + i * 4096, buf, sizeof(buf)); msync(data, file_size - file_offset, MS_SYNC)) } ----------------[END mmaptest]-------------------- The output of the script looks something like this: BEFORE MMAP: 281ed1d5ae50e8419f9b978aab16de83 /mnt/testfile AFTER MMAP: 6604a1c31f10780331a6850371b3a313 /mnt/testfile AFTER REMOUNT: 281ed1d5ae50e8419f9b978aab16de83 /mnt/testfile So it is clear, that the changes done using mmap() do not survive a remount. This can be reproduced a 100% of the time. The problem was introduced in commit 136e8770cd5d ("nilfs2: fix issue of nilfs_set_page_dirty() for page at EOF boundary"). If the page was read with mpage_readpage() or mpage_readpages() for example, then it has no buffers attached to it. In that case page_has_buffers(page) in nilfs_set_page_dirty() will be false. Therefore nilfs_set_file_dirty() is never called and the pages are never collected and never written to disk. This patch fixes the problem by also calling nilfs_set_file_dirty() if the page has no buffers attached to it. [akpm@linux-foundation.org: s/PAGE_SHIFT/PAGE_CACHE_SHIFT/] Signed-off-by: Andreas Rohner Tested-by: Andreas Rohner Signed-off-by: Ryusuke Konishi Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Ben Hutchings --- fs/nilfs2/inode.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) --- a/fs/nilfs2/inode.c +++ b/fs/nilfs2/inode.c @@ -24,6 +24,7 @@ #include #include #include +#include #include #include #include "nilfs.h" @@ -195,10 +196,10 @@ static int nilfs_writepage(struct page * static int nilfs_set_page_dirty(struct page *page) { + struct inode *inode = page->mapping->host; int ret = __set_page_dirty_nobuffers(page); if (page_has_buffers(page)) { - struct inode *inode = page->mapping->host; unsigned nr_dirty = 0; struct buffer_head *bh, *head; @@ -221,6 +222,10 @@ static int nilfs_set_page_dirty(struct p if (nr_dirty) nilfs_set_file_dirty(inode, nr_dirty); + } else if (ret) { + unsigned nr_dirty = 1 << (PAGE_CACHE_SHIFT - inode->i_blkbits); + + nilfs_set_file_dirty(inode, nr_dirty); } return ret; } -- 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/