From 4e800c0359d9a53e6bf0ab216954971b2515247f Mon Sep 17 00:00:00 2001 From: wangguang Date: Thu, 15 Sep 2016 11:32:46 -0400 Subject: [PATCH] ext4: bugfix for mmaped pages in mpage_release_unused_pages() MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Pages clear buffers after ext4 delayed block allocation failed, However, it does not clean its pte_dirty flag. if the pages unmap ,in cording to the pte_dirty , unmap_page_range may try to call __set_page_dirty, which may lead to the bugon at mpage_prepare_extent_to_map:head = page_buffers(page);. This patch just call clear_page_dirty_for_io to clean pte_dirty at mpage_release_unused_pages for pages mmaped. Steps to reproduce the bug: （1） mmap a file in ext4 addr = (char *)mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); memset(addr, 'i', 4096); （2） return EIO at ext4_writepages->mpage_map_and_submit_extent->mpage_map_one_extent which causes this log message to be print: ext4_msg(sb, KERN_CRIT, "Delayed block allocation failed for " "inode %lu at logical offset %llu with" " max blocks %u with error %d", inode->i_ino, (unsigned long long)map->m_lblk, (unsigned)map->m_len, -err); (3）Unmap the addr cause warning at __set_page_dirty:WARN_ON_ONCE(warn && !PageUptodate(page)); (4) wait for a minute,then bugon happen. Cc: stable@vger.kernel.org Signed-off-by: wangguang Signed-off-by: Theodore Ts'o --- fs/ext4/inode.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index f058afbc4c46..9b464e5272bb 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1649,6 +1649,8 @@ static void mpage_release_unused_pages(struct mpage_da_data *mpd, BUG_ON(!PageLocked(page)); BUG_ON(PageWriteback(page)); if (invalidate) { + if (page_mapped(page)) + clear_page_dirty_for_io(page); block_invalidatepage(page, 0, PAGE_SIZE); ClearPageUptodate(page); } -- 2.20.1