From 9b623df614576680cadeaa4d7e0b5884de8f7c17 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Fri, 30 Sep 2016 02:02:29 -0400 Subject: [PATCH] ext4: unmap metadata when zeroing blocks When zeroing blocks for DAX allocations, we also have to unmap aliases in the block device mappings. Otherwise writeback can overwrite zeros with stale data from block device page cache. Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o Cc: stable@kernel.org --- fs/ext4/inode.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index d8a4afc5eedb..cd918823b352 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -647,11 +647,19 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode, /* * We have to zeroout blocks before inserting them into extent * status tree. Otherwise someone could look them up there and - * use them before they are really zeroed. + * use them before they are really zeroed. We also have to + * unmap metadata before zeroing as otherwise writeback can + * overwrite zeros with stale data from block device. */ if (flags & EXT4_GET_BLOCKS_ZERO && map->m_flags & EXT4_MAP_MAPPED && map->m_flags & EXT4_MAP_NEW) { + ext4_lblk_t i; + + for (i = 0; i < map->m_len; i++) { + unmap_underlying_metadata(inode->i_sb->s_bdev, + map->m_pblk + i); + } ret = ext4_issue_zeroout(inode, map->m_lblk, map->m_pblk, map->m_len); if (ret) {