ext4: race-condition protection for ext4_convert_unwritten_extents_endio
We assumed that at the time we call ext4_convert_unwritten_extents_endio() extent in question is fully inside [map.m_lblk, map->m_len] because it was already split during submission. But this may not be true due to a race between writeback vs fallocate. If extent in question is larger than requested we will split it again. Special precautions should being done if zeroout required because [map.m_lblk, map->m_len] already contains valid data. Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: stable@vger.kernel.org
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@ -52,6 +52,9 @@
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#define EXT4_EXT_MARK_UNINIT1 0x2 /* mark first half uninitialized */
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#define EXT4_EXT_MARK_UNINIT2 0x4 /* mark second half uninitialized */
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#define EXT4_EXT_DATA_VALID1 0x8 /* first half contains valid data */
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#define EXT4_EXT_DATA_VALID2 0x10 /* second half contains valid data */
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static __le32 ext4_extent_block_csum(struct inode *inode,
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struct ext4_extent_header *eh)
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{
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@ -2914,6 +2917,9 @@ static int ext4_split_extent_at(handle_t *handle,
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unsigned int ee_len, depth;
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int err = 0;
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BUG_ON((split_flag & (EXT4_EXT_DATA_VALID1 | EXT4_EXT_DATA_VALID2)) ==
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(EXT4_EXT_DATA_VALID1 | EXT4_EXT_DATA_VALID2));
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ext_debug("ext4_split_extents_at: inode %lu, logical"
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"block %llu\n", inode->i_ino, (unsigned long long)split);
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@ -2972,7 +2978,14 @@ static int ext4_split_extent_at(handle_t *handle,
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err = ext4_ext_insert_extent(handle, inode, path, &newex, flags);
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if (err == -ENOSPC && (EXT4_EXT_MAY_ZEROOUT & split_flag)) {
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err = ext4_ext_zeroout(inode, &orig_ex);
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if (split_flag & (EXT4_EXT_DATA_VALID1|EXT4_EXT_DATA_VALID2)) {
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if (split_flag & EXT4_EXT_DATA_VALID1)
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err = ext4_ext_zeroout(inode, ex2);
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else
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err = ext4_ext_zeroout(inode, ex);
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} else
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err = ext4_ext_zeroout(inode, &orig_ex);
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if (err)
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goto fix_extent_len;
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/* update the extent length and mark as initialized */
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@ -3025,12 +3038,13 @@ static int ext4_split_extent(handle_t *handle,
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uninitialized = ext4_ext_is_uninitialized(ex);
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if (map->m_lblk + map->m_len < ee_block + ee_len) {
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split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT ?
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EXT4_EXT_MAY_ZEROOUT : 0;
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split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT;
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flags1 = flags | EXT4_GET_BLOCKS_PRE_IO;
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if (uninitialized)
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split_flag1 |= EXT4_EXT_MARK_UNINIT1 |
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EXT4_EXT_MARK_UNINIT2;
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if (split_flag & EXT4_EXT_DATA_VALID2)
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split_flag1 |= EXT4_EXT_DATA_VALID1;
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err = ext4_split_extent_at(handle, inode, path,
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map->m_lblk + map->m_len, split_flag1, flags1);
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if (err)
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@ -3043,8 +3057,8 @@ static int ext4_split_extent(handle_t *handle,
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return PTR_ERR(path);
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if (map->m_lblk >= ee_block) {
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split_flag1 = split_flag & EXT4_EXT_MAY_ZEROOUT ?
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EXT4_EXT_MAY_ZEROOUT : 0;
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split_flag1 = split_flag & (EXT4_EXT_MAY_ZEROOUT |
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EXT4_EXT_DATA_VALID2);
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if (uninitialized)
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split_flag1 |= EXT4_EXT_MARK_UNINIT1;
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if (split_flag & EXT4_EXT_MARK_UNINIT2)
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@ -3323,26 +3337,47 @@ static int ext4_split_unwritten_extents(handle_t *handle,
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split_flag |= ee_block + ee_len <= eof_block ? EXT4_EXT_MAY_ZEROOUT : 0;
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split_flag |= EXT4_EXT_MARK_UNINIT2;
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if (flags & EXT4_GET_BLOCKS_CONVERT)
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split_flag |= EXT4_EXT_DATA_VALID2;
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flags |= EXT4_GET_BLOCKS_PRE_IO;
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return ext4_split_extent(handle, inode, path, map, split_flag, flags);
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}
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static int ext4_convert_unwritten_extents_endio(handle_t *handle,
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struct inode *inode,
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struct ext4_ext_path *path)
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struct inode *inode,
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struct ext4_map_blocks *map,
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struct ext4_ext_path *path)
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{
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struct ext4_extent *ex;
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ext4_lblk_t ee_block;
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unsigned int ee_len;
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int depth;
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int err = 0;
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depth = ext_depth(inode);
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ex = path[depth].p_ext;
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ee_block = le32_to_cpu(ex->ee_block);
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ee_len = ext4_ext_get_actual_len(ex);
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ext_debug("ext4_convert_unwritten_extents_endio: inode %lu, logical"
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"block %llu, max_blocks %u\n", inode->i_ino,
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(unsigned long long)le32_to_cpu(ex->ee_block),
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ext4_ext_get_actual_len(ex));
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(unsigned long long)ee_block, ee_len);
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/* If extent is larger than requested then split is required */
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if (ee_block != map->m_lblk || ee_len > map->m_len) {
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err = ext4_split_unwritten_extents(handle, inode, map, path,
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EXT4_GET_BLOCKS_CONVERT);
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if (err < 0)
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goto out;
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ext4_ext_drop_refs(path);
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path = ext4_ext_find_extent(inode, map->m_lblk, path);
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if (IS_ERR(path)) {
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err = PTR_ERR(path);
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goto out;
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}
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depth = ext_depth(inode);
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ex = path[depth].p_ext;
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}
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err = ext4_ext_get_access(handle, inode, path + depth);
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if (err)
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@ -3652,7 +3687,7 @@ ext4_ext_handle_uninitialized_extents(handle_t *handle, struct inode *inode,
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}
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/* IO end_io complete, convert the filled extent to written */
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if ((flags & EXT4_GET_BLOCKS_CONVERT)) {
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ret = ext4_convert_unwritten_extents_endio(handle, inode,
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ret = ext4_convert_unwritten_extents_endio(handle, inode, map,
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path);
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if (ret >= 0) {
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ext4_update_inode_fsync_trans(handle, inode, 1);
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