ext4: ext4_split_extent should take care of extent zeroout (357b66fd) · Commits · 戴 / test

When ext4_split_extent_at() ends up doing zeroout & conversion to initialized instead of split & conversion, ext4_split_extent() gets confused and can wrongly mark the extent back as uninitialized resulting in end IO code getting confused from large unwritten extents and may result in data loss. The example of problematic behavior is: lblk len lblk len ext4_split_extent() (ex=[1000,30,uninit], map=[1010,10]) ext4_split_extent_at() (split [1000,30,uninit] at 1020) ext4_ext_insert_extent() -> ENOSPC ext4_ext_zeroout() -> extent [1000,30] is now initialized ext4_split_extent_at() (split [1000,30,init] at 1010, MARK_UNINIT1 | MARK_UNINIT2) -> extent is split and parts marked as uninitialized Fix the problem by rechecking extent type after the first ext4_split_extent_at() returns. None of split_flags can not be applied to initialized extent so this patch also add BUG_ON to prevent similar issues in future. TESTCASE: https://github.com/dmonakhov/xfstests/commit/b8a55eb5ce28c6ff29e620ab090902fcd5833597 Signed-off-by:

Dmitry Monakhov <dmonakhov@openvz.org> Signed-off-by:

"Theodore Ts'o" <tytso@mit.edu> Reviewed-by:

Jan Kara <jack@suse.cz>

fs/ext4/extents.c

+17 −6

Original line number	Diff line number	Diff line
		@@ -2943,6 +2943,10 @@ static int ext4_split_extent_at(handle_t *handle,
		newblock = split - ee_block + ext4_ext_pblock(ex);

		BUG_ON(split < ee_block \|\| split >= (ee_block + ee_len));
		BUG_ON(!ext4_ext_is_uninitialized(ex) &&
		split_flag & (EXT4_EXT_MAY_ZEROOUT \|
		EXT4_EXT_MARK_UNINIT1 \|
		EXT4_EXT_MARK_UNINIT2));

		err = ext4_ext_get_access(handle, inode, path + depth);
		if (err)
		@@ -3061,19 +3065,26 @@ static int ext4_split_extent(handle_t *handle,
		if (err)
		goto out;
		}

		/*
		* Update path is required because previous ext4_split_extent_at() may
		* result in split of original leaf or extent zeroout.
		*/
		ext4_ext_drop_refs(path);
		path = ext4_ext_find_extent(inode, map->m_lblk, path);
		if (IS_ERR(path))
		return PTR_ERR(path);
		depth = ext_depth(inode);
		ex = path[depth].p_ext;
		uninitialized = ext4_ext_is_uninitialized(ex);
		split_flag1 = 0;

		if (map->m_lblk >= ee_block) {
		split_flag1 = split_flag & (EXT4_EXT_MAY_ZEROOUT \|
		EXT4_EXT_DATA_VALID2);
		if (uninitialized)
		split_flag1 = split_flag & EXT4_EXT_DATA_VALID2;
		if (uninitialized) {
		split_flag1 \|= EXT4_EXT_MARK_UNINIT1;
		if (split_flag & EXT4_EXT_MARK_UNINIT2)
		split_flag1 \|= EXT4_EXT_MARK_UNINIT2;
		split_flag1 \|= split_flag & (EXT4_EXT_MAY_ZEROOUT \|
		EXT4_EXT_MARK_UNINIT2);
		}
		err = ext4_split_extent_at(handle, inode, path,
		map->m_lblk, split_flag1, flags);
		if (err)

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