Commit 6dd834ef authored Apr 18, 2014 by Lukas Czerner Committed by Theodore Ts'o Apr 18, 2014

ext4: fix extent merging in ext4_ext_shift_path_extents()



There is a bug in ext4_ext_shift_path_extents() where if we actually
manage to merge a extent we would skip shifting the next extent. This
will result in in one extent in the extent tree not being properly
shifted.

This is causing failure in various xfstests tests using fsx or fsstress
with collapse range support. It will also cause file system corruption
which looks something like:

 e2fsck 1.42.9 (4-Feb-2014)
 Pass 1: Checking inodes, blocks, and sizes
 Inode 20 has out of order extents
        (invalid logical block 3, physical block 492938, len 2)
 Clear? yes
 ...

when running e2fsck.

It's also very easily reproducible just by running fsx without any
parameters. I can usually hit the problem within a minute.

Fix it by increasing ex_start only if we're not merging the extent.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Namjae Jeon <namjae.jeon@samsung.com>

parent ef24f6c2

fs/ext4/extents.c

+8 −7

Original line number	Diff line number	Diff line
		@@ -5245,12 +5245,13 @@ ext4_ext_shift_path_extents(struct ext4_ext_path *path, ext4_lblk_t shift,

		while (ex_start <= ex_last) {
		le32_add_cpu(&ex_start->ee_block, -shift);
		if (ex_start >
		EXT_FIRST_EXTENT(path[depth].p_hdr)) {
		if (ext4_ext_try_to_merge_right(inode,
		/* Try to merge to the left. */
		if ((ex_start >
		EXT_FIRST_EXTENT(path[depth].p_hdr)) &&
		ext4_ext_try_to_merge_right(inode,
		path, ex_start - 1))
		ex_last--;
		}
		else
		ex_start++;
		}
		err = ext4_ext_dirty(handle, inode, path + depth);

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