ext4: serialize fallocate with ext4_convert_unwritten_extents
Fallocate should wait for pended ext4_convert_unwritten_extents()
otherwise following race may happen:
ftruncate( ,12288);
fallocate( ,0, 4096)
io_sibmit( ,0, 4096); /* Write to fallocated area, split extent if needed */
fallocate( ,0, 8192); /* Grow extent and broke assumption about extent */
Later kwork completion will do:
->ext4_convert_unwritten_extents (0, 4096)
->ext4_map_blocks(handle, inode, &map, EXT4_GET_BLOCKS_IO_CONVERT_EXT);
->ext4_ext_map_blocks() /* Will find new extent: ex = [0,2] !!!!!! */
->ext4_ext_handle_uninitialized_extents()
->ext4_convert_unwritten_extents_endio()
/* convert [0,2] extent to initialized, but only[0,1] was written */
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 1c94cca..c278927 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4428,6 +4428,9 @@
*/
if (len <= EXT_UNINIT_MAX_LEN << blkbits)
flags |= EXT4_GET_BLOCKS_NO_NORMALIZE;
+
+ /* Prevent race condition between unwritten */
+ ext4_flush_unwritten_io(inode);
retry:
while (ret >= 0 && ret < max_blocks) {
map.m_lblk = map.m_lblk + ret;