ext4: update extent status tree after an extent is zeroed out

When we try to split an extent, this extent could be zeroed out and mark
as initialized.  But we don't know this in ext4_map_blocks because it
only returns a length of allocated extent.  Meanwhile we will mark this
extent as uninitialized because we only check m_flags.

This commit update extent status tree when we try to split an unwritten
extent.  We don't need to worry about the status of this extent because
we always mark it as initialized.

Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Dmitry Monakhov <dmonakhov@openvz.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 3186a43fa4b0..4f1d54a88d8c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -722,6 +722,15 @@ found:
                 }
 #endif
 
+                /*
+                 * If the extent has been zeroed out, we don't need to update
+                 * extent status tree.
+                 */
+                if ((flags & EXT4_GET_BLOCKS_PRE_IO) &&
+                    ext4_es_lookup_extent(inode, map->m_lblk, &es)) {
+                        if (ext4_es_is_written(&es))
+                                goto has_zeroout;
+                }
                 status = map->m_flags & EXT4_MAP_UNWRITTEN ?
                                 EXTENT_STATUS_UNWRITTEN : EXTENT_STATUS_WRITTEN;
                 if (!(flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) &&
@@ -734,6 +743,7 @@ found:
                         retval = ret;
         }
 
+has_zeroout:
         up_write((&EXT4_I(inode)->i_data_sem));
         if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
                 int ret = check_block_validity(inode, map);