ext4: clean up ext4_ext_convert_to_initialized() error handling

If ext4_ext_convert_to_initialized() fails when called within
ext4_ext_handle_unwritten_extents(), immediately error out through the
exit point at function end.  Fix the error handling in the event
ext4_ext_convert_to_initialized() returns 0, which it shouldn't do when
converting an existing extent.  The current code returns the passed in
value of allocated (which is likely non-zero) while failing to set
m_flags, m_pblk, and m_len.

Signed-off-by: Eric Whitney <enwlinux@gmail.com>
Link: https://lore.kernel.org/r/20200430185320.23001-5-enwlinux@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index c63bc13..03b94c6 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3872,15 +3872,28 @@ ext4_ext_handle_unwritten_extents(handle_t *handle, struct inode *inode,
                goto out1;
        }
 
-       /* buffered write, writepage time, convert*/
+       /*
+        * Default case when (flags & EXT4_GET_BLOCKS_CREATE) == 1.
+        * For buffered writes, at writepage time, etc.  Convert a
+        * discovered unwritten extent to written.
+        */
        ret = ext4_ext_convert_to_initialized(handle, inode, map, ppath, flags);
-       if (ret >= 0)
-               ext4_update_inode_fsync_trans(handle, inode, 1);
-
-       if (ret <= 0) {
+       if (ret < 0) {
                err = ret;
                goto out2;
        }
+       ext4_update_inode_fsync_trans(handle, inode, 1);
+       /*
+        * shouldn't get a 0 return when converting an unwritten extent
+        * unless m_len is 0 (bug) or extent has been corrupted
+        */
+       if (unlikely(ret == 0)) {
+               EXT4_ERROR_INODE(inode, "unexpected ret == 0, m_len = %u",
+                                map->m_len);
+               err = -EFSCORRUPTED;
+               goto out2;
+       }
+
 out:
        allocated = ret;
        map->m_flags |= EXT4_MAP_NEW;