ext4: clean up GET_BLOCKS_PRE_IO error handling

If the call to ext4_split_convert_extents() fails in the
EXT4_GET_BLOCKS_PRE_IO case within ext4_ext_handle_unwritten_extents(),
error out through the exit point at function end rather than jumping
through an intermediate point.  Fix the error handling in the event
ext4_split_convert_extents() returns 0, which it shouldn't do when
splitting 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/20200430185320.23001-4-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 57f02e2d2f52a230e878b9cdca164547b5a070c5..c63bc13f9a723b364450920b8d26341bae886b02 100644 (file)
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -3818,12 +3818,25 @@ ext4_ext_handle_unwritten_extents(handle_t *handle, struct inode *inode,
        trace_ext4_ext_handle_unwritten_extents(inode, map, flags,
                                                    allocated, newblock);
 
-       /* get_block() before submit the IO, split the extent */
+       /* get_block() before submitting IO, split the extent */
        if (flags & EXT4_GET_BLOCKS_PRE_IO) {
                ret = ext4_split_convert_extents(handle, inode, map, ppath,
                                         flags | EXT4_GET_BLOCKS_CONVERT);
-               if (ret <= 0)
-                       goto out;
+               if (ret < 0) {
+                       err = ret;
+                       goto out2;
+               }
+               /*
+                * shouldn't get a 0 return when splitting an 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;
+               }
                map->m_flags |= EXT4_MAP_UNWRITTEN;
                goto out;
        }
@@ -3863,12 +3876,13 @@ ext4_ext_handle_unwritten_extents(handle_t *handle, struct inode *inode,
        ret = ext4_ext_convert_to_initialized(handle, inode, map, ppath, flags);
        if (ret >= 0)
                ext4_update_inode_fsync_trans(handle, inode, 1);
-out:
+
        if (ret <= 0) {
                err = ret;
                goto out2;
-       } else
-               allocated = ret;
+       }
+out:
+       allocated = ret;
        map->m_flags |= EXT4_MAP_NEW;
 map_out:
        map->m_flags |= EXT4_MAP_MAPPED;