ext4: don't ignore return values from ext4_ext_dirty()

Don't ignore return values from ext4_ext_dirty, since the errors
indicate valid failures below Ext4.  In all of the other instances of
ext4_ext_dirty calls, the error return value is handled in some
way. This patch makes those remaining couple of places to handle
ext4_ext_dirty errors as well. In case of ext4_split_extent_at(), the
ignorance of return value is intentional. The reason is that we are
already in error path and there isn't much we can do if ext4_ext_dirty
returns error. This patch adds a comment for that case explaining why
we ignore the return value.

In the longer run, we probably should
make sure that errors from other mark_dirty routines are handled as
well.

Ran gce-xfstests smoke tests and verified that there were no
regressions.
Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20200427013438.219117-2-harshadshirwadkar@gmail.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/extents.c

@@ -3243,6 +3243,10 @@ static int ext4_split_extent_at(handle_t *handle,
 
 fix_extent_len:
 	ex->ee_len = orig_ex.ee_len;
+	/*
+	 * Ignore ext4_ext_dirty return value since we are already in error path
+	 * and err is a non-zero error code.
+	 */
 	ext4_ext_dirty(handle, inode, path + path->p_depth);
 	return err;
 }
@@ -3502,7 +3506,7 @@ static int ext4_ext_convert_to_initialized(handle_t *handle,
 	}
 	if (allocated) {
 		/* Mark the block containing both extents as dirty */
-		ext4_ext_dirty(handle, inode, path + depth);
+		err = ext4_ext_dirty(handle, inode, path + depth);
 
 		/* Update path to point to the right extent */
 		path[depth].p_ext = abut_ex;