iomap: fiemap should honor the FIEMAP_FLAG_SYNC flag

The flag is checked as supported, but then we do an unconditional
sync of the file, regardless of whether the flag is set or not. Make
the sync conditional on having the FIEMAP_FLAG_SYNC flag set.
Signed-off-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDave Chinner <david@fromorbit.com>

fs/iomap.c

@@ -467,9 +467,11 @@ int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
 	if (ret)
 		return ret;
 
-	ret = filemap_write_and_wait(inode->i_mapping);
-	if (ret)
-		return ret;
+	if (fi->fi_flags & FIEMAP_FLAG_SYNC) {
+		ret = filemap_write_and_wait(inode->i_mapping);
+		if (ret)
+			return ret;
+	}
 
 	while (len > 0) {
 		ret = iomap_apply(inode, start, len, 0, ops, &ctx,