ext4: Enable extent format for symlinks.

This patch enables extent-formatted normal symlinks.  Using extents
format allows a symlink to refer to a block number larger than 2^32
on large filesystems.  We still don't enable extent format for fast
symlinks, which are contained in the inode itself.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 486e46a..cb14646 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -750,8 +750,8 @@
 		goto fail_free_drop;
 	}
 	if (test_opt(sb, EXTENTS)) {
-		/* set extent flag only for directory and file */
-		if (S_ISDIR(mode) || S_ISREG(mode)) {
+		/* set extent flag only for diretory, file and normal symlink*/
+		if (S_ISDIR(mode) || S_ISREG(mode) || S_ISLNK(mode)) {
 			EXT4_I(inode)->i_flags |= EXT4_EXTENTS_FL;
 			ext4_ext_tree_init(handle, inode);
 			err = ext4_update_incompat_feature(handle, sb,