ext4: Introduce ext4_update_*_feature

Introduce ext4_update_*_feature and use them instead
of opencoding.


Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 7b5cfa6..00b152b 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -748,13 +748,10 @@
 	if (test_opt(sb, EXTENTS)) {
 		EXT4_I(inode)->i_flags |= EXT4_EXTENTS_FL;
 		ext4_ext_tree_init(handle, inode);
-		if (!EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_EXTENTS)) {
-			err = ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh);
-			if (err) goto fail;
-			EXT4_SET_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_EXTENTS);
-			BUFFER_TRACE(EXT4_SB(sb)->s_sbh, "call ext4_journal_dirty_metadata");
-			err = ext4_journal_dirty_metadata(handle, EXT4_SB(sb)->s_sbh);
-		}
+		err = ext4_update_incompat_feature(handle, sb,
+						EXT4_FEATURE_INCOMPAT_EXTENTS);
+		if (err)
+			goto fail;
 	}
 
 	ext4_debug("allocating inode %lu\n", inode->i_ino);