f2fs: Don't update the xattr data that same as the exist

f2fs removes the old xattr data and appends the new data although
the new data is same as the exist.
Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/xattr.c

@@ -545,6 +545,13 @@ ssize_t f2fs_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
 	return error;
 }
 
+static bool f2fs_xattr_value_same(struct f2fs_xattr_entry *entry,
+					const void *value, size_t size)
+{
+	void *pval = entry->e_name + entry->e_name_len;
+	return (entry->e_value_size == size) && !memcmp(pval, value, size);
+}
+
 static int __f2fs_setxattr(struct inode *inode, int index,
 			const char *name, const void *value, size_t size,
 			struct page *ipage, int flags)
@@ -579,14 +586,19 @@ static int __f2fs_setxattr(struct inode *inode, int index,
 
 	found = IS_XATTR_LAST_ENTRY(here) ? 0 : 1;
 
-	if ((flags & XATTR_REPLACE) && !found) {
-		error = -ENODATA;
-		goto exit;
-	} else if ((flags & XATTR_CREATE) && found) {
+	if (found) {
+		if ((flags & XATTR_CREATE)) {
 			error = -EEXIST;
 			goto exit;
 		}
 
+		if (f2fs_xattr_value_same(here, value, size))
+			goto exit;
+	} else if ((flags & XATTR_REPLACE)) {
+		error = -ENODATA;
+		goto exit;
+	}
+
 	last = here;
 	while (!IS_XATTR_LAST_ENTRY(last))
 		last = XATTR_NEXT_ENTRY(last);