ext4: constify static data that is never modified

Constify static data in ext4 that is never (intentionally) modified so
that it is placed in .rodata and benefits from memory protection.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 996e790..a9ce2cf 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -81,7 +81,7 @@
 static int ext4_xattr_list(struct dentry *dentry, char *buffer,
 			   size_t buffer_size);
 
-static const struct xattr_handler *ext4_xattr_handler_map[] = {
+static const struct xattr_handler * const ext4_xattr_handler_map[] = {
 	[EXT4_XATTR_INDEX_USER]		     = &ext4_xattr_user_handler,
 #ifdef CONFIG_EXT4_FS_POSIX_ACL
 	[EXT4_XATTR_INDEX_POSIX_ACL_ACCESS]  = &posix_acl_access_xattr_handler,