fs: add generic xattr_acl handlers

With the ->set_acl inode operation we can implement the Posix ACL
xattr handlers in generic code instead of duplicating them all
over the tree.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/include/linux/posix_acl_xattr.h b/include/linux/posix_acl_xattr.h
index ad93ad0..6f14ee2 100644
--- a/include/linux/posix_acl_xattr.h
+++ b/include/linux/posix_acl_xattr.h
@@ -69,4 +69,7 @@
 int posix_acl_to_xattr(struct user_namespace *user_ns,
 		       const struct posix_acl *acl, void *buffer, size_t size);
 
+extern const struct xattr_handler posix_acl_access_xattr_handler;
+extern const struct xattr_handler posix_acl_default_xattr_handler;
+
 #endif	/* _POSIX_ACL_XATTR_H */