+----------------------- xattr_handler operations -----------------------
+prototypes:
+ bool (*list)(struct dentry *dentry);
+ int (*get)(const struct xattr_handler *handler, struct dentry *dentry,
+ struct inode *inode, const char *name, void *buffer,
+ size_t size);
+ int (*set)(const struct xattr_handler *handler, struct dentry *dentry,
+ struct inode *inode, const char *name, const void *buffer,
+ size_t size, int flags);
+
+locking rules:
+ all may block
+ i_mutex(inode)
+list: no
+get: no
+set: yes
+