switch ->get_link() to delayed_call, kill ->put_link()

Signed-off-by: Al Viro <[e-mail]>

Documentation/filesystems/Locking

···
 			struct inode *, struct dentry *, unsigned int);
 	int (*readlink) (struct dentry *, char __user *,int);
 	const char *(*get_link) (struct dentry *, struct inode *, void **);
-	void (*put_link) (struct inode *, void *);
 	void (*truncate) (struct inode *);
 	int (*permission) (struct inode *, int, unsigned int);
 	int (*get_acl)(struct inode *, int);
···
 rename2:	yes (all)	(see below)
 readlink:	no
 get_link:	no
-put_link:	no
 setattr:	yes
 permission:	no (may not block if called in rcu-walk mode)
 get_acl:	no

Documentation/filesystems/porting

···
 		* ->get_link() gets inode as a separate argument
 		* ->get_link() may be called in RCU mode - in that case NULL
 		  dentry is passed
+--
+[mandatory]
+	->get_link() gets struct delayed_call *done now, and should do
+	set_delayed_call() where it used to set *cookie.
+	->put_link() is gone - just give the destructor to set_delayed_call()
+	in ->get_link().

Documentation/filesystems/vfs.txt

···
 	int (*rename2) (struct inode *, struct dentry *,
 			struct inode *, struct dentry *, unsigned int);
 	int (*readlink) (struct dentry *, char __user *,int);
-	const char *(*follow_link) (struct dentry *, void **);
-	void (*put_link) (struct inode *, void *);
+	const char *(*get_link) (struct dentry *, struct inode *,
+				 struct delayed_call *);
 	int (*permission) (struct inode *, int);
 	int (*get_acl)(struct inode *, int);
 	int (*setattr) (struct dentry *, struct iattr *);
···
   readlink: called by the readlink(2) system call. Only required if
 	you want to support reading symbolic links
 
-  follow_link: called by the VFS to follow a symbolic link to the
+  get_link: called by the VFS to follow a symbolic link to the
 	inode it points to.  Only required if you want to support
 	symbolic links.  This method returns the symlink body
 	to traverse (and possibly resets the current position with
 	nd_jump_link()).  If the body won't go away until the inode
 	is gone, nothing else is needed; if it needs to be otherwise
-	pinned, the data needed to release whatever we'd grabbed
-	is to be stored in void * variable passed by address to
-	follow_link() instance.
-
-  put_link: called by the VFS to release resources allocated by
-	follow_link().  The cookie stored by follow_link() is passed
-	to this method as the last parameter; only called when
-	cookie isn't NULL.
+	pinned, arrange for its release by having get_link(..., ..., done)
+	do set_delayed_call(done, destructor, argument).
+	In that case destructor(argument) will be called once VFS is
+	done with the body you've returned.
+	May be called in RCU mode; that is indicated by NULL dentry
+	argument.  If request can't be handled without leaving RCU mode,
+	have it return ERR_PTR(-ECHILD).
 
   permission: called by the VFS to check for access rights on a POSIX-like
   	filesystem.

drivers/staging/lustre/lustre/llite/symlink.c

···
 	return rc;
 }
 
+static void ll_put_link(void *p)
+{
+	ptlrpc_req_finished(p);
+}
+
 static const char *ll_get_link(struct dentry *dentry,
-			       struct inode *inode, void **cookie)
+			       struct inode *inode,
+			       struct delayed_call *done)
 {
 	struct ptlrpc_request *request = NULL;
 	int rc;
···
 	}
 
 	/* symname may contain a pointer to the request message buffer,
-	 * we delay request releasing until ll_put_link then.
+	 * we delay request releasing then.
 	 */
-	*cookie = request;
+	set_delayed_call(done, ll_put_link, request);
 	return symname;
-}
-
-static void ll_put_link(struct inode *unused, void *cookie)
-{
-	ptlrpc_req_finished(cookie);
 }
 
 struct inode_operations ll_fast_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.setattr	= ll_setattr,
 	.get_link	= ll_get_link,
-	.put_link	= ll_put_link,
 	.getattr	= ll_getattr,
 	.permission	= ll_inode_permission,
 	.setxattr	= ll_setxattr,

fs/9p/vfs_inode.c

···
  * v9fs_vfs_get_link - follow a symlink path
  * @dentry: dentry for symlink
  * @inode: inode for symlink
- * @cookie: place to pass the data to put_link()
+ * @done: delayed call for when we are done with the return value
  */
 
 static const char *v9fs_vfs_get_link(struct dentry *dentry,
-				     struct inode *inode, void **cookie)
+				     struct inode *inode,
+				     struct delayed_call *done)
 {
 	struct v9fs_session_info *v9ses;
 	struct p9_fid *fid;
···
 
 	p9stat_free(st);
 	kfree(st);
-	return *cookie = res;
+	set_delayed_call(done, kfree_link, res);
+	return res;
 }
 
 /**
···
 static const struct inode_operations v9fs_symlink_inode_operations = {
 	.readlink = generic_readlink,
 	.get_link = v9fs_vfs_get_link,
-	.put_link = kfree_put_link,
 	.getattr = v9fs_vfs_getattr,
 	.setattr = v9fs_vfs_setattr,
 };

fs/9p/vfs_inode_dotl.c

···
  * v9fs_vfs_get_link_dotl - follow a symlink path
  * @dentry: dentry for symlink
  * @inode: inode for symlink
- * @cookie: place to pass the data to put_link()
+ * @done: destructor for return value
  */
 
 static const char *
 v9fs_vfs_get_link_dotl(struct dentry *dentry,
-		       struct inode *inode, void **cookie)
+		       struct inode *inode,
+		       struct delayed_call *done)
 {
 	struct p9_fid *fid;
 	char *target;
···
 	retval = p9_client_readlink(fid, &target);
 	if (retval)
 		return ERR_PTR(retval);
-	return *cookie = target;
+	set_delayed_call(done, kfree_link, target);
+	return target;
 }
 
 int v9fs_refresh_inode_dotl(struct p9_fid *fid, struct inode *inode)
···
 const struct inode_operations v9fs_symlink_inode_operations_dotl = {
 	.readlink = generic_readlink,
 	.get_link = v9fs_vfs_get_link_dotl,
-	.put_link = kfree_put_link,
 	.getattr = v9fs_vfs_getattr_dotl,
 	.setattr = v9fs_vfs_setattr_dotl,
 	.setxattr = generic_setxattr,

fs/affs/symlink.c

···
 const struct inode_operations affs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= page_get_link,
-	.put_link	= page_put_link,
 	.setattr	= affs_notify_change,
 };

fs/autofs4/symlink.c

···
 #include "autofs_i.h"
 
 static const char *autofs4_get_link(struct dentry *dentry,
-				    struct inode *inode, void **cookie)
+				    struct inode *inode,
+				    struct delayed_call *done)
 {
 	struct autofs_sb_info *sbi;
 	struct autofs_info *ino;

fs/btrfs/inode.c

···
 static const struct inode_operations btrfs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= page_get_link,
-	.put_link	= page_put_link,
 	.getattr	= btrfs_getattr,
 	.setattr	= btrfs_setattr,
 	.permission	= btrfs_permission,

fs/cifs/cifsfs.c

···
 const struct inode_operations cifs_symlink_inode_ops = {
 	.readlink = generic_readlink,
 	.get_link = cifs_get_link,
-	.put_link = kfree_put_link,
 	.permission = cifs_permission,
 	/* BB add the following two eventually */
 	/* revalidate: cifs_revalidate,

fs/cifs/cifsfs.h

···
 #endif
 
 /* Functions related to symlinks */
-extern const char *cifs_get_link(struct dentry *, struct inode *, void **);
+extern const char *cifs_get_link(struct dentry *, struct inode *,
+			struct delayed_call *);
 extern int cifs_symlink(struct inode *inode, struct dentry *direntry,
 			const char *symname);
 extern int	cifs_removexattr(struct dentry *, const char *);

fs/cifs/link.c

···
 }
 
 const char *
-cifs_get_link(struct dentry *direntry, struct inode *inode, void **cookie)
+cifs_get_link(struct dentry *direntry, struct inode *inode,
+	      struct delayed_call *done)
 {
 	int rc = -ENOMEM;
 	unsigned int xid;
···
 		kfree(target_path);
 		return ERR_PTR(rc);
 	}
-	return *cookie = target_path;
+	set_delayed_call(done, kfree_link, target_path);
+	return target_path;
 }
 
 int

fs/coda/cnode.c

···
 static const struct inode_operations coda_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= page_get_link,
-	.put_link	= page_put_link,
 	.setattr	= coda_setattr,
 };
 

fs/configfs/symlink.c

···
 }
 
 static const char *configfs_get_link(struct dentry *dentry,
-				     struct inode *inode, void **cookie)
+				     struct inode *inode,
+				     struct delayed_call *done)
 {
-	char *page;
+	char *body;
 	int error;
 
 	if (!dentry)
 		return ERR_PTR(-ECHILD);
 
-	page = kzalloc(PAGE_SIZE, GFP_KERNEL);
-	if (!page)
+	body = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!body)
 		return ERR_PTR(-ENOMEM);
 
-	error = configfs_getlink(dentry, page);
+	error = configfs_getlink(dentry, body);
 	if (!error) {
-		return *cookie = page;
+		set_delayed_call(done, kfree_link, body);
+		return body;
 	}
 
-	kfree(page);
+	kfree(body);
 	return ERR_PTR(error);
 }
 
 const struct inode_operations configfs_symlink_inode_operations = {
 	.get_link = configfs_get_link,
 	.readlink = generic_readlink,
-	.put_link = kfree_put_link,
 	.setattr = configfs_setattr,
 };
 

fs/ecryptfs/inode.c

···
 }
 
 static const char *ecryptfs_get_link(struct dentry *dentry,
-				     struct inode *inode, void **cookie)
+				     struct inode *inode,
+				     struct delayed_call *done)
 {
 	size_t len;
 	char *buf;
···
 	fsstack_copy_attr_atime(d_inode(dentry),
 				d_inode(ecryptfs_dentry_to_lower(dentry)));
 	buf[len] = '\0';
-	return *cookie = buf;
+	set_delayed_call(done, kfree_link, buf);
+	return buf;
 }
 
 /**
···
 const struct inode_operations ecryptfs_symlink_iops = {
 	.readlink = generic_readlink,
 	.get_link = ecryptfs_get_link,
-	.put_link = kfree_put_link,
 	.permission = ecryptfs_permission,
 	.setattr = ecryptfs_setattr,
 	.getattr = ecryptfs_getattr_link,

fs/ext2/symlink.c

···
 const struct inode_operations ext2_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= page_get_link,
-	.put_link	= page_put_link,
 	.setattr	= ext2_setattr,
 #ifdef CONFIG_EXT2_FS_XATTR
 	.setxattr	= generic_setxattr,

fs/ext4/symlink.c

···
 
 #ifdef CONFIG_EXT4_FS_ENCRYPTION
 static const char *ext4_encrypted_get_link(struct dentry *dentry,
-					   struct inode *inode, void **cookie)
+					   struct inode *inode,
+					   struct delayed_call *done)
 {
 	struct page *cpage = NULL;
 	char *caddr, *paddr = NULL;
···
 		paddr[res] = '\0';
 	if (cpage)
 		page_cache_release(cpage);
-	return *cookie = paddr;
+	set_delayed_call(done, kfree_link, paddr);
+	return paddr;
 errout:
 	if (cpage)
 		page_cache_release(cpage);
···
 const struct inode_operations ext4_encrypted_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= ext4_encrypted_get_link,
-	.put_link       = kfree_put_link,
 	.setattr	= ext4_setattr,
 	.setxattr	= generic_setxattr,
 	.getxattr	= generic_getxattr,
···
 const struct inode_operations ext4_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= page_get_link,
-	.put_link	= page_put_link,
 	.setattr	= ext4_setattr,
 	.setxattr	= generic_setxattr,
 	.getxattr	= generic_getxattr,

fs/f2fs/namei.c

···
 }
 
 static const char *f2fs_get_link(struct dentry *dentry,
-				 struct inode *inode, void **cookie)
+				 struct inode *inode,
+				 struct delayed_call *done)
 {
-	const char *link = page_get_link(dentry, inode, cookie);
+	const char *link = page_get_link(dentry, inode, done);
 	if (!IS_ERR(link) && !*link) {
 		/* this is broken symlink case */
-		page_put_link(NULL, *cookie);
+		do_delayed_call(done);
+		clear_delayed_call(done);
 		link = ERR_PTR(-ENOENT);
 	}
 	return link;
···
 
 #ifdef CONFIG_F2FS_FS_ENCRYPTION
 static const char *f2fs_encrypted_get_link(struct dentry *dentry,
-					   struct inode *inode, void **cookie)
+					   struct inode *inode,
+					   struct delayed_call *done)
 {
 	struct page *cpage = NULL;
 	char *caddr, *paddr = NULL;
···
 	paddr[res] = '\0';
 
 	page_cache_release(cpage);
-	return *cookie = paddr;
+	set_delayed_call(done, kfree_link, paddr);
+	return paddr;
 errout:
 	kfree(cstr.name);
 	f2fs_fname_crypto_free_buffer(&pstr);
···
 const struct inode_operations f2fs_encrypted_symlink_inode_operations = {
 	.readlink       = generic_readlink,
 	.get_link       = f2fs_encrypted_get_link,
-	.put_link       = kfree_put_link,
 	.getattr	= f2fs_getattr,
 	.setattr	= f2fs_setattr,
 	.setxattr	= generic_setxattr,
···
 const struct inode_operations f2fs_symlink_inode_operations = {
 	.readlink       = generic_readlink,
 	.get_link       = f2fs_get_link,
-	.put_link       = page_put_link,
 	.getattr	= f2fs_getattr,
 	.setattr	= f2fs_setattr,
 #ifdef CONFIG_F2FS_FS_XATTR

fs/fuse/dir.c

···
 }
 
 static const char *fuse_get_link(struct dentry *dentry,
-				 struct inode *inode, void **cookie)
+				 struct inode *inode,
+				 struct delayed_call *done)
 {
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	FUSE_ARGS(args);
···
 		link = ERR_PTR(ret);
 	} else {
 		link[ret] = '\0';
-		*cookie = link;
+		set_delayed_call(done, kfree_link, link);
 	}
 	fuse_invalidate_atime(inode);
 	return link;
···
 static const struct inode_operations fuse_symlink_inode_operations = {
 	.setattr	= fuse_setattr,
 	.get_link	= fuse_get_link,
-	.put_link	= kfree_put_link,
 	.readlink	= generic_readlink,
 	.getattr	= fuse_getattr,
 	.setxattr	= fuse_setxattr,

fs/gfs2/inode.c

···
  * gfs2_get_link - Follow a symbolic link
  * @dentry: The dentry of the link
  * @inode: The inode of the link
- * @cookie: place to store the information for ->put_link()
+ * @done: destructor for return value
  *
  * This can handle symlinks of any size.
  *
···
  */
 
 static const char *gfs2_get_link(struct dentry *dentry,
-				 struct inode *inode, void **cookie)
+				 struct inode *inode,
+				 struct delayed_call *done)
 {
 	struct gfs2_inode *ip = GFS2_I(inode);
 	struct gfs2_holder i_gh;
···
 out:
 	gfs2_glock_dq_uninit(&i_gh);
 	if (!IS_ERR(buf))
-		*cookie = buf;
+		set_delayed_call(done, kfree_link, buf);
 	return buf;
 }
 
···
 const struct inode_operations gfs2_symlink_iops = {
 	.readlink = generic_readlink,
 	.get_link = gfs2_get_link,
-	.put_link = kfree_put_link,
 	.permission = gfs2_permission,
 	.setattr = gfs2_setattr,
 	.getattr = gfs2_getattr,

fs/hostfs/hostfs_kern.c

···
 };
 
 static const char *hostfs_get_link(struct dentry *dentry,
-				   struct inode *inode, void **cookie)
+				   struct inode *inode,
+				   struct delayed_call *done)
 {
 	char *link;
 	if (!dentry)
 		return ERR_PTR(-ECHILD);
-	link = __getname();
+	link = kmalloc(PATH_MAX, GFP_KERNEL);
 	if (link) {
 		char *path = dentry_name(dentry);
 		int err = -ENOMEM;
···
 			__putname(path);
 		}
 		if (err < 0) {
-			__putname(link);
+			kfree(link);
 			return ERR_PTR(err);
 		}
 	} else {
 		return ERR_PTR(-ENOMEM);
 	}
 
-	return *cookie = link;
-}
-
-static void hostfs_put_link(struct inode *unused, void *cookie)
-{
-	__putname(cookie);
+	set_delayed_call(done, kfree_link, link);
+	return link;
 }
 
 static const struct inode_operations hostfs_link_iops = {
 	.readlink	= generic_readlink,
 	.get_link	= hostfs_get_link,
-	.put_link	= hostfs_put_link,
 };
 
 static int hostfs_fill_sb_common(struct super_block *sb, void *d, int silent)

fs/jfs/symlink.c

···
 const struct inode_operations jfs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= page_get_link,
-	.put_link	= page_put_link,
 	.setattr	= jfs_setattr,
 	.setxattr	= jfs_setxattr,
 	.getxattr	= jfs_getxattr,

fs/kernfs/symlink.c

···
 }
 
 static const char *kernfs_iop_get_link(struct dentry *dentry,
-				       struct inode *inode, void **cookie)
+				       struct inode *inode,
+				       struct delayed_call *done)
 {
-	int error = -ENOMEM;
-	char *page;
+	char *body;
+	int error;
 
 	if (!dentry)
 		return ERR_PTR(-ECHILD);
-	page = kzalloc(PAGE_SIZE, GFP_KERNEL);
-	if (!page)
+	body = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!body)
 		return ERR_PTR(-ENOMEM);
-	error = kernfs_getlink(dentry, page);
+	error = kernfs_getlink(dentry, body);
 	if (unlikely(error < 0)) {
-		kfree(page);
+		kfree(body);
 		return ERR_PTR(error);
 	}
-	return *cookie = page;
+	set_delayed_call(done, kfree_link, body);
+	return body;
 }
 
 const struct inode_operations kernfs_symlink_iops = {
···
 	.listxattr	= kernfs_iop_listxattr,
 	.readlink	= generic_readlink,
 	.get_link	= kernfs_iop_get_link,
-	.put_link	= kfree_put_link,
 	.setattr	= kernfs_iop_setattr,
 	.getattr	= kernfs_iop_getattr,
 	.permission	= kernfs_iop_permission,

fs/libfs.c

···
 }
 EXPORT_SYMBOL(noop_fsync);
 
-void kfree_put_link(struct inode *unused, void *cookie)
+/* Because kfree isn't assignment-compatible with void(void*) ;-/ */
+void kfree_link(void *p)
 {
-	kfree(cookie);
+	kfree(p);
 }
-EXPORT_SYMBOL(kfree_put_link);
+EXPORT_SYMBOL(kfree_link);
 
 /*
  * nop .set_page_dirty method so that people can use .page_mkwrite on
···
 EXPORT_SYMBOL(simple_nosetlease);
 
 const char *simple_get_link(struct dentry *dentry, struct inode *inode,
-			    void **cookie)
+			    struct delayed_call *done)
 {
 	return inode->i_link;
 }

fs/minix/inode.c

···
 static const struct inode_operations minix_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= page_get_link,
-	.put_link	= page_put_link,
 	.getattr	= minix_getattr,
 };
 

fs/namei.c

···
 	int		total_link_count;
 	struct saved {
 		struct path link;
-		void *cookie;
+		struct delayed_call done;
 		const char *name;
-		struct inode *inode;
 		unsigned seq;
 	} *stack, internal[EMBEDDED_LEVELS];
 	struct filename	*name;
 	struct nameidata *saved;
+	struct inode	*link_inode;
 	unsigned	root_seq;
 	int		dfd;
 };
···
 	int i = nd->depth;
 	while (i--) {
 		struct saved *last = nd->stack + i;
-		struct inode *inode = last->inode;
-		if (last->cookie && inode->i_op->put_link) {
-			inode->i_op->put_link(inode, last->cookie);
-			last->cookie = NULL;
-		}
+		do_delayed_call(&last->done);
+		clear_delayed_call(&last->done);
 	}
 }
 
···
 static inline void put_link(struct nameidata *nd)
 {
 	struct saved *last = nd->stack + --nd->depth;
-	struct inode *inode = last->inode;
-	if (last->cookie && inode->i_op->put_link)
-		inode->i_op->put_link(inode, last->cookie);
+	do_delayed_call(&last->done);
 	if (!(nd->flags & LOOKUP_RCU))
 		path_put(&last->link);
 }
···
 		return 0;
 
 	/* Allowed if owner and follower match. */
-	inode = nd->stack[0].inode;
+	inode = nd->link_inode;
 	if (uid_eq(current_cred()->fsuid, inode->i_uid))
 		return 0;
 
···
 {
 	struct saved *last = nd->stack + nd->depth - 1;
 	struct dentry *dentry = last->link.dentry;
-	struct inode *inode = last->inode;
+	struct inode *inode = nd->link_inode;
 	int error;
 	const char *res;
 
···
 	nd->last_type = LAST_BIND;
 	res = inode->i_link;
 	if (!res) {
+		const char * (*get)(struct dentry *, struct inode *,
+				struct delayed_call *);
+		get = inode->i_op->get_link;
 		if (nd->flags & LOOKUP_RCU) {
-			res = inode->i_op->get_link(NULL, inode,
-						    &last->cookie);
+			res = get(NULL, inode, &last->done);
 			if (res == ERR_PTR(-ECHILD)) {
 				if (unlikely(unlazy_walk(nd, NULL, 0)))
 					return ERR_PTR(-ECHILD);
-				res = inode->i_op->get_link(dentry, inode,
-						            &last->cookie);
+				res = get(dentry, inode, &last->done);
 			}
 		} else {
-			res = inode->i_op->get_link(dentry, inode,
-						    &last->cookie);
+			res = get(dentry, inode, &last->done);
 		}
-		if (IS_ERR_OR_NULL(res)) {
-			last->cookie = NULL;
+		if (IS_ERR_OR_NULL(res))
 			return res;
-		}
 	}
 	if (*res == '/') {
 		if (nd->flags & LOOKUP_RCU) {
···
 
 	last = nd->stack + nd->depth++;
 	last->link = *link;
-	last->cookie = NULL;
-	last->inode = inode;
+	clear_delayed_call(&last->done);
+	nd->link_inode = inode;
 	last->seq = seq;
 	return 1;
 }
···
  */
 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 {
-	void *cookie;
+	DEFINE_DELAYED_CALL(done);
 	struct inode *inode = d_inode(dentry);
 	const char *link = inode->i_link;
 	int res;
 
 	if (!link) {
-		link = inode->i_op->get_link(dentry, inode, &cookie);
+		link = inode->i_op->get_link(dentry, inode, &done);
 		if (IS_ERR(link))
 			return PTR_ERR(link);
 	}
 	res = readlink_copy(buffer, buflen, link);
-	if (inode->i_op->put_link)
-		inode->i_op->put_link(inode, cookie);
+	do_delayed_call(&done);
 	return res;
 }
 EXPORT_SYMBOL(generic_readlink);
 
 /* get the link contents into pagecache */
 const char *page_get_link(struct dentry *dentry, struct inode *inode,
-				 void **cookie)
+			  struct delayed_call *callback)
 {
 	char *kaddr;
 	struct page *page;
···
 		if (IS_ERR(page))
 			return (char*)page;
 	}
-	*cookie = page;
+	set_delayed_call(callback, page_put_link, page);
 	BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
 	kaddr = page_address(page);
 	nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
···
 
 EXPORT_SYMBOL(page_get_link);
 
-void page_put_link(struct inode *unused, void *cookie)
+void page_put_link(void *arg)
 {
-	struct page *page = cookie;
-	page_cache_release(page);
+	put_page(arg);
 }
 EXPORT_SYMBOL(page_put_link);
 
 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 {
-	void *cookie = NULL;
+	DEFINE_DELAYED_CALL(done);
 	int res = readlink_copy(buffer, buflen,
 				page_get_link(dentry, d_inode(dentry),
-					      &cookie));
-	if (cookie)
-		page_put_link(NULL, cookie);
+					      &done));
+	do_delayed_call(&done);
 	return res;
 }
 EXPORT_SYMBOL(page_readlink);
···
 const struct inode_operations page_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= page_get_link,
-	.put_link	= page_put_link,
 };
 EXPORT_SYMBOL(page_symlink_inode_operations);

fs/ncpfs/inode.c

···
 static const struct inode_operations ncp_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= page_get_link,
-	.put_link	= page_put_link,
 	.setattr	= ncp_notify_change,
 };
 #endif

fs/nfs/symlink.c

···
 }
 
 static const char *nfs_get_link(struct dentry *dentry,
-				struct inode *inode, void **cookie)
+				struct inode *inode,
+				struct delayed_call *done)
 {
 	struct page *page;
 	void *err;
···
 		if (IS_ERR(page))
 			return ERR_CAST(page);
 	}
-	*cookie = page;
+	set_delayed_call(done, page_put_link, page);
 	return page_address(page);
 }
 
···
 const struct inode_operations nfs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= nfs_get_link,
-	.put_link	= page_put_link,
 	.getattr	= nfs_getattr,
 	.setattr	= nfs_setattr,
 };

fs/nilfs2/namei.c

···
 const struct inode_operations nilfs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= page_get_link,
-	.put_link	= page_put_link,
 	.permission     = nilfs_permission,
 };
 

fs/ocfs2/symlink.c

···
 const struct inode_operations ocfs2_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= page_get_link,
-	.put_link	= page_put_link,
 	.getattr	= ocfs2_getattr,
 	.setattr	= ocfs2_setattr,
 	.setxattr	= generic_setxattr,

fs/overlayfs/inode.c

···
 	return err;
 }
 
-
-struct ovl_link_data {
-	struct dentry *realdentry;
-	void *cookie;
-};
-
 static const char *ovl_get_link(struct dentry *dentry,
-				struct inode *inode, void **cookie)
+				struct inode *inode,
+				struct delayed_call *done)
 {
 	struct dentry *realdentry;
 	struct inode *realinode;
-	struct ovl_link_data *data = NULL;
-	const char *ret;
 
 	if (!dentry)
 		return ERR_PTR(-ECHILD);
···
 	if (WARN_ON(!realinode->i_op->get_link))
 		return ERR_PTR(-EPERM);
 
-	if (realinode->i_op->put_link) {
-		data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
-		if (!data)
-			return ERR_PTR(-ENOMEM);
-		data->realdentry = realdentry;
-	}
-
-	ret = realinode->i_op->get_link(realdentry, realinode, cookie);
-	if (IS_ERR_OR_NULL(ret)) {
-		kfree(data);
-		return ret;
-	}
-
-	if (data)
-		data->cookie = *cookie;
-
-	*cookie = data;
-
-	return ret;
-}
-
-static void ovl_put_link(struct inode *unused, void *c)
-{
-	struct inode *realinode;
-	struct ovl_link_data *data = c;
-
-	if (!data)
-		return;
-
-	realinode = data->realdentry->d_inode;
-	realinode->i_op->put_link(realinode, data->cookie);
-	kfree(data);
+	return realinode->i_op->get_link(realdentry, realinode, done);
 }
 
 static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
···
 static const struct inode_operations ovl_symlink_inode_operations = {
 	.setattr	= ovl_setattr,
 	.get_link	= ovl_get_link,
-	.put_link	= ovl_put_link,
 	.readlink	= ovl_readlink,
 	.getattr	= ovl_getattr,
 	.setxattr	= ovl_setxattr,

fs/proc/base.c

···
 }
 
 static const char *proc_pid_get_link(struct dentry *dentry,
-				     struct inode *inode, void **cookie)
+				     struct inode *inode,
+				     struct delayed_call *done)
 {
 	struct path path;
 	int error = -EACCES;
···
  */
 static const char *
 proc_map_files_get_link(struct dentry *dentry,
-			struct inode *inode, void **cookie)
+			struct inode *inode,
+		        struct delayed_call *done)
 {
 	if (!capable(CAP_SYS_ADMIN))
 		return ERR_PTR(-EPERM);
 
-	return proc_pid_get_link(dentry, inode, NULL);
+	return proc_pid_get_link(dentry, inode, done);
 }
 
 /*

fs/proc/inode.c

···
 };
 #endif
 
+static void proc_put_link(void *p)
+{
+	unuse_pde(p);
+}
+
 static const char *proc_get_link(struct dentry *dentry,
-				 struct inode *inode, void **cookie)
+				 struct inode *inode,
+				 struct delayed_call *done)
 {
 	struct proc_dir_entry *pde = PDE(inode);
 	if (unlikely(!use_pde(pde)))
 		return ERR_PTR(-EINVAL);
-	*cookie = pde;
+	set_delayed_call(done, proc_put_link, pde);
 	return pde->data;
-}
-
-static void proc_put_link(struct inode *unused, void *p)
-{
-	unuse_pde(p);
 }
 
 const struct inode_operations proc_link_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= proc_get_link,
-	.put_link	= proc_put_link,
 };
 
 struct inode *proc_get_inode(struct super_block *sb, struct proc_dir_entry *de)

fs/proc/namespaces.c

···
 };
 
 static const char *proc_ns_get_link(struct dentry *dentry,
-				    struct inode *inode, void **cookie)
+				    struct inode *inode,
+				    struct delayed_call *done)
 {
 	const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns_ops;
 	struct task_struct *task;

fs/proc/self.c

···
 }
 
 static const char *proc_self_get_link(struct dentry *dentry,
-				      struct inode *inode, void **cookie)
+				      struct inode *inode,
+				      struct delayed_call *done)
 {
 	struct pid_namespace *ns = inode->i_sb->s_fs_info;
 	pid_t tgid = task_tgid_nr_ns(current, ns);
···
 	if (unlikely(!name))
 		return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
 	sprintf(name, "%d", tgid);
-	return *cookie = name;
+	set_delayed_call(done, kfree_link, name);
+	return name;
 }
 
 static const struct inode_operations proc_self_inode_operations = {
 	.readlink	= proc_self_readlink,
 	.get_link	= proc_self_get_link,
-	.put_link	= kfree_put_link,
 };
 
 static unsigned self_inum;

fs/proc/thread_self.c

···
 }
 
 static const char *proc_thread_self_get_link(struct dentry *dentry,
-					     struct inode *inode, void **cookie)
+					     struct inode *inode,
+					     struct delayed_call *done)
 {
 	struct pid_namespace *ns = inode->i_sb->s_fs_info;
 	pid_t tgid = task_tgid_nr_ns(current, ns);
···
 	if (unlikely(!name))
 		return dentry ? ERR_PTR(-ENOMEM) : ERR_PTR(-ECHILD);
 	sprintf(name, "%d/task/%d", tgid, pid);
-	return *cookie = name;
+	set_delayed_call(done, kfree_link, name);
+	return name;
 }
 
 static const struct inode_operations proc_thread_self_inode_operations = {
 	.readlink	= proc_thread_self_readlink,
 	.get_link	= proc_thread_self_get_link,
-	.put_link	= kfree_put_link,
 };
 
 static unsigned thread_self_inum;

fs/reiserfs/namei.c

···
 const struct inode_operations reiserfs_symlink_inode_operations = {
 	.readlink = generic_readlink,
 	.get_link	= page_get_link,
-	.put_link = page_put_link,
 	.setattr = reiserfs_setattr,
 	.setxattr = reiserfs_setxattr,
 	.getxattr = reiserfs_getxattr,

fs/squashfs/symlink.c

···
 const struct inode_operations squashfs_symlink_inode_ops = {
 	.readlink = generic_readlink,
 	.get_link = page_get_link,
-	.put_link = page_put_link,
 	.getxattr = generic_getxattr,
 	.listxattr = squashfs_listxattr
 };

fs/sysv/inode.c

···
 static const struct inode_operations sysv_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= page_get_link,
-	.put_link	= page_put_link,
 	.getattr	= sysv_getattr,
 };
 

fs/xfs/xfs_iops.c

···
 xfs_vn_get_link(
 	struct dentry		*dentry,
 	struct inode		*inode,
-	void			**cookie)
+	struct delayed_call	*done)
 {
 	char			*link;
 	int			error = -ENOMEM;
···
 	if (unlikely(error))
 		goto out_kfree;
 
-	return *cookie = link;
+	set_delayed_call(done, kfree_link, link);
+	return link;
 
  out_kfree:
 	kfree(link);
···
 static const struct inode_operations xfs_symlink_inode_operations = {
 	.readlink		= generic_readlink,
 	.get_link		= xfs_vn_get_link,
-	.put_link		= kfree_put_link,
 	.getattr		= xfs_vn_getattr,
 	.setattr		= xfs_vn_setattr,
 	.setxattr		= generic_setxattr,

include/linux/delayed_call.h

···
+#ifndef _DELAYED_CALL_H
+#define _DELAYED_CALL_H
+
+/*
+ * Poor man's closures; I wish we could've done them sanely polymorphic,
+ * but...
+ */
+
+struct delayed_call {
+	void (*fn)(void *);
+	void *arg;
+};
+
+#define DEFINE_DELAYED_CALL(name) struct delayed_call name = {NULL, NULL}
+
+/* I really wish we had closures with sane typechecking... */
+static inline void set_delayed_call(struct delayed_call *call,
+		void (*fn)(void *), void *arg)
+{
+	call->fn = fn;
+	call->arg = arg;
+}
+
+static inline void do_delayed_call(struct delayed_call *call)
+{
+	if (call->fn)
+		call->fn(call->arg);
+}
+
+static inline void clear_delayed_call(struct delayed_call *call)
+{
+	call->fn = NULL;
+}
+#endif

include/linux/fs.h

···
 #include <linux/blk_types.h>
 #include <linux/workqueue.h>
 #include <linux/percpu-rwsem.h>
+#include <linux/delayed_call.h>
 
 #include <asm/byteorder.h>
 #include <uapi/linux/fs.h>
···
 
 struct inode_operations {
 	struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
-	const char * (*get_link) (struct dentry *, struct inode *, void **);
+	const char * (*get_link) (struct dentry *, struct inode *, struct delayed_call *);
 	int (*permission) (struct inode *, int);
 	struct posix_acl * (*get_acl)(struct inode *, int);
 
 	int (*readlink) (struct dentry *, char __user *,int);
-	void (*put_link) (struct inode *, void *);
 
 	int (*create) (struct inode *,struct dentry *, umode_t, bool);
 	int (*link) (struct dentry *,struct inode *,struct dentry *);
···
 
 extern int readlink_copy(char __user *, int, const char *);
 extern int page_readlink(struct dentry *, char __user *, int);
-extern const char *page_get_link(struct dentry *, struct inode *, void **);
-extern void page_put_link(struct inode *, void *);
+extern const char *page_get_link(struct dentry *, struct inode *,
+				 struct delayed_call *);
+extern void page_put_link(void *);
 extern int __page_symlink(struct inode *inode, const char *symname, int len,
 		int nofs);
 extern int page_symlink(struct inode *inode, const char *symname, int len);
 extern const struct inode_operations page_symlink_inode_operations;
-extern void kfree_put_link(struct inode *, void *);
+extern void kfree_link(void *);
 extern int generic_readlink(struct dentry *, char __user *, int);
 extern void generic_fillattr(struct inode *, struct kstat *);
 int vfs_getattr_nosec(struct path *path, struct kstat *stat);
···
 void inode_sub_bytes(struct inode *inode, loff_t bytes);
 loff_t inode_get_bytes(struct inode *inode);
 void inode_set_bytes(struct inode *inode, loff_t bytes);
-const char *simple_get_link(struct dentry *, struct inode *, void **);
+const char *simple_get_link(struct dentry *, struct inode *,
+			    struct delayed_call *);
 extern const struct inode_operations simple_symlink_inode_operations;
 
 extern int iterate_dir(struct file *, struct dir_context *);

mm/shmem.c

···
 	return 0;
 }
 
+static void shmem_put_link(void *arg)
+{
+	mark_page_accessed(arg);
+	put_page(arg);
+}
+
 static const char *shmem_get_link(struct dentry *dentry,
-				  struct inode *inode, void **cookie)
+				  struct inode *inode,
+				  struct delayed_call *done)
 {
 	struct page *page = NULL;
 	int error;
···
 			return ERR_PTR(error);
 		unlock_page(page);
 	}
-	*cookie = page;
+	set_delayed_call(done, shmem_put_link, page);
 	return page_address(page);
-}
-
-static void shmem_put_link(struct inode *unused, void *cookie)
-{
-	struct page *page = cookie;
-	mark_page_accessed(page);
-	page_cache_release(page);
 }
 
 #ifdef CONFIG_TMPFS_XATTR
···
 static const struct inode_operations shmem_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.get_link	= shmem_get_link,
-	.put_link	= shmem_put_link,
 #ifdef CONFIG_TMPFS_XATTR
 	.setxattr	= shmem_setxattr,
 	.getxattr	= shmem_getxattr,