replace ->follow_link() with new method that could stay in RCU mode

new method: ->get_link(); replacement of ->follow_link().  The differences
are:
	* inode and dentry are passed separately
	* might be called both in RCU and non-RCU mode;
the former is indicated by passing it a NULL dentry.
	* when called that way it isn't allowed to block
and should return ERR_PTR(-ECHILD) if it needs to be called
in non-RCU mode.

It's a flagday change - the old method is gone, all in-tree instances
converted.  Conversion isn't hard; said that, so far very few instances
do not immediately bail out when called in RCU mode.  That'll change
in the next commits.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Documentation/filesystems/Locking

@@ -50,7 +50,7 @@ prototypes:
 	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 **);
+	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);
@@ -83,7 +83,7 @@ rmdir:		yes (both)	(see below)
 rename:		yes (all)	(see below)
 rename2:	yes (all)	(see below)
 readlink:	no
-follow_link:	no
+get_link:	no
 put_link:	no
 setattr:	yes
 permission:	no (may not block if called in rcu-walk mode)

Documentation/filesystems/porting

@@ -509,3 +509,9 @@ in your dentry operations instead.
 	any symlink that might use page_follow_link_light/page_put_link() must
 	have inode_nohighmem(inode) called before anything might start playing with
 	its pagecache.
+--
+[mandatory]
+	->follow_link() is replaced with ->get_link(); same API, except that
+		* ->get_link() gets inode as a separate argument
+		* ->get_link() may be called in RCU mode - in that case NULL
+		  dentry is passed

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

@@ -118,12 +118,14 @@ failed:
 	return rc;
 }
 
-static const char *ll_follow_link(struct dentry *dentry, void **cookie)
+static const char *ll_get_link(struct dentry *dentry,
+			       struct inode *inode, void **cookie)
 {
-	struct inode *inode = d_inode(dentry);
 	struct ptlrpc_request *request = NULL;
 	int rc;
 	char *symname = NULL;
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
 
 	CDEBUG(D_VFSTRACE, "VFS Op\n");
 	ll_inode_size_lock(inode);
@@ -149,7 +151,7 @@ static void ll_put_link(struct inode *unused, void *cookie)
 struct inode_operations ll_fast_symlink_inode_operations = {
 	.readlink	= generic_readlink,
 	.setattr	= ll_setattr,
-	.follow_link	= ll_follow_link,
+	.get_link	= ll_get_link,
 	.put_link	= ll_put_link,
 	.getattr	= ll_getattr,
 	.permission	= ll_inode_permission,

fs/9p/vfs_inode.c

@@ -1223,18 +1223,25 @@ ino_t v9fs_qid2ino(struct p9_qid *qid)
 }
 
 /**
- * v9fs_vfs_follow_link - follow a symlink path
+ * 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()
  */
 
-static const char *v9fs_vfs_follow_link(struct dentry *dentry, void **cookie)
+static const char *v9fs_vfs_get_link(struct dentry *dentry,
+				     struct inode *inode, void **cookie)
 {
-	struct v9fs_session_info *v9ses = v9fs_dentry2v9ses(dentry);
-	struct p9_fid *fid = v9fs_fid_lookup(dentry);
+	struct v9fs_session_info *v9ses;
+	struct p9_fid *fid;
 	struct p9_wstat *st;
 	char *res;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
+	v9ses = v9fs_dentry2v9ses(dentry);
+	fid = v9fs_fid_lookup(dentry);
 	p9_debug(P9_DEBUG_VFS, "%pd\n", dentry);
 
 	if (IS_ERR(fid))
@@ -1452,7 +1459,7 @@ static const struct inode_operations v9fs_file_inode_operations = {
 
 static const struct inode_operations v9fs_symlink_inode_operations = {
 	.readlink = generic_readlink,
-	.follow_link = v9fs_vfs_follow_link,
+	.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

@@ -899,20 +899,26 @@ error:
 }
 
 /**
- * v9fs_vfs_follow_link_dotl - follow a symlink path
+ * 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()
  */
 
 static const char *
-v9fs_vfs_follow_link_dotl(struct dentry *dentry, void **cookie)
+v9fs_vfs_get_link_dotl(struct dentry *dentry,
+		       struct inode *inode, void **cookie)
 {
-	struct p9_fid *fid = v9fs_fid_lookup(dentry);
+	struct p9_fid *fid;
 	char *target;
 	int retval;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	p9_debug(P9_DEBUG_VFS, "%pd\n", dentry);
 
+	fid = v9fs_fid_lookup(dentry);
 	if (IS_ERR(fid))
 		return ERR_CAST(fid);
 	retval = p9_client_readlink(fid, &target);
@@ -984,7 +990,7 @@ const struct inode_operations v9fs_file_inode_operations_dotl = {
 
 const struct inode_operations v9fs_symlink_inode_operations_dotl = {
 	.readlink = generic_readlink,
-	.follow_link = v9fs_vfs_follow_link_dotl,
+	.get_link = v9fs_vfs_get_link_dotl,
 	.put_link = kfree_put_link,
 	.getattr = v9fs_vfs_getattr_dotl,
 	.setattr = v9fs_vfs_setattr_dotl,

fs/affs/symlink.c

@@ -20,7 +20,7 @@ static int affs_symlink_readpage(struct file *file, struct page *page)
 	char			 c;
 	char			 lc;
 
-	pr_debug("follow_link(ino=%lu)\n", inode->i_ino);
+	pr_debug("get_link(ino=%lu)\n", inode->i_ino);
 
 	bh = affs_bread(inode->i_sb, inode->i_ino);
 	if (!bh)
@@ -71,7 +71,7 @@ const struct address_space_operations affs_symlink_aops = {
 
 const struct inode_operations affs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.setattr	= affs_notify_change,
 };

fs/autofs4/symlink.c

@@ -12,10 +12,15 @@
 
 #include "autofs_i.h"
 
-static const char *autofs4_follow_link(struct dentry *dentry, void **cookie)
+static const char *autofs4_get_link(struct dentry *dentry,
+				    struct inode *inode, void **cookie)
 {
-	struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb);
-	struct autofs_info *ino = autofs4_dentry_ino(dentry);
+	struct autofs_sb_info *sbi;
+	struct autofs_info *ino;
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+	sbi = autofs4_sbi(dentry->d_sb);
+	ino = autofs4_dentry_ino(dentry);
 	if (ino && !autofs4_oz_mode(sbi))
 		ino->last_used = jiffies;
 	return d_inode(dentry)->i_private;
@@ -23,5 +28,5 @@ static const char *autofs4_follow_link(struct dentry *dentry, void **cookie)
 
 const struct inode_operations autofs4_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= autofs4_follow_link
+	.get_link	= autofs4_get_link
 };

fs/btrfs/inode.c

@@ -10096,7 +10096,7 @@ static const struct inode_operations btrfs_special_inode_operations = {
 };
 static const struct inode_operations btrfs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.getattr	= btrfs_getattr,
 	.setattr	= btrfs_setattr,

fs/ceph/inode.c

@@ -1756,7 +1756,7 @@ retry:
  */
 static const struct inode_operations ceph_symlink_iops = {
 	.readlink = generic_readlink,
-	.follow_link = simple_follow_link,
+	.get_link = simple_get_link,
 	.setattr = ceph_setattr,
 	.getattr = ceph_getattr,
 	.setxattr = ceph_setxattr,

fs/cifs/cifsfs.c

@@ -900,7 +900,7 @@ const struct inode_operations cifs_file_inode_ops = {
 
 const struct inode_operations cifs_symlink_inode_ops = {
 	.readlink = generic_readlink,
-	.follow_link = cifs_follow_link,
+	.get_link = cifs_get_link,
 	.put_link = kfree_put_link,
 	.permission = cifs_permission,
 	/* BB add the following two eventually */

fs/cifs/cifsfs.h

@@ -120,9 +120,7 @@ extern struct vfsmount *cifs_dfs_d_automount(struct path *path);
 #endif
 
 /* Functions related to symlinks */
-extern const char *cifs_follow_link(struct dentry *direntry, void **cookie);
-extern int cifs_readlink(struct dentry *direntry, char __user *buffer,
-			 int buflen);
+extern const char *cifs_get_link(struct dentry *, struct inode *, void **);
 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

@@ -627,9 +627,8 @@ cifs_hl_exit:
 }
 
 const char *
-cifs_follow_link(struct dentry *direntry, void **cookie)
+cifs_get_link(struct dentry *direntry, struct inode *inode, void **cookie)
 {
-	struct inode *inode = d_inode(direntry);
 	int rc = -ENOMEM;
 	unsigned int xid;
 	char *full_path = NULL;
@@ -639,6 +638,9 @@ cifs_follow_link(struct dentry *direntry, void **cookie)
 	struct cifs_tcon *tcon;
 	struct TCP_Server_Info *server;
 
+	if (!direntry)
+		return ERR_PTR(-ECHILD);
+
 	xid = get_xid();
 
 	tlink = cifs_sb_tlink(cifs_sb);

fs/coda/cnode.c

@@ -18,7 +18,7 @@ static inline int coda_fideq(struct CodaFid *fid1, struct CodaFid *fid2)
 
 static const struct inode_operations coda_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.setattr	= coda_setattr,
 };

fs/configfs/symlink.c

@@ -279,11 +279,16 @@ static int configfs_getlink(struct dentry *dentry, char * path)
 
 }
 
-static const char *configfs_follow_link(struct dentry *dentry, void **cookie)
+static const char *configfs_get_link(struct dentry *dentry,
+				     struct inode *inode, void **cookie)
 {
-	unsigned long page = get_zeroed_page(GFP_KERNEL);
+	unsigned long page;
 	int error;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
+	page = get_zeroed_page(GFP_KERNEL);
 	if (!page)
 		return ERR_PTR(-ENOMEM);
 
@@ -297,7 +302,7 @@ static const char *configfs_follow_link(struct dentry *dentry, void **cookie)
 }
 
 const struct inode_operations configfs_symlink_inode_operations = {
-	.follow_link = configfs_follow_link,
+	.get_link = configfs_get_link,
 	.readlink = generic_readlink,
 	.put_link = free_page_put_link,
 	.setattr = configfs_setattr,

fs/dcache.c

@@ -1734,7 +1734,7 @@ static unsigned d_flags_for_inode(struct inode *inode)
 	}
 
 	if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
-		if (unlikely(inode->i_op->follow_link)) {
+		if (unlikely(inode->i_op->get_link)) {
 			add_flags = DCACHE_SYMLINK_TYPE;
 			goto type_determined;
 		}

fs/ecryptfs/inode.c

@@ -674,10 +674,16 @@ out:
 	return rc ? ERR_PTR(rc) : buf;
 }
 
-static const char *ecryptfs_follow_link(struct dentry *dentry, void **cookie)
+static const char *ecryptfs_get_link(struct dentry *dentry,
+				     struct inode *inode, void **cookie)
 {
 	size_t len;
-	char *buf = ecryptfs_readlink_lower(dentry, &len);
+	char *buf;
+
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
+	buf = ecryptfs_readlink_lower(dentry, &len);
 	if (IS_ERR(buf))
 		return buf;
 	fsstack_copy_attr_atime(d_inode(dentry),
@@ -1095,7 +1101,7 @@ out:
 
 const struct inode_operations ecryptfs_symlink_iops = {
 	.readlink = generic_readlink,
-	.follow_link = ecryptfs_follow_link,
+	.get_link = ecryptfs_get_link,
 	.put_link = kfree_put_link,
 	.permission = ecryptfs_permission,
 	.setattr = ecryptfs_setattr,

fs/ext2/symlink.c

@@ -22,7 +22,7 @@
 
 const struct inode_operations ext2_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.setattr	= ext2_setattr,
 #ifdef CONFIG_EXT2_FS_XATTR
@@ -35,7 +35,7 @@ const struct inode_operations ext2_symlink_inode_operations = {
  
 const struct inode_operations ext2_fast_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= simple_follow_link,
+	.get_link	= simple_get_link,
 	.setattr	= ext2_setattr,
 #ifdef CONFIG_EXT2_FS_XATTR
 	.setxattr	= generic_setxattr,

fs/ext4/symlink.c

@@ -23,17 +23,20 @@
 #include "xattr.h"
 
 #ifdef CONFIG_EXT4_FS_ENCRYPTION
-static const char *ext4_encrypted_follow_link(struct dentry *dentry, void **cookie)
+static const char *ext4_encrypted_get_link(struct dentry *dentry,
+					   struct inode *inode, void **cookie)
 {
 	struct page *cpage = NULL;
 	char *caddr, *paddr = NULL;
 	struct ext4_str cstr, pstr;
-	struct inode *inode = d_inode(dentry);
 	struct ext4_encrypted_symlink_data *sd;
 	loff_t size = min_t(loff_t, i_size_read(inode), PAGE_SIZE - 1);
 	int res;
 	u32 plen, max_size = inode->i_sb->s_blocksize;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	res = ext4_get_encryption_info(inode);
 	if (res)
 		return ERR_PTR(res);
@@ -87,7 +90,7 @@ errout:
 
 const struct inode_operations ext4_encrypted_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link    = ext4_encrypted_follow_link,
+	.get_link	= ext4_encrypted_get_link,
 	.put_link       = kfree_put_link,
 	.setattr	= ext4_setattr,
 	.setxattr	= generic_setxattr,
@@ -99,7 +102,7 @@ const struct inode_operations ext4_encrypted_symlink_inode_operations = {
 
 const struct inode_operations ext4_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.setattr	= ext4_setattr,
 	.setxattr	= generic_setxattr,
@@ -110,7 +113,7 @@ const struct inode_operations ext4_symlink_inode_operations = {
 
 const struct inode_operations ext4_fast_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link    = simple_follow_link,
+	.get_link	= simple_get_link,
 	.setattr	= ext4_setattr,
 	.setxattr	= generic_setxattr,
 	.getxattr	= generic_getxattr,

fs/f2fs/namei.c

@@ -315,9 +315,10 @@ fail:
 	return err;
 }
 
-static const char *f2fs_follow_link(struct dentry *dentry, void **cookie)
+static const char *f2fs_get_link(struct dentry *dentry,
+				 struct inode *inode, void **cookie)
 {
-	const char *link = page_follow_link_light(dentry, cookie);
+	const char *link = page_get_link(dentry, inode, cookie);
 	if (!IS_ERR(link) && !*link) {
 		/* this is broken symlink case */
 		page_put_link(NULL, *cookie);
@@ -924,18 +925,21 @@ static int f2fs_rename2(struct inode *old_dir, struct dentry *old_dentry,
 }
 
 #ifdef CONFIG_F2FS_FS_ENCRYPTION
-static const char *f2fs_encrypted_follow_link(struct dentry *dentry, void **cookie)
+static const char *f2fs_encrypted_get_link(struct dentry *dentry,
+					   struct inode *inode, void **cookie)
 {
 	struct page *cpage = NULL;
 	char *caddr, *paddr = NULL;
 	struct f2fs_str cstr;
 	struct f2fs_str pstr = FSTR_INIT(NULL, 0);
-	struct inode *inode = d_inode(dentry);
 	struct f2fs_encrypted_symlink_data *sd;
 	loff_t size = min_t(loff_t, i_size_read(inode), PAGE_SIZE - 1);
 	u32 max_size = inode->i_sb->s_blocksize;
 	int res;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	res = f2fs_get_encryption_info(inode);
 	if (res)
 		return ERR_PTR(res);
@@ -994,7 +998,7 @@ errout:
 
 const struct inode_operations f2fs_encrypted_symlink_inode_operations = {
 	.readlink       = generic_readlink,
-	.follow_link    = f2fs_encrypted_follow_link,
+	.get_link       = f2fs_encrypted_get_link,
 	.put_link       = kfree_put_link,
 	.getattr	= f2fs_getattr,
 	.setattr	= f2fs_setattr,
@@ -1030,7 +1034,7 @@ const struct inode_operations f2fs_dir_inode_operations = {
 
 const struct inode_operations f2fs_symlink_inode_operations = {
 	.readlink       = generic_readlink,
-	.follow_link    = f2fs_follow_link,
+	.get_link       = f2fs_get_link,
 	.put_link       = page_put_link,
 	.getattr	= f2fs_getattr,
 	.setattr	= f2fs_setattr,

fs/fuse/dir.c

@@ -1365,14 +1365,17 @@ static int fuse_readdir(struct file *file, struct dir_context *ctx)
 	return err;
 }
 
-static const char *fuse_follow_link(struct dentry *dentry, void **cookie)
+static const char *fuse_get_link(struct dentry *dentry,
+				 struct inode *inode, void **cookie)
 {
-	struct inode *inode = d_inode(dentry);
 	struct fuse_conn *fc = get_fuse_conn(inode);
 	FUSE_ARGS(args);
 	char *link;
 	ssize_t ret;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	link = (char *) __get_free_page(GFP_KERNEL);
 	if (!link)
 		return ERR_PTR(-ENOMEM);
@@ -1909,7 +1912,7 @@ static const struct inode_operations fuse_common_inode_operations = {
 
 static const struct inode_operations fuse_symlink_inode_operations = {
 	.setattr	= fuse_setattr,
-	.follow_link	= fuse_follow_link,
+	.get_link	= fuse_get_link,
 	.put_link	= free_page_put_link,
 	.readlink	= generic_readlink,
 	.getattr	= fuse_getattr,

fs/gfs2/inode.c

@@ -1712,24 +1712,29 @@ static int gfs2_rename2(struct inode *odir, struct dentry *odentry,
 }
 
 /**
- * gfs2_follow_link - Follow a symbolic link
+ * gfs2_get_link - Follow a symbolic link
  * @dentry: The dentry of the link
- * @nd: Data that we pass to vfs_follow_link()
+ * @inode: The inode of the link
+ * @cookie: place to store the information for ->put_link()
  *
  * This can handle symlinks of any size.
  *
  * Returns: 0 on success or error code
  */
 
-static const char *gfs2_follow_link(struct dentry *dentry, void **cookie)
+static const char *gfs2_get_link(struct dentry *dentry,
+				 struct inode *inode, void **cookie)
 {
-	struct gfs2_inode *ip = GFS2_I(d_inode(dentry));
+	struct gfs2_inode *ip = GFS2_I(inode);
 	struct gfs2_holder i_gh;
 	struct buffer_head *dibh;
 	unsigned int size;
 	char *buf;
 	int error;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	gfs2_holder_init(ip->i_gl, LM_ST_SHARED, 0, &i_gh);
 	error = gfs2_glock_nq(&i_gh);
 	if (error) {
@@ -2132,7 +2137,7 @@ const struct inode_operations gfs2_dir_iops = {
 
 const struct inode_operations gfs2_symlink_iops = {
 	.readlink = generic_readlink,
-	.follow_link = gfs2_follow_link,
+	.get_link = gfs2_get_link,
 	.put_link = kfree_put_link,
 	.permission = gfs2_permission,
 	.setattr = gfs2_setattr,

fs/hostfs/hostfs_kern.c

@@ -892,9 +892,13 @@ static const struct inode_operations hostfs_dir_iops = {
 	.setattr	= hostfs_setattr,
 };
 
-static const char *hostfs_follow_link(struct dentry *dentry, void **cookie)
+static const char *hostfs_get_link(struct dentry *dentry,
+				   struct inode *inode, void **cookie)
 {
-	char *link = __getname();
+	char *link;
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+	link = __getname();
 	if (link) {
 		char *path = dentry_name(dentry);
 		int err = -ENOMEM;
@@ -922,7 +926,7 @@ static void hostfs_put_link(struct inode *unused, void *cookie)
 
 static const struct inode_operations hostfs_link_iops = {
 	.readlink	= generic_readlink,
-	.follow_link	= hostfs_follow_link,
+	.get_link	= hostfs_get_link,
 	.put_link	= hostfs_put_link,
 };
 

fs/jffs2/symlink.c

@@ -14,7 +14,7 @@
 const struct inode_operations jffs2_symlink_inode_operations =
 {
 	.readlink =	generic_readlink,
-	.follow_link =	simple_follow_link,
+	.get_link =	simple_get_link,
 	.setattr =	jffs2_setattr,
 	.setxattr =	jffs2_setxattr,
 	.getxattr =	jffs2_getxattr,

fs/jfs/symlink.c

@@ -23,7 +23,7 @@
 
 const struct inode_operations jfs_fast_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= simple_follow_link,
+	.get_link	= simple_get_link,
 	.setattr	= jfs_setattr,
 	.setxattr	= jfs_setxattr,
 	.getxattr	= jfs_getxattr,
@@ -33,7 +33,7 @@ const struct inode_operations jfs_fast_symlink_inode_operations = {
 
 const struct inode_operations jfs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.setattr	= jfs_setattr,
 	.setxattr	= jfs_setxattr,

fs/kernfs/symlink.c

@@ -112,10 +112,15 @@ static int kernfs_getlink(struct dentry *dentry, char *path)
 	return error;
 }
 
-static const char *kernfs_iop_follow_link(struct dentry *dentry, void **cookie)
+static const char *kernfs_iop_get_link(struct dentry *dentry,
+				       struct inode *inode, void **cookie)
 {
 	int error = -ENOMEM;
-	unsigned long page = get_zeroed_page(GFP_KERNEL);
+	unsigned long page;
+
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+	page = get_zeroed_page(GFP_KERNEL);
 	if (!page)
 		return ERR_PTR(-ENOMEM);
 	error = kernfs_getlink(dentry, (char *)page);
@@ -132,7 +137,7 @@ const struct inode_operations kernfs_symlink_iops = {
 	.getxattr	= kernfs_iop_getxattr,
 	.listxattr	= kernfs_iop_listxattr,
 	.readlink	= generic_readlink,
-	.follow_link	= kernfs_iop_follow_link,
+	.get_link	= kernfs_iop_get_link,
 	.put_link	= free_page_put_link,
 	.setattr	= kernfs_iop_setattr,
 	.getattr	= kernfs_iop_getattr,

fs/libfs.c

@@ -1092,14 +1092,15 @@ simple_nosetlease(struct file *filp, long arg, struct file_lock **flp,
 }
 EXPORT_SYMBOL(simple_nosetlease);
 
-const char *simple_follow_link(struct dentry *dentry, void **cookie)
+const char *simple_get_link(struct dentry *dentry, struct inode *inode,
+			    void **cookie)
 {
-	return d_inode(dentry)->i_link;
+	return inode->i_link;
 }
-EXPORT_SYMBOL(simple_follow_link);
+EXPORT_SYMBOL(simple_get_link);
 
 const struct inode_operations simple_symlink_inode_operations = {
-	.follow_link = simple_follow_link,
+	.get_link = simple_get_link,
 	.readlink = generic_readlink
 };
 EXPORT_SYMBOL(simple_symlink_inode_operations);

fs/minix/inode.c

@@ -435,7 +435,7 @@ static const struct address_space_operations minix_aops = {
 
 static const struct inode_operations minix_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.getattr	= minix_getattr,
 };

fs/namei.c

@@ -842,7 +842,7 @@ static inline void path_to_nameidata(const struct path *path,
 }
 
 /*
- * Helper to directly jump to a known parsed path from ->follow_link,
+ * Helper to directly jump to a known parsed path from ->get_link,
  * caller must have taken a reference to path beforehand.
  */
 void nd_jump_link(struct path *path)
@@ -1005,10 +1005,18 @@ const char *get_link(struct nameidata *nd)
 	res = inode->i_link;
 	if (!res) {
 		if (nd->flags & LOOKUP_RCU) {
-			if (unlikely(unlazy_walk(nd, NULL, 0)))
-				return ERR_PTR(-ECHILD);
+			res = inode->i_op->get_link(NULL, inode,
+						    &last->cookie);
+			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);
+			}
+		} else {
+			res = inode->i_op->get_link(dentry, inode,
+						    &last->cookie);
 		}
-		res = inode->i_op->follow_link(dentry, &last->cookie);
 		if (IS_ERR_OR_NULL(res)) {
 			last->cookie = NULL;
 			return res;
@@ -4495,8 +4503,8 @@ EXPORT_SYMBOL(readlink_copy);
 
 /*
  * A helper for ->readlink().  This should be used *ONLY* for symlinks that
- * have ->follow_link() touching nd only in nd_set_link().  Using (or not
- * using) it for any given inode is up to filesystem.
+ * have ->get_link() not calling nd_jump_link().  Using (or not using) it
+ * for any given inode is up to filesystem.
  */
 int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 {
@@ -4506,7 +4514,7 @@ int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 	int res;
 
 	if (!link) {
-		link = inode->i_op->follow_link(dentry, &cookie);
+		link = inode->i_op->get_link(dentry, inode, &cookie);
 		if (IS_ERR(link))
 			return PTR_ERR(link);
 	}
@@ -4518,26 +4526,27 @@ int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 EXPORT_SYMBOL(generic_readlink);
 
 /* get the link contents into pagecache */
-static const char *page_getlink(struct dentry * dentry, void **cookie)
+const char *page_get_link(struct dentry *dentry, struct inode *inode,
+				 void **cookie)
 {
 	char *kaddr;
 	struct page *page;
-	struct address_space *mapping = dentry->d_inode->i_mapping;
+	struct address_space *mapping = inode->i_mapping;
+
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	page = read_mapping_page(mapping, 0, NULL);
 	if (IS_ERR(page))
 		return (char*)page;
 	*cookie = page;
 	BUG_ON(mapping_gfp_mask(mapping) & __GFP_HIGHMEM);
 	kaddr = page_address(page);
-	nd_terminate_link(kaddr, dentry->d_inode->i_size, PAGE_SIZE - 1);
+	nd_terminate_link(kaddr, inode->i_size, PAGE_SIZE - 1);
 	return kaddr;
 }
 
-const char *page_follow_link_light(struct dentry *dentry, void **cookie)
-{
-	return page_getlink(dentry, cookie);
-}
-EXPORT_SYMBOL(page_follow_link_light);
+EXPORT_SYMBOL(page_get_link);
 
 void page_put_link(struct inode *unused, void *cookie)
 {
@@ -4549,7 +4558,9 @@ EXPORT_SYMBOL(page_put_link);
 int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 {
 	void *cookie = NULL;
-	int res = readlink_copy(buffer, buflen, page_getlink(dentry, &cookie));
+	int res = readlink_copy(buffer, buflen,
+				page_get_link(dentry, d_inode(dentry),
+					      &cookie));
 	if (cookie)
 		page_put_link(NULL, cookie);
 	return res;
@@ -4600,7 +4611,7 @@ EXPORT_SYMBOL(page_symlink);
 
 const struct inode_operations page_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 };
 EXPORT_SYMBOL(page_symlink_inode_operations);

fs/ncpfs/inode.c

@@ -244,7 +244,7 @@ static void ncp_set_attr(struct inode *inode, struct ncp_entry_info *nwinfo)
 #if defined(CONFIG_NCPFS_EXTRAS) || defined(CONFIG_NCPFS_NFS_NS)
 static const struct inode_operations ncp_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.setattr	= ncp_notify_change,
 };

fs/nfs/symlink.c

@@ -42,12 +42,15 @@ error:
 	return -EIO;
 }
 
-static const char *nfs_follow_link(struct dentry *dentry, void **cookie)
+static const char *nfs_get_link(struct dentry *dentry,
+				struct inode *inode, void **cookie)
 {
-	struct inode *inode = d_inode(dentry);
 	struct page *page;
 	void *err;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	err = ERR_PTR(nfs_revalidate_mapping(inode, inode->i_mapping));
 	if (err)
 		return err;
@@ -64,7 +67,7 @@ static const char *nfs_follow_link(struct dentry *dentry, void **cookie)
  */
 const struct inode_operations nfs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= nfs_follow_link,
+	.get_link	= nfs_get_link,
 	.put_link	= page_put_link,
 	.getattr	= nfs_getattr,
 	.setattr	= nfs_setattr,

fs/nilfs2/namei.c

@@ -569,7 +569,7 @@ const struct inode_operations nilfs_special_inode_operations = {
 
 const struct inode_operations nilfs_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.permission     = nilfs_permission,
 };

fs/ocfs2/symlink.c

@@ -88,7 +88,7 @@ const struct address_space_operations ocfs2_fast_symlink_aops = {
 
 const struct inode_operations ocfs2_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.getattr	= ocfs2_getattr,
 	.setattr	= ocfs2_setattr,

fs/overlayfs/inode.c

@@ -137,17 +137,21 @@ struct ovl_link_data {
 	void *cookie;
 };
 
-static const char *ovl_follow_link(struct dentry *dentry, void **cookie)
+static const char *ovl_get_link(struct dentry *dentry,
+				struct inode *inode, void **cookie)
 {
 	struct dentry *realdentry;
 	struct inode *realinode;
 	struct ovl_link_data *data = NULL;
 	const char *ret;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	realdentry = ovl_dentry_real(dentry);
 	realinode = realdentry->d_inode;
 
-	if (WARN_ON(!realinode->i_op->follow_link))
+	if (WARN_ON(!realinode->i_op->get_link))
 		return ERR_PTR(-EPERM);
 
 	if (realinode->i_op->put_link) {
@@ -157,7 +161,7 @@ static const char *ovl_follow_link(struct dentry *dentry, void **cookie)
 		data->realdentry = realdentry;
 	}
 
-	ret = realinode->i_op->follow_link(realdentry, cookie);
+	ret = realinode->i_op->get_link(realdentry, realinode, cookie);
 	if (IS_ERR_OR_NULL(ret)) {
 		kfree(data);
 		return ret;
@@ -378,7 +382,7 @@ static const struct inode_operations ovl_file_inode_operations = {
 
 static const struct inode_operations ovl_symlink_inode_operations = {
 	.setattr	= ovl_setattr,
-	.follow_link	= ovl_follow_link,
+	.get_link	= ovl_get_link,
 	.put_link	= ovl_put_link,
 	.readlink	= ovl_readlink,
 	.getattr	= ovl_getattr,

fs/proc/base.c

@@ -1564,12 +1564,15 @@ static int proc_exe_link(struct dentry *dentry, struct path *exe_path)
 		return -ENOENT;
 }
 
-static const char *proc_pid_follow_link(struct dentry *dentry, void **cookie)
+static const char *proc_pid_get_link(struct dentry *dentry,
+				     struct inode *inode, void **cookie)
 {
-	struct inode *inode = d_inode(dentry);
 	struct path path;
 	int error = -EACCES;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	/* Are we allowed to snoop on the tasks file descriptors? */
 	if (!proc_fd_access_allowed(inode))
 		goto out;
@@ -1630,7 +1633,7 @@ out:
 
 const struct inode_operations proc_pid_link_inode_operations = {
 	.readlink	= proc_pid_readlink,
-	.follow_link	= proc_pid_follow_link,
+	.get_link	= proc_pid_get_link,
 	.setattr	= proc_setattr,
 };
 
@@ -1895,7 +1898,7 @@ static const struct dentry_operations tid_map_files_dentry_operations = {
 	.d_delete	= pid_delete_dentry,
 };
 
-static int proc_map_files_get_link(struct dentry *dentry, struct path *path)
+static int map_files_get_link(struct dentry *dentry, struct path *path)
 {
 	unsigned long vm_start, vm_end;
 	struct vm_area_struct *vma;
@@ -1945,20 +1948,21 @@ struct map_files_info {
  * path to the file in question.
  */
 static const char *
-proc_map_files_follow_link(struct dentry *dentry, void **cookie)
+proc_map_files_get_link(struct dentry *dentry,
+			struct inode *inode, void **cookie)
 {
 	if (!capable(CAP_SYS_ADMIN))
 		return ERR_PTR(-EPERM);
 
-	return proc_pid_follow_link(dentry, NULL);
+	return proc_pid_get_link(dentry, inode, NULL);
 }
 
 /*
- * Identical to proc_pid_link_inode_operations except for follow_link()
+ * Identical to proc_pid_link_inode_operations except for get_link()
  */
 static const struct inode_operations proc_map_files_link_inode_operations = {
 	.readlink	= proc_pid_readlink,
-	.follow_link	= proc_map_files_follow_link,
+	.get_link	= proc_map_files_get_link,
 	.setattr	= proc_setattr,
 };
 
@@ -1975,7 +1979,7 @@ proc_map_files_instantiate(struct inode *dir, struct dentry *dentry,
 		return -ENOENT;
 
 	ei = PROC_I(inode);
-	ei->op.proc_get_link = proc_map_files_get_link;
+	ei->op.proc_get_link = map_files_get_link;
 
 	inode->i_op = &proc_map_files_link_inode_operations;
 	inode->i_size = 64;

fs/proc/inode.c

@@ -393,9 +393,10 @@ static const struct file_operations proc_reg_file_ops_no_compat = {
 };
 #endif
 
-static const char *proc_follow_link(struct dentry *dentry, void **cookie)
+static const char *proc_get_link(struct dentry *dentry,
+				 struct inode *inode, void **cookie)
 {
-	struct proc_dir_entry *pde = PDE(d_inode(dentry));
+	struct proc_dir_entry *pde = PDE(inode);
 	if (unlikely(!use_pde(pde)))
 		return ERR_PTR(-EINVAL);
 	*cookie = pde;
@@ -409,7 +410,7 @@ static void proc_put_link(struct inode *unused, void *p)
 
 const struct inode_operations proc_link_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= proc_follow_link,
+	.get_link	= proc_get_link,
 	.put_link	= proc_put_link,
 };
 

fs/proc/namespaces.c

@@ -30,14 +30,17 @@ static const struct proc_ns_operations *ns_entries[] = {
 	&mntns_operations,
 };
 
-static const char *proc_ns_follow_link(struct dentry *dentry, void **cookie)
+static const char *proc_ns_get_link(struct dentry *dentry,
+				    struct inode *inode, void **cookie)
 {
-	struct inode *inode = d_inode(dentry);
 	const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns_ops;
 	struct task_struct *task;
 	struct path ns_path;
 	void *error = ERR_PTR(-EACCES);
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	task = get_proc_task(inode);
 	if (!task)
 		return error;
@@ -74,7 +77,7 @@ static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int bufl
 
 static const struct inode_operations proc_ns_link_inode_operations = {
 	.readlink	= proc_ns_readlink,
-	.follow_link	= proc_ns_follow_link,
+	.get_link	= proc_ns_get_link,
 	.setattr	= proc_setattr,
 };
 

fs/proc/self.c

@@ -18,12 +18,15 @@ static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
 	return readlink_copy(buffer, buflen, tmp);
 }
 
-static const char *proc_self_follow_link(struct dentry *dentry, void **cookie)
+static const char *proc_self_get_link(struct dentry *dentry,
+				      struct inode *inode, void **cookie)
 {
-	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
+	struct pid_namespace *ns = inode->i_sb->s_fs_info;
 	pid_t tgid = task_tgid_nr_ns(current, ns);
 	char *name;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
 	if (!tgid)
 		return ERR_PTR(-ENOENT);
 	/* 11 for max length of signed int in decimal + NULL term */
@@ -36,7 +39,7 @@ static const char *proc_self_follow_link(struct dentry *dentry, void **cookie)
 
 static const struct inode_operations proc_self_inode_operations = {
 	.readlink	= proc_self_readlink,
-	.follow_link	= proc_self_follow_link,
+	.get_link	= proc_self_get_link,
 	.put_link	= kfree_put_link,
 };
 

fs/proc/thread_self.c

@@ -19,13 +19,16 @@ static int proc_thread_self_readlink(struct dentry *dentry, char __user *buffer,
 	return readlink_copy(buffer, buflen, tmp);
 }
 
-static const char *proc_thread_self_follow_link(struct dentry *dentry, void **cookie)
+static const char *proc_thread_self_get_link(struct dentry *dentry,
+					     struct inode *inode, void **cookie)
 {
-	struct pid_namespace *ns = dentry->d_sb->s_fs_info;
+	struct pid_namespace *ns = inode->i_sb->s_fs_info;
 	pid_t tgid = task_tgid_nr_ns(current, ns);
 	pid_t pid = task_pid_nr_ns(current, ns);
 	char *name;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
 	if (!pid)
 		return ERR_PTR(-ENOENT);
 	name = kmalloc(PROC_NUMBUF + 6 + PROC_NUMBUF, GFP_KERNEL);
@@ -37,7 +40,7 @@ static const char *proc_thread_self_follow_link(struct dentry *dentry, void **co
 
 static const struct inode_operations proc_thread_self_inode_operations = {
 	.readlink	= proc_thread_self_readlink,
-	.follow_link	= proc_thread_self_follow_link,
+	.get_link	= proc_thread_self_get_link,
 	.put_link	= kfree_put_link,
 };
 

fs/reiserfs/namei.c

@@ -1665,7 +1665,7 @@ const struct inode_operations reiserfs_dir_inode_operations = {
  */
 const struct inode_operations reiserfs_symlink_inode_operations = {
 	.readlink = generic_readlink,
-	.follow_link = page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link = page_put_link,
 	.setattr = reiserfs_setattr,
 	.setxattr = reiserfs_setxattr,

fs/squashfs/symlink.c

@@ -119,7 +119,7 @@ const struct address_space_operations squashfs_symlink_aops = {
 
 const struct inode_operations squashfs_symlink_inode_ops = {
 	.readlink = generic_readlink,
-	.follow_link = page_follow_link_light,
+	.get_link = page_get_link,
 	.put_link = page_put_link,
 	.getxattr = generic_getxattr,
 	.listxattr = squashfs_listxattr

fs/sysv/inode.c

@@ -146,7 +146,7 @@ static inline void write3byte(struct sysv_sb_info *sbi,
 
 static const struct inode_operations sysv_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= page_follow_link_light,
+	.get_link	= page_get_link,
 	.put_link	= page_put_link,
 	.getattr	= sysv_getattr,
 };

fs/ubifs/file.c

@@ -1608,7 +1608,7 @@ const struct inode_operations ubifs_file_inode_operations = {
 
 const struct inode_operations ubifs_symlink_inode_operations = {
 	.readlink    = generic_readlink,
-	.follow_link = simple_follow_link,
+	.get_link    = simple_get_link,
 	.setattr     = ubifs_setattr,
 	.getattr     = ubifs_getattr,
 	.setxattr    = ubifs_setxattr,

fs/xfs/xfs_iops.c

@@ -414,13 +414,17 @@ xfs_vn_rename(
  * uio is kmalloced for this reason...
  */
 STATIC const char *
-xfs_vn_follow_link(
+xfs_vn_get_link(
 	struct dentry		*dentry,
+	struct inode		*inode,
 	void			**cookie)
 {
 	char			*link;
 	int			error = -ENOMEM;
 
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+
 	link = kmalloc(MAXPATHLEN+1, GFP_KERNEL);
 	if (!link)
 		goto out_err;
@@ -1172,7 +1176,7 @@ static const struct inode_operations xfs_dir_ci_inode_operations = {
 
 static const struct inode_operations xfs_symlink_inode_operations = {
 	.readlink		= generic_readlink,
-	.follow_link		= xfs_vn_follow_link,
+	.get_link		= xfs_vn_get_link,
 	.put_link		= kfree_put_link,
 	.getattr		= xfs_vn_getattr,
 	.setattr		= xfs_vn_setattr,

include/linux/fs.h

@@ -1633,7 +1633,7 @@ struct file_operations {
 
 struct inode_operations {
 	struct dentry * (*lookup) (struct inode *,struct dentry *, unsigned int);
-	const char * (*follow_link) (struct dentry *, void **);
+	const char * (*get_link) (struct dentry *, struct inode *, void **);
 	int (*permission) (struct inode *, int);
 	struct posix_acl * (*get_acl)(struct inode *, int);
 
@@ -2736,7 +2736,7 @@ extern const struct file_operations generic_ro_fops;
 
 extern int readlink_copy(char __user *, int, const char *);
 extern int page_readlink(struct dentry *, char __user *, int);
-extern const char *page_follow_link_light(struct dentry *, void **);
+extern const char *page_get_link(struct dentry *, struct inode *, void **);
 extern void page_put_link(struct inode *, void *);
 extern int __page_symlink(struct inode *inode, const char *symname, int len,
 		int nofs);
@@ -2754,7 +2754,7 @@ void __inode_sub_bytes(struct inode *inode, loff_t bytes);
 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_follow_link(struct dentry *, void **);
+const char *simple_get_link(struct dentry *, struct inode *, void **);
 extern const struct inode_operations simple_symlink_inode_operations;
 
 extern int iterate_dir(struct file *, struct dir_context *);

mm/shmem.c

@@ -2496,10 +2496,14 @@ static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *s
 	return 0;
 }
 
-static const char *shmem_follow_link(struct dentry *dentry, void **cookie)
+static const char *shmem_get_link(struct dentry *dentry,
+				  struct inode *inode, void **cookie)
 {
 	struct page *page = NULL;
-	int error = shmem_getpage(d_inode(dentry), 0, &page, SGP_READ, NULL);
+	int error;
+	if (!dentry)
+		return ERR_PTR(-ECHILD);
+	error = shmem_getpage(inode, 0, &page, SGP_READ, NULL);
 	if (error)
 		return ERR_PTR(error);
 	unlock_page(page);
@@ -2656,7 +2660,7 @@ static ssize_t shmem_listxattr(struct dentry *dentry, char *buffer, size_t size)
 
 static const struct inode_operations shmem_short_symlink_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= simple_follow_link,
+	.get_link	= simple_get_link,
 #ifdef CONFIG_TMPFS_XATTR
 	.setxattr	= shmem_setxattr,
 	.getxattr	= shmem_getxattr,
@@ -2667,7 +2671,7 @@ static const struct inode_operations shmem_short_symlink_operations = {
 
 static const struct inode_operations shmem_symlink_inode_operations = {
 	.readlink	= generic_readlink,
-	.follow_link	= shmem_follow_link,
+	.get_link	= shmem_get_link,
 	.put_link	= shmem_put_link,
 #ifdef CONFIG_TMPFS_XATTR
 	.setxattr	= shmem_setxattr,