fs: remove vfs_follow_link

For a long time no filesystem has been using vfs_follow_link, and as seen
by recent filesystem submissions any new use is accidental as well.

Remove vfs_follow_link, document the replacement in
Documentation/filesystems/porting and also rename __vfs_follow_link
to match its only caller better.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

Documentation/filesystems/porting

@@ -451,3 +451,7 @@ in your dentry operations instead.
 --
 [mandatory]
 	->readdir() is gone now; switch to ->iterate()
+[mandatory]
+	vfs_follow_link has been removed.  Filesystems must use nd_set_link
+	from ->follow_link for normal symlinks, or nd_jump_link for magic
+	/proc/<pid> style links.

fs/namei.c

@@ -660,7 +660,7 @@ static __always_inline void set_root_rcu(struct nameidata *nd)
 	}
 }
 
-static __always_inline int __vfs_follow_link(struct nameidata *nd, const char *link)
+static __always_inline int __follow_link(struct nameidata *nd, const char *link)
 {
 	int ret;
 
@@ -874,7 +874,7 @@ follow_link(struct path *link, struct nameidata *nd, void **p)
 	error = 0;
 	s = nd_get_link(nd);
 	if (s) {
-		error = __vfs_follow_link(nd, s);
+		error = __follow_link(nd, s);
 		if (unlikely(error))
 			put_link(nd, link, *p);
 	}
@@ -4236,11 +4236,6 @@ int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
 	return res;
 }
 
-int vfs_follow_link(struct nameidata *nd, const char *link)
-{
-	return __vfs_follow_link(nd, link);
-}
-
 /* get the link contents into pagecache */
 static char *page_getlink(struct dentry * dentry, struct page **ppage)
 {
@@ -4352,7 +4347,6 @@ EXPORT_SYMBOL(vfs_path_lookup);
 EXPORT_SYMBOL(inode_permission);
 EXPORT_SYMBOL(unlock_rename);
 EXPORT_SYMBOL(vfs_create);
-EXPORT_SYMBOL(vfs_follow_link);
 EXPORT_SYMBOL(vfs_link);
 EXPORT_SYMBOL(vfs_mkdir);
 EXPORT_SYMBOL(vfs_mknod);

include/linux/fs.h

@@ -2494,7 +2494,6 @@ extern const struct file_operations generic_ro_fops;
 #define special_file(m) (S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))
 
 extern int vfs_readlink(struct dentry *, char __user *, int, const char *);
-extern int vfs_follow_link(struct nameidata *, const char *);
 extern int page_readlink(struct dentry *, char __user *, int);
 extern void *page_follow_link_light(struct dentry *, struct nameidata *);
 extern void page_put_link(struct dentry *, struct nameidata *, void *);