new ->follow_link() and ->put_link() calling conventions

a) instead of storing the symlink body (via nd_set_link()) and returning
an opaque pointer later passed to ->put_link(), ->follow_link() _stores_
that opaque pointer (into void * passed by address by caller) and returns
the symlink body.  Returning ERR_PTR() on error, NULL on jump (procfs magic
symlinks) and pointer to symlink body for normal symlinks.  Stored pointer
is ignored in all cases except the last one.

Storing NULL for opaque pointer (or not storing it at all) means no call
of ->put_link().

b) the body used to be passed to ->put_link() implicitly (via nameidata).
Now only the opaque pointer is.  In the cases when we used the symlink body
to free stuff, ->follow_link() now should store it as opaque pointer in addition
to returning it.

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

2 files changed, 14 insertions, 16 deletions

diff --git a/fs/cifs/cifsfs.h b/fs/cifs/cifsfs.h
index 252f5c15806b..61012da7e9d8 100644
--- a/fs/cifs/cifsfs.h
+++ b/fs/cifs/cifsfs.h
@@ -120,7 +120,7 @@ extern struct vfsmount *cifs_dfs_d_automount(struct path *path);
 #endif
 
 /* Functions related to symlinks */
-extern void *cifs_follow_link(struct dentry *direntry, struct nameidata *nd);
+extern const char *cifs_follow_link(struct dentry *direntry, void **cookie, struct nameidata *nd);
 extern int cifs_readlink(struct dentry *direntry, char __user *buffer,
 			 int buflen);
 extern int cifs_symlink(struct inode *inode, struct dentry *direntry,
diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index 252e672d5604..4a439c2c0c7f 100644
--- a/fs/cifs/link.c
+++ b/fs/cifs/link.c
@@ -626,8 +626,8 @@ cifs_hl_exit:
 	return rc;
 }
 
-void *
-cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
+const char *
+cifs_follow_link(struct dentry *direntry, void **cookie, struct nameidata *nd)
 {
 	struct inode *inode = d_inode(direntry);
 	int rc = -ENOMEM;
@@ -643,16 +643,18 @@ cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
 
 	tlink = cifs_sb_tlink(cifs_sb);
 	if (IS_ERR(tlink)) {
-		rc = PTR_ERR(tlink);
-		tlink = NULL;
-		goto out;
+		free_xid(xid);
+		return ERR_CAST(tlink);
 	}
 	tcon = tlink_tcon(tlink);
 	server = tcon->ses->server;
 
 	full_path = build_path_from_dentry(direntry);
-	if (!full_path)
-		goto out;
+	if (!full_path) {
+		free_xid(xid);
+		cifs_put_tlink(tlink);
+		return ERR_PTR(-ENOMEM);
+	}
 
 	cifs_dbg(FYI, "Full path: %s inode = 0x%p\n", full_path, inode);
 
@@ -670,17 +672,13 @@ cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
 						&target_path, cifs_sb);
 
 	kfree(full_path);
-out:
+	free_xid(xid);
+	cifs_put_tlink(tlink);
 	if (rc != 0) {
 		kfree(target_path);
-		target_path = ERR_PTR(rc);
+		return ERR_PTR(rc);
 	}
-
-	free_xid(xid);
-	if (tlink)
-		cifs_put_tlink(tlink);
-	nd_set_link(nd, target_path);
-	return NULL;
+	return *cookie = target_path;
 }
 
 int