ovl: rearrange ovl_follow_link to it doesn't need to call ->put_link

ovl_follow_link current calls ->put_link on an error path.
However ->put_link is about to change in a way that it will be
impossible to call it from ovl_follow_link.

So rearrange the code to avoid the need for that error path.
Specifically: move the kmalloc() call before the ->follow_link()
call to the subordinate filesystem.

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

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 04f1248..1b4b9c5 100644 (file)
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -145,6 +145,7 @@ static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
        void *ret;
        struct dentry *realdentry;
        struct inode *realinode;
+       struct ovl_link_data *data = NULL;
 
        realdentry = ovl_dentry_real(dentry);
        realinode = realdentry->d_inode;
@@ -152,25 +153,23 @@ static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd)
        if (WARN_ON(!realinode->i_op->follow_link))
                return ERR_PTR(-EPERM);
 
-       ret = realinode->i_op->follow_link(realdentry, nd);
-       if (IS_ERR(ret))
-               return ret;
-
        if (realinode->i_op->put_link) {
-               struct ovl_link_data *data;
-
                data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
-               if (!data) {
-                       realinode->i_op->put_link(realdentry, nd, ret);
+               if (!data)
                        return ERR_PTR(-ENOMEM);
-               }
                data->realdentry = realdentry;
-               data->cookie = ret;
+       }
 
-               return data;
-       } else {
-               return NULL;
+       ret = realinode->i_op->follow_link(realdentry, nd);
+       if (IS_ERR(ret)) {
+               kfree(data);
+               return ret;
        }
+
+       if (data)
+               data->cookie = ret;
+
+       return data;
 }
 
 static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c)