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>

1 files changed, 12 insertions, 13 deletions

diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 04f124884687..1b4b9c5e51b7 100644
--- 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)