NFS: Fix nfs_migrate_page()

The call to migrate_page() will cause the page->private field to be
cleared.
Also fix up the locking around the page->private transfer, so that we ensure
that calls to nfs_page_find_request() don't end up racing.

Finally, fix up a double free bug: nfs_unlock_request() already calls
nfs_release_request() for us...

Reported-by: Wu Fengguang <fengguang.wu@intel.com>
Tested-by: Andi Kleen <andi@firstfloor.org>
Cc: stable@kernel.org
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index a28123be08a..6d40a538e3d 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1611,15 +1611,16 @@ int nfs_migrate_page(struct address_space *mapping, struct page *newpage,
         if (ret)
                 goto out_unlock;
         page_cache_get(newpage);
+        spin_lock(&mapping->host->i_lock);
         req->wb_page = newpage;
         SetPagePrivate(newpage);
-        set_page_private(newpage, page_private(page));
+        set_page_private(newpage, (unsigned long)req);
         ClearPagePrivate(page);
         set_page_private(page, 0);
+        spin_unlock(&mapping->host->i_lock);
         page_cache_release(page);
 out_unlock:
         nfs_clear_page_tag_locked(req);
-        nfs_release_request(req);
 out:
         return ret;
 }