Re: [PATCH] nfs_unlink() race (was: nfs_refresh_inode: inode number mismatch)

From: Trond Myklebust (
Date: Tue Jun 10 2003 - 20:59:10 EST

>>>>> " " == viro <> writes:

> On Mon, Jun 09, 2003 at 06:51:41AM -0700, Frank Cusack wrote:
>> When foo is unlinked, nfs_unlink() does a sillyrename, this
>> puts the dentry on nfs_delete_queue, and (in the VFS) unhashes
>> it from the dcache. This causes a problem, because
>> dentry->d_parent->d_inode is now guaranteed to remain stale.
>> (OK, I'm not really sure about this last part.)

> ????


AFAICS the problem is the following:

  - NFS sillyrenames dentry 1
  - Upon return from nfs_unlink(), VFS unhashes dentry 1

  - Upon next lookup, VFS+NFS conspire to create aliased dentry 2 to
    sillyrenamed file
  - Upon last close of files associated with dentry 1, NFS completes
    sillyrename. File is unlinked on server.
  - Aliased dentry 2 is still around, but it is now pointing to stale

IOW we just want to prevent VFS from unhashing the dentry in the first
place: dentry aliasing cannot work together with sillyrename.

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