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

[Trond Myklebust]

>>>>> " " == viro  <[e-mail]> 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.)

     > ????

Al,

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
    fh.

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

Cheers,
  Trond