On Sat, Jun 12, 2010 at 11:56:10AM +0300, Mikolaj Golub wrote: > > On Sun, 6 Jun 2010 16:44:43 +0200 Leon Me??ner wrote: > > LM> Hi, > LM> I hope this is not the wrong list to ask. Didn't get any answers on > LM> -questions. > > LM> When you try to do the following inside a nullfs mounted directory, > LM> where the nullfs origin is itself mounted via nfs you get an error: > > LM> # foo > LM> # tail -f foo& > LM> # rm -f foo > LM> tail: foo: Stale NFS file handle > LM> # fg > > LM> This is really a problem when running services inside jails and using > LM> NFS as storage. As of [2] it looks like this problem is known for a > LM> while. On a normal NFS mount this does not happen as "silly renaming" > LM> [1] works there (producing nasty little .nfsXXXX files). > > nfs_sillyrename() is called when vnode's usecount is more then 1. It is > expected that unlink() syscall increases vnode's usecount in namei() and if > the file has been already opened usecount will be more then 1. > > But with nullfs layer present the reference counts are held by the upper node, > not the lower (nfs) one, so when unlink() is called it increases usecount of > the upper vnode, not nfs vnode and nfs_sillyrename() is never called. > > The strightforward solution looks like to implement null_remove() that will > increase lower vnode's refcount before calling null_bypass() and then > decrement it after the call. See the attached patch (it works for me on both > 8-STABLE and CURRENT).
The upper vnode holds a reference to the lower vnode, as you noted. Now, with your patch, I believe that _all_ calls to the nfs_remove() are happen with refcount > 1.
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