Re: [PATCH] SGI 882960: Busy inodes after unmount, oops

[Olaf Kirch <okir@suse.de>]

Hi Greg,

On Thu, Feb 05, 2004 at 09:41:32AM +1100, Greg Banks wrote:
> BTW (not directly related to this bug) I found by experiment that I
> could umount an NFS mount when there were open file descriptors for
> unlinked files in the mount, and even keep writing.  All the NFS
> and RPC structures stay alive until the last file descriptor closes,
> thanks to the magic of refcounts.  All this despite the vfsmount
> reference taken in struct file, which I thought was supposed to
> prevent umount.

Then something else must be wrong big time.

> >  -      __rpc_execute notices the task is dead (no tk_action),
> >         leaves the loop and invokes task->tk_exit == nfs_async_unlink_done
> 
> No.  In a crash dump taken after the umount has completed, the dir dentry has
> 1 leaked d_count for every async unlink present at umount, even though the
> async unlink tasks have been cleaned up.  This indicates that task->tk_exit
> is not being called but task->tk_release is, so the dput is not happening.

But then prune_dcache shouldn't touch these dentries at all, because their
refcount is still 1. They would be leaked, but there would be no crash.

> It's not entirely clear to me how __rpc_execute can do that, but the evidence
> is that it does so.

Very strange... maybe we have a refcounting problem elsewhere, and the
refcount was 2 before calling tk_exit? But somehow I doubt this... I
think we'd see far more massive problems in this case.

Would you share your test case?

Olaf
-- 
Olaf Kirch     |  Stop wasting entropy - start using predictable
okir@suse.de   |  tempfile names today!
---------------+ 


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