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SubjectRe: NFS lockdep lock misordering mmap_sem<->i_mutex_key with 2.6.32-git1
On Mon, Dec 07, 2009 at 09:19:28PM +0900, KOSAKI Motohiro wrote:
> >
> > While booting 2.6.32-git1 on a NFS root box I got the following
> > lockdep warning early at boot. I haven't looked at details.
>
> It seems typical ABBA deadlock.
>
> vfs_readdir [grab i_mutex]
> nfs_readdir
> nfs_do_filldir
> filldir
> copy_to_user
> [page_fault] [grab mmap_sem]
>
> sys_mmap [grab mmap_sem]
> do_mmap_pgoff
> mmap_region
> nfs_file_mmap
> nfs_revalidate_mapping
> nfs_invalidate_mapping [grab i_mutex]
>
> I guess recent lockdep improvement find old bug.

Thanks for the analysis.

I guess should never do copy_*_user while holding i_mutex? There might
be lots of cases like that.

-Andi


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