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SubjectRe: [RFC PATCH 0/2] Fix up the NFS mmap code
On Fri, Jan 08, 2010 at 06:22:01PM -0800, Linus Torvalds wrote:
>
>
> On Sat, 9 Jan 2010, Al Viro wrote:
> >
> > Well, sure - it steps on i_mutex-before-mmmap_sem first from ls somewhere and
> > records the ordering for posterity. Then NFS steps into mmap() (on a
> > different inode) and gets conflicting ordering.
>
> Look closer: the inodes for directories and for non-directories have
> i_mutex in different lockdep classes.
>
> So that "on a different inode" thing should have made it a non-issue,
> since there is no actual chain back. There is "mmap_sem ->
> i_mutex_regular_file" (for mmap) and there is "i_mutex_directory ->
> mmap_sem" (for filldir), but that isn't an ABBA.
>
> The problem _seems_ to be (if I read Andi's chain correctly) that a
> directory hasn't gone through the i_mutex_dir_key change, so filldir ends
> up being counted against the default i_mutex_key.

Interesting... There's nfs_update_inode(), but it ought to scream bloody
murder on the type change (and its return value is ignore by nfs_fhget(),
BTW).


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