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SubjectRe: [PATCH 3/4] unionfs: restructure unionfs_setattr
In message <Pine.LNX.4.64.0712190030390.5639@blonde.wat.veritas.com>, Hugh Dickins writes:
> On Tue, 18 Dec 2007, Erez Zadok wrote:
> > In message <Pine.LNX.4.64.0712182213300.28390@blonde.wat.veritas.com>, Hugh Dickins writes:
> > > In order to fix unionfs truncation, we need to move the lower notify_change
> > > out of the loop in unionfs_setattr. But when I came to do that, I couldn't
> > [...]
> >
> > Hugh, I want to understand how patches 3/4 and 4/4 are related. In patch 3
> > you say "in order to fix truncation" but you mention a truncation problem
> > only in patch 4; is there a patch ordering problem, or they're both related
> > to the same issue (with 3/4 being a code cleanup, and 4/4 actually fixing
> > the problem)?
>
> I needed to move that notify_change out of the loop, to fix the truncation
> problem, but had great difficulty understanding the loop. So, just as you
> say, made the code cleanup first in 3/4, then fixed the problem in 4/4.
>
> But that cleanup does need your review and testing.

A quick look at your setattr patches seems very promising. And I've further
realized more cleanup is possible: because we call revalidate_chain at the
opening to ->setattr, we're guaranteed to have a valid lower dentry, so for
example we can remove the else case for "if (lower_dentry)".
I'll be testing this and your other patches, plus look into the locking
issues you brought up.

Thanks,
Erez.


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