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SubjectRe: [PATCH] fs: fput() can be called from interrupt context
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On Thu, 2009-03-12 at 06:39 -0700, Davide Libenzi wrote:
> On Wed, 11 Mar 2009, Andrew Morton wrote:
>
> > > Take the time to check how fs/aio.c handle the fput(req->ki_filp) case
> > > (or read my 2nd patch, it should spot the thing)
> >
> > Well yes, a kludge like that seems a bit safer.
> >
> > It's somewhat encouraging that we're apparently already doing fput()
> > from within keventd (although how frequently?). There might be
> > problems with file locking, security code, etc from doing fput() from
> > an unexpected thread. And then there are all the usual weird problem
> > with using the keventd queues which take a long time to get discovered.
>
> Would it be a huge problem, performance-wise, to stop making ->f_count
> tricks in __aio_put_req, and always offload to fput_work the task of
> releasing the requests?
> If that's a huge problem, IMO the lower impact fix would be to use
> aio_fput_routine to loop into a second list, releasing the eventual
> eventfd file*. There's no need, IMO, to turn the whole fput() into
> IRQ-callable just for this case, when we can contain it into the
> particular KAIO+eventfd usage.
>

Do you really want to see eventd doing umounts and remote flock() calls?
This really needs to be run in a thread that can cope with __long__
waits, unavailable servers, etc...

Trond



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