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Subject: Re: ubifs: another scheduling while atomic back trace
From: Artem Bityutskiy <dedekind@infradead.org>
To: Cal Page <pagcal@runbox.com>
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Date: Thu, 18 Dec 2008 15:53:38 +0200
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On Thu, 2008-12-18 at 08:34 -0500, Cal Page wrote:
> I tracked it down to fs/ubifs/journal.c in make_reservation()?

How did you track? And what pointed you to this function?

> the code is:
>     again:
>        down_read()
>        err =3D reserve_space()
>        if ( !err) return 0
>        up_read()

That code really looks hacky, because it takes the lock and assumes the
caller unlocks it. We tried to come up with a better solution, and
debated on this, but concluded that this is the best way.

IOW, this is fine, because the caller unlocks the lock using
'finish_reservation()' call.

Moreover, rw semaphore should not make the code to be atomic.


> Also, I notice fs/fs-writeback.c in writeback_inodes does a=20
> down_read_trylock. Won't this interfear with the down_read above?

Sorry, I do not see how and what should interfere there.

--=20
Best regards,
Artem Bityutskiy (=D0=91=D0=B8=D1=82=D1=8E=D1=86=D0=BA=D0=B8=D0=B9 =D0=90=
=D1=80=D1=82=D1=91=D0=BC)