Re: Hang on large copy_from_user with PREEMPT_NONE

From: Dave Jones
Date: Tue Apr 07 2015 - 17:10:20 EST

On Tue, Apr 07, 2015 at 11:12:31AM -0700, Linus Torvalds wrote:
> On Apr 7, 2015 10:58 AM, "Dave Jones" <davej@xxxxxxxxxxxxxxxxx> wrote:
> > >
> > > +#define COPY_CHUNK_SIZE (16*PAGE_SIZE)
> >
> > This needs to be bigger, just to accomodate things like xfs, which
> > on my system is over 1mb. I think some out-of-tree modules
> > (not that I care deeply) are even bigger.
> Umm. It will happily copy megabytes of data. Or gigabytes. It just doors it
> in smaller chunks, and make sure to test the return value and possibly
> reschedule in between.

brain no worky. You are of course, correct.

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