linux-kernel - Re: [PATCH]fix VM_CAN_NONLINEAR check in sys_remap_file

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Message-Id: <200710081745.39254.nickpiggin@yahoo.com.au>
Date:	Mon, 8 Oct 2007 17:45:38 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>
Cc:	Randy Dunlap <randy.dunlap@...cle.com>, yanzheng@...n.com,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, ltp-list@...ts.sourceforge.net
Subject: Re: [PATCH]fix VM_CAN_NONLINEAR check in sys_remap_file_pages

On Tuesday 09 October 2007 03:51, Andrew Morton wrote:
> On Mon, 8 Oct 2007 10:28:43 -0700

> > I'll now add remap_file_pages soon.
> > Maybe those other 2 tests aren't strong enough (?).
> > Or maybe they don't return a non-0 exit status even when they fail...
> > (I'll check.)
>
> Perhaps Yan Zheng can tell us what test was used to demonstrate this?

Was probably found by review. Otherwise, you could probably reproduce
it by mmaping, say, drm device node, running remap_file_pages() on it
to create a nonlinear mapping, and then finding that you get the wrong
data.

> > > I'm surprise that LTP doesn't have any remap_file_pages() tests.
> >
> > quick grep didn't find any for me.
>
> Me either.  There are a few lying around the place which could be
> integrated.
>
> It would be good if LTP were to have some remap_file_pages() tests
> (please).  As we see here, it is something which we can easily break, and
> leave broken for some time.

Here is Ingo's old test, since cleaned up and fixed a bit by me....
I'm sure he would distribute it GPL, but I've cc'ed him because I didn't
find an explicit statement about that.


View attachment "remap-file-pages.c" of type "text/x-csrc" (2181 bytes)