Re: [PATCH 02 of 66] mm, migration: Fix race between shift_arg_pages and rmap_walk by guaranteeing rmap_walk finds PTEs created within the temporary stack

Andrea Arcangeli
2010-11-19T17:40:18Z

On Thu, Nov 18, 2010 at 11:13:49AM +0000, Mel Gorman wrote:
> This old chestnut. IIRC, this was the more complete solution to a fix that made
> it into mainline. The patch still looks reasonable. It does add a kmalloc()
> but I can't remember if we decided we were ok with it or not. Can you remind

We decided the kmalloc was ok, but Linus didn't like this approach. I
kept it in my tree because I didn't want to remember when/if to add the
special check in the accurate rmap walks. I find it simpler if all
rmap walks are accurate by default.

> me? More importantly, it appears to be surviving the original testcase that
> this bug was about (20 minutes so far but will leave it a few hours). Assuming
> the test does not crash;

Sure the patch is safe.

If Linus still doesn't like this, I will immediately remove this patch
and add the special checks to the rmap walks in huge_memory.c, you
know my preference but this is a detail and my preference is
irrelevant.

Thanks,
Andrea