Re: [PATCH 0/3] hugetlbfs fallocate hole punch race with page faults

From: Andrew Morton
Date: Mon Oct 19 2015 - 19:18:46 EST


On Fri, 16 Oct 2015 15:08:27 -0700 Mike Kravetz <mike.kravetz@xxxxxxxxxx> wrote:

> The hugetlbfs fallocate hole punch code can race with page faults. The
> result is that after a hole punch operation, pages may remain within the
> hole. No other side effects of this race were observed.
>
> In preparation for adding userfaultfd support to hugetlbfs, it is desirable
> to plug or significantly shrink this hole. This patch set uses the same
> mechanism employed in shmem (see commit f00cdc6df7).
>

"still buggy but not as bad as before" isn't what we strive for ;) What
would it take to fix this for real? An exhaustive description of the
bug would be a good starting point, thanks.
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