From: Liam Howlett <liam.howlett@oracle.com>
To: Hugh Dickins <hughd@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Oleg Nesterov <oleg@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [PATCH mmotm] mempolicy: mbind_range() set_policy() after vma_merge()
Date: Sat, 5 Mar 2022 02:00:39 +0000 [thread overview]
Message-ID: <20220305020021.qmwg5dkham4lyz6v@revolver> (raw)
In-Reply-To: <6038ebc2-bc88-497d-a3f3-5936726fb023@google.com>
* Hugh Dickins <hughd@google.com> [220304 17:48]:
> On Fri, 4 Mar 2022, Liam Howlett wrote:
> > * Liam R. Howlett <Liam.Howlett@Oracle.com> [220304 13:49]:
> > > * Hugh Dickins <hughd@google.com> [220303 23:36]:
> >
> > I just thought of something after my initial email
> >
> > How does the ->set_policy() requirement on tmpfs play out for the
> > mpol_equal() check earlier in that for loop?
>
> It took me a while to page all this back in (and remind myself of
> what is case 8) to answer that question!
>
> The answer is that the mpol_equal() check at the top of the loop is on
> an existing, unmodified vma; so it's right to assume that any necessary
> set_policy() has already been done.
>
> Whereas the mpol_equal() check being removed in this patch, is being
> done on a vma which may have just been extended to cover a greater range:
> so although the relevant set_policy() may have already been done on a part
> of its range, there is now another part which needs the policy applied.
Doesn't the policy get checked during vma_merge()? Specifically the
mpol_equal(policy, vma_policy(next)) check?
>
> > > Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
>
> Thank you, your review is very welcome (but mainly I Cc'ed to alert
> you to how I'm probably stepping on your toes a little here - sorry).
Yes, I figured as much and I really appreciate it. I'm quite confident
I translated this bug to my patch set.
Thanks,
Liam
next prev parent reply other threads:[~2022-03-05 2:00 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-04 4:36 [PATCH mmotm] mempolicy: mbind_range() set_policy() after vma_merge() Hugh Dickins
2022-03-04 18:06 ` Oleg Nesterov
2022-03-04 22:33 ` Hugh Dickins
2022-03-04 18:49 ` Liam Howlett
2022-03-04 19:05 ` Liam Howlett
2022-03-04 22:48 ` Hugh Dickins
2022-03-05 2:00 ` Liam Howlett [this message]
2022-03-05 2:28 ` Hugh Dickins
2022-03-08 16:05 ` Liam Howlett
2022-03-08 21:32 ` Hugh Dickins
2022-03-09 12:41 ` Vlastimil Babka
2022-03-09 19:10 ` Liam Howlett
2022-03-11 9:33 ` Hugh Dickins
2022-03-11 8:54 ` Hugh Dickins
2022-03-11 12:47 ` Vlastimil Babka
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