From: Oscar Salvador <osalvador@suse.de>
To: Mike Kravetz <mike.kravetz@oracle.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Michal Hocko <mhocko@kernel.org>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Muchun Song <songmuchun@bytedance.com>,
David Hildenbrand <david@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC PATCH 2/3] hugetlb: convert page_huge_active() to HPageMigratable flag
Date: Fri, 15 Jan 2021 21:38:03 +0100 [thread overview]
Message-ID: <20210115203803.GB3322@localhost.localdomain> (raw)
In-Reply-To: <d98039ef-8489-6d8c-a323-44e3f0d8acee@oracle.com>
On Fri, Jan 15, 2021 at 09:43:36AM -0800, Mike Kravetz wrote:
> > Before the page_huge_active() in scan_movable_pages() we have the
> > if (!PageHuge(page)) check, but could it be that between that check and
> > the page_huge_active(), the page gets dissolved, and so we are checking
> > a wrong page[1]? Am I making sense?
>
> Yes, you are making sense.
>
> The reason I decided to drop the check is because it does not eliminate the
> race. Even with that check in page_huge_active, the page could be dissolved
> between that check and check of page[1]. There really is no way to eliminate
> the race without holding a reference to the page (or hugetlb_lock). That
> check in page_huge_active just shortens the race window.
Yeah, you are right, the race already exists.
Anyway, do_migrate_range should take care of making sure what it is
handling, so I think we are good.
--
Oscar Salvador
SUSE L3
next prev parent reply other threads:[~2021-01-15 20:38 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 21:01 [RFC PATCH 0/3] create hugetlb flags to consolidate state Mike Kravetz
2021-01-11 21:01 ` [RFC PATCH 1/3] hugetlb: use page.private for hugetlb specific page flags Mike Kravetz
2021-01-12 3:24 ` [External] " Muchun Song
2021-01-13 13:54 ` Oscar Salvador
2021-01-13 17:49 ` Mike Kravetz
2021-01-13 14:45 ` Matthew Wilcox
2021-01-13 17:51 ` Mike Kravetz
2021-01-11 21:01 ` [RFC PATCH 2/3] hugetlb: convert page_huge_active() to HPageMigratable flag Mike Kravetz
2021-01-12 3:45 ` [External] " Muchun Song
2021-01-15 9:17 ` Oscar Salvador
2021-01-15 17:43 ` Mike Kravetz
2021-01-15 20:05 ` Mike Kravetz
2021-01-15 20:29 ` Oscar Salvador
2021-01-15 21:25 ` Mike Kravetz
2021-01-15 20:38 ` Oscar Salvador [this message]
2021-01-11 21:01 ` [RFC PATCH 3/3] hugetlb: convert PageHugeTemporary() to HPageTempSurplus Mike Kravetz
2021-01-15 10:16 ` Oscar Salvador
2021-01-15 17:47 ` Mike Kravetz
2021-01-12 10:41 ` [RFC PATCH 0/3] create hugetlb flags to consolidate state David Hildenbrand
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