From: Oscar Salvador <osalvador@suse.de>
To: Muchun Song <songmuchun@bytedance.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Vlastimil Babka <vbabka@suse.cz>
Subject: Re: [PATCH v2] mm/page_isolation: do not isolate the max order page
Date: Mon, 7 Dec 2020 14:42:08 +0100 [thread overview]
Message-ID: <20201207134208.GB12191@linux> (raw)
In-Reply-To: <20201203162237.21885-1-songmuchun@bytedance.com>
On Fri, Dec 04, 2020 at 12:22:37AM +0800, Muchun Song wrote:
> The max order page has no buddy page and never merge to other order.
> So isolating and then freeing it is pointless. And if order == MAX_ORDER
> - 1, then the buddy can actually be a !pfn_valid() in some corner case?
> pfn_valid_within(buddy_pfn) that follows would only catch it on archs
> with holes in zone. Then is_migrate_isolate_page(buddy) might access an
> invalid buddy. So this is also a bug fix.
>
> Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock")
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
> ---
> Changes in v2:
> - Add Fixes tag in the commit log.
>
> mm/page_isolation.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index a254e1f370a3..bddf788f45bf 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -88,7 +88,7 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
> */
> if (PageBuddy(page)) {
> order = buddy_order(page);
> - if (order >= pageblock_order) {
> + if (order >= pageblock_order && order < MAX_ORDER - 1) {
> pfn = page_to_pfn(page);
> buddy_pfn = __find_buddy_pfn(pfn, order);
> buddy = page + (buddy_pfn - pfn);
> --
> 2.11.0
>
>
--
Oscar Salvador
SUSE L3
prev parent reply other threads:[~2020-12-07 13:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-03 16:22 [PATCH v2] mm/page_isolation: do not isolate the max order page Muchun Song
2020-12-03 16:28 ` David Hildenbrand
2020-12-04 16:12 ` [External] " Muchun Song
2020-12-04 17:12 ` David Hildenbrand
2020-12-07 13:42 ` Oscar Salvador [this message]
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