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Tue, 07 Oct 2025 19:32:19 -0700 (PDT) Date: Wed, 8 Oct 2025 02:32:18 +0000 From: Wei Yang To: Andrew Morton Cc: Wei Yang , vbabka@suse.cz, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, david@redhat.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, iamjoonsoo.kim@lge.com, linux-mm@kvack.org Subject: Re: [PATCH 0/2] mm/compaction: some fix for the range passed to pageblock_pfn_to_page() Message-ID: <20251008023218.g53gm33vmrdt5nw7@master> Reply-To: Wei Yang References: <20251002033140.24462-1-richard.weiyang@gmail.com> <20251007182922.4a254daff78633b1452bdcc3@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251007182922.4a254daff78633b1452bdcc3@linux-foundation.org> User-Agent: NeoMutt/20170113 (1.7.2) X-Stat-Signature: kxxgjkik6s6jou8jeo7b6pmd6p187rtc X-Rspamd-Queue-Id: 99F7140005 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1759890741-108598 X-HE-Meta: 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 OrQVI65N 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Oct 07, 2025 at 06:29:22PM -0700, Andrew Morton wrote: >On Thu, 2 Oct 2025 03:31:38 +0000 Wei Yang wrote: > >> During the code reading of isolate_migratepages_range(), first spot the range >> passed to pageblock_pfn_to_page() is different from that to >> isolate_migratepages_block(). >> >> This implies there is a chance that pageblock_pfn_to_page() thinks the range >> is in the same zone, but isolate_migratepages_block() will isolate range in >> two different zones. This is not what we expect. >> >> Then I found pageblock_pfn_to_page() has an optimization if zone->contiguous, >> this means even the range is across two different zones, it will think the >> range is within the same zone. >> >> So introduce two patches to fix it: > >What do you think might be the worst-case userspace-visible effects >of the bug? I don't see userspace-visible effect yet. Since I lack the knowledge of the consequence of isolating cross zone range, currently I can't tell the effect accurately. The worst case in my mind is we put some page on a different zone's freelist. But I don't totally understand the behavior now. > >Thanks. -- Wei Yang Help you, Help me