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Wed, 08 Oct 2025 02:13:01 -0700 (PDT) Date: Wed, 8 Oct 2025 09:13:01 +0000 From: Wei Yang To: Michal Hocko Cc: Wei Yang , Andrew Morton , vbabka@suse.cz, surenb@google.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: <20251008091301.44xerz33fmrgnjyt@master> Reply-To: Wei Yang References: <20251002033140.24462-1-richard.weiyang@gmail.com> <20251007182922.4a254daff78633b1452bdcc3@linux-foundation.org> <20251008023218.g53gm33vmrdt5nw7@master> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-Rspam-User: X-Stat-Signature: ft5n3abm138izfpcmgrykr3p8wcz39mi X-Rspamd-Queue-Id: 191E31C0005 X-Rspamd-Server: rspam09 X-HE-Tag: 1759914783-754457 X-HE-Meta: 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 BXKP/J4E 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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 Wed, Oct 08, 2025 at 09:52:51AM +0200, Michal Hocko wrote: >On Wed 08-10-25 02:32:18, Wei Yang wrote: >> 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. > >Is there any actual problem to fix here then? I don't see an actual problem in practice yet. >-- >Michal Hocko >SUSE Labs -- Wei Yang Help you, Help me