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b=pHM38j/jlOiQlTLAIbLCyEaRonoDYBtZg7J5alRunu6drq9vnCfEHNvyj1r5Zj15K rfkn+uABWjCsr/dV2r46UPB+sE5/eINf5sCMlYjMuX83UVX1tNuqpqdldnfyDjcbn3 T0EXyMtqw+d7Oy1+8E8LbSL36k/a8zDCG9sfxW7o= Date: Tue, 7 Oct 2025 18:29:22 -0700 From: Andrew Morton To: Wei Yang Cc: 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: <20251007182922.4a254daff78633b1452bdcc3@linux-foundation.org> In-Reply-To: <20251002033140.24462-1-richard.weiyang@gmail.com> References: <20251002033140.24462-1-richard.weiyang@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: jpy5as5bgiusffd7w4ogs18crnegocs6 X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E7057120008 X-HE-Tag: 1759886964-149250 X-HE-Meta: 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 M+arVkVA qORSRqF8En1iSfIBFa3n1Xoco9Sz3Wm06q2p2ctE+3OQ4xb6ttXoKEUxtiPjS7j7+DXmSjOc/LgR+zv+WCa3SUlH6l1cURHWraQfru7LJHWzGigAICwCoaZaHw7qj50GvBAktnyy0DRiLhYCj3ZzGbdQoNdsyfANEt4hfMDUEJpR6owXCXsS2BZvhkOurYR2aOdZvID74OEjDf5qCVFM3IW6Ni5vGLB4UUw1G9b4t9QSejKixn+io0nJBVI8feh+zpseaR+tfV0sACIZR6iU/yuWRjZ7CIl2GwmnRMdz1+2awio9Z1uxluLDROpcRiCOAmokbvyi3uGwhYYsQiPMrKlIJ4+fSkVMj4ClYsHWQlomqxMGIGjQZku+Hej1RVASPwaCprACQqWiz33+TGh4rvFNhhyPuMFwFZR67KZQBw3Hlvp0= 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 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? Thanks.