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[109.81.95.234]) by smtp.gmail.com with UTF8SMTPSA id 4fb4d7f45d1cf-6378811f14bsm14561504a12.45.2025.10.08.04.16.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Oct 2025 04:16:14 -0700 (PDT) Date: Wed, 8 Oct 2025 13:16:14 +0200 From: Michal Hocko To: David Hildenbrand Cc: Wei Yang , akpm@linux-foundation.org, vbabka@suse.cz, surenb@google.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, iamjoonsoo.kim@lge.com, linux-mm@kvack.org Subject: Re: [PATCH 2/2] mm/compaction: fix the range to pageblock_pfn_to_page() Message-ID: References: <20251002033140.24462-1-richard.weiyang@gmail.com> <20251002033140.24462-3-richard.weiyang@gmail.com> <3ec7d5c9-27c4-4395-b859-8931eed72272@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3ec7d5c9-27c4-4395-b859-8931eed72272@redhat.com> X-Rspamd-Server: rspam05 X-Stat-Signature: dwhphgfwayr8zpbn15f39iq913wc4u68 X-Rspam-User: X-Rspamd-Queue-Id: E3470C000D X-HE-Tag: 1759922176-289458 X-HE-Meta: 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 rm6WhWaZ P6F5DmV/XpuwyttmVj2PevztmX94a6Nd0sql1G6Jw4IWWNLmIcWRIRaKtCjHi7fGoncCK8NrVLxGKefRNAclJpRPvxC6P4Is5XvF61dIWQMmZ0VMrgM280CBazpRdNsv7K0+PSzwwSN9jK175FsyJjPL1w4YCcsvBLhuDdC6sHUrGyoUFjpVKoS17sa9zXw2s7FAopBASM2h+/ju/y+FtJ5ixNQFFy9Bu1Ip1nSp6jGNf2Jtv31CoUDqcoYZ+DVeVlvjWf4bB883pMPsHqimIO11s2iwciYAy4zB3xpsAg8ZMZW/hUwR75qnWPVIbzVstVSlkQmTMEpSNWkEYBgYE4UKoYEty1ABVcoTIiei4ePUhKFJ1oy9riMF1fs0iMJmXZ0NYJq/UfbF498B9ffO213diJTrGapZPlupzMPLcqf2y7otyB7sRHxS2MA== 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 08-10-25 12:17:29, David Hildenbrand wrote: > On 02.10.25 05:31, Wei Yang wrote: > > Current code may skip some part of the range to > > pageblock_pfn_to_page() to check whether the range is in the same zone. > > > > Function pageblock_pfn_to_page() is first introduced by commit 7d49d8868336 > > ("mm, compaction: reduce zone checking frequency in the migration scanner"), > > in which it checks and isolates on the same range [pfn, block_end_pfn]. > > > > While after commit e1409c325fdc ("mm/compaction: pass only pageblock > > aligned range to pageblock_pfn_to_page"), we operate on two different > > ranges for check and isolation. > > > > * [block_start_pfn, block_end_pfn] to check it is in the same zone > > * [pfn, block_end_pfn] to do isolation > > > > It miss some range to check when start_pfn and zone->zone_start_pfn is > > in the same pageblock but (start_pfn < zone->zone_start_pfn). The range > > before zone_start_pfn is missed. > > > > start_pfn zone_start_pfn > > +----+-------------+-------------------+ > > block_start_pfn block_end_pfn > > > > This leads to the range check is passed, but it will isolate a range in > > two different zones. > > Can that actually happen? I recall that a zone always spans full pageblocks. My recollection as well and we should rather focus on enforcing that to be true than complicating already quite a complicated code. -- Michal Hocko SUSE Labs