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b=cSvFRN/mhHSAQXCQEMuBxWu+v0Tq1/2HT/clHFDF4YgQHodKBT3OqePuzaOO2/Sst 2i8N4QjsHT0BgxxEdFh2MOYQHf5Zshlgxdep53NV+H3sVhpjyv4asGgBLtAwmIQnPB uFDh98MhonM8FQeRS8h82RS7R35Etn9fHT29gX7suGrBEj+KYRHZBTnnKo+nuesbt1 nyEEFxOxVrWjpW0l6bAnyN3aNWZ8PcdDYcEfTgqUm1M5SYx7+Qr4GAsAztVu99iTgV ZMWMDBAZ9+tRdKVYuVgQVNUhTLkloPXYv6vqQpPDQrOj+ZuVY+UmJrFidNIO5NMZ25 TPQHWkLY7hhxQ== Message-ID: Date: Mon, 9 Feb 2026 16:46:54 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm/page_alloc: clear page->private in free_pages_prepare() To: Vlastimil Babka , Mikhail Gavrilov , linux-mm@kvack.org Cc: akpm@linux-foundation.org, surenb@google.com, mhocko@suse.com, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, npiggin@gmail.com, linux-kernel@vger.kernel.org, kasong@tencent.com, hughd@google.com, chrisl@kernel.org, ryncsn@gmail.com, stable@vger.kernel.org, willy@infradead.org References: <209207FE-D3A9-4BE2-8DA7-9BE38A19F387@nvidia.com> <20260207173615.146159-1-mikhail.v.gavrilov@gmail.com> <51f96b31-fb59-4cda-9d33-e3cebc45686b@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 6A5BBC0007 X-Stat-Signature: k1m4mpsmybn9z7kicnz57wzh16ddm6od X-Rspam-User: X-HE-Tag: 1770652023-104892 X-HE-Meta: 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 EUCOT2/l aJTLy2UD/P5TwuwjPy+CAaw5U7pCMpY5eeN45Xpy0NaGw6596ApsWYcYmGp8dMHSYinV9Fjgccx3zSSqkR79NvUK/0h2i1cPZ8/kWvFc4iHDXiTjBd14Vf4tIdrbhAnRIlExKb2rpeM6FhTkofCS2ck3ew6qBllVvqJyZaQZb5G/S/JDP8Z72mZx3XZmfJNUGMAFpc43zLIHbin0VdG7a4fSr7OvM2JD1qSNQrLhJowz4nlqAb26kFhF6mxx81dR7W5rF45UydOhonjxgRTIfQ7Ldwl8mjeYw0itiCDRosEcjVuhQlAoxqJkj1VzpY0dv9Xw5yA2kM9xGdS6lmiXKod0cr+yCr/nlQCUAwkMIXjJIab4poMPtSRpymj+Ttn0Q7ia5fU3IelhbtloDt8MpflbpfA== 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 2/9/26 12:17, Vlastimil Babka wrote: > On 2/7/26 23:08, David Hildenbrand (Arm) wrote: >>> >>> -               /* >>> -                * page->private should not be set in tail pages. Fix up >>> and warn once >>> -                * if private is unexpectedly set. >>> -                */ >>> -               if (unlikely(new_folio->private)) { >>> -                       VM_WARN_ON_ONCE_PAGE(true, new_head); >>> -                       new_folio->private = NULL; >>> -               } >> >> BTW, I wonder whether we should bring that check back for non-device folios. > > If the rule is now that when upon freeing in free_pages_prepare() we clear > private in the head page and not tail pages (where we expect the owner of > the page to do it), maybe that check for tail pages should be done in the > is_check_pages_enabled() part of free_pages_prepare(). > > Or should the check be also in the split path because somebody can set a > tail private between allocation and split? (and not just inherit it from a > previous allocation that didn't clear it?). We ran into that check in the past, when folio->X overlayed page->private in a tail, and would actually have to be zeroed out. So it should be part of this splitting code I think. -- Cheers, David