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b=tofKyyaHNySBvmVGxOieuISUQJKPo7gB0JxdO/edPBHPVbFEj9+IsHJsrXkKW8HZb fHbP+n1gJOaTrnWcF0QbNqSmSwzcrqFPs62xhGskO2V58hmk89BmgIJRiUBpUxxC2m RMQw/pt1VMkKFgR5hyiVYycYfd9i+YVTrZkVN6ZlAH74PqSMsTO+ghpJa3I6mEikLj 1nktx901SdMLELeM31yHBlMyEpj0uoi7+NPTmFR5OZrqfYSowozi5NFF94aZvLTjtu KCWXf2epb6M75Jw0hS6Fyp689VUul4FErkC9317L8hfRb4rBq8SxjJa4ojgGXrdfWF qSZzJ5xw5edag== Date: Thu, 12 Oct 2023 12:19:06 +0300 From: Mike Rapoport To: Yajun Deng Cc: David Hildenbrand , akpm@linux-foundation.org, mike.kravetz@oracle.com, muchun.song@linux.dev, willy@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/2] mm: Init page count in reserve_bootmem_region when MEMINIT_EARLY Message-ID: <20231012091906.GQ3303@kernel.org> References: <15233624-f32e-172e-b2f6-7ca7bffbc96d@linux.dev> <20231001185934.GX3303@kernel.org> <90342474-432a-9fe3-2f11-915a04f0053f@linux.dev> <20231002084708.GZ3303@kernel.org> <20231002111051.GA3303@kernel.org> <3057dab3-19f2-99ca-f125-e91a094975ed@redhat.com> <8c9ee3bd-6d71-4111-8f4e-91bc52b42ed4@linux.dev> <20231005050619.GB3303@kernel.org> <6545ac4c-1205-6c09-49ea-e00c24d1a2ff@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <6545ac4c-1205-6c09-49ea-e00c24d1a2ff@linux.dev> X-Rspam-User: X-Stat-Signature: 6dg1jw4zr46ruk4j1gwe31bt33zuc83h X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 3918D40004 X-HE-Tag: 1697102410-278133 X-HE-Meta: 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 YJ4X5geM lurFDSsD9fr6kXEzhe6ele5JrSr4JSnsCOnKn4LhOSc7VxowmbG/cc0iFjHbpb9VLsdewEIoM3iwpn+3wjxlKSLtpO8Dw4CAcUO80VjEC2qwFItHXQJYYLtOTrKsOecRT+nMxm8dQLpnFHJlrYvwA7zbopKhZ16w59m+iNFiiQWX6JE8BupLPI7+u4qMFzgEIxionzUQOusadUaK+W9bRUTcU2ynyOQpxuiMCfq5zuKURYWqIdpr8iWoM8A== 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: On Thu, Oct 05, 2023 at 10:04:28PM +0800, Yajun Deng wrote: > > > > > > > > That 'if' breaks the invariant that __free_pages_core is > > > > > > > always called for pages with initialized page count. Adding > > > > > > > it may lead to subtle bugs and random memory corruption so we > > > > > > > don't want to add it at the first place. > > > > > > > > > > > > As long as we have to special-case memory hotplug, we know that > > > > > > we are always coming via generic_online_page() in that case. We > > > > > > could either move some logic over there, or let > > > > > > __free_pages_core() know what it should do. > > > > > > > > > > Looks like the patch rather special cases MEMINIT_EARLY, although > > > > > I didn't check throughfully other code paths. Anyway, relying on > > > > > page_count() to be correct in different ways for different > > > > > callers of __free_pages_core() does not sound right to me. > > > > > > > > Absolutely agreed. > > > > > > > I already sent v5  a few days ago. Comments, please... > > > > Does it address all the feedback from this thread? > > Except hotplug. Please reread carefully the last comments from me and from David above. -- Sincerely yours, Mike.