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Thu, 4 Jun 2026 07:04:35 -0400 (EDT) Date: Thu, 4 Jun 2026 12:04:34 +0100 From: Kiryl Shutsemau To: ilya.gladyshev@linux.dev Cc: ivgorbunov@me.com, Liam.Howlett@oracle.com, akpm@linux-foundation.org, apopple@nvidia.com, artem.kuzin@huawei.com, baolin.wang@linux.alibaba.com, david@kernel.org, foxido@foxido.dev, harry.yoo@oracle.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, mhocko@suse.com, muchun.song@linux.dev, rppt@kernel.org, surenb@google.com, torvalds@linuxfoundation.org, vbabka@suse.cz, willy@infradead.org, yuzhao@google.com, ziy@nvidia.com, pfalcato@suse.de Subject: Re: [PATCH v3 1/2] mm: drop page refcount zero state semantics Message-ID: References: <5dabf3a748fee0c7b142c74367e7586f5db1ed1e@linux.dev> <7c28d766b007345f5f31ba9a086a3bffe95a013d@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <7c28d766b007345f5f31ba9a086a3bffe95a013d@linux.dev> X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 03B9C1C0018 X-Stat-Signature: xry68xan3xn846w39e9ycm9bcg7phto1 X-HE-Tag: 1780571078-538170 X-HE-Meta: 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 VvX0NPB2 HWGZ97JL64h8q5BxIGJqTR64G6wSBd2X5Q8n66ffDWAXtJeo/nu2qhUSuCDMcFEUiQmtfnrJuU81dx0NaXPoo0bbgXUs3riJzuZ+p85dzAT58sxcMVQIm8HSi9cRzeaB0oMxXymlY6mKRpoKEVk6OHX+8LBSOiIbWZh3T0F+G8+2Nz+dxxTXu+PfX+ALguQ6wpJYTATcVBh3oL8NvJEf29LamkPnbpM3XYSaU8bsRECBVTJqNibAQQJg1WbSOqE67Nb2yw+4+3pF7VvshyvourWfCiHVkXIG1Ux0RYWnG19RItQUebOvSdB75aeKJAi2iXsLwvYIXoJvfQBwBTp4HztEFBNREssvy9rfwPTX/wO7KNkGNmxrZs4nW0+S0dAOmz4f/d8iHC3UnSku86aBOZ7dTubQ08ARCBjDKYEjzDjt8X5X9azKANGG2ST13eZslkia7 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jun 04, 2026 at 10:15:12AM +0000, ilya.gladyshev@linux.dev wrote: > @@ -115,8 +120,14 @@ static inline void init_page_count(struct page *page) > set_page_count(page, 1); > } > > +static inline void set_page_count_as_frozen(struct page *page) > +{ > + set_page_count(page, 0); > +} > + This name is strange. Maybe something like init_page_count_frozen()? And don't you want to update it in patch 2 to set the bit? > static inline void page_ref_add(struct page *page, int nr) > { > + VM_BUG_ON(__page_count_is_frozen(page_count(page))); Hm. These VM_BUG_ONs are useless after patch 2. In patch 2, you make __page_count_is_frozen() check the frozen bit and page_count() masks out frozen bit. I guess you want to read raw ref number here, no? And why not VM_BUG_ON_PAGE/FOLIO()? > atomic_add(nr, &page->_refcount); > if (page_ref_tracepoint_active(page_ref_mod)) > __page_ref_mod(page, nr); -- Kiryl Shutsemau / Kirill A. Shutemov