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Mon, 07 Sep 2026 21:11:22 -0700 (PDT) Received: from google.com ([2a00:79e0:2031:6:56ed:100b:a906:b2eb]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-39b3312f9a8sm21325570a91.2.2026.09.07.21.11.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Sep 2026 21:11:22 -0700 (PDT) Date: Tue, 8 Sep 2026 13:11:16 +0900 From: Sergey Senozhatsky To: Zi Yan Cc: David Hildenbrand , "Matthew Wilcox (Oracle)" , Andrew Morton , Muchun Song , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Gregory Price , Ying Huang , Alistair Popple , Johannes Weiner , Qi Zheng , Shakeel Butt , Kairui Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Minchan Kim , Sergey Senozhatsky Subject: Re: [PATCH v3 01/14] mm/zsmalloc: replace PG_private with pointer comparison Message-ID: References: <20260907-remove-pg_private-v3-0-6ae22f9d9272@nvidia.com> <20260907-remove-pg_private-v3-1-6ae22f9d9272@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260907-remove-pg_private-v3-1-6ae22f9d9272@nvidia.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 6390020002 X-Stat-Signature: s3ocn8b86y74rpdfkeu1roeo3s3oyw46 X-Rspam-User: X-HE-Tag: 1788840684-363906 X-HE-Meta: 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 QwxBNpRM 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On (26/09/07 22:56), Zi Yan wrote: > zsmalloc uses PG_private to indicate first zpdesc in a zspage chain. It is > equivalent to check zpdesc == zspage->first_zpdesc. Replace > is_first_zpdesc() with zpdesc == zspage->first_zpdesc in obj_allocated(). > > For get_first_zpdesc(), first_zpdesc is from zspage->first_zpdesc, so > replace is_first_zpdesc() with first_zpdesc->zspage == zspage, the second > requirement of a zspage chain, where all zpdescs point to the same zspage. > > is_first_zpdesc(), is only used in VM_BUG_ON_PAGE(), so performance impact > should be negligible. While at it, change VM_BUG_ON() to > VM_WARN_ON_ONCE_PAGE(). > > It prepares for a future commit that remove PG_private. > > No functional change intended. > > Assisted-by: Claude:claude-opus-4-8 > Assisted-by: Codex:gpt-5 > To: Minchan Kim > To: Sergey Senozhatsky > To: Andrew Morton > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > Acked-by: Johannes Weiner > Signed-off-by: Zi Yan Reviewed-by: Sergey Senozhatsky