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Tue, 27 Feb 2024 20:34:02 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:50c1:1ad2:3268:cacd]) by smtp.gmail.com with ESMTPSA id c7-20020a17090abf0700b0029acce2420asm424101pjs.10.2024.02.27.20.34.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Feb 2024 20:34:02 -0800 (PST) Date: Wed, 28 Feb 2024 13:33:58 +0900 From: Sergey Senozhatsky To: Chengming Zhou Cc: yosryahmed@google.com, Sergey Senozhatsky , hannes@cmpxchg.org, nphamcs@gmail.com, Andrew Morton , Minchan Kim , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH 1/2] mm/zsmalloc: don't hold locks of all pages when free_zspage() Message-ID: <20240228043358.GF11972@google.com> References: <20240226-zsmalloc-zspage-rcu-v1-0-456b0ef1a89d@bytedance.com> <20240226-zsmalloc-zspage-rcu-v1-1-456b0ef1a89d@bytedance.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240226-zsmalloc-zspage-rcu-v1-1-456b0ef1a89d@bytedance.com> On (24/02/27 03:02), Chengming Zhou wrote: [..] > @@ -978,10 +974,11 @@ static struct zspage *alloc_zspage(struct zs_pool *pool, > pages[i] = page; > } > > - create_page_chain(class, zspage, pages); > init_zspage(class, zspage); > zspage->pool = pool; > zspage->class = class->index; > + /* RCU set_zspage() after zspage initialized. */ > + create_page_chain(class, zspage, pages); So this hasn't been tested, has it? init_zspage() does not like to be invoked before create_page_chain(), because we haven't setup required pointers yet. So when init_zspage() calls get_first_page() it gets NULL zspage->first_page which we then use in is_first_page(first_page)->PagePrivate(page). As far as I can tell.