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AJvYcCXoyytEsKeu+8vvAVgnHW9IeEF5u8xTkNeddZj8yEktOBqNgVsjlsDVppU+ZnH9S2X62JZpSm1gUZCauI73E7FJWJapIwrxLcn05dku X-Gm-Message-State: AOJu0YyvKbJZ8fnjjYuvkDvVXLzv4fYPLMtmdt4J7CEGLR/l8Nmdqp4i v9FFdVVSteo6dJ1CexYw8fsPJ1Zn0PMC9M4v9mrxVIc9MdZzr5t+EZaTzTgN2vc= X-Google-Smtp-Source: AGHT+IGn1WTzy+QP7GoYHjjKhbmY/dTV/RzlOdfgmAWM2wYTzRqVoIZUZ6pNgpAYsdfo4cFoXCfVIA== X-Received: by 2002:a05:6a00:1acb:b0:6e4:6a40:1b36 with SMTP id f11-20020a056a001acb00b006e46a401b36mr4723444pfv.12.1708404710901; Mon, 19 Feb 2024 20:51:50 -0800 (PST) Received: from [10.254.117.3] ([139.177.225.234]) by smtp.gmail.com with ESMTPSA id h15-20020a056a00000f00b006dd843734c8sm5247248pfk.81.2024.02.19.20.51.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 Feb 2024 20:51:50 -0800 (PST) Message-ID: <4f3c6c96-3bea-4369-a2de-e3c559505bba@bytedance.com> Date: Tue, 20 Feb 2024 12:51:46 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/3] mm/zsmalloc: remove migrate_write_lock_nested() Content-Language: en-US To: Sergey Senozhatsky Cc: nphamcs@gmail.com, yosryahmed@google.com, Minchan Kim , Andrew Morton , hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240219-b4-szmalloc-migrate-v1-0-34cd49c6545b@bytedance.com> <20240219-b4-szmalloc-migrate-v1-2-34cd49c6545b@bytedance.com> <20240220044825.GD11472@google.com> From: Chengming Zhou In-Reply-To: <20240220044825.GD11472@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2024/2/20 12:48, Sergey Senozhatsky wrote: > On (24/02/19 13:33), Chengming Zhou wrote: >> static void migrate_write_unlock(struct zspage *zspage) >> { >> write_unlock(&zspage->lock); >> @@ -2003,19 +1997,17 @@ static unsigned long __zs_compact(struct zs_pool *pool, >> dst_zspage = isolate_dst_zspage(class); >> if (!dst_zspage) >> break; >> - migrate_write_lock(dst_zspage); >> } >> >> src_zspage = isolate_src_zspage(class); >> if (!src_zspage) >> break; >> >> - migrate_write_lock_nested(src_zspage); >> - >> + migrate_write_lock(src_zspage); >> migrate_zspage(pool, src_zspage, dst_zspage); >> - fg = putback_zspage(class, src_zspage); >> migrate_write_unlock(src_zspage); >> >> + fg = putback_zspage(class, src_zspage); > > Hmm. Lockless putback doesn't look right to me. We modify critical > zspage fileds in putback_zspage(). Which I think is protected by pool->lock, right? We already held it. > >> if (fg == ZS_INUSE_RATIO_0) { >> free_zspage(pool, class, src_zspage); >> pages_freed += class->pages_per_zspage; >> @@ -2025,7 +2017,6 @@ static unsigned long __zs_compact(struct zs_pool *pool, >> if (get_fullness_group(class, dst_zspage) == ZS_INUSE_RATIO_100 >> || spin_is_contended(&pool->lock)) { >> putback_zspage(class, dst_zspage); >> - migrate_write_unlock(dst_zspage); >> dst_zspage = NULL; >> >> spin_unlock(&pool->lock); >> @@ -2034,15 +2025,12 @@ static unsigned long __zs_compact(struct zs_pool *pool, >> } >> } >> >> - if (src_zspage) { >> + if (src_zspage) >> putback_zspage(class, src_zspage); >> - migrate_write_unlock(src_zspage); >> - } >> >> - if (dst_zspage) { >> + if (dst_zspage) >> putback_zspage(class, dst_zspage); >> - migrate_write_unlock(dst_zspage); >> - }