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Sun, 04 Feb 2024 17:08:17 -0800 (PST) MIME-Version: 1.0 References: <20240204125404.2112384-1-hezhongkun.hzk@bytedance.com> In-Reply-To: From: Zhongkun He Date: Mon, 5 Feb 2024 09:08:05 +0800 Message-ID: Subject: Re: [External] Re: [PATCH] mm/z3fold: remove unneeded spinlock To: Matthew Wilcox Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 8276F4000F X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 5grbrhgcn55hm3gjs91a9ni6unqayqa8 X-HE-Tag: 1707095299-370924 X-HE-Meta: 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 B5FNnnY7 Wra+RP+UXrWBQWA6ooTjSQOfnypQC40nabARauFmcEqIFMVzRE9GmkPtkkmEk38RNyOV39XzPWbb4Axmc7YvXwUWkTPUc+NFsqGwBXO+jy36JNQ9Gx9hLZxIxi/n/TB0yMLE/7qh5PkULfDqq6VSmdyFG92y8GokGJHtngi55XVK3cK55ZaX/Bus2rjrtupXP1AMoCrSQPiuPj2tJU9RjfBnZibrbN1XtgbUVD6cIHTq6kORkr5ZHcdF3P4xMJg79fwHfTsCWbJ7dplThkFiKtFwmwSnwTCl5HL41RP8QSjVxDXQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000007, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Feb 5, 2024 at 2:46=E2=80=AFAM Matthew Wilcox = wrote: > > On Sun, Feb 04, 2024 at 08:54:04PM +0800, Zhongkun He wrote: > > There is no need to use spinlock in this section, so > > remove it. > > I don't know this code at all, but the idiom is (relatively) common. > It waits until anybody _currently_ holding the lock has released it. > > That would, eg, make it safe to free the 'pool' memory. > > > - spin_lock(&pool->lock); > > - spin_unlock(&pool->lock); > no, please see the commit 'e774a7bc7f0adb'. spin_lock(&pool->lock); - if (!list_empty(&page->lru)) - list_del_init(&page->lru); spin_unlock(&pool->lock); The original purpose of this lock was to protect page->lru, which was removed now, so the spinlock is unnecessary. Thanks for your time.