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b=HYUcO5MpMzN6wi5pD+JUCPWDtxPsRImIKOIoK99ULMG0OiEBghKnlWUB82bTpGfVJ Ql/+23VSVy0jOuAbM4o6v+q/9iPetGbCaDt1xF4MXjqNP1Kq8ndaGEnsrHdJDoK2mx /nLuyjHKyYDoD+XLFnBFUc0YyG9LlkeuCpZhv3rA= Date: Fri, 2 Feb 2024 01:22:51 -0800 From: Andrew Morton To: Zhiguo Jiang Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, opensource.kernel@vivo.com Subject: Re: [PATCH v2] mm:vmscan: shrink skip folio mapped by an exiting task Message-Id: <20240202012251.1aa5afbfdf2f8b3a862bced3@linux-foundation.org> In-Reply-To: <20240131131244.1144-1-justinjiang@vivo.com> References: <20240131131244.1144-1-justinjiang@vivo.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: yj87ckb514qa93ouz7j6genkscy9mhkg X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 4CF2810000E X-Rspam-User: X-HE-Tag: 1706865776-464433 X-HE-Meta: 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 dgUpQAAg nzfI9cl6bX71A3ke1DtQgTqmpNKa6YKDBamzHVZAH+NKNrYEKn59c1pw0Qvrnd6/NkyhOiburfXuqgo65QKK6KRCGJQVUrOB/Ln12Juslwd382xT6uOmVoiRUo6S4wBwH/XsNm+vwZrvVw3Ph8ZfXPzpxjzxdPa577OSI6LIJh72rV9VtkHXJQv2vCV01XBGgJ6AlEdZa0xQLY8YOa4MzffcDh+gPTq+F51OkX2KK3lKEbsP808EX8a1wNz71qe35/Z+qQkq4ZopzukChgiGL94y3bvvi027la2UW X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 Wed, 31 Jan 2024 21:12:44 +0800 Zhiguo Jiang wrote: > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -840,6 +840,13 @@ static bool folio_referenced_one(struct folio *folio, > int referenced = 0; > unsigned long start = address, ptes = 0; > > + /* Skip this folio if it's mapped by an exiting task */ > + if (unlikely(!atomic_read(&vma->vm_mm->mm_users)) || > + unlikely(test_bit(MMF_OOM_SKIP, &vma->vm_mm->flags))) { > + pra->referenced = -1; > + return false; > + } The code comment explains what the code does. This is, as usual, pretty obvious from reading the code! A better comment is one which explains *why* the code is doing what it does.