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[209.85.220.65]) by mx.google.com with SMTPS id q20sor123459pfh.71.2019.05.29.10.01.47 for (Google Transport Security); Wed, 29 May 2019 10:01:48 -0700 (PDT) Received-SPF: pass (google.com: domain of hannes@cmpxchg.org designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@cmpxchg-org.20150623.gappssmtp.com header.s=20150623 header.b=fS3Hs1Yr; spf=pass (google.com: domain of hannes@cmpxchg.org designates 209.85.220.65 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=cmpxchg.org DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=ATiPYb6QVWJfqMIRxjJk9r0kehuG42lflrhOEdSkzdU=; b=fS3Hs1YrlmBlz66o8yW5j5lJGSOwB0f40hHewi73HAkx1JkP8DwsKVJD3oke6zsRzo x3fMWyGXird0w3TURVE6SpXs1vh+EXvXFX+S2l39bwxgPWpsnuiqtHTXSHy/76uj084s 0Dv6zXlongF8W7DXnu5evVUrGLh4ybGOUGEz1bbh3XR1KW5896ZcsiDuBO47TbnlwDyG 3vZoshv5HWBgvFFtKtUnr43MrUzIo47WoFFv+5Ji8d6NnEpjJYObsEu4TW2G3At+06Ib /WObBpQZR6BBmjPUDVJl4px+X23Sm4HF5D6Y4zYzIlmBVrbHAollpowPIcoI60LS1xBu 7N7w== X-Google-Smtp-Source: APXvYqyjE5P+va9ALwJlSxEieGnZMQxMLtmWGpxHFSU9l2LuRvYdbs8NYV7CWHPt1o3YB8YBJN2GYQ== X-Received: by 2002:a17:90a:be0b:: with SMTP id a11mr13482926pjs.88.1559149306648; Wed, 29 May 2019 10:01:46 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::1:a47c]) by smtp.gmail.com with ESMTPSA id l38sm103167pje.12.2019.05.29.10.01.45 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 29 May 2019 10:01:45 -0700 (PDT) Date: Wed, 29 May 2019 13:01:44 -0400 From: Johannes Weiner To: Andrew Morton Cc: Hillf Danton , Mel Gorman , linux-mm@kvack.org, Minchan Kim , Yang Shi Subject: Re: [PATCH] mm: vmscan: Add warn on inadvertently reclaiming mapped page Message-ID: <20190529170144.GA30884@cmpxchg.org> References: <20190526062353.14684-1-hdanton@sina.com> <20190528212257.f795b405ac1b88d72bb3fa2f@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190528212257.f795b405ac1b88d72bb3fa2f@linux-foundation.org> User-Agent: Mutt/1.11.4 (2019-03-13) 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: On Tue, May 28, 2019 at 09:22:57PM -0700, Andrew Morton wrote: > On Sun, 26 May 2019 14:23:53 +0800 Hillf Danton wrote: > > > In the function isolate_lru_pages(), we check scan_control::may_unmap and set > > isolation mode accordingly in order to not isolate from the lru list any page > > that does not match the isolation mode. For example, we should skip all sill > > mapped pages if isolation mode is set to be ISOLATE_UNMAPPED. > > > > So complain, while scanning the isolated pages, about the very unlikely event > > that we hit a mapped page that we should never have isolated. Note no change > > is added in the current scanning behavior without VM debug configured. > > The patch is inoffensive enough, but one wonders what inspired it. Do > you have reason to believe that this will trigger? I don't think this patch makes sense. There isn't anything preventing someone from mapping the page between the LRU isolation and shrink_page_list(). The isolation filter is only an optimization to reduce unnecessary LRU churn, not a guarantee.