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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id l24sm280100qtf.27.2019.03.05.19.14.30 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 05 Mar 2019 19:14:30 -0800 (PST) Subject: Re: low-memory crash with patch "capture a page under direct compaction" From: Qian Cai To: Mel Gorman Cc: vbabka@suse.cz, Linux-MM References: <604a92ae-cbbb-7c34-f9aa-f7c08925bedf@lca.pw> <20190305144234.GH9565@techsingularity.net> <1551798804.7087.7.camel@lca.pw> <20190305152759.GI9565@techsingularity.net> <1d3a13fc-72b4-005a-7d73-2203b1ff25e4@lca.pw> Message-ID: <5eecbceb-2522-c880-7d6a-af20cf548500@lca.pw> Date: Tue, 5 Mar 2019 22:14:29 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.3.3 MIME-Version: 1.0 In-Reply-To: <1d3a13fc-72b4-005a-7d73-2203b1ff25e4@lca.pw> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000011, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: I don't understand this part. @@ -2279,14 +2286,24 @@ static enum compact_result compact_zone_order(struct zone *zone, int order, .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY), .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY) }; + struct capture_control capc = { + .cc = &cc, + .page = NULL, + }; + + if (capture) + current->capture_control = &capc; That check will always be true as it is, struct page **capture; *capture could be NULL, but not capture because in __alloc_pages_direct_compact(), it does, struct page *page = NULL; capture = &page;