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[2003:cb:c726:9300:1711:356:6550:7502]) by smtp.gmail.com with ESMTPSA id b1-20020adfee81000000b002ca864b807csm21720280wro.0.2023.04.28.09.22.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 28 Apr 2023 09:22:39 -0700 (PDT) Message-ID: Date: Fri, 28 Apr 2023 18:22:38 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0 Subject: Re: [PATCH] mm/memory_hotplug: fix dead loop in offline_pages() To: Michal Hocko , Yajun Deng Cc: osalvador@suse.de, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20230428100846.95535-1-yajun.deng@linux.dev> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: E50F340015 X-Rspamd-Server: rspam09 X-Stat-Signature: 44sskr31dhzk717ap7ig9sc89ds8pifd X-HE-Tag: 1682698974-40815 X-HE-Meta: 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 E0RRO/S9 HFUCl4TrjE8O4QmL1NbvJzmNsZeQKQrUErQklo0Yvxon+2s06ClA9K67fcL/wVtrYRM+WlueJUFBSMR8PUDuQowkXXUev79a3DlIdiHoHsfqCWepQodNKBf9D2Q9KP+y0o4iaWU/oiuAxTyqkmzQm7ZcqQRePcoPxxLTBo3jtA2O0p5PlUL/UEN4nC7tQAkaSflyddt+Cy6ANIcDwRCHCTT1ytms1nvoNA2Eh/1rh0BBYOutkO+IRkIWqxwA4NxShPTqN/zj0W7Jn26u6gH4LJO3CX8kF9UyOJFRMIb+SeKzAGmJLkekgnrmTpp0NNqcXOK7HZKHSBosKddQFNJTZob+jSGP4qNYvEwN0IBL8lrtlCI6kHYYOFS66JlD6s9njRdftBj0EgDkY/5MWBS8H0JOyR7TIR+1F6Tw8lwY87IxjfzSxNDRoOcwUd9di8YwNA4rY83Grg1nxb17atVbDCbfq8Rr16J96JkM3EUpe4DMfQ4Q= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000558, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 28.04.23 13:07, Michal Hocko wrote: > On Fri 28-04-23 18:08:46, Yajun Deng wrote: >> When migration failure in do_migrate_range() and then the >> scan_movable_pages() will most likely return the same movable pfn. >> In this case, there is no condition to bail out, they will >> always run like this: >> >> ... >> [878020.623959] migrating pfn 1727813 failed ret:1 >> [878020.623960] page:00000000faa9673c refcount:3 mapcount:0 mapping:00000000144ccd79 index:0x14280025 pfn:0x1727813 >> [878020.623962] memcg:ffffa0ff82d5a000 >> [878020.623962] aops:def_blk_aops ino:fd00001 >> [878020.623964] flags: 0x17ffffc000206a(referenced|dirty|active|workingset|private|node=0|zone=2|lastcpupid=0x1fffff) >> [878020.623966] raw: 0017ffffc000206a ffffb0d14f50fbd8 ffffb0d14f50fbd8 ffffa0ff9c155018 >> [878020.623967] raw: 0000000014280025 ffffa10327d702d8 00000003ffffffff ffffa0ff82d5a000 >> [878020.623968] page dumped because: migration failure >> [878020.626196] migrating pfn 1727813 failed ret:1 >> [878020.626198] page:00000000faa9673c refcount:3 mapcount:0 mapping:00000000144ccd79 index:0x14280025 pfn:0x1727813 >> [878020.626200] memcg:ffffa0ff82d5a000 >> [878020.626200] aops:def_blk_aops ino:fd00001 >> [878020.626202] flags: 0x17ffffc000206a(referenced|dirty|active|workingset|private|node=0|zone=2|lastcpupid=0x1fffff) >> [878020.626204] raw: 0017ffffc000206a ffffb0d14f50fbd8 ffffb0d14f50fbd8 ffffa0ff9c155018 >> [878020.626205] raw: 0000000014280025 ffffa10327d702d8 00000003ffffffff ffffa0ff82d5a000 >> [878020.626206] page dumped because: migration failure >> ... >> >> Bail out when migration failures reach 3 times. >> >> Fixes: bb8965bd82fd ("mm, memory_hotplug: deobfuscate migration part of offlining") >> Signed-off-by: Yajun Deng > > Any hard coded failure retry limit will lead to premature failures. Have > a look at 72b39cfc4d75 ("mm, memory_hotplug: do not fail offlining too > early"). A proper way to deal with this is to implement termination from > the userspace (e.g. timeout $TIMEOUT /bin/echo 0 > $PATH_TO_MEM/online) > Nacked-by: Michal Hocko Agreed; it's a bit more complicated when offlining is triggered by ACPI code :( -- Thanks, David / dhildenb