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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id x22sm13300250qtr.57.2020.05.12.17.36.52 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 May 2020 17:36:52 -0700 (PDT) From: Qian Cai Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.80.23.2.2\)) Subject: zswap z3fold + memory offline = infinite loop Message-Id: Date: Tue, 12 May 2020 20:36:51 -0400 Cc: Michal Hocko , David Hildenbrand , Linux-MM , LKML , Minchan Kim , Seth Jennings , Dan Streetman To: Vitaly Wool X-Mailer: Apple Mail (2.3608.80.23.2.2) 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: Put zswap z3fold pages into the memory and then offline those memory = would trigger an infinite loop here in __offline_pages() --> do_migrate_range() because there is no error = handling, if (pfn) { /* * TODO: fatal migration failures should = bail * out */ do_migrate_range(pfn, end_pfn); There, isolate_movable_page() will always return -EBUSY because, if (!mapping->a_ops->isolate_page(page, mode)) goto out_no_isolated; i.e., z3fold_page_isolate() will always return false because, zhdr->mapped_count =3D=3D 2 It should be easy to reproduce. Otherwise, use this one, https://github.com/cailca/linux-mm/blob/master/random.c and then watch the console burning with those, [12661.793667][T566417] failed to isolate pfn 1045b2 [12661.793745][T566417] page:c00c000004116c80 refcount:2 mapcount:0 = mapping:00000000999f9672 index:0x0 [12661.793865][T566417] mapping->a_ops:z3fold_aops [12661.793919][T566417] flags: 0x3fffc000000000() [12661.793969][T566417] raw: 003fffc000000000 c00c000003cef388 = c00c000006b0da08 c000001275b87f6a [12661.794071][T566417] raw: 0000000000000000 0000000000000000 = 00000002ffffffff 0000000000000000 [12661.794158][T566417] page dumped because: isolation failed [12661.794226][T566417] page_owner tracks the page as allocated [12661.794292][T566417] page last allocated via order 0, migratetype = Unmovable, gfp_mask 0x12800(GFP_NOWAIT|__GFP_NOWARN|__GFP_NORETRY) [12661.794463][T566417] prep_new_page+0x3d0/0x450 [12661.794508][T566417] get_page_from_freelist+0x1bb8/0x27c0 [12661.794575][T566417] = __alloc_pages_slowpath.constprop.60+0x240/0x15a0 [12661.794654][T566417] __alloc_pages_nodemask+0x520/0x650 [12661.794715][T566417] alloc_pages_current+0xbc/0x140 [12661.794772][T566417] z3fold_zpool_malloc+0x6cc/0xe20 [12661.794826][T566417] zpool_malloc+0x34/0x50 [12661.794888][T566417] zswap_frontswap_store+0x60c/0xe20 [12661.794942][T566417] __frontswap_store+0x128/0x330 [12661.794995][T566417] swap_writepage+0x58/0x110 [12661.795048][T566417] pageout+0x16c/0xa40 [12661.795092][T566417] shrink_page_list+0x1ab4/0x2490 [12661.795155][T566417] shrink_inactive_list+0x25c/0x710 [12661.795206][T566417] shrink_lruvec+0x444/0x1260 [12661.795274][T566417] shrink_node+0x288/0x9a0 [12661.795330][T566417] do_try_to_free_pages+0x158/0x640 [12661.795383][T566417] page last free stack trace: [12661.795437][T566417] free_pcp_prepare+0x52c/0x590 [12661.795493][T566417] free_unref_page+0x38/0xf0 [12662.156109][T566417] free_z3fold_page+0x58/0x120 [12662.156131][T566417] free_pages_work+0x148/0x1c0 [12662.156195][T566417] process_one_work+0x310/0x900 [12662.156257][T566417] worker_thread+0x78/0x530 [12662.156306][T566417] kthread+0x1c4/0x1d0 [12662.156354][T566417] ret_from_kernel_thread+0x5c/0x74