I have applied your patch against vanilla v5.3-rc5. There was no config changes. So far I've gotten couple of these GPF. I guess this is different issue. It will take several hours to get full view. I've attached one full console log as: console-1566235171.001993084.log [ 13.821223] general protection fault: 0000 [#1] SMP PTI [ 13.821882] CPU: 0 PID: 151 Comm: kswapd0 Tainted: G W 5.3.0-rc5+ #71 [ 13.822755] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.12.0-2.fc30 04/01/2014 [ 13.824272] RIP: 0010:handle_to_buddy+0x20/0x30 [ 13.824786] Code: 84 00 00 00 00 00 0f 1f 40 00 0f 1f 44 00 00 53 48 89 fb 83 e7 01 0f 85 31 26 00 00 48 8b 03 5b 48 89 c2 48 81 e2 00 f0 ff ff <0f> b6 92 ca 00 00 00 29 d0 83 e0 03 c3 0f 1f 00 0f 1f 44 00 00 55 [ 13.826854] RSP: 0000:ffffb18cc01977f0 EFLAGS: 00010206 [ 13.827452] RAX: 00ffff97dd890fd0 RBX: fffff63080243f40 RCX: 0000000000000000 [ 13.828256] RDX: 00ffff97dd890000 RSI: ffff97ddbe5d89c8 RDI: ffff97ddbe5d89c8 [ 13.829056] RBP: ffff97dd890fd000 R08: ffff97ddbe5d89c8 R09: 0000000000000000 [ 13.829860] R10: 0000000000000000 R11: 0000000000000000 R12: ffff97dd890fd001 [ 13.830660] R13: ffff97dd890fd010 R14: ffff97ddb5f96408 R15: ffffb18cc0197838 [ 13.831468] FS: 0000000000000000(0000) GS:ffff97ddbe400000(0000) knlGS:0000000000000000 [ 13.832673] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 13.833593] CR2: 00007fec8745f010 CR3: 0000000006212004 CR4: 0000000000160ef0 [ 13.834508] Call Trace: [ 13.834828] z3fold_zpool_map+0x76/0x110 [ 13.835332] zswap_writeback_entry+0x50/0x410 [ 13.835888] z3fold_zpool_shrink+0x3d1/0x570 [ 13.836434] ? sched_clock_cpu+0xc/0xc0 [ 13.836919] zswap_frontswap_store+0x424/0x7c1 [ 13.837484] __frontswap_store+0xc4/0x162 [ 13.837992] swap_writepage+0x39/0x70 [ 13.838460] pageout.isra.0+0x12c/0x5d0 [ 13.838950] shrink_page_list+0x1124/0x1830 [ 13.839484] shrink_inactive_list+0x1da/0x460 [ 13.840036] shrink_node_memcg+0x202/0x770 [ 13.840746] shrink_node+0xdf/0x490 [ 13.841931] balance_pgdat+0x2db/0x580 [ 13.842396] kswapd+0x239/0x500 [ 13.842772] ? finish_wait+0x90/0x90 [ 13.847323] kthread+0x108/0x140 [ 13.848358] ? balance_pgdat+0x580/0x580 [ 13.849626] ? kthread_park+0x80/0x80 [ 13.850352] ret_from_fork+0x3a/0x50 [ 13.851086] Modules linked in: ip6t_rpfilter ip6t_REJECT nf_reject_ipv6 ipt_REJECT nf_reject_ipv4 xt_conntrack ip6table_nat ip6table_mangle ip6table_raw ip6table_security iptable_nat nf_nat iptable_mangle iptable_raw iptable_security nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 libcrc32c ip_set nfnetlink ip6table_filter ip6_tables iptable_filter ip_tables crct10dif_pclmul crc32_pclmul ghash_clmulni_intel virtio_net virtio_balloon net_failover failover intel_agp intel_gtt qxl drm_kms_helper syscopyarea sysfillrect sysimgblt fb_sys_fops ttm drm crc32c_intel virtio_blk virtio_console serio_raw agpgart qemu_fw_cfg [ 13.857818] ---[ end trace 4517028df5e476fe ]--- [ 13.858400] RIP: 0010:handle_to_buddy+0x20/0x30 [ 13.859761] Code: 84 00 00 00 00 00 0f 1f 40 00 0f 1f 44 00 00 53 48 89 fb 83 e7 01 0f 85 31 26 00 00 48 8b 03 5b 48 89 c2 48 81 e2 00 f0 ff ff <0f> b6 92 ca 00 00 00 29 d0 83 e0 03 c3 0f 1f 00 0f 1f 44 00 00 55 [ 13.862703] RSP: 0000:ffffb18cc01977f0 EFLAGS: 00010206 [ 13.864232] RAX: 00ffff97dd890fd0 RBX: fffff63080243f40 RCX: 0000000000000000 [ 13.865834] RDX: 00ffff97dd890000 RSI: ffff97ddbe5d89c8 RDI: ffff97ddbe5d89c8 [ 13.867362] RBP: ffff97dd890fd000 R08: ffff97ddbe5d89c8 R09: 0000000000000000 [ 13.869121] R10: 0000000000000000 R11: 0000000000000000 R12: ffff97dd890fd001 [ 13.871091] R13: ffff97dd890fd010 R14: ffff97ddb5f96408 R15: ffffb18cc0197838 [ 13.872742] FS: 0000000000000000(0000) GS:ffff97ddbe400000(0000) knlGS:0000000000000000 [ 13.874448] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 13.876382] CR2: 00007fec8745f010 CR3: 0000000006212004 CR4: 0000000000160ef0 [ 13.878007] ------------[ cut here ]------------ (gdb) l *handle_to_buddy+0x20 0xffffffff813376b0 is in handle_to_buddy (/src/linux/mm/z3fold.c:429). 424 unsigned long addr; 425 426 WARN_ON(handle & (1 << PAGE_HEADLESS)); 427 addr = *(unsigned long *)handle; 428 zhdr = (struct z3fold_header *)(addr & PAGE_MASK); 429 return (addr - zhdr->first_num) & BUDDY_MASK; 430 } 431 432 static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr) 433 { (gdb) l *z3fold_zpool_map+0x76 0xffffffff81337cb6 is in z3fold_zpool_map (/src/linux/mm/z3fold.c:1257). 1252 if (test_bit(PAGE_HEADLESS, &page->private)) 1253 goto out; 1254 1255 z3fold_page_lock(zhdr); 1256 buddy = handle_to_buddy(handle); 1257 switch (buddy) { 1258 case FIRST: 1259 addr += ZHDR_SIZE_ALIGNED; 1260 break; 1261 case MIDDLE: (gdb) l *zswap_writeback_entry+0x50 0xffffffff812e8260 is in zswap_writeback_entry (/src/linux/mm/zswap.c:858). 853 .sync_mode = WB_SYNC_NONE, 854 }; 855 856 /* extract swpentry from data */ 857 zhdr = zpool_map_handle(pool, handle, ZPOOL_MM_RO); 858 swpentry = zhdr->swpentry; /* here */ 859 zpool_unmap_handle(pool, handle); 860 tree = zswap_trees[swp_type(swpentry)]; 861 offset = swp_offset(swpentry); (gdb) l *z3fold_zpool_shrink+0x3d1 0xffffffff81338821 is in z3fold_zpool_shrink (/src/linux/mm/z3fold.c:1186). 1181 ret = pool->ops->evict(pool, middle_handle); 1182 if (ret) 1183 goto next; 1184 } 1185 if (first_handle) { 1186 ret = pool->ops->evict(pool, first_handle); 1187 if (ret) 1188 goto next; 1189 } 1190 if (last_handle) { To compare, I got following Call Trace "signatures" against vanilla v5.3-rc5. Some of them might not be related to zswap at all. [ 15.469831] Call Trace: [ 15.470171] migrate_pages+0x20c/0xfb0 [ 15.470678] ? isolate_freepages_block+0x410/0x410 [ 15.471344] ? __ClearPageMovable+0x90/0x90 [ 15.471914] compact_zone+0x74c/0xef0 -- [ 105.611480] Call Trace: [ 105.611817] zswap_writeback_entry+0x50/0x410 [ 105.612417] z3fold_zpool_shrink+0x29d/0x540 [ 105.612947] zswap_frontswap_store+0x424/0x7c1 [ 105.613494] __frontswap_store+0xc4/0x162 -- [ 15.103942] Call Trace: [ 15.104280] z3fold_zpool_map+0x76/0x110 [ 15.104824] zswap_writeback_entry+0x50/0x410 [ 15.105398] z3fold_zpool_shrink+0x3c4/0x540 [ 15.105960] zswap_frontswap_store+0x424/0x7c1 -- [ 632.066122] Call Trace: [ 632.066124] z3fold_zpool_map+0x76/0x110 [ 632.066128] zswap_writeback_entry+0x50/0x410 [ 632.069101] do_user_addr_fault+0x1fe/0x480 [ 632.069650] z3fold_zpool_shrink+0x3c4/0x540 -- [ 133.419601] Call Trace: [ 133.420199] zswap_writeback_entry+0x50/0x410 [ 133.421244] z3fold_zpool_shrink+0x4a6/0x540 [ 133.422266] zswap_frontswap_store+0x424/0x7c1 [ 133.423386] __frontswap_store+0xc4/0x162 -- [ 155.374773] Call Trace: [ 155.375122] get_page_from_freelist+0x57d/0x1a40 [ 155.375725] __alloc_pages_nodemask+0x19d/0x400 [ 155.376354] alloc_pages_vma+0xcc/0x170 [ 155.376854] __read_swap_cache_async+0x1e9/0x3e0 -- [ 23.849834] Call Trace: [ 23.851038] get_page_from_freelist+0x57d/0x1a40 [ 23.853300] ? wake_all_kswapds+0x54/0xb0 [ 23.855280] __alloc_pages_slowpath+0x1ae/0x1000 [ 23.857512] ? __lock_acquire+0x247/0x1900 -- [ 197.206331] Call Trace: [ 197.207923] __release_z3fold_page.constprop.0+0x7e/0x130 [ 197.211387] do_compact_page+0x2c9/0x430 [ 197.213830] process_one_work+0x272/0x5a0 [ 197.216392] worker_thread+0x50/0x3b0