[Linux-cachefs] fscache broken since kernel 5.8

[Greg M]

Hi David,

<Apologies for the re-send, the original email was sent to the wrong mailing list address.>

I have been attempting to upgrade my Gentoo webservers from kernel 5.7 to 5.8 however I have been running into a cachefiles bug since 5.8.0 - which is still occurring on 5.8.14.

This is the dmesg output:

[31033.884329] CacheFiles:
[31033.887797] CacheFiles: Assertion failed
[31033.891300] ------------[ cut here ]------------
[31033.894826] kernel BUG at fs/cachefiles/rdwr.c:715!
[31033.894829] invalid opcode: 0000 [#73] SMP PTI
[31033.894830] CPU: 8 PID: 4435 Comm: php-fpm Tainted: G      D           5.8.14-gentoo-x86_64 #1
[31033.894830] Hardware name: Supermicro Super Server/X11SCL-F, BIOS 1.4 05/26/2020
[31033.894833] RIP: 0010:cachefiles_read_or_alloc_pages+0xc4/0x5e4
[31033.894834] Code: ff 0f 0b 49 8b 47 30 48 8b 40 70 48 83 78 20 00 75 1a 48 c7 c7 c7 39 da 9d e8 48 28 dd ff 48 c7 c7 d7 39 da 9d e8 3c 28 dd ff <0f> 0b 49 8b 47 28 ba 0c 00 00 00 66 c7 44 24 48 00 00 45 31 f6 0f
[31033.894835] RSP: 0018:ffffa097c7887a40 EFLAGS: 00010246
[31033.894835] RAX: 000000000000001c RBX: ffffa097c7887d20 RCX: 0000000000000000
[31033.894836] RDX: 0000000000000000 RSI: ffff91490ec17890 RDI: ffff91490ec17890
[31033.894836] RBP: ffffa097c7887bbc R08: 000000000000000f R09: 0000000000000000
[31033.894836] R10: 0000000000aaaaaa R11: ffffa097c12ff020 R12: ffff914550d26e40
[31033.894837] R13: ffffa097c7887bbc R14: ffff914550d26e40 R15: ffff914807998670
[31033.894837] FS:  00007f0fcc832980(0000) GS:ffff91490ec00000(0000) knlGS:0000000000000000
[31033.894838] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[31033.894838] CR2: 00007f0f8c07d000 CR3: 0000000736fb8002 CR4: 00000000003606e0
[31033.894839] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[31033.894839] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[31033.894839] Call Trace:
[31033.894842]  ? rpc_wake_up_first_on_wq+0xf0/0xf7
[31033.894844]  ? kmem_cache_alloc_trace+0xe3/0xf2
[31033.894860]  ? fscache_run_op+0x82/0x90
[31033.894861]  __fscache_read_or_alloc_pages+0x23b/0x2d8
[31033.894863]  __nfs_readpages_from_fscache+0x46/0xa8
[31033.894865]  nfs_readpages+0x108/0x170
[31033.894867]  ? nfs4_file_open+0x19b/0x1d4
[31033.996631]  read_pages+0x8d/0x114
[31033.996633]  page_cache_readahead_unbounded+0xd0/0x19e
[31033.996634]  generic_file_buffered_read+0x11e/0x4fa
[31033.996636]  nfs_file_read+0x54/0x7d
[31033.996638]  new_sync_read+0x77/0xaa
[31033.996639]  vfs_read+0xc6/0x103
[31033.996640]  ksys_read+0x71/0xba
[31033.996642]  do_syscall_64+0x48/0x67
[31033.996644]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
[31033.996645] RIP: 0033:0x7f0fce4c545e
[31033.996646] Code: c0 e9 b6 fe ff ff 50 48 8d 3d be e0 09 00 e8 f9 e4 01 00 66 0f 1f 84 00 00 00 00 00 64 8b 04 25 18 00 00 00 85 c0 75 14 0f 05 <48> 3d 00 f0 ff ff 77 5a c3 66 0f 1f 84 00 00 00 00 00 48 83 ec 28
[31033.996647] RSP: 002b:00007ffc0174dbb8 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
[31033.996647] RAX: ffffffffffffffda RBX: 00007f0fcc6e8380 RCX: 00007f0fce4c545e
[31033.996648] RDX: 0000000000002000 RSI: 00007f0fcc6a4000 RDI: 0000000000000008
[31033.996648] RBP: 00007f0fcc6a4000 R08: 00007f0fcc6a4000 R09: 0000003fffffffff
[31033.996649] R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000003
[31033.996649] R13: 0000000000002000 R14: 00007f0fcc67d480 R15: 00007f0fcc6e8380
[31033.996650] Modules linked in: ip6t_REJECT nf_reject_ipv6 ip6table_filter binfmt_misc x86_pkg_temp_thermal input_leds joydev led_class i40e coretemp i2c_i801 efivars pcspkr i2c_smbus ahci libahci libata
[31033.997353] ---[ end trace c44b03d0e3d7bd38 ]---
[31034.069000] RIP: 0010:cachefiles_read_or_alloc_pages+0xc4/0x5e4
[31034.069001] Code: ff 0f 0b 49 8b 47 30 48 8b 40 70 48 83 78 20 00 75 1a 48 c7 c7 c7 39 da 9d e8 48 28 dd ff 48 c7 c7 d7 39 da 9d e8 3c 28 dd ff <0f> 0b 49 8b 47 28 ba 0c 00 00 00 66 c7 44 24 48 00 00 45 31 f6 0f
[31034.069002] RSP: 0018:ffffa097c0933940 EFLAGS: 00010246
[31034.084198] RAX: 000000000000001c RBX: ffffa097c0933c20 RCX: 0000000000000027
[31034.084199] RDX: 0000000000000000 RSI: 0000000000000002 RDI: ffff91490ec57890
[31034.084199] RBP: ffffa097c0933abc R08: 0000000000000001 R09: ffff91492efdd400
[31034.084200] R10: 00000000000002f2 R11: 000000000000003c R12: ffff9147889503c0
[31034.084200] R13: ffffa097c0933abc R14: ffff9147889503c0 R15: ffff914817910a20
[31034.084201] FS:  00007f0fcc832980(0000) GS:ffff91490ec00000(0000) knlGS:0000000000000000
[31034.084202] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[31034.109695] CR2: 00007f0f8c07d000 CR3: 0000000736fb8002 CR4: 00000000003606e0
[31034.109696] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[31034.109696] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

I don't really have much else to report other than the above. Eventually my webserver will crash and require a power cycle.

Kind Regards,

Greg M