Comment 47 for bug 1867916

Eoan / Testing
====

modified
--------

$ uname -rv
5.3.0-63-generic #57+lp1867916.1 SMP Mon Jul 6 18:33:27 -03 2020

$ sudo make-bcache --bdev $DEV --block 8k
[ 29.620685] bcache: bcache_device_init() bcache0: sb/logical block size (8192) greater than page size (4096) falling back to device logical block size (512)
[ 29.624382] bcache: register_bdev() registered backing device loop0

original
--------

$ uname -rv
5.3.0-63-generic #57-Ubuntu SMP Thu Jul 2 10:38:35 UTC 2020

$ sudo make-bcache --bdev $DEV --block 8k
[ 40.416094] bcache: register_bdev() registered backing device loop0
[ 40.418547] BUG: kernel NULL pointer dereference, address: 0000000000000000
[ 40.423539] #PF: supervisor write access in kernel mode
[ 40.424608] #PF: error_code(0x0002) - not-present page
[ 40.425610] PGD 80000001374fb067 P4D 80000001374fb067 PUD 138349067 PMD 0
[ 40.426901] Oops: 0002 [#1] SMP PTI
[ 40.427542] CPU: 3 PID: 1546 Comm: bcache-register Not tainted 5.3.0-63-generic #57-Ubuntu
[ 40.428937] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
[ 40.430476] RIP: 0010:create_empty_buffers+0x24/0x110
[ 40.431373] Code: 00 00 00 00 66 90 0f 1f 44 00 00 55 48 89 e5 41 55 49 89 d5 ba 01 00 00 00 41 54 53 48 89 fb e8 52 f4 ff ff 49 89 c4 4$ 89 c2 <4c> 09 2a 48 89 d0 48 8b 52 08 48 85 d2 75 f1 4c 89 60 08 48 8b 43
[ 40.434484] RSP: 0018:ffffb2ec803ab820 EFLAGS: 00010286
[ 40.435397] RAX: 0000000000000000 RBX: fffff0c884a2d000 RCX: ffff9f3af9141000
[ 40.436602] RDX: 0000000000000000 RSI: ffff9f3af9141000 RDI: fffff0c884a2d000
[ 40.437820] RBP: ffffb2ec803ab838 R08: ffff9f3af9141000 R09: 0000000000000000
[ 40.439040] R10: 0000000000000001 R11: ffff9f3af602f198 R12: 0000000000000000
[ 40.440260] R13: 0000000000000000 R14: ffff9f3af64d1c60 R15: 0000000000000000
[ 40.441480] FS: 00007fed73c25700(0000) GS:ffff9f3afbb80000(0000) knlGS:0000000000000000
[ 40.443000] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 40.444068] CR2: 0000000000000000 CR3: 0000000128bd2000 CR4: 00000000000006e0
[ 40.445325] Call Trace:
[ 40.445858] create_page_buffers+0x52/0x60
[ 40.446656] block_read_full_page+0x4e/0x3a0
[ 40.447477] ? blkdev_direct_IO+0x70/0x70
[ 40.448255] ? __add_to_page_cache_locked+0x2e5/0x340
[ 40.449193] ? scan_shadow_nodes+0x30/0x30
[ 40.449982] blkdev_readpage+0x18/0x20
[ 40.450722] do_read_cache_page+0x2f6/0x830
[ 40.451527] ? update_load_avg+0x7c/0x670
[ 40.452300] ? prep_new_page+0x128/0x160
[ 40.453064] read_cache_page+0x12/0x20
[ 40.453801] read_dev_sector+0x27/0xd0
[ 40.454551] read_lba+0xbd/0x220
[ 40.455207] ? kmem_cache_alloc_trace+0x16c/0x240
[ 40.456074] efi_partition+0x1e0/0x6fd
[ 40.456796] ? vsnprintf+0x39e/0x4e0
[ 40.457494] ? snprintf+0x49/0x60
[ 40.458155] check_partition+0x154/0x244
[ 40.458916] rescan_partitions+0xae/0x280
[ 40.459675] bdev_disk_changed+0x5f/0x70
[ 40.460426] __blkdev_get+0x3f8/0x550
[ 40.461138] blkdev_get+0x3d/0x140
[ 40.461807] __device_add_disk+0x388/0x480
[ 40.462603] device_add_disk+0x13/0x20
[ 40.463346] bch_cached_dev_run+0x66/0x190 [bcache]
[ 40.464265] register_bcache.cold+0x140/0x193 [bcache]
[ 40.465205] ? __handle_mm_fault+0x4c5/0x7a0
[ 40.466002] kobj_attr_store+0x12/0x20
[ 40.466731] sysfs_kf_write+0x3e/0x50
[ 40.467444] kernfs_fop_write+0xda/0x1b0
[ 40.468188] __vfs_write+0x1b/0x40
[ 40.468855] vfs_write+0xb9/0x1a0
[ 40.469510] ksys_write+0x67/0xe0
[ 40.470160] __x64_sys_write+0x1a/0x20
[ 40.470894] do_syscall_64+0x5a/0x130
[ 40.471608] entry_SYSCALL_64_after_hwframe+0x44/0xa9
[ 40.472518] RIP: 0033:0x7fed737352c0
[ 40.473204] Code: 73 01 c3 48 8b 0d d8 cb 2c 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 89 24 2d 00 00 75 10 b8 01 00 00 00
 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 fe dd 01 00 48 89 04 24
[ 40.476366] RSP: 002b:00007ffeffea2f78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
[ 40.477720] RAX: ffffffffffffffda RBX: 000000000000000b RCX: 00007fed737352c0
[ 40.478947] RDX: 000000000000000b RSI: 000000000233a010 RDI: 0000000000000003
[ 40.480169] RBP: 000000000233a010 R08: 0000000000000000 R09: 000000000000000b
[ 40.481395] R10: 000000000000000a R11: 0000000000000246 R12: 000000000000000b
[ 40.482628] R13: 0000000000000001 R14: 00007ffeffea2ff0 R15: 0000000000000000
[ 40.483877] Modules linked in: bcache crc64 isofs kvm_intel kvm joydev irqbypass input_leds serio_raw ib_iser rdma_cm iw_cm ib_cm ib_core
 iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi autofs4 btrfs xor zstd_compress raid6_pq libcrc32c virtio_net net_failover failover ps
mouse virtio_blk floppy
[ 40.488263] CR2: 0000000000000000
[ 40.488945] ---[ end trace 8e856c7273ff61a8 ]---
[ 40.489810] RIP: 0010:create_empty_buffers+0x24/0x110
[ 40.490737] Code: 00 00 00 00 66 90 0f 1f 44 00 00 55 48 89 e5 41 55 49 89 d5 ba 01 00 00 00 41 54 53 48 89 fb e8 52 f4 ff ff 49 89 c4 48
 89 c2 <4c> 09 2a 48 89 d0 48 8b 52 08 48 85 d2 75 f1 4c 89 60 08 48 8b 43
[ 40.493878] RSP: 0018:ffffb2ec803ab820 EFLAGS: 00010286
[ 40.494824] RAX: 0000000000000000 RBX: fffff0c884a2d000 RCX: ffff9f3af9141000
[ 40.496034] RDX: 0000000000000000 RSI: ffff9f3af9141000 RDI: fffff0c884a2d000
[ 40.497252] RBP: ffffb2ec803ab838 R08: ffff9f3af9141000 R09: 0000000000000000
[ 40.498489] R10: 0000000000000001 R11: ffff9f3af602f198 R12: 0000000000000000
[ 40.499711] R13: 0000000000000000 R14: ffff9f3af64d1c60 R15: 0000000000000000
[ 40.500942] FS: 00007fed73c25700(0000) GS:ffff9f3afbb80000(0000) knlGS:0000000000000000
[ 40.502741] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 40.503760] CR2: 0000000000000000 CR3: 0000000128bd2000 CR4: 00000000000006e0