Comment 58 for bug 1867916

Verification done on xenial-proposed.

The kernel in -proposed logs the block size change.
The kernel in -updates fails.

xenial-proposed:
---

 $ uname -rv
 4.4.0-187-generic #217-Ubuntu SMP Tue Jul 21 04:18:15 UTC 2020

 $ apt-cache madison linux-image-4.4.0-187-generic
 linux-image-4.4.0-187-generic | 4.4.0-187.217 | http://archive.ubuntu.com/ubuntu xenial-proposed/main amd64 Packages

 $ sudo make-bcache --bdev $DEV --block 8k
 ...
 [ 88.514012] bcache: bcache_device_init() bcache0: sb/logical block size (8192) greater than page size (4096) falling back to device logical block size (512)
 [ 88.516852] bcache: register_bdev() registered backing device loop0

xenial-updates:
---

 $ uname -rv
 4.4.0-186-generic #216-Ubuntu SMP Wed Jul 1 05:34:05 UTC 2020

 $ apt-cache madison linux-image-4.4.0-186-generic | grep updates
 linux-image-4.4.0-186-generic | 4.4.0-186.216 | http://archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages

 $ sudo make-bcache --bdev $DEV --block 8k
 ...
 [ 56.341127] bcache: register_bdev() registered backing device loop0
 [ 56.344996] BUG: unable to handle kernel NULL pointer dereference at 0000000000000098
 [ 56.346996] IP: [<ffffffff8125acb0>] bdev_read_page+0x10/0xb0
 ...
 [ 56.379801] Call Trace:
 [ 56.380315] [<ffffffff81261bbe>] do_mpage_readpage+0x52e/0x7a0
 [ 56.381452] [<ffffffff8125a6b0>] ? I_BDEV+0x20/0x20
 [ 56.382550] [<ffffffff811abebe>] ? lru_cache_add+0xe/0x10
 [ 56.383544] [<ffffffff81261f42>] mpage_readpages+0x112/0x190
 [ 56.384508] [<ffffffff8125a6b0>] ? I_BDEV+0x20/0x20
 [ 56.385369] [<ffffffff8125a6b0>] ? I_BDEV+0x20/0x20
 [ 56.386196] [<ffffffff811f09dc>] ? alloc_pages_current+0x8c/0x110
 [ 56.387279] [<ffffffff8125b1cd>] blkdev_readpages+0x1d/0x20
 [ 56.388316] [<ffffffff811a9f39>] __do_page_cache_readahead+0x199/0x240
 [ 56.389394] [<ffffffff811aa34a>] force_page_cache_readahead+0xaa/0x100
 [ 56.390445] [<ffffffff811aa3df>] page_cache_sync_readahead+0x3f/0x50
 [ 56.391600] [<ffffffff8119d0ba>] generic_file_read_iter+0x54a/0x6b0
 [ 56.392734] [<ffffffff8125bcc5>] blkdev_read_iter+0x35/0x40
 [ 56.393658] [<ffffffff8121e14e>] new_sync_read+0x9e/0xe0
 [ 56.394620] [<ffffffff8121e1b9>] __vfs_read+0x29/0x40
 [ 56.395540] [<ffffffff8121e926>] vfs_read+0x86/0x130
 [ 56.396373] [<ffffffff8121f67c>] SyS_read+0x5c/0xe0
 [ 56.397192] [<ffffffff8186991b>] entry_SYSCALL_64_fastpath+0x22/0xd0
 ...