[PATCH] nvmet-file: clamp-down file namespace lba_shift

[sagi@grimberg.me (Sagi Grimberg)]

>> When the backing file is a tempfile for example, the inode i_blkbits
>> can be 1M in size which causes problems for hosts to support as the
>> disk block size.
>>
>> Signed-off-by: Sagi Grimberg <sagi at grimberg.me>
>> ---
>> This issue was observed in I/O errors in the log running test nvme/009.
>>
> We are not doing any I/O in nvme/009 explicitly using dd/fio, is this
> due to internal commands we send as a part of connect and disconnect ?
> Or test number is different ?

The former.

Also, I just now hit a divide by zero BUG when running test 009 with
multipath enabled.

Quick look shows that this is coming from blk_queue_stack_limits for the
ns_head.

Looks like nvme_update_disk_info() is reading a bs=0:
--
         unsigned short bs = 1 << ns->lba_shift;
--

bs is 16 bits and lba_shift is 20
(coming directly from the tempfile file_inode(ns->file)->i_blkbits)

So this fixes that one as well. Regardless, I think bs should be
unsigned int?