[dm-devel] [PATCH 2/7] dm: Simplify dm_table_determine_type()

[Bart Van Assche]

On 11/16/2016 01:11 PM, Mike Snitzer wrote:
> On Wed, Nov 16 2016 at  3:14pm -0500,
> Bart Van Assche <bart.vanassche at sandisk.com> wrote:
>> After having added WARN_ON_ONCE(sq_count == 0 && mq_count == 0)
>> close to the end of dm_table_determine_type() the following output
>> appeared:
>>
>> WARNING: CPU: 0 PID: 2458 at drivers/md/dm-table.c:966
>> dm_table_complete+0x60e/0x6b0 [dm_mod]
>> [ ... ]
>> Call Trace:
>>  [<ffffffff81329b45>] dump_stack+0x68/0x93
>>  [<ffffffff810650e6>] __warn+0xc6/0xe0
>>  [<ffffffff810651b8>] warn_slowpath_null+0x18/0x20
>>  [<ffffffffa0021c8e>] dm_table_complete+0x60e/0x6b0 [dm_mod]
>>  [<ffffffffa00245cd>] table_load+0x13d/0x330 [dm_mod]
>>  [<ffffffffa0024490>] ? retrieve_status+0x1b0/0x1b0 [dm_mod]
>>  [<ffffffffa0025145>] ctl_ioctl+0x1f5/0x520 [dm_mod]
>>  [<ffffffffa002547e>] dm_ctl_ioctl+0xe/0x20 [dm_mod]
>>  [<ffffffff811f26cf>] do_vfs_ioctl+0x8f/0x6b0
>>  [<ffffffff811ff41c>] ? __fget+0x10c/0x200
>>  [<ffffffff811ff310>] ? expand_files+0x2a0/0x2a0
>>  [<ffffffff811f2d2c>] SyS_ioctl+0x3c/0x70
>>  [<ffffffff8163f9aa>] entry_SYSCALL_64_fastpath+0x18/0xad
>>
>> Is it intentional that dm_table_determine_type() can get called for
>> a dm device with an empty table?
>
> What table were you trying to load when this occurred?
>
> Targets like the 'error' target don't have any devices.

Hello Mike,

This was the result of a table load issued by multipathd. Do you want me 
to add more debug code such that the details of the table load request 
are logged?

Thanks,

Bart.