On 11/16/2016 01:11 PM, Mike Snitzer wrote:
On Wed, Nov 16 2016 at  3:14pm -0500,
Bart Van Assche <bart.vanass...@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.


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