[dm-devel] dm-mq and end_clone_request()

[Bart Van Assche]

On 08/02/2016 10:45 AM, Mike Snitzer wrote:
> Please do these same tests against a v4.7 kernel with the 4 patches from
> this branch applied (no need for your other debug patches):
> https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/log/?h=dm-4.7-mpath-fixes
> 
> I've had good results with my blk-mq SRP based testing.

Hello Mike,

Thanks again for having made these patches available. The results of my
tests are as follows:

(1) CONFIG_DM_MQ_DEFAULT=y, fio running on top of xfs

The first simulated cable pull caused the following messages to appear:

[  428.716566] mpath 254:1: queue_if_no_path 1 -> 0
[  428.729671] __multipath_map(): (a) returning -5
[  428.729730] map_request(): clone_and_map_rq() returned -5
[  428.729788] dm_complete_request: error = -5
[  428.729846] dm_softirq_done: dm-1 tio->error = -5
[  428.729904] blk_update_request: 880 callbacks suppressed
[  428.729970] blk_update_request: I/O error (-5), dev dm-1, sector 2097024

(2) CONFIG_DM_MQ_DEFAULT=y, fio running on top of ext4

The first simulated cable pull caused the following messages to appear:

[  162.894737] mpath 254:0: queue_if_no_path 0 -> 1
[  162.903155] executing DM ioctl DEV_SUSPEND on mpathbe
[  162.903207] mpath 254:0: queue_if_no_path 1 -> 0
[  162.903255] device-mapper: multipath: must_push_back: queue_if_no_path=0 suspend_active=1 suspending=0
[  162.903256] __multipath_map(): (a) returning -5
[  162.903257] map_request(): clone_and_map_rq() returned -5
[  162.903258] dm_complete_request: error = -5
[  162.903259] dm_softirq_done: dm-0 tio->error = -5
[  162.903261] blk_update_request: I/O error (-5), dev dm-0, sector 263424
[  162.903284] Buffer I/O error on dev dm-0, logical block 32928, lost sync page write

(3) CONFIG_DM_MQ_DEFAULT=n, fio running on top of xfs

This test passed once but on the second run fio reported "bad magic header" after
a large number of iterations. I'm still analyzing the logs.

(4) CONFIG_DM_MQ_DEFAULT=n, fio running on top of ext4

Ran this test three times. The first two runs passed but during the third run
fio reported again I/O errors and I found the following in the kernel log:

[  954.048860] __multipath_map(): (a) returning -5
[  954.048861] map_request(): clone_and_map_rq() returned -5
[  954.048862] dm_complete_request: error = -5
[  954.048870] dm_softirq_done: dm-0 tio->error = -5
[  954.048873] blk_update_request: 15 callbacks suppressed
[  954.048874] blk_update_request: I/O error (-5), dev dm-0, sector 159976

Bart.