On 05/09/2017 01:54 AM, Jes Sorensen wrote:

On 05/07/2017 09:50 PM, Zhilong Liu wrote:

quoted

On 05/05/2017 11:31 AM, Liu Zhilong wrote:

quoted

On 05/04/2017 10:54 PM, Jes Sorensen wrote:

quoted

On 05/04/2017 08:20 AM, Zhilong Liu wrote:

quoted

Hi Jes,

apply for review, this is a bug I ever encountered.

Zhilong,

Under what circumstances do you see this?

Issued the command:
linux-g0sr:/home/test # ./mdadm -CR /dev/md0 -l1 -n2 -b internal
/dev/loop[0-1] --size 63
... ... ...
mdadm: Given bitmap chunk size not supported.
linux-g0sr:/home/test # ls /dev/md0
/dev/md0
linux-g0sr:/home/test # ls /sys/block/md0/md/
array_size   bitmap      component_size  level metadata_version
raid_disks         reshape_position safe_mode_delay
array_state  chunk_size  layout          max_read_errors
new_dev           reshape_direction  resync_start

create_mddev() writes the devnm to
/sys/module/md_mod/parameter/new_array,
then in md.c, module_param_call() called the 'set' function of
add_named_array(),
md_alloc() init_and_add the kobject for devm, finally the devnm device
has created
and sysfs has registered after create_mddev executed successfully.
Thus it's better
to STOP_ARRAY in any case after create_mddev() invoked.

this patch depends on the kernel commit:
039b7225e6e9 ("md: allow creation of mdNNN arrays via
md_mod/parameters/new_array")
Neil's patch has set "mddev->hold_active = UNTIL_STOP", thus the
STOP_ARRAY can work
well on this situation.

OK now I am confused - are you saying this change will only work after 
Neil's kernel patch has been applied? That would be no good, mdadm 
needs to work on older kernels too.

Yes, I do agree your kindly reminding. In order to fix this scenario that
exit the process abnormally but create_mddev() has invoked, so how
about declaring one utility function to do STOP_ARRAY like following,
it's a better way to stop the array if it opened by O_EXCL flag.

cut the piece code from Manage_stop():
... ...
     /* As we have an O_EXCL open, any use of the device
      * which blocks STOP_ARRAY is probably a transient use,
      * so it is reasonable to retry for a while - 5 seconds.
      */
     count = 25; err = 0;
     while (count && fd >= 0
            && (err = ioctl(fd, STOP_ARRAY, NULL)) < 0
            && errno == EBUSY) {
         usleep(200000);
         count --;
     }
... ...

Thanks,
-Zhilong

Jes