Re: The dev node can't be released at once after stopping raid

[Zhilong Liu <zlliu@suse.com>]

On 06/01/2017 11:47 AM, Xiao Ni wrote:
> Hi all
>
> I tried with the latest linux stable kernel and latest mdadm.
>
> After stopping a raid device, the dev node directory can't be released
> at once. I did a simple test, the script is:
>
> #!/bin/sh
>
> while [ 1 ]; do
> mdadm -CR /dev/md0 -l1 -n2 /dev/loop0 /dev/loop1
> sleep 5
> mdadm -S /dev/md0
> ls /dev/md0
> sleep 1
> ls /dev/md0
> done
>
> mdadm: stopped /dev/md0
> /dev/md0
> ls: cannot access /dev/md0: No such file or directory
>
> It usually detects dev node /dev/md0 isn't released after stopping raid.
> I'm not sure whether it's a bug or not. Do we need to do some job to
> make sure that the node should be released before command mdadm -S return?

it's waiting for processing the udev events. we can monitor it via to "# 
udevadm monitor".

For mdadm -S /dev/md0, Manage_stop() has already did the errno checking,

cut piece of code from Manage.c
.. .. .. ..
done:

     /* 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 --;
     }

Best regards,
-Zhilong

> Best Regards
> Xiao
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