Re: [PATCH] Remove: container should wait for an array to release a drive

[Jes Sorensen <Jes.Sorensen@redhat.com>]

"John Stoffel" <john@stoffel.org> writes:
>>>>>> "Tomasz" == Tomasz Majchrzak <tomasz.majchrzak@intel.com> writes:
>
> Tomasz> A 'faulty' drive is being removed from a container after it
> Tomasz> has been released by an array, however there is a race
> Tomasz> there. The drive is released asynchronously by a monitor but
> Tomasz> sometimes it doesn't happen before container checks it. It
> Tomasz> results in a container refusing to remove a drive as it still
> Tomasz> seems to be a part of some array.
>
> Tomasz> It seems 'ping_monitor' could be a solution here to assure
> Tomasz> monitor has had a chance to process the events, however it
> Tomasz> doesn't resolve the problem - sometimes an array has to
> Tomasz> request a release of the drive few times (as the array is
> Tomasz> busy) and single 'ping_monitor' call is not sufficient. As
> Tomasz> there is no way to query monitor progress, it forces us to
> Tomasz> retry a check several times before an error is returned.
>
> Tomasz> Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@intel.com>
> Tomasz> ---
> Tomasz>  Manage.c | 38 +++++++++++++++++++++++++-------------
> Tomasz>  1 file changed, 25 insertions(+), 13 deletions(-)
>
> Tomasz> diff --git a/Manage.c b/Manage.c
> Tomasz> index e2e88b8..7f8eb88 100644
> Tomasz> --- a/Manage.c
> Tomasz> +++ b/Manage.c
> Tomasz> @@ -1125,19 +1125,31 @@ int Manage_remove(struct supertype *tst, int fd, struct mddev_dev *dv,
> Tomasz>  		 */
> Tomasz>  		if (rdev == 0)
> Tomasz>  			ret = -1;
> Tomasz> -		else
> Tomasz> -			ret = sysfs_unique_holder(devnm, rdev);
> Tomasz> -		if (ret == 0) {
> Tomasz> -			pr_err("%s is not a member, cannot remove.\n",
> Tomasz> -			       dv->devname);
> Tomasz> -			close(lfd);
> Tomasz> -			return -1;
> Tomasz> -		}
> Tomasz> -		if (ret >= 2) {
> Tomasz> -			pr_err("%s is still in use, cannot remove.\n",
> Tomasz> -			       dv->devname);
> Tomasz> -			close(lfd);
> Tomasz> -			return -1;
> Tomasz> +		else {
> Tomasz> +			/* The drive has already been set to 'faulty', however monitor might
> Tomasz> +			 * not have had time to process it and the drive might still have
> Tomasz> +			 * an entry in the 'holders' directory. Try a few times to avoid
> Tomasz> +			 * a false error */
> Tomasz> +			int count = 20;
> Tomasz> +			do {
> Tomasz> +				ret = sysfs_unique_holder(devnm, rdev);
> Tomasz> +				if (ret < 2)
> Tomasz> +					break;
> Tomasz> +				usleep(100000);
>
> Really, you're sleeping 10 seconds without telling the user?  That
> seems to be a bit obnoxious.  Logging something here would be good.

Hi,

Sorry just back from vacation and just started attacking the mountain of
email.

I agree with John here, please add some logging message. Also is 10
seconds really needed? It seems an awful lot per iteration.

Cheers,
Jes