Re: [PATCH 1/2] md-cluster: update comments for MD_CLUSTER_SEND_LOCKED_ALREADY

[NeilBrown <neilb@suse.com>]

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On Sat, Dec 05 2015, Guoqing Jiang wrote:

> 1. fix unbalanced parentheses.
> 2. add more description about that MD_CLUSTER_SEND_LOCKED_ALREADY
>    will be cleared after set it in add_new_disk.
>
> Signed-off-by: Guoqing Jiang <gqjiang@suse.com>

Applied, thanks.

NeilBrown

> ---
>  drivers/md/md-cluster.c | 23 ++++++++++++++++++-----
>  1 file changed, 18 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
> index ad3ec7d..0ded8e9 100644
> --- a/drivers/md/md-cluster.c
> +++ b/drivers/md/md-cluster.c
> @@ -53,11 +53,12 @@ struct resync_info {
>   * accomodate lock and hold. See next comment.
>   */
>  #define		MD_CLUSTER_SEND_LOCK			4
> -/* If cluster operations must lock the communication channel,
> - * so as to perform extra operations (and no other operation
> - * is allowed on the MD, such as adding a disk. Token needs
> - * to be locked and held until the operation completes with
> - * a md_update_sb(), which would eventually release the lock.
> +/* If cluster operations (such as adding a disk) must lock the
> + * communication channel, so as to perform extra operations
> + * (update metadata) and no other operation is allowed on the
> + * MD. Token needs to be locked and held until the operation
> + * completes witha md_update_sb(), which would eventually release
> + * the lock.
>   */
>  #define		MD_CLUSTER_SEND_LOCKED_ALREADY		5
>  
> @@ -1021,6 +1022,18 @@ static int add_new_disk(struct mddev *mddev, struct md_rdev *rdev)
>  		unlock_comm(cinfo);
>  	else {
>  		dlm_lock_sync(cinfo->no_new_dev_lockres, DLM_LOCK_CR);
> +		/* Since MD_CHANGE_DEVS will be set in add_bound_rdev which
> +		 * will run soon after add_new_disk, the below path will be
> +		 * invoked:
> +		 *   md_wakeup_thread(mddev->thread)
> +		 *	-> conf->thread (raid1d)
> +		 *	-> md_check_recovery -> md_update_sb
> +		 *	-> metadata_update_start/finish
> +		 * MD_CLUSTER_SEND_LOCKED_ALREADY will be cleared eventually.
> +		 *
> +		 * For other failure cases, metadata_update_cancel and
> +		 * add_new_disk_cancel also clear below bit as well.
> +		 * */
>  		set_bit(MD_CLUSTER_SEND_LOCKED_ALREADY, &cinfo->state);
>  		wake_up(&cinfo->wait);
>  	}
> -- 
> 2.1.4

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