RE: DM does not activate the paths if there are more than one path in path group during failover

[Chandra Seetharaman <sekharan@us.ibm.com>]

Will look into this problem and get back to you.

chandra
On Tue, 2008-11-11 at 10:13 -0700, Moger, Babu wrote:
> Thanks for the response.
> 
> If pg_init is intended to be called only once then problem is elsewhere.
> 
> During the pg_init, the activate_path is called. The activate_path calls scsi_dh_activate(then rdac_activate) which will set path state to active(h->state = RDAC_STATE_ACTIVE;). My understanding is, h->state is specific to each path. How does d-m sets h->state to RDAC_STATE_ACTIVE for all the paths available in the path group.
> 
> This is what happening in my case. On path group failure, d-m switches the path group initiates path group. It then selects the first path (in the path group) starts I/O. After exhausting the repeat_count it then selects the next path in the path group.  Then rdac_prep_fn is called. This function finds h->state is still passive and fails the path which becomes unusable.
> 
> This function returns BLKPREP_KILL which is leading to fail failure.
> 
> static int rdac_prep_fn(struct scsi_device *sdev, struct request *req)
> {
>         struct rdac_dh_data *h = get_rdac_data(sdev);
>         int ret = BLKPREP_OK;
> 
>         if (h->state != RDAC_STATE_ACTIVE) {
>                 ret = BLKPREP_KILL;
>                 req->cmd_flags |= REQ_QUIET;
>         }
>         return ret;
> }
> 
> This is my understanding so far. Please correct me if there is anything wrong.
> 
> 
> -----Original Message-----
> From: dm-devel-bounces@redhat.com [mailto:dm-devel-bounces@redhat.com] On Behalf Of Alasdair G Kergon
> Sent: Monday, November 10, 2008 6:59 PM
> To: device-mapper development
> Cc: andmike@linux.vnet.ibm.com; linux-scsi@vger.kernel.org
> Subject: Re: [dm-devel] DM does not activate the paths if there are more than one path in path group during failover
> 
> pg_init is a function intended to be called *once* when there is a switch to a new group of paths.  It is not per-path initialisation.
> 
> Alasdair
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