Re: [PATCH] iSCSI: let session recovery_tmo sysfs writes persist across recovery

Mike Christie
2015-06-17T15:40:00Z

On 06/16/2015 06:07 PM, Chris Leech wrote:
> The iSCSI session recovery_tmo setting is writeable in sysfs, but it's
> also set every time a connection is established when parameters are set
> from iscsid over netlink. That results in the timeout being reset to
> the default value after every recovery.
>
> The DM multipath tools want to use the sysfs interface to lower the
> default timeout when there are multiple paths to fail over. It has
> caused confusion that we have a writeable sysfs value that seem to keep
> resetting itself.
>
> This patch adds an in-kernel flag that gets set once a sysfs write
> occurs, and then ignores netlink parameter setting once it's been
> modified via the sysfs interface. My thinking here is that the sysfs
> interface is much simpler for external tools to influence the session
> timeout, but if we're going to allow it to be modified directly we
> should ensure that setting is maintained.
>
> Signed-off-by: Chris Leech <cleech-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> ---
> drivers/scsi/scsi_transport_iscsi.c | 11 ++++++++---
> include/scsi/scsi_transport_iscsi.h | 1 +
> 2 files changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
> index 67d43e3..35ef55f 100644
> --- a/drivers/scsi/scsi_transport_iscsi.c
> +++ b/drivers/scsi/scsi_transport_iscsi.c
> @@ -2040,6 +2040,7 @@ iscsi_alloc_session(struct Scsi_Host *shost, struct iscsi_transport *transport,
> session->transport = transport;
> session->creator = -1;
> session->recovery_tmo = 120;
> + session->recovery_tmo_sysfs_override = false;
> session->state = ISCSI_SESSION_FREE;
> INIT_DELAYED_WORK(&session->recovery_work, session_recovery_timedout);
> INIT_LIST_HEAD(&session->sess_list);
> @@ -2784,7 +2785,8 @@ iscsi_set_param(struct iscsi_transport *transport, struct iscsi_uevent *ev)
> switch (ev->u.set_param.param) {
> case ISCSI_PARAM_SESS_RECOVERY_TMO:
> sscanf(data, "%d", &value);
> - session->recovery_tmo = value;
> + if (!session->recovery_tmo_sysfs_override)
> + session->recovery_tmo = value;
> break;
> default:
> err = transport->set_param(conn, ev->u.set_param.param,
> @@ -4047,13 +4049,15 @@ store_priv_session_##field(struct device *dev, \
> if ((session->state == ISCSI_SESSION_FREE) || \
> (session->state == ISCSI_SESSION_FAILED)) \
> return -EBUSY; \
> - if (strncmp(buf, "off", 3) == 0) \
> + if (strncmp(buf, "off", 3) == 0) { \
> session->field = -1; \
> - else { \
> + session->field##_sysfs_override = true; \
> + } else { \
> val = simple_strtoul(buf, &cp, 0); \
> if (*cp != '\0' && *cp != '\n') \
> return -EINVAL; \
> session->field = val; \
> + session->field##_sysfs_override = true; \
> } \
> return count; \
> }
> @@ -4064,6 +4068,7 @@ store_priv_session_##field(struct device *dev, \
> static ISCSI_CLASS_ATTR(priv_sess, field, S_IRUGO | S_IWUSR, \
> show_priv_session_##field, \
> store_priv_session_##field)
> +
> iscsi_priv_session_rw_attr(recovery_tmo, "%d");
>
> static struct attribute *iscsi_session_attrs[] = {
> diff --git a/include/scsi/scsi_transport_iscsi.h b/include/scsi/scsi_transport_iscsi.h
> index 2555ee5..6183d20 100644
> --- a/include/scsi/scsi_transport_iscsi.h
> +++ b/include/scsi/scsi_transport_iscsi.h
> @@ -241,6 +241,7 @@ struct iscsi_cls_session {
>
> /* recovery fields */
> int recovery_tmo;
> + bool recovery_tmo_sysfs_override;
> struct delayed_work recovery_work;
>
> unsigned int target_id;
>

Looks ok to me.

Reviewed-by: Mike Christie <michaelc-hcNo3dDEHLuVc3sceRu5cw@public.gmane.org>