From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCH 22/23] scsi_dh_alua: update 'access_state' field Date: Fri, 12 Feb 2016 08:20:20 +0100 Message-ID: <56BD87B4.7060702@suse.de> References: <1454942086-128704-1-git-send-email-hare@suse.de> <1454942086-128704-23-git-send-email-hare@suse.de> <1455223025.22112.340.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mx2.suse.de ([195.135.220.15]:49215 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750771AbcBLHUW (ORCPT ); Fri, 12 Feb 2016 02:20:22 -0500 In-Reply-To: <1455223025.22112.340.camel@localhost.localdomain> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: emilne@redhat.com Cc: "Martin K. Petersen" , Christoph Hellwig , Bart van Assche , James Bottomley , linux-scsi@vger.kernel.org On 02/11/2016 09:37 PM, Ewan Milne wrote: > On Mon, 2016-02-08 at 15:34 +0100, Hannes Reinecke wrote: >> Track attached SCSI devices and update the 'access_state' field >> whenever an ALUA state change has been detected. >> >> Signed-off-by: Hannes Reinecke >> --- >> drivers/scsi/device_handler/scsi_dh_alua.c | 45 +++++++++++++++++++= +++++++++-- >> 1 file changed, 43 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c b/drivers/sc= si/device_handler/scsi_dh_alua.c >> index 51126b78..7bcc075 100644 >> --- a/drivers/scsi/device_handler/scsi_dh_alua.c >> +++ b/drivers/scsi/device_handler/scsi_dh_alua.c >> @@ -24,6 +24,7 @@ >> #include >> #include >> #include >> +#include >> #include >> #include >> #include >> @@ -75,6 +76,7 @@ struct alua_port_group { >> struct kref kref; >> struct rcu_head rcu; >> struct list_head node; >> + struct list_head dh_list; >> unsigned char device_id_str[256]; >> int device_id_len; >> int group_id; >> @@ -92,6 +94,7 @@ struct alua_port_group { >> }; >> =20 >> struct alua_dh_data { >> + struct list_head node; >> struct alua_port_group *pg; >> int group_id; >> spinlock_t pg_lock; >> @@ -247,6 +250,7 @@ struct alua_port_group *alua_alloc_pg(struct scs= i_device *sdev, >> INIT_DELAYED_WORK(&pg->rtpg_work, alua_rtpg_work); >> INIT_LIST_HEAD(&pg->rtpg_list); >> INIT_LIST_HEAD(&pg->node); >> + INIT_LIST_HEAD(&pg->dh_list); >> spin_lock_init(&pg->lock); >> =20 >> spin_lock(&port_group_lock); >> @@ -328,6 +332,8 @@ static int alua_check_vpd(struct scsi_device *sd= ev, struct alua_dh_data *h, >> { >> int rel_port =3D -1, group_id; >> struct alua_port_group *pg, *old_pg =3D NULL; >> + bool pg_updated; >> + unsigned long flags; >> =20 >> group_id =3D scsi_vpd_tpg_id(sdev, &rel_port); >> if (group_id < 0) { >> @@ -357,13 +363,25 @@ static int alua_check_vpd(struct scsi_device *= sdev, struct alua_dh_data *h, >> old_pg =3D h->pg; >> if (old_pg !=3D pg) { >> /* port group has changed. Update to new port group */ >> + if (h->pg) { >> + spin_lock_irqsave(&old_pg->lock, flags); >> + list_del_rcu(&h->node); >> + spin_unlock_irqrestore(&old_pg->lock, flags); >> + } >> rcu_assign_pointer(h->pg, pg); >> + pg_updated =3D true; >> } >> if (sdev->synchronous_alua) >> pg->flags |=3D ALUA_SYNC_STPG; >> alua_rtpg_queue(h->pg, sdev, NULL, true); >> spin_unlock(&h->pg_lock); >> =20 >> + if (pg_updated) { >> + spin_lock_irqsave(&pg->lock, flags); >> + list_add_rcu(&h->node, &pg->dh_list); >> + spin_unlock_irqrestore(&pg->lock, flags); >> + } >> + >> if (old_pg) >> kref_put(&old_pg->kref, release_port_group); >> =20 >> @@ -613,8 +631,18 @@ static int alua_rtpg(struct scsi_device *sdev, = struct alua_port_group *pg) >> if (spin_trylock_irqsave(&tmp_pg->lock, flags)) { >> if ((tmp_pg =3D=3D pg) || >> !(tmp_pg->flags & ALUA_PG_RUNNING)) { >> + struct alua_dh_data *h; >> + >> tmp_pg->state =3D desc[0] & 0x0f; >> tmp_pg->pref =3D desc[0] >> 7; >> + rcu_read_lock(); >> + list_for_each_entry_rcu(h, >> + &tmp_pg->dh_list, node) { >> + /* h->sdev should always be valid */ >> + BUG_ON(!h->sdev); >> + h->sdev->access_state =3D desc[0]; >=20 > Here you did not mask desc[0] with 0x0f like you did in other places = in the code. >=20 Because the access_state field is a 1:1 copy of the 'desc[0]' field, containing both the value and the pref bit. >> + } >> + rcu_read_unlock(); >> } >> if (tmp_pg =3D=3D pg) >> valid_states =3D desc[1]; >> @@ -646,10 +674,19 @@ static int alua_rtpg(struct scsi_device *sdev,= struct alua_port_group *pg) >> pg->interval =3D 2; >> err =3D SCSI_DH_RETRY; >> } else { >> + struct alua_dh_data *h; >> + >> /* Transitioning time exceeded, set port to standby */ >> err =3D SCSI_DH_IO; >> pg->state =3D SCSI_ACCESS_STATE_STANDBY; >> pg->expiry =3D 0; >> + rcu_read_lock(); >> + list_for_each_entry_rcu(h, &pg->dh_list, node) { >> + BUG_ON(!h->sdev); >> + h->sdev->access_state =3D (pg->state & 0x0f) | >> + (pg->pref << 7); >=20 > Since SCSI_ACCESS_STATE_PREFERRED is #defined as 0x80 in scsi_proto.h= you > should use | (pg->pref ? SCSI_ACCESS_STATE_PREFERRED : 0) here rather= than > just shifting, otherwise you will have a hard to find bug if somebody > changes the constant. (But I would prefer keeping them separate anyw= ay.) >=20 _Actually_ I was pondering to make it the other way around, namely shifting pg->pref on top of pg->state, then this whole thing would become a simple assignment. But I didn't as I wanted to keep the original code as-is. So yeah, there is an inconsistency, but some I would like to resolve in exactly the other direction :-) Cheers, Hannes --=20 Dr. Hannes Reinecke Teamlead Storage & Networking hare@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N=C3=BCrnberg GF: F. Imend=C3=B6rffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG N=C3=BCrnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html