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 <[email protected]>
>> ---
>> 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/scsi/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 <linux/module.h>
>> #include <asm/unaligned.h>
>> #include <scsi/scsi.h>
>> +#include <scsi/scsi_proto.h>
>> #include <scsi/scsi_dbg.h>
>> #include <scsi/scsi_eh.h>
>> #include <scsi/scsi_dh.h>
>> @@ -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 {
>> };
>>
>> 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 scsi_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);
>>
>> spin_lock(&port_group_lock);
>> @@ -328,6 +332,8 @@ static int alua_check_vpd(struct scsi_device *sdev,
>> struct alua_dh_data *h,
>> {
>> int rel_port = -1, group_id;
>> struct alua_port_group *pg, *old_pg = NULL;
>> + bool pg_updated;
>> + unsigned long flags;
>>
>> group_id = 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 = h->pg;
>> if (old_pg != 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 = true;
>> }
>> if (sdev->synchronous_alua)
>> pg->flags |= ALUA_SYNC_STPG;
>> alua_rtpg_queue(h->pg, sdev, NULL, true);
>> spin_unlock(&h->pg_lock);
>>
>> + 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);
>>
>> @@ -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 == pg) ||
>> !(tmp_pg->flags & ALUA_PG_RUNNING)) {
>> + struct alua_dh_data *h;
>> +
>> tmp_pg->state = desc[0] & 0x0f;
>> tmp_pg->pref = 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 = desc[0];
>
> Here you did not mask desc[0] with 0x0f like you did in other places in the
> code.
>
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 == pg)
>> valid_states = desc[1];
>> @@ -646,10 +674,19 @@ static int alua_rtpg(struct scsi_device *sdev, struct
>> alua_port_group *pg)
>> pg->interval = 2;
>> err = SCSI_DH_RETRY;
>> } else {
>> + struct alua_dh_data *h;
>> +
>> /* Transitioning time exceeded, set port to standby */
>> err = SCSI_DH_IO;
>> pg->state = SCSI_ACCESS_STATE_STANDBY;
>> pg->expiry = 0;
>> + rcu_read_lock();
>> + list_for_each_entry_rcu(h, &pg->dh_list, node) {
>> + BUG_ON(!h->sdev);
>> + h->sdev->access_state = (pg->state & 0x0f) |
>> + (pg->pref << 7);
>
> 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 anyway.)
>
_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
--
Dr. Hannes Reinecke Teamlead Storage & Networking
[email protected] +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
HRB 21284 (AG Nürnberg)
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