Re: [PATCHv7 14/23] scsi_dh_alua: Allow workqueue to run synchronously

[Bart Van Assche]

On 02/15/2016 12:24 AM, Hannes Reinecke wrote:

Some arrays may only capable of handling one STPG at a time,
so this patch adds a singlethreaded workqueue for STPGs to be
submitted synchronously.


Reviewed-by: Bart Van Assche 
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[PATCHv7 14/23] scsi_dh_alua: Allow workqueue to run synchronously

[Hannes Reinecke]

Some arrays may only capable of handling one STPG at a time,
so this patch adds a singlethreaded workqueue for STPGs to be
submitted synchronously.

Reviewed-by: Christoph Hellwig 
Signed-off-by: Hannes Reinecke 
---
 drivers/scsi/device_handler/scsi_dh_alua.c | 21 ++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/device_handler/scsi_dh_alua.c 
b/drivers/scsi/device_handler/scsi_dh_alua.c
index ede850b..43bf6ac 100644
--- a/drivers/scsi/device_handler/scsi_dh_alua.c
+++ b/drivers/scsi/device_handler/scsi_dh_alua.c
@@ -64,6 +64,7 @@
 /* device handler flags */
 #define ALUA_OPTIMIZE_STPG 0x01
 #define ALUA_RTPG_EXT_HDR_UNSUPP   0x02
+#define ALUA_SYNC_STPG 0x04
 /* State machine flags */
 #define ALUA_PG_RUN_RTPG   0x10
 #define ALUA_PG_RUN_STPG   0x20
@@ -76,6 +77,7 @@ MODULE_PARM_DESC(optimize_stpg, "Allow use of a non-optimized 
path, rather than
 static LIST_HEAD(port_group_list);
 static DEFINE_SPINLOCK(port_group_lock);
 static struct workqueue_struct *kaluad_wq;
+static struct workqueue_struct *kaluad_sync_wq;
 
 struct alua_port_group {
struct kref kref;
@@ -688,6 +690,7 @@ static void alua_rtpg_work(struct work_struct *work)
int err = SCSI_DH_OK;
struct alua_queue_data *qdata, *tmp;
unsigned long flags;
+   struct workqueue_struct *alua_wq = kaluad_wq;
 
spin_lock_irqsave(>lock, flags);
sdev = pg->rtpg_sdev;
@@ -697,6 +700,8 @@ static void alua_rtpg_work(struct work_struct *work)
spin_unlock_irqrestore(>lock, flags);
return;
}
+   if (pg->flags & ALUA_SYNC_STPG)
+   alua_wq = kaluad_sync_wq;
pg->flags |= ALUA_PG_RUNNING;
if (pg->flags & ALUA_PG_RUN_RTPG) {
pg->flags &= ~ALUA_PG_RUN_RTPG;
@@ -707,7 +712,7 @@ static void alua_rtpg_work(struct work_struct *work)
pg->flags &= ~ALUA_PG_RUNNING;
pg->flags |= ALUA_PG_RUN_RTPG;
spin_unlock_irqrestore(>lock, flags);
-   queue_delayed_work(kaluad_wq, >rtpg_work,
+   queue_delayed_work(alua_wq, >rtpg_work,
   pg->interval * HZ);
return;
}
@@ -724,7 +729,7 @@ static void alua_rtpg_work(struct work_struct *work)
pg->interval = 0;
pg->flags &= ~ALUA_PG_RUNNING;
spin_unlock_irqrestore(>lock, flags);
-   queue_delayed_work(kaluad_wq, >rtpg_work,
+   queue_delayed_work(alua_wq, >rtpg_work,
   pg->interval * HZ);
return;
}
@@ -753,6 +758,7 @@ static void alua_rtpg_queue(struct alua_port_group *pg,
 {
int start_queue = 0;
unsigned long flags;
+   struct workqueue_struct *alua_wq = kaluad_wq;
 
if (!pg)
return;
@@ -770,10 +776,12 @@ static void alua_rtpg_queue(struct alua_port_group *pg,
scsi_device_get(sdev);
start_queue = 1;
}
+   if (pg->flags & ALUA_SYNC_STPG)
+   alua_wq = kaluad_sync_wq;
spin_unlock_irqrestore(>lock, flags);
 
if (start_queue &&
-   !queue_delayed_work(kaluad_wq, >rtpg_work,
+   !queue_delayed_work(alua_wq, >rtpg_work,
msecs_to_jiffies(ALUA_RTPG_DELAY_MSECS))) {
scsi_device_put(sdev);
kref_put(>kref, release_port_group);
@@ -992,10 +1000,16 @@ static int __init alua_init(void)
/* Temporary failure, bypass */
return SCSI_DH_DEV_TEMP_BUSY;
}
+   kaluad_sync_wq = create_workqueue("kaluad_sync");
+   if (!kaluad_sync_wq) {
+   destroy_workqueue(kaluad_wq);
+   return SCSI_DH_DEV_TEMP_BUSY;
+   }
r = scsi_register_device_handler(_dh);
if (r != 0) {
printk(KERN_ERR "%s: Failed to register scsi device handler",
ALUA_DH_NAME);
+   destroy_workqueue(kaluad_sync_wq);
destroy_workqueue(kaluad_wq);
}
return r;
@@ -1004,6 +1018,7 @@ static int __init alua_init(void)
 static void __exit alua_exit(void)
 {
scsi_unregister_device_handler(_dh);
+   destroy_workqueue(kaluad_sync_wq);
destroy_workqueue(kaluad_wq);
 }
 
-- 
1.8.5.6

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