s390/scm_block: make the number of reqs per HW req configurable

Introduce a module parameter to specify the number of requests
we try to handle with one HW request.

Suggested-by: Peter Oberparleiter <peter.oberparleiter@de.ibm.com>
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

2 files changed, 34 insertions, 17 deletions

diff --git a/drivers/s390/block/scm_blk.c b/drivers/s390/block/scm_blk.c
index cd27cb92ac6d..75d9896deccb 100644
--- a/drivers/s390/block/scm_blk.c
+++ b/drivers/s390/block/scm_blk.c
@@ -25,10 +25,14 @@ static mempool_t *aidaw_pool;
 static DEFINE_SPINLOCK(list_lock);
 static LIST_HEAD(inactive_requests);
 static unsigned int nr_requests = 64;
+static unsigned int nr_requests_per_io = 8;
 static atomic_t nr_devices = ATOMIC_INIT(0);
 module_param(nr_requests, uint, S_IRUGO);
 MODULE_PARM_DESC(nr_requests, "Number of parallel requests.");
 
+module_param(nr_requests_per_io, uint, S_IRUGO);
+MODULE_PARM_DESC(nr_requests_per_io, "Number of requests per IO.");
+
 MODULE_DESCRIPTION("Block driver for s390 storage class memory.");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("scm:scmdev*");
@@ -39,6 +43,7 @@ static void __scm_free_rq(struct scm_request *scmrq)
 
         free_page((unsigned long) scmrq->aob);
         __scm_free_rq_cluster(scmrq);
+        kfree(scmrq->request);
         kfree(aobrq);
 }
 
@@ -69,15 +74,16 @@ static int __scm_alloc_rq(void)
 
         scmrq = (void *) aobrq->data;
         scmrq->aob = (void *) get_zeroed_page(GFP_DMA);
-        if (!scmrq->aob) {
-                __scm_free_rq(scmrq);
-                return -ENOMEM;
-        }
+        if (!scmrq->aob)
+                goto free;
 
-        if (__scm_alloc_rq_cluster(scmrq)) {
-                __scm_free_rq(scmrq);
-                return -ENOMEM;
-        }
+        scmrq->request = kcalloc(nr_requests_per_io, sizeof(scmrq->request[0]),
+                                 GFP_KERNEL);
+        if (!scmrq->request)
+                goto free;
+
+        if (__scm_alloc_rq_cluster(scmrq))
+                goto free;
 
         INIT_LIST_HEAD(&scmrq->list);
         spin_lock_irq(&list_lock);
@@ -85,6 +91,9 @@ static int __scm_alloc_rq(void)
         spin_unlock_irq(&list_lock);
 
         return 0;
+free:
+        __scm_free_rq(scmrq);
+        return -ENOMEM;
 }
 
 static int scm_alloc_rqs(unsigned int nrqs)
@@ -122,7 +131,7 @@ static void scm_request_done(struct scm_request *scmrq)
         u64 aidaw;
         int i;
 
-        for (i = 0; i < SCM_RQ_PER_IO && scmrq->request[i]; i++) {
+        for (i = 0; i < nr_requests_per_io && scmrq->request[i]; i++) {
                 msb = &scmrq->aob->msb[i];
                 aidaw = msb->data_addr;
 
@@ -214,7 +223,8 @@ static inline void scm_request_init(struct scm_blk_dev *bdev,
         struct aob_rq_header *aobrq = to_aobrq(scmrq);
         struct aob *aob = scmrq->aob;
 
-        memset(scmrq->request, 0, sizeof(scmrq->request));
+        memset(scmrq->request, 0,
+               nr_requests_per_io * sizeof(scmrq->request[0]));
         memset(aob, 0, sizeof(*aob));
         aobrq->scmdev = bdev->scmdev;
         aob->request.cmd_code = ARQB_CMD_MOVE;
@@ -223,7 +233,7 @@ static inline void scm_request_init(struct scm_blk_dev *bdev,
         scmrq->retries = 4;
         scmrq->error = 0;
         /* We don't use all msbs - place aidaws at the end of the aob page. */
-        scmrq->next_aidaw = (void *) &aob->msb[SCM_RQ_PER_IO];
+        scmrq->next_aidaw = (void *) &aob->msb[nr_requests_per_io];
         scm_request_cluster_init(scmrq);
 }
 
@@ -242,7 +252,7 @@ void scm_request_requeue(struct scm_request *scmrq)
         int i;
 
         scm_release_cluster(scmrq);
-        for (i = 0; i < SCM_RQ_PER_IO && scmrq->request[i]; i++)
+        for (i = 0; i < nr_requests_per_io && scmrq->request[i]; i++)
                 blk_requeue_request(bdev->rq, scmrq->request[i]);
 
         atomic_dec(&bdev->queued_reqs);
@@ -256,7 +266,7 @@ void scm_request_finish(struct scm_request *scmrq)
         int i;
 
         scm_release_cluster(scmrq);
-        for (i = 0; i < SCM_RQ_PER_IO && scmrq->request[i]; i++)
+        for (i = 0; i < nr_requests_per_io && scmrq->request[i]; i++)
                 blk_end_request_all(scmrq->request[i], scmrq->error);
 
         atomic_dec(&bdev->queued_reqs);
@@ -342,7 +352,7 @@ static void scm_blk_request(struct request_queue *rq)
                 }
                 blk_start_request(req);
 
-                if (scmrq->aob->request.msb_count < SCM_RQ_PER_IO)
+                if (scmrq->aob->request.msb_count < nr_requests_per_io)
                         continue;
 
                 if (scm_request_start(scmrq))
@@ -551,11 +561,19 @@ void scm_blk_set_available(struct scm_blk_dev *bdev)
         spin_unlock_irqrestore(&bdev->lock, flags);
 }
 
+static bool __init scm_blk_params_valid(void)
+{
+        if (!nr_requests_per_io || nr_requests_per_io > 64)
+                return false;
+
+        return scm_cluster_size_valid();
+}
+
 static int __init scm_blk_init(void)
 {
         int ret = -EINVAL;
 
-        if (!scm_cluster_size_valid())
+        if (!scm_blk_params_valid())
                 goto out;
 
         ret = register_blkdev(0, "scm");
diff --git a/drivers/s390/block/scm_blk.h b/drivers/s390/block/scm_blk.h
index 3dae0a3570ce..09218cdc5129 100644
--- a/drivers/s390/block/scm_blk.h
+++ b/drivers/s390/block/scm_blk.h
@@ -11,7 +11,6 @@
 #include <asm/eadm.h>
 
 #define SCM_NR_PARTS 8
-#define SCM_RQ_PER_IO 8
 #define SCM_QUEUE_DELAY 5
 
 struct scm_blk_dev {
@@ -32,7 +31,7 @@ struct scm_blk_dev {
 struct scm_request {
         struct scm_blk_dev *bdev;
         struct aidaw *next_aidaw;
-        struct request *request[SCM_RQ_PER_IO];
+        struct request **request;
         struct aob *aob;
         struct list_head list;
         u8 retries;