IB/srp: try to use larger FMR sizes to cover our mappings

Now that we can get larger SG lists, we can take advantage of HCAs that
allow us to use larger FMR sizes. In many cases, we can use up to 512
entries, so start there and work our way down.

Signed-off-by: David Dillow <dillowda@ornl.gov>

drivers/infiniband/ulp/srp/ib_srp.c

@@ -2300,7 +2300,7 @@ static void srp_add_one(struct ib_device *device)
 	struct ib_device_attr *dev_attr;
 	struct ib_fmr_pool_param fmr_param;
 	struct srp_host *host;
-	int fmr_page_shift, s, e, p;
+	int max_pages_per_fmr, fmr_page_shift, s, e, p;
 
 	dev_attr = kmalloc(sizeof *dev_attr, GFP_KERNEL);
 	if (!dev_attr)
@@ -2340,17 +2340,24 @@ static void srp_add_one(struct ib_device *device)
 	if (IS_ERR(srp_dev->mr))
 		goto err_pd;
 
-	memset(&fmr_param, 0, sizeof fmr_param);
-	fmr_param.pool_size	    = SRP_FMR_POOL_SIZE;
-	fmr_param.dirty_watermark   = SRP_FMR_DIRTY_SIZE;
-	fmr_param.cache		    = 1;
-	fmr_param.max_pages_per_fmr = SRP_FMR_SIZE;
-	fmr_param.page_shift	    = fmr_page_shift;
-	fmr_param.access	    = (IB_ACCESS_LOCAL_WRITE |
-				       IB_ACCESS_REMOTE_WRITE |
-				       IB_ACCESS_REMOTE_READ);
-
-	srp_dev->fmr_pool = ib_create_fmr_pool(srp_dev->pd, &fmr_param);
+	for (max_pages_per_fmr = SRP_FMR_SIZE;
+			max_pages_per_fmr >= SRP_FMR_MIN_SIZE;
+			max_pages_per_fmr /= 2, srp_dev->fmr_max_size /= 2) {
+		memset(&fmr_param, 0, sizeof fmr_param);
+		fmr_param.pool_size	    = SRP_FMR_POOL_SIZE;
+		fmr_param.dirty_watermark   = SRP_FMR_DIRTY_SIZE;
+		fmr_param.cache		    = 1;
+		fmr_param.max_pages_per_fmr = max_pages_per_fmr;
+		fmr_param.page_shift	    = fmr_page_shift;
+		fmr_param.access	    = (IB_ACCESS_LOCAL_WRITE |
+					       IB_ACCESS_REMOTE_WRITE |
+					       IB_ACCESS_REMOTE_READ);
+
+		srp_dev->fmr_pool = ib_create_fmr_pool(srp_dev->pd, &fmr_param);
+		if (!IS_ERR(srp_dev->fmr_pool))
+			break;
+	}
+
 	if (IS_ERR(srp_dev->fmr_pool))
 		srp_dev->fmr_pool = NULL;
 

drivers/infiniband/ulp/srp/ib_srp.h

@@ -69,7 +69,8 @@ enum {
 	SRP_TAG_NO_REQ		= ~0U,
 	SRP_TAG_TSK_MGMT	= 1U << 31,
 
-	SRP_FMR_SIZE		= 256,
+	SRP_FMR_SIZE		= 512,
+	SRP_FMR_MIN_SIZE	= 128,
 	SRP_FMR_POOL_SIZE	= 1024,
 	SRP_FMR_DIRTY_SIZE	= SRP_FMR_POOL_SIZE / 4,