megaraid_sas : N-drive primary raid level 1 load balancing

Resending the patch. Addressed the review comments from Tomas Henzl.

Current driver does fast path read load balancing between arm and mirror disk
for two Drive Raid-1 configuration only.

Now, Driver support fast path read load balancing for all (any number of disk) Raid-1 configuration.
Signed-off-by: Sumit Saxena <sumit.saxena@avagotech.com>
Signed-off-by: Kashyap Desai <kashyap.desai@avagotech.com>
Reviewed-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/scsi/megaraid/megaraid_sas.h

@@ -1188,7 +1188,8 @@ union megasas_sgl_frame {
 typedef union _MFI_CAPABILITIES {
 	struct {
 #if   defined(__BIG_ENDIAN_BITFIELD)
-		u32     reserved:28;
+		u32     reserved:27;
+		u32     support_ndrive_r1_lb:1;
 		u32	support_max_255lds:1;
 		u32	reserved1:1;
 		u32     support_additional_msix:1;
@@ -1198,7 +1199,8 @@ typedef union _MFI_CAPABILITIES {
 		u32     support_additional_msix:1;
 		u32	reserved1:1;
 		u32	support_max_255lds:1;
-		u32     reserved:28;
+		u32     support_ndrive_r1_lb:1;
+		u32     reserved:27;
 #endif
 	} mfi_capabilities;
 	u32     reg;
@@ -1914,6 +1916,8 @@ u16 MR_LdSpanArrayGet(u32 ld, u32 span, struct MR_DRV_RAID_MAP_ALL *map);
 u16 MR_PdDevHandleGet(u32 pd, struct MR_DRV_RAID_MAP_ALL *map);
 u16 MR_GetLDTgtId(u32 ld, struct MR_DRV_RAID_MAP_ALL *map);
 
+u16 get_updated_dev_handle(struct megasas_instance *instance,
+	struct LD_LOAD_BALANCE_INFO *lbInfo, struct IO_REQUEST_INFO *in_info);
 void mr_update_load_balance_params(struct MR_DRV_RAID_MAP_ALL *map,
 	struct LD_LOAD_BALANCE_INFO *lbInfo);
 int megasas_get_ctrl_info(struct megasas_instance *instance,

drivers/scsi/megaraid/megaraid_sas_fp.c

@@ -55,6 +55,13 @@
 #include "megaraid_sas.h"
 #include <asm/div64.h>
 
+#define LB_PENDING_CMDS_DEFAULT 4
+static unsigned int lb_pending_cmds = LB_PENDING_CMDS_DEFAULT;
+module_param(lb_pending_cmds, int, S_IRUGO);
+MODULE_PARM_DESC(lb_pending_cmds, "Change raid-1 load balancing outstanding "
+	"threshold. Valid Values are 1-128. Default: 4");
+
+
 #define ABS_DIFF(a, b)   (((a) > (b)) ? ((a) - (b)) : ((b) - (a)))
 #define MR_LD_STATE_OPTIMAL 3
 #define FALSE 0
@@ -769,6 +776,7 @@ static u8 mr_spanset_get_phy_params(struct megasas_instance *instance, u32 ld,
 	*pdBlock += stripRef + le64_to_cpu(MR_LdSpanPtrGet(ld, span, map)->startBlk);
 	pRAID_Context->spanArm = (span << RAID_CTX_SPANARM_SPAN_SHIFT) |
 					physArm;
+	io_info->span_arm = pRAID_Context->spanArm;
 	return retval;
 }
 
@@ -865,6 +873,7 @@ u8 MR_GetPhyParams(struct megasas_instance *instance, u32 ld, u64 stripRow,
 	*pdBlock += stripRef + le64_to_cpu(MR_LdSpanPtrGet(ld, span, map)->startBlk);
 	pRAID_Context->spanArm = (span << RAID_CTX_SPANARM_SPAN_SHIFT) |
 		physArm;
+	io_info->span_arm = pRAID_Context->spanArm;
 	return retval;
 }
 
@@ -1131,7 +1140,7 @@ MR_BuildRaidContext(struct megasas_instance *instance,
 *
 */
 void mr_update_span_set(struct MR_DRV_RAID_MAP_ALL *map,
-			PLD_SPAN_INFO ldSpanInfo)
+	PLD_SPAN_INFO ldSpanInfo)
 {
 	u8   span, count;
 	u32  element, span_row_width;
@@ -1239,90 +1248,105 @@ void mr_update_span_set(struct MR_DRV_RAID_MAP_ALL *map,
 
 }
 
-void
-mr_update_load_balance_params(struct MR_DRV_RAID_MAP_ALL *map,
-			      struct LD_LOAD_BALANCE_INFO *lbInfo)
+void mr_update_load_balance_params(struct MR_DRV_RAID_MAP_ALL *drv_map,
+	struct LD_LOAD_BALANCE_INFO *lbInfo)
 {
 	int ldCount;
 	u16 ld;
 	struct MR_LD_RAID *raid;
 
+	if (lb_pending_cmds > 128 || lb_pending_cmds < 1)
+		lb_pending_cmds = LB_PENDING_CMDS_DEFAULT;
+
 	for (ldCount = 0; ldCount < MAX_LOGICAL_DRIVES_EXT; ldCount++) {
-		ld = MR_TargetIdToLdGet(ldCount, map);
+		ld = MR_TargetIdToLdGet(ldCount, drv_map);
 		if (ld >= MAX_LOGICAL_DRIVES_EXT) {
 			lbInfo[ldCount].loadBalanceFlag = 0;
 			continue;
 		}
 
-		raid = MR_LdRaidGet(ld, map);
-
-		/* Two drive Optimal RAID 1 */
-		if ((raid->level == 1)  &&  (raid->rowSize == 2) &&
-		    (raid->spanDepth == 1) && raid->ldState ==
-		    MR_LD_STATE_OPTIMAL) {
-			u32 pd, arRef;
-
-			lbInfo[ldCount].loadBalanceFlag = 1;
-
-			/* Get the array on which this span is present */
-			arRef = MR_LdSpanArrayGet(ld, 0, map);
-
-			/* Get the Pd */
-			pd = MR_ArPdGet(arRef, 0, map);
-			/* Get dev handle from Pd */
-			lbInfo[ldCount].raid1DevHandle[0] =
-				MR_PdDevHandleGet(pd, map);
-			/* Get the Pd */
-			pd = MR_ArPdGet(arRef, 1, map);
-
-			/* Get the dev handle from Pd */
-			lbInfo[ldCount].raid1DevHandle[1] =
-				MR_PdDevHandleGet(pd, map);
-		} else
+		raid = MR_LdRaidGet(ld, drv_map);
+		if ((raid->level != 1) ||
+			(raid->ldState != MR_LD_STATE_OPTIMAL)) {
 			lbInfo[ldCount].loadBalanceFlag = 0;
+			continue;
+		}
+		lbInfo[ldCount].loadBalanceFlag = 1;
 	}
 }
 
-u8 megasas_get_best_arm(struct LD_LOAD_BALANCE_INFO *lbInfo, u8 arm, u64 block,
-			u32 count)
+u8 megasas_get_best_arm_pd(struct megasas_instance *instance,
+	struct LD_LOAD_BALANCE_INFO *lbInfo, struct IO_REQUEST_INFO *io_info)
 {
-	u16     pend0, pend1;
+	struct fusion_context *fusion;
+	struct MR_LD_RAID  *raid;
+	struct MR_DRV_RAID_MAP_ALL *drv_map;
+	u16     pend0, pend1, ld;
 	u64     diff0, diff1;
-	u8      bestArm;
+	u8      bestArm, pd0, pd1, span, arm;
+	u32     arRef, span_row_size;
+
+	u64 block = io_info->ldStartBlock;
+	u32 count = io_info->numBlocks;
+
+	span = ((io_info->span_arm & RAID_CTX_SPANARM_SPAN_MASK)
+			>> RAID_CTX_SPANARM_SPAN_SHIFT);
+	arm = (io_info->span_arm & RAID_CTX_SPANARM_ARM_MASK);
+
+
+	fusion = instance->ctrl_context;
+	drv_map = fusion->ld_drv_map[(instance->map_id & 1)];
+	ld = MR_TargetIdToLdGet(io_info->ldTgtId, drv_map);
+	raid = MR_LdRaidGet(ld, drv_map);
+	span_row_size = instance->UnevenSpanSupport ?
+			SPAN_ROW_SIZE(drv_map, ld, span) : raid->rowSize;
+
+	arRef = MR_LdSpanArrayGet(ld, span, drv_map);
+	pd0 = MR_ArPdGet(arRef, arm, drv_map);
+	pd1 = MR_ArPdGet(arRef, (arm + 1) >= span_row_size ?
+		(arm + 1 - span_row_size) : arm + 1, drv_map);
 
 	/* get the pending cmds for the data and mirror arms */
-	pend0 = atomic_read(&lbInfo->scsi_pending_cmds[0]);
-	pend1 = atomic_read(&lbInfo->scsi_pending_cmds[1]);
+	pend0 = atomic_read(&lbInfo->scsi_pending_cmds[pd0]);
+	pend1 = atomic_read(&lbInfo->scsi_pending_cmds[pd1]);
 
 	/* Determine the disk whose head is nearer to the req. block */
-	diff0 = ABS_DIFF(block, lbInfo->last_accessed_block[0]);
-	diff1 = ABS_DIFF(block, lbInfo->last_accessed_block[1]);
-	bestArm = (diff0 <= diff1 ? 0 : 1);
+	diff0 = ABS_DIFF(block, lbInfo->last_accessed_block[pd0]);
+	diff1 = ABS_DIFF(block, lbInfo->last_accessed_block[pd1]);
+	bestArm = (diff0 <= diff1 ? arm : arm ^ 1);
 
-	/*Make balance count from 16 to 4 to keep driver in sync with Firmware*/
-	if ((bestArm == arm && pend0 > pend1 + 4)  ||
-	    (bestArm != arm && pend1 > pend0 + 4))
+	if ((bestArm == arm && pend0 > pend1 + lb_pending_cmds)  ||
+			(bestArm != arm && pend1 > pend0 + lb_pending_cmds))
 		bestArm ^= 1;
 
 	/* Update the last accessed block on the correct pd */
-	lbInfo->last_accessed_block[bestArm] = block + count - 1;
-
-	return bestArm;
+	io_info->pd_after_lb = (bestArm == arm) ? pd0 : pd1;
+	lbInfo->last_accessed_block[io_info->pd_after_lb] = block + count - 1;
+	io_info->span_arm = (span << RAID_CTX_SPANARM_SPAN_SHIFT) | bestArm;
+#if SPAN_DEBUG
+	if (arm != bestArm)
+		dev_dbg(&instance->pdev->dev, "LSI Debug R1 Load balance "
+			"occur - span 0x%x arm 0x%x bestArm 0x%x "
+			"io_info->span_arm 0x%x\n",
+			span, arm, bestArm, io_info->span_arm);
+#endif
+	return io_info->pd_after_lb;
 }
 
-u16 get_updated_dev_handle(struct LD_LOAD_BALANCE_INFO *lbInfo,
-			   struct IO_REQUEST_INFO *io_info)
+u16 get_updated_dev_handle(struct megasas_instance *instance,
+	struct LD_LOAD_BALANCE_INFO *lbInfo, struct IO_REQUEST_INFO *io_info)
 {
-	u8 arm, old_arm;
+	u8 arm_pd;
 	u16 devHandle;
+	struct fusion_context *fusion;
+	struct MR_DRV_RAID_MAP_ALL *drv_map;
 
-	old_arm = lbInfo->raid1DevHandle[0] == io_info->devHandle ? 0 : 1;
-
-	/* get best new arm */
-	arm  = megasas_get_best_arm(lbInfo, old_arm, io_info->ldStartBlock,
-				    io_info->numBlocks);
-	devHandle = lbInfo->raid1DevHandle[arm];
-	atomic_inc(&lbInfo->scsi_pending_cmds[arm]);
+	fusion = instance->ctrl_context;
+	drv_map = fusion->ld_drv_map[(instance->map_id & 1)];
 
+	/* get best new arm (PD ID) */
+	arm_pd  = megasas_get_best_arm_pd(instance, lbInfo, io_info);
+	devHandle = MR_PdDevHandleGet(arm_pd, drv_map);
+	atomic_inc(&lbInfo->scsi_pending_cmds[arm_pd]);
 	return devHandle;
 }

drivers/scsi/megaraid/megaraid_sas_fusion.c

@@ -76,8 +76,6 @@ megasas_issue_polled(struct megasas_instance *instance,
 void
 megasas_check_and_restore_queue_depth(struct megasas_instance *instance);
 
-u16 get_updated_dev_handle(struct LD_LOAD_BALANCE_INFO *lbInfo,
-			   struct IO_REQUEST_INFO *in_info);
 int megasas_transition_to_ready(struct megasas_instance *instance, int ocr);
 void megaraid_sas_kill_hba(struct megasas_instance *instance);
 
@@ -654,6 +652,8 @@ megasas_ioc_init_fusion(struct megasas_instance *instance)
 		= 1;
 	init_frame->driver_operations.mfi_capabilities.support_max_255lds
 		= 1;
+	init_frame->driver_operations.mfi_capabilities.support_ndrive_r1_lb
+		= 1;
 	/* Convert capability to LE32 */
 	cpu_to_le32s((u32 *)&init_frame->driver_operations.mfi_capabilities);
 
@@ -1606,10 +1606,11 @@ megasas_build_ldio_fusion(struct megasas_instance *instance,
 		if ((fusion->load_balance_info[device_id].loadBalanceFlag) &&
 		    (io_info.isRead)) {
 			io_info.devHandle =
-				get_updated_dev_handle(
+				get_updated_dev_handle(instance,
 					&fusion->load_balance_info[device_id],
 					&io_info);
 			scp->SCp.Status |= MEGASAS_LOAD_BALANCE_FLAG;
+			cmd->pd_r1_lb = io_info.pd_after_lb;
 		} else
 			scp->SCp.Status &= ~MEGASAS_LOAD_BALANCE_FLAG;
 		cmd->request_desc->SCSIIO.DevHandle = io_info.devHandle;
@@ -1942,7 +1943,7 @@ complete_cmd_fusion(struct megasas_instance *instance, u32 MSIxIndex)
 	struct megasas_cmd *cmd_mfi;
 	struct megasas_cmd_fusion *cmd_fusion;
 	u16 smid, num_completed;
-	u8 reply_descript_type, arm;
+	u8 reply_descript_type;
 	u32 status, extStatus, device_id;
 	union desc_value d_val;
 	struct LD_LOAD_BALANCE_INFO *lbinfo;
@@ -1993,10 +1994,7 @@ complete_cmd_fusion(struct megasas_instance *instance, u32 MSIxIndex)
 			lbinfo = &fusion->load_balance_info[device_id];
 			if (cmd_fusion->scmd->SCp.Status &
 			    MEGASAS_LOAD_BALANCE_FLAG) {
-				arm = lbinfo->raid1DevHandle[0] ==
-					cmd_fusion->io_request->DevHandle ? 0 :
-					1;
-				atomic_dec(&lbinfo->scsi_pending_cmds[arm]);
+				atomic_dec(&lbinfo->scsi_pending_cmds[cmd_fusion->pd_r1_lb]);
 				cmd_fusion->scmd->SCp.Status &=
 					~MEGASAS_LOAD_BALANCE_FLAG;
 			}

drivers/scsi/megaraid/megaraid_sas_fusion.h

@@ -630,6 +630,8 @@ struct IO_REQUEST_INFO {
 	u8 start_span;
 	u8 reserved;
 	u64 start_row;
+	u8  span_arm;	/* span[7:5], arm[4:0] */
+	u8  pd_after_lb;
 };
 
 struct MR_LD_TARGET_SYNC {
@@ -681,14 +683,14 @@ struct megasas_cmd_fusion {
 	u32 sync_cmd_idx;
 	u32 index;
 	u8 flags;
+	u8 pd_r1_lb;
 };
 
 struct LD_LOAD_BALANCE_INFO {
 	u8	loadBalanceFlag;
 	u8	reserved1;
-	u16     raid1DevHandle[2];
-	atomic_t     scsi_pending_cmds[2];
-	u64     last_accessed_block[2];
+	atomic_t     scsi_pending_cmds[MAX_PHYSICAL_DEVICES];
+	u64     last_accessed_block[MAX_PHYSICAL_DEVICES];
 };
 
 /* SPAN_SET is info caclulated from span info from Raid map per LD */