megaraid_sas : MFI MPT linked list corruption fix

Resending the patch. Addressed the review comments from Tomas Henzl.
Added comment for to-do work.

Problem statement:
MFI link list in megaraid_sas driver is used from mfi-mpt pass-through commands.
This list can be corrupted due to many possible race conditions in driver and
eventually we may see kernel panic.

One example -
MFI frame is freed from calling process as driver send command via polling method and interrupt
for that command comes after driver free mfi frame (actually even after some other context reuse
the mfi frame). When driver receive MPT frame in ISR, driver will be using the index of MFI and
access that MFI frame and finally in-used MFI frame’s list will be corrupted.

High level description of new solution -
Free MFI and MPT command from same context.
Free both the command either from process (from where mfi-mpt pass-through was called) or from
ISR context. Do not split freeing of MFI and MPT, because it creates the race condition which
will do MFI/MPT list corruption.

Renamed the cmd_pool_lock which is used in instance as well as fusion with below name.
mfi_pool_lock and mpt_pool_lock to add more code readability.

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>

1 files changed, 78 insertions, 23 deletions

diff --git a/drivers/scsi/megaraid/megaraid_sas_fusion.c b/drivers/scsi/megaraid/megaraid_sas_fusion.c
index 54c720ccb3e..f37eed682c7 100644
--- a/drivers/scsi/megaraid/megaraid_sas_fusion.c
+++ b/drivers/scsi/megaraid/megaraid_sas_fusion.c
@@ -50,6 +50,7 @@
 #include <scsi/scsi_cmnd.h>
 #include <scsi/scsi_device.h>
 #include <scsi/scsi_host.h>
+#include <scsi/scsi_dbg.h>
 
 #include "megaraid_sas_fusion.h"
 #include "megaraid_sas.h"
@@ -163,7 +164,7 @@ struct megasas_cmd_fusion *megasas_get_cmd_fusion(struct megasas_instance
 		(struct fusion_context *)instance->ctrl_context;
 	struct megasas_cmd_fusion *cmd = NULL;
 
-	spin_lock_irqsave(&fusion->cmd_pool_lock, flags);
+	spin_lock_irqsave(&fusion->mpt_pool_lock, flags);
 
 	if (!list_empty(&fusion->cmd_pool)) {
 		cmd = list_entry((&fusion->cmd_pool)->next,
@@ -173,7 +174,7 @@ struct megasas_cmd_fusion *megasas_get_cmd_fusion(struct megasas_instance
 		printk(KERN_ERR "megasas: Command pool (fusion) empty!\n");
 	}
 
-	spin_unlock_irqrestore(&fusion->cmd_pool_lock, flags);
+	spin_unlock_irqrestore(&fusion->mpt_pool_lock, flags);
 	return cmd;
 }
 
@@ -182,21 +183,47 @@ struct megasas_cmd_fusion *megasas_get_cmd_fusion(struct megasas_instance
  * @instance:		Adapter soft state
  * @cmd:		Command packet to be returned to free command pool
  */
-static inline void
-megasas_return_cmd_fusion(struct megasas_instance *instance,
-			  struct megasas_cmd_fusion *cmd)
+inline void megasas_return_cmd_fusion(struct megasas_instance *instance,
+	struct megasas_cmd_fusion *cmd)
 {
 	unsigned long flags;
 	struct fusion_context *fusion =
 		(struct fusion_context *)instance->ctrl_context;
 
-	spin_lock_irqsave(&fusion->cmd_pool_lock, flags);
+	spin_lock_irqsave(&fusion->mpt_pool_lock, flags);
 
 	cmd->scmd = NULL;
 	cmd->sync_cmd_idx = (u32)ULONG_MAX;
-	list_add_tail(&cmd->list, &fusion->cmd_pool);
+	list_add(&cmd->list, (&fusion->cmd_pool)->next);
 
-	spin_unlock_irqrestore(&fusion->cmd_pool_lock, flags);
+	spin_unlock_irqrestore(&fusion->mpt_pool_lock, flags);
+}
+
+/**
+ * megasas_return_mfi_mpt_pthr - Return a mfi and mpt to free command pool
+ * @instance:		Adapter soft state
+ * @cmd_mfi:		MFI Command packet to be returned to free command pool
+ * @cmd_mpt:		MPT Command packet to be returned to free command pool
+ */
+inline void megasas_return_mfi_mpt_pthr(struct megasas_instance *instance,
+		struct megasas_cmd *cmd_mfi,
+		struct megasas_cmd_fusion *cmd_fusion)
+{
+	unsigned long flags;
+
+	/*
+	 * TO DO: optimize this code and use only one lock instead of two
+	 * locks being used currently- mpt_pool_lock is acquired
+	 * inside mfi_pool_lock
+	 */
+	spin_lock_irqsave(&instance->mfi_pool_lock, flags);
+	megasas_return_cmd_fusion(instance, cmd_fusion);
+	if (atomic_read(&cmd_mfi->mfi_mpt_pthr) != MFI_MPT_ATTACHED)
+		dev_err(&instance->pdev->dev, "Possible bug from %s %d\n",
+			__func__, __LINE__);
+	atomic_set(&cmd_mfi->mfi_mpt_pthr, MFI_MPT_DETACHED);
+	__megasas_return_cmd(instance, cmd_mfi);
+	spin_unlock_irqrestore(&instance->mfi_pool_lock, flags);
 }
 
 /**
@@ -562,9 +589,11 @@ wait_and_poll(struct megasas_instance *instance, struct megasas_cmd *cmd,
 {
 	int i;
 	struct megasas_header *frame_hdr = &cmd->frame->hdr;
+	struct fusion_context *fusion;
 
 	u32 msecs = seconds * 1000;
 
+	fusion = instance->ctrl_context;
 	/*
 	 * Wait for cmd_status to change
 	 */
@@ -573,8 +602,12 @@ wait_and_poll(struct megasas_instance *instance, struct megasas_cmd *cmd,
 		msleep(20);
 	}
 
-	if (frame_hdr->cmd_status == 0xff)
+	if (frame_hdr->cmd_status == 0xff) {
+		if (fusion)
+			megasas_return_mfi_mpt_pthr(instance, cmd,
+				cmd->mpt_pthr_cmd_blocked);
 		return -ETIME;
+	}
 
 	return 0;
 }
@@ -777,14 +810,17 @@ megasas_get_ld_map_info(struct megasas_instance *instance)
 	dcmd->sgl.sge32[0].phys_addr = cpu_to_le32(ci_h);
 	dcmd->sgl.sge32[0].length = cpu_to_le32(size_map_info);
 
-	if (!megasas_issue_polled(instance, cmd))
-		ret = 0;
-	else {
-		printk(KERN_ERR "megasas: Get LD Map Info Failed\n");
-		ret = -1;
-	}
+	if (instance->ctrl_context && !instance->mask_interrupts)
+		ret = megasas_issue_blocked_cmd(instance, cmd,
+			MEGASAS_BLOCKED_CMD_TIMEOUT);
+	else
+		ret = megasas_issue_polled(instance, cmd);
 
-	megasas_return_cmd(instance, cmd);
+	if (instance->ctrl_context && cmd->mpt_pthr_cmd_blocked)
+		megasas_return_mfi_mpt_pthr(instance, cmd,
+			cmd->mpt_pthr_cmd_blocked);
+	else
+		megasas_return_cmd(instance, cmd);
 
 	return ret;
 }
@@ -2018,10 +2054,19 @@ complete_cmd_fusion(struct megasas_instance *instance, u32 MSIxIndex)
 			break;
 		case MEGASAS_MPI2_FUNCTION_PASSTHRU_IO_REQUEST: /*MFI command */
 			cmd_mfi = instance->cmd_list[cmd_fusion->sync_cmd_idx];
+
+			if (!cmd_mfi->mpt_pthr_cmd_blocked) {
+				if (megasas_dbg_lvl == 5)
+					dev_info(&instance->pdev->dev,
+						"freeing mfi/mpt pass-through "
+						"from %s %d\n",
+						 __func__, __LINE__);
+				megasas_return_mfi_mpt_pthr(instance, cmd_mfi,
+					cmd_fusion);
+			}
+
 			megasas_complete_cmd(instance, cmd_mfi, DID_OK);
 			cmd_fusion->flags = 0;
-			megasas_return_cmd_fusion(instance, cmd_fusion);
-
 			break;
 		}
 
@@ -2181,6 +2226,7 @@ build_mpt_mfi_pass_thru(struct megasas_instance *instance,
 	struct megasas_cmd_fusion *cmd;
 	struct fusion_context *fusion;
 	struct megasas_header *frame_hdr = &mfi_cmd->frame->hdr;
+	u32 opcode;
 
 	cmd = megasas_get_cmd_fusion(instance);
 	if (!cmd)
@@ -2188,9 +2234,20 @@ build_mpt_mfi_pass_thru(struct megasas_instance *instance,
 
 	/*  Save the smid. To be used for returning the cmd */
 	mfi_cmd->context.smid = cmd->index;
-
 	cmd->sync_cmd_idx = mfi_cmd->index;
 
+	/* Set this only for Blocked commands */
+	opcode = le32_to_cpu(mfi_cmd->frame->dcmd.opcode);
+	if ((opcode == MR_DCMD_LD_MAP_GET_INFO)
+		&& (mfi_cmd->frame->dcmd.mbox.b[1] == 1))
+		mfi_cmd->is_wait_event = 1;
+
+	if (opcode == MR_DCMD_CTRL_EVENT_WAIT)
+		mfi_cmd->is_wait_event = 1;
+
+	if (mfi_cmd->is_wait_event)
+		mfi_cmd->mpt_pthr_cmd_blocked = cmd;
+
 	/*
 	 * For cmds where the flag is set, store the flag and check
 	 * on completion. For cmds with this flag, don't call
@@ -2279,6 +2336,7 @@ megasas_issue_dcmd_fusion(struct megasas_instance *instance,
 		printk(KERN_ERR "Couldn't issue MFI pass thru cmd\n");
 		return;
 	}
+	atomic_set(&cmd->mfi_mpt_pthr, MFI_MPT_ATTACHED);
 	instance->instancet->fire_cmd(instance, req_desc->u.low,
 				      req_desc->u.high, instance->reg_set);
 }
@@ -2750,10 +2808,7 @@ int megasas_reset_fusion(struct Scsi_Host *shost, int iotimeout)
 					cmd_list[cmd_fusion->sync_cmd_idx];
 					if (cmd_mfi->frame->dcmd.opcode ==
 					    cpu_to_le32(MR_DCMD_LD_MAP_GET_INFO)) {
-						megasas_return_cmd(instance,
-								   cmd_mfi);
-						megasas_return_cmd_fusion(
-							instance, cmd_fusion);
+						megasas_return_mfi_mpt_pthr(instance, cmd_mfi, cmd_fusion);
 					} else  {
 						req_desc =
 						megasas_get_request_descriptor(