Re: [PATCH] mtip32xx: mtip_async_complete() bug fixes

[Sam Bradshaw <sbradshaw@micron.com>]

On 03/13/2014 02:02 PM, Jens Axboe wrote:
> On 03/13/2014 03:09 PM, Sam Bradshaw wrote:
>> This patch fixes 2 issues in the fast completion path:
>> 1) Possible double completions / double dma_unmap_sg() calls due to lack
>> of atomicity in the check and subsequent dereference of the upper layer
>> callback function. Fixed with cmpxchg before unmap and callback.
>> 2) Regression in unaligned IO constraining workaround for p420m devices.
>> Fixed by checking if IO is unaligned and using proper semaphore if so.
> 
> Sam, what is this patch against? It doesn't apply to -rc6 and it doesn't 
> apply to for-3.15/drivers (the latter would be preferred/required). It 
> also seems to have line break issues.
> 

It's against for-3.15/drivers.  Sorry about the breaks; if I remove them
does it apply cleanly?


diff --git a/drivers/block/mtip32xx/mtip32xx.c b/drivers/block/mtip32xx/mtip32xx.c
index b2012b7..624e9d9 100644
--- a/drivers/block/mtip32xx/mtip32xx.c
+++ b/drivers/block/mtip32xx/mtip32xx.c
@@ -252,38 +252,45 @@ static void mtip_async_complete(struct mtip_port *port,
 				void *data,
 				int status)
 {
-	struct mtip_cmd *command;
+	struct mtip_cmd *cmd;
 	struct driver_data *dd = data;
-	int cb_status = status ? -EIO : 0;
+	int unaligned, cb_status = status ? -EIO : 0;
+	void (*func)(void *, int);
 
 	if (unlikely(!dd) || unlikely(!port))
 		return;
 
-	command = &port->commands[tag];
+	cmd = &port->commands[tag];
 
 	if (unlikely(status == PORT_IRQ_TF_ERR)) {
 		dev_warn(&port->dd->pdev->dev,
 			"Command tag %d failed due to TFE\n", tag);
 	}
 
-	/* Unmap the DMA scatter list entries */
-	dma_unmap_sg(&dd->pdev->dev,
-		command->sg,
-		command->scatter_ents,
-		command->direction);
+	/* Clear the active flag */
+	atomic_set(&port->commands[tag].active, 0);
 
 	/* Upper layer callback */
-	if (likely(command->async_callback))
-		command->async_callback(command->async_data, cb_status);
+	func = cmd->async_callback;
+	if (likely(func && cmpxchg(&cmd->async_callback, func, 0) == func)) {
 
-	command->async_callback = NULL;
-	command->comp_func = NULL;
+		/* Unmap the DMA scatter list entries */
+		dma_unmap_sg(&dd->pdev->dev,
+			cmd->sg,
+			cmd->scatter_ents,
+			cmd->direction);
 
-	/* Clear the allocated and active bits for the command */
-	atomic_set(&port->commands[tag].active, 0);
-	release_slot(port, tag);
+		func(cmd->async_data, cb_status);
+		unaligned = cmd->unaligned;
 
-	up(&port->cmd_slot);
+		/* Clear the allocated bit for the command */
+		release_slot(port, tag);
+
+		if (unlikely(unaligned))
+			up(&port->cmd_slot_unal);
+		else
+			up(&port->cmd_slot);
+	}
 }
 
 /*
@@ -660,11 +667,12 @@ static void mtip_timeout_function(unsigned long int data)
 {
 	struct mtip_port *port = (struct mtip_port *) data;
 	struct host_to_dev_fis *fis;
-	struct mtip_cmd *command;
-	int tag, cmdto_cnt = 0;
+	struct mtip_cmd *cmd;
+	int unaligned, tag, cmdto_cnt = 0;
 	unsigned int bit, group;
 	unsigned int num_command_slots;
 	unsigned long to, tagaccum[SLOTBITS_IN_LONGS];
+	void (*func)(void *, int);
 
 	if (unlikely(!port))
 		return;
@@ -694,8 +702,8 @@ static void mtip_timeout_function(unsigned long int data)
 			group = tag >> 5;
 			bit = tag & 0x1F;
 
-			command = &port->commands[tag];
-			fis = (struct host_to_dev_fis *) command->command;
+			cmd = &port->commands[tag];
+			fis = (struct host_to_dev_fis *) cmd->command;
 
 			set_bit(tag, tagaccum);
 			cmdto_cnt++;
@@ -709,27 +717,30 @@ static void mtip_timeout_function(unsigned long int data)
 			 */
 			writel(1 << bit, port->completed[group]);
 
-			/* Unmap the DMA scatter list entries */
-			dma_unmap_sg(&port->dd->pdev->dev,
-					command->sg,
-					command->scatter_ents,
-					command->direction);
+			/* Clear the active flag for the command */
+			atomic_set(&port->commands[tag].active, 0);
 
-			/* Call the async completion callback. */
-			if (likely(command->async_callback))
-				command->async_callback(command->async_data,
-							 -EIO);
-			command->async_callback = NULL;
-			command->comp_func = NULL;
+			func = cmd->async_callback;
+			if (func &&
+			    cmpxchg(&cmd->async_callback, func, 0) == func) {
 
-			/*
-			 * Clear the allocated bit and active tag for the
-			 * command.
-			 */
-			atomic_set(&port->commands[tag].active, 0);
-			release_slot(port, tag);
+				/* Unmap the DMA scatter list entries */
+				dma_unmap_sg(&port->dd->pdev->dev,
+						cmd->sg,
+						cmd->scatter_ents,
+						cmd->direction);
 
-			up(&port->cmd_slot);
+				func(cmd->async_data, -EIO);
+				unaligned = cmd->unaligned;
+
+				/* Clear the allocated bit for the command. */
+				release_slot(port, tag);
+
+				if (unaligned)
+					up(&port->cmd_slot_unal);
+				else
+					up(&port->cmd_slot);
+			}
 		}
 	}
 
diff --git a/drivers/block/mtip32xx/mtip32xx.h b/drivers/block/mtip32xx/mtip32xx.h
index 54174cb..ffb955e 100644
--- a/drivers/block/mtip32xx/mtip32xx.h
+++ b/drivers/block/mtip32xx/mtip32xx.h
@@ -92,7 +92,7 @@
 
 /* Driver name and version strings */
 #define MTIP_DRV_NAME		"mtip32xx"
-#define MTIP_DRV_VERSION	"1.3.0"
+#define MTIP_DRV_VERSION	"1.3.1"
 
 /* Maximum number of minor device numbers per device. */
 #define MTIP_MAX_MINORS		16