firewire: ohci: avoid reallocation of AR buffers

Freeing an AR buffer page just to allocate a new page immediately afterwards is not only a pointless effort but also dangerous because the allocation can fail, which would result in an oops later. Split ar_context_add_page() into two functions so that we can reuse the old page directly. Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Tested-by: Maxim Levitsky <maximlevitsky@gmail.com> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

firewire: ohci: avoid reallocation of AR buffers
Freeing an AR buffer page just to allocate a new page immediately afterwards is not only a pointless effort but also dangerous because the allocation can fail, which would result in an oops later. Split ar_context_add_page() into two functions so that we can reuse the old page directly. Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Tested-by: Maxim Levitsky <maximlevitsky@gmail.com> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Clemens Ladisch · Stefan Richter
1 parent a1f805e5e7
Showing 1 changed file with 16 additions and 12 deletions Side-by-side Diff
drivers/firewire/ohci.c
@@ -577,17 +577,11 @@
 	return ret;
 }
  
-static int ar_context_add_page(struct ar_context *ctx)
+static void ar_context_link_page(struct ar_context *ctx,
+				 struct ar_buffer *ab, dma_addr_t ab_bus)
 {
-	struct device *dev = ctx->ohci->card.device;
-	struct ar_buffer *ab;
-	dma_addr_t uninitialized_var(ab_bus);
 	size_t offset;
  
-	ab = dma_alloc_coherent(dev, PAGE_SIZE, &ab_bus, GFP_ATOMIC);
-	if (ab == NULL)
-		return -ENOMEM;
-
 	ab->next = NULL;
 	memset(&ab->descriptor, 0, sizeof(ab->descriptor));
 	ab->descriptor.control        = cpu_to_le16(DESCRIPTOR_INPUT_MORE |
  
@@ -606,7 +600,20 @@
  
 	reg_write(ctx->ohci, CONTROL_SET(ctx->regs), CONTEXT_WAKE);
 	flush_writes(ctx->ohci);
+}
  
+static int ar_context_add_page(struct ar_context *ctx)
+{
+	struct device *dev = ctx->ohci->card.device;
+	struct ar_buffer *ab;
+	dma_addr_t uninitialized_var(ab_bus);
+
+	ab = dma_alloc_coherent(dev, PAGE_SIZE, &ab_bus, GFP_ATOMIC);
+	if (ab == NULL)
+		return -ENOMEM;
+
+	ar_context_link_page(ctx, ab, ab_bus);
+
 	return 0;
 }
  
@@ -730,7 +737,6 @@
 static void ar_context_tasklet(unsigned long data)
 {
 	struct ar_context *ctx = (struct ar_context *)data;
-	struct fw_ohci *ohci = ctx->ohci;
 	struct ar_buffer *ab;
 	struct descriptor *d;
 	void *buffer, *end;
@@ -799,9 +805,7 @@
 			ctx->current_buffer = ab;
 			ctx->pointer = end;
  
-			dma_free_coherent(ohci->card.device, PAGE_SIZE,
-					  start, start_bus);
-			ar_context_add_page(ctx);
+			ar_context_link_page(ctx, start, start_bus);
 		} else {
 			ctx->pointer = start + PAGE_SIZE;
 		}
...	...	@@ -577,17 +577,11 @@
577	577	return ret;
578	578	}
579	579
580		-static int ar_context_add_page(struct ar_context *ctx)
	580	+static void ar_context_link_page(struct ar_context *ctx,
	581	+ struct ar_buffer *ab, dma_addr_t ab_bus)
581	582	{
582		- struct device *dev = ctx->ohci->card.device;
583		- struct ar_buffer *ab;
584		- dma_addr_t uninitialized_var(ab_bus);
585	583	size_t offset;
586	584
587		- ab = dma_alloc_coherent(dev, PAGE_SIZE, &ab_bus, GFP_ATOMIC);
588		- if (ab == NULL)
589		- return -ENOMEM;
590		-
591	585	ab->next = NULL;
592	586	memset(&ab->descriptor, 0, sizeof(ab->descriptor));
593	587	ab->descriptor.control = cpu_to_le16(DESCRIPTOR_INPUT_MORE \|
594	588
...	...	@@ -606,7 +600,20 @@
606	600
607	601	reg_write(ctx->ohci, CONTROL_SET(ctx->regs), CONTEXT_WAKE);
608	602	flush_writes(ctx->ohci);
	603	+}
609	604
	605	+static int ar_context_add_page(struct ar_context *ctx)
	606	+{
	607	+ struct device *dev = ctx->ohci->card.device;
	608	+ struct ar_buffer *ab;
	609	+ dma_addr_t uninitialized_var(ab_bus);
	610	+
	611	+ ab = dma_alloc_coherent(dev, PAGE_SIZE, &ab_bus, GFP_ATOMIC);
	612	+ if (ab == NULL)
	613	+ return -ENOMEM;
	614	+
	615	+ ar_context_link_page(ctx, ab, ab_bus);
	616	+
610	617	return 0;
611	618	}
612	619
...	...	@@ -730,7 +737,6 @@
730	737	static void ar_context_tasklet(unsigned long data)
731	738	{
732	739	struct ar_context ctx = (struct ar_context )data;
733		- struct fw_ohci *ohci = ctx->ohci;
734	740	struct ar_buffer *ab;
735	741	struct descriptor *d;
736	742	void buffer, end;
...	...	@@ -799,9 +805,7 @@
799	805	ctx->current_buffer = ab;
800	806	ctx->pointer = end;
801	807
802		- dma_free_coherent(ohci->card.device, PAGE_SIZE,
803		- start, start_bus);
804		- ar_context_add_page(ctx);
	808	+ ar_context_link_page(ctx, start, start_bus);
805	809	} else {
806	810	ctx->pointer = start + PAGE_SIZE;
807	811	}