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>

1 files changed, 16 insertions, 12 deletions

diff --git a/drivers/firewire/ohci.c b/drivers/firewire/ohci.c
index 7570b71a2453..b5ba66656c6c 100644
--- a/drivers/firewire/ohci.c
+++ b/drivers/firewire/ohci.c
@@ -577,17 +577,11 @@ static int ohci_update_phy_reg(struct fw_card *card, int addr,
         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 |
@@ -606,6 +600,19 @@ static int ar_context_add_page(struct ar_context *ctx)
 
         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 __le32 *handle_ar_packet(struct ar_context *ctx, __le32 *buffer)
 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 @@ static void ar_context_tasklet(unsigned long data)
                         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;
                 }