firewire: fw-ohci: plug dma memory leak in AR handler

There's an ugly little memory leak in firewire-ohci's
ar_context_tasklet(), where we're not freeing up some of the memory we
use for each ar_buffer, due to a moving pointer. The problem has been
there for a while, but didn't get noticed until after converting the AR
routines over to use coherent DMA and I started running into I/O stall-
outs with the following message output repeatedly to the console:

PCI-DMA: Out of IOMMU space for 53248 bytes at device 0000:04:09.0

Plugging this leak is definitely necessary, but unfortunately, isn't the
entire answer to my problem, it only increases the amount of I/O that I
can do before hitting the problem. Still working on tracking down the
root cause..

Signed-off-by: Jarod Wilson <jwilson@redhat.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

1 files changed, 5 insertions, 4 deletions

diff --git a/drivers/firewire/fw-ohci.c b/drivers/firewire/fw-ohci.c
index 996d61f0d460..ca6d51efd8bb 100644
--- a/drivers/firewire/fw-ohci.c
+++ b/drivers/firewire/fw-ohci.c
@@ -401,7 +401,8 @@ static void ar_context_tasklet(unsigned long data)
 
         if (d->res_count == 0) {
                 size_t size, rest, offset;
-                dma_addr_t buffer_bus;
+                dma_addr_t start_bus;
+                void *start;
 
                 /*
                  * This descriptor is finished and we may have a
@@ -410,9 +411,9 @@ static void ar_context_tasklet(unsigned long data)
                  */
 
                 offset = offsetof(struct ar_buffer, data);
-                buffer_bus = le32_to_cpu(ab->descriptor.data_address) - offset;
+                start = buffer = ab;
+                start_bus = le32_to_cpu(ab->descriptor.data_address) - offset;
 
-                buffer = ab;
                 ab = ab->next;
                 d = &ab->descriptor;
                 size = buffer + PAGE_SIZE - ctx->pointer;
@@ -427,7 +428,7 @@ static void ar_context_tasklet(unsigned long data)
                         buffer = handle_ar_packet(ctx, buffer);
 
                 dma_free_coherent(ohci->card.device, PAGE_SIZE,
-                                  buffer, buffer_bus);
+                                  start, start_bus);
                 ar_context_add_page(ctx);
         } else {
                 buffer = ctx->pointer;