firewire: octlet AT payloads can be stack-allocated

We do not need slab allocations anymore in order to satisfy
streaming DMA mapping constraints, thanks to commit da28947e7e36
"firewire: ohci: avoid separate DMA mapping for small AT payloads".

(Besides, the slab-allocated buffers that firewire-core, firewire-sbp2,
and firedtv used to provide for 8-byte write and lock requests were
still not fully portable since they crossed cacheline boundaries or
shared a cacheline with unrelated CPU-accessed data.  snd-firewire-lib
got this aspect right by using an extra kmalloc/ kfree just for the
8-byte transaction buffer.)

This change replaces kmalloc'ed lock transaction scratch buffers in
firewire-core, firedtv, and snd-firewire-lib by local stack allocations.
Perhaps the most notable result of the change is simpler locking because
there is no need to serialize usages of preallocated per-device buffers
anymore.  Also, allocations and deallocations are simpler.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: Clemens Ladisch <clemens@ladisch.de>

1 files changed, 1 insertions, 3 deletions

diff --git a/drivers/firewire/core-cdev.c b/drivers/firewire/core-cdev.c
index 62ac111af243..2a3f1c4d6906 100644
--- a/drivers/firewire/core-cdev.c
+++ b/drivers/firewire/core-cdev.c
@@ -141,7 +141,6 @@ struct iso_resource {
         int generation;
         u64 channels;
         s32 bandwidth;
-        __be32 transaction_data[2];
         struct iso_resource_event *e_alloc, *e_dealloc;
 };
 
@@ -1229,8 +1228,7 @@ static void iso_resource_work(struct work_struct *work)
                         r->channels, &channel, &bandwidth,
                         todo == ISO_RES_ALLOC ||
                         todo == ISO_RES_REALLOC ||
-                        todo == ISO_RES_ALLOC_ONCE,
-                        r->transaction_data);
+                        todo == ISO_RES_ALLOC_ONCE);
         /*
          * Is this generation outdated already?  As long as this resource sticks
          * in the idr, it will be scheduled again for a newer generation or at