kfifo: move struct kfifo in place
This is a new generic kernel FIFO implementation.
The current kernel fifo API is not very widely used, because it has to
many constrains. Only 17 files in the current 2.6.31-rc5 used it.
FIFO's are like list's a very basic thing and a kfifo API which handles
the most use case would save a lot of development time and memory
resources.
I think this are the reasons why kfifo is not in use:
- The API is to simple, important functions are missing
- A fifo can be only allocated dynamically
- There is a requirement of a spinlock whether you need it or not
- There is no support for data records inside a fifo
So I decided to extend the kfifo in a more generic way without blowing up
the API to much. The new API has the following benefits:
- Generic usage: For kernel internal use and/or device driver.
- Provide an API for the most use case.
- Slim API: The whole API provides 25 functions.
- Linux style habit.
- DECLARE_KFIFO, DEFINE_KFIFO and INIT_KFIFO Macros
- Direct copy_to_user from the fifo and copy_from_user into the fifo.
- The kfifo itself is an in place member of the using data structure, this save an
indirection access and does not waste the kernel allocator.
- Lockless access: if only one reader and one writer is active on the fifo,
which is the common use case, no additional locking is necessary.
- Remove spinlock - give the user the freedom of choice what kind of locking to use if
one is required.
- Ability to handle records. Three type of records are supported:
- Variable length records between 0-255 bytes, with a record size
field of 1 bytes.
- Variable length records between 0-65535 bytes, with a record size
field of 2 bytes.
- Fixed size records, which no record size field.
- Preserve memory resource.
- Performance!
- Easy to use!
This patch:
Since most users want to have the kfifo as part of another object,
reorganize the code to allow including struct kfifo in another data
structure. This requires changing the kfifo_alloc and kfifo_init
prototypes so that we pass an existing kfifo pointer into them. This
patch changes the implementation and all existing users.
[akpm@linux-foundation.org: fix warning]
Signed-off-by: Stefani Seibold <stefani@seibold.net>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/scsi/libsrp.c b/drivers/scsi/libsrp.c
index 9ad38e8..b1b5e51 100644
--- a/drivers/scsi/libsrp.c
+++ b/drivers/scsi/libsrp.c
@@ -58,19 +58,16 @@
goto free_pool;
spin_lock_init(&q->lock);
- q->queue = kfifo_init((void *) q->pool, max * sizeof(void *),
- GFP_KERNEL, &q->lock);
- if (IS_ERR(q->queue))
- goto free_item;
+ kfifo_init(&q->queue, (void *) q->pool, max * sizeof(void *),
+ &q->lock);
for (i = 0, iue = q->items; i < max; i++) {
- __kfifo_put(q->queue, (void *) &iue, sizeof(void *));
+ __kfifo_put(&q->queue, (void *) &iue, sizeof(void *));
iue->sbuf = ring[i];
iue++;
}
return 0;
-free_item:
kfree(q->items);
free_pool:
kfree(q->pool);
@@ -167,7 +164,7 @@
{
struct iu_entry *iue = NULL;
- kfifo_get(target->iu_queue.queue, (void *) &iue, sizeof(void *));
+ kfifo_get(&target->iu_queue.queue, (void *) &iue, sizeof(void *));
if (!iue)
return iue;
iue->target = target;
@@ -179,7 +176,7 @@
void srp_iu_put(struct iu_entry *iue)
{
- kfifo_put(iue->target->iu_queue.queue, (void *) &iue, sizeof(void *));
+ kfifo_put(&iue->target->iu_queue.queue, (void *) &iue, sizeof(void *));
}
EXPORT_SYMBOL_GPL(srp_iu_put);