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>

1 files changed, 5 insertions, 8 deletions

diff --git a/drivers/scsi/libsrp.c b/drivers/scsi/libsrp.c
index 9ad38e81e34..b1b5e51ca8e 100644
--- a/drivers/scsi/libsrp.c
+++ b/drivers/scsi/libsrp.c
@@ -58,19 +58,16 @@ static int srp_iu_pool_alloc(struct srp_queue *q, size_t max,
                 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 *srp_iu_get(struct srp_target *target)
 {
         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 @@ EXPORT_SYMBOL_GPL(srp_iu_get);
 
 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);