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>

4 files changed, 10 insertions, 8 deletions

diff --git a/include/linux/kfifo.h b/include/linux/kfifo.h
index ad6bdf5..c3f8d82 100644
--- a/include/linux/kfifo.h
+++ b/include/linux/kfifo.h
@@ -1,6 +1,7 @@
 /*
- * A simple kernel FIFO implementation.
+ * A generic kernel FIFO implementation.
  *
+ * Copyright (C) 2009 Stefani Seibold <stefani@seibold.net>
  * Copyright (C) 2004 Stelian Pop <stelian@popies.net>
  *
  * This program is free software; you can redistribute it and/or modify
@@ -32,10 +33,10 @@ struct kfifo {
 	spinlock_t *lock;	/* protects concurrent modifications */
 };
 
-extern struct kfifo *kfifo_init(unsigned char *buffer, unsigned int size,
-				gfp_t gfp_mask, spinlock_t *lock);
-extern struct kfifo *kfifo_alloc(unsigned int size, gfp_t gfp_mask,
-				 spinlock_t *lock);
+extern void kfifo_init(struct kfifo *fifo, unsigned char *buffer,
+			unsigned int size, spinlock_t *lock);
+extern __must_check int kfifo_alloc(struct kfifo *fifo, unsigned int size,
+			gfp_t gfp_mask, spinlock_t *lock);
 extern void kfifo_free(struct kfifo *fifo);
 extern unsigned int __kfifo_put(struct kfifo *fifo,
 				const unsigned char *buffer, unsigned int len);
diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h
index 7394e3b..ff92b46 100644
--- a/include/scsi/libiscsi.h
+++ b/include/scsi/libiscsi.h
@@ -28,6 +28,7 @@
 #include <linux/mutex.h>
 #include <linux/timer.h>
 #include <linux/workqueue.h>
+#include <linux/kfifo.h>
 #include <scsi/iscsi_proto.h>
 #include <scsi/iscsi_if.h>
 #include <scsi/scsi_transport_iscsi.h>
@@ -231,7 +232,7 @@ struct iscsi_conn {
 };
 
 struct iscsi_pool {
-	struct kfifo		*queue;		/* FIFO Queue */
+	struct kfifo		queue;		/* FIFO Queue */
 	void			**pool;		/* Pool of elements */
 	int			max;		/* Max number of elements */
 };
diff --git a/include/scsi/libiscsi_tcp.h b/include/scsi/libiscsi_tcp.h
index 9e3182e..741ae7e 100644
--- a/include/scsi/libiscsi_tcp.h
+++ b/include/scsi/libiscsi_tcp.h
@@ -80,7 +80,7 @@ struct iscsi_tcp_task {
 	int			data_offset;
 	struct iscsi_r2t_info	*r2t;		/* in progress solict R2T */
 	struct iscsi_pool	r2tpool;
-	struct kfifo		*r2tqueue;
+	struct kfifo		r2tqueue;
 	void			*dd_data;
 };
 
diff --git a/include/scsi/libsrp.h b/include/scsi/libsrp.h
index ba615e4..07e3add 100644
--- a/include/scsi/libsrp.h
+++ b/include/scsi/libsrp.h
@@ -21,7 +21,7 @@ struct srp_buf {
 struct srp_queue {
 	void *pool;
 	void *items;
-	struct kfifo *queue;
+	struct kfifo queue;
 	spinlock_t lock;
 };