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>

net/dccp/probe.c

@@ -43,7 +43,7 @@ static int bufsize = 64 * 1024;
 static const char procname[] = "dccpprobe";
 
 static struct {
-	struct kfifo	  *fifo;
+	struct kfifo	  fifo;
 	spinlock_t	  lock;
 	wait_queue_head_t wait;
 	struct timespec	  tstart;
@@ -67,7 +67,7 @@ static void printl(const char *fmt, ...)
 	len += vscnprintf(tbuf+len, sizeof(tbuf)-len, fmt, args);
 	va_end(args);
 
-	kfifo_put(dccpw.fifo, tbuf, len);
+	kfifo_put(&dccpw.fifo, tbuf, len);
 	wake_up(&dccpw.wait);
 }
 
@@ -109,7 +109,7 @@ static struct jprobe dccp_send_probe = {
 
 static int dccpprobe_open(struct inode *inode, struct file *file)
 {
-	kfifo_reset(dccpw.fifo);
+	kfifo_reset(&dccpw.fifo);
 	getnstimeofday(&dccpw.tstart);
 	return 0;
 }
@@ -131,11 +131,11 @@ static ssize_t dccpprobe_read(struct file *file, char __user *buf,
 		return -ENOMEM;
 
 	error = wait_event_interruptible(dccpw.wait,
-					 __kfifo_len(dccpw.fifo) != 0);
+					 __kfifo_len(&dccpw.fifo) != 0);
 	if (error)
 		goto out_free;
 
-	cnt = kfifo_get(dccpw.fifo, tbuf, len);
+	cnt = kfifo_get(&dccpw.fifo, tbuf, len);
 	error = copy_to_user(buf, tbuf, cnt) ? -EFAULT : 0;
 
 out_free:
@@ -156,10 +156,8 @@ static __init int dccpprobe_init(void)
 
 	init_waitqueue_head(&dccpw.wait);
 	spin_lock_init(&dccpw.lock);
-	dccpw.fifo = kfifo_alloc(bufsize, GFP_KERNEL, &dccpw.lock);
-	if (IS_ERR(dccpw.fifo))
-		return PTR_ERR(dccpw.fifo);
-
+	if (kfifo_alloc(&dccpw.fifo, bufsize, GFP_KERNEL, &dccpw.lock))
+		return ret;
 	if (!proc_net_fops_create(&init_net, procname, S_IRUSR, &dccpprobe_fops))
 		goto err0;
 
@@ -172,14 +170,14 @@ static __init int dccpprobe_init(void)
 err1:
 	proc_net_remove(&init_net, procname);
 err0:
-	kfifo_free(dccpw.fifo);
+	kfifo_free(&dccpw.fifo);
 	return ret;
 }
 module_init(dccpprobe_init);
 
 static __exit void dccpprobe_exit(void)
 {
-	kfifo_free(dccpw.fifo);
+	kfifo_free(&dccpw.fifo);
 	proc_net_remove(&init_net, procname);
 	unregister_jprobe(&dccp_send_probe);