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/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 @@
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_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 @@
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_queue {
void *pool;
void *items;
- struct kfifo *queue;
+ struct kfifo queue;
spinlock_t lock;
};