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/net/dccp/probe.c b/net/dccp/probe.c
index dc32842..6230ceb 100644
--- a/net/dccp/probe.c
+++ b/net/dccp/probe.c
@@ -43,7 +43,7 @@
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 @@
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 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 @@
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 @@
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 @@
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);