4546548789
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>
78 lines
1.5 KiB
C
78 lines
1.5 KiB
C
#ifndef __LIBSRP_H__
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#define __LIBSRP_H__
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#include <linux/list.h>
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#include <scsi/scsi_cmnd.h>
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#include <scsi/scsi_host.h>
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#include <scsi/srp.h>
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enum iue_flags {
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V_DIOVER,
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V_WRITE,
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V_LINKED,
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V_FLYING,
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};
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struct srp_buf {
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dma_addr_t dma;
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void *buf;
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};
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struct srp_queue {
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void *pool;
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void *items;
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struct kfifo queue;
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spinlock_t lock;
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};
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struct srp_target {
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struct Scsi_Host *shost;
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struct device *dev;
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spinlock_t lock;
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struct list_head cmd_queue;
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size_t srp_iu_size;
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struct srp_queue iu_queue;
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size_t rx_ring_size;
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struct srp_buf **rx_ring;
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void *ldata;
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};
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struct iu_entry {
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struct srp_target *target;
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struct list_head ilist;
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dma_addr_t remote_token;
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unsigned long flags;
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struct srp_buf *sbuf;
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};
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typedef int (srp_rdma_t)(struct scsi_cmnd *, struct scatterlist *, int,
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struct srp_direct_buf *, int,
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enum dma_data_direction, unsigned int);
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extern int srp_target_alloc(struct srp_target *, struct device *, size_t, size_t);
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extern void srp_target_free(struct srp_target *);
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extern struct iu_entry *srp_iu_get(struct srp_target *);
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extern void srp_iu_put(struct iu_entry *);
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extern int srp_cmd_queue(struct Scsi_Host *, struct srp_cmd *, void *, u64, u64);
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extern int srp_transfer_data(struct scsi_cmnd *, struct srp_cmd *,
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srp_rdma_t, int, int);
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static inline struct srp_target *host_to_srp_target(struct Scsi_Host *host)
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{
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return (struct srp_target *) host->hostdata;
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}
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static inline int srp_cmd_direction(struct srp_cmd *cmd)
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{
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return (cmd->buf_fmt >> 4) ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
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}
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#endif
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