include/linux/iobuf.h

   1 /*
   2  * iobuf.h
   3  *
   4  * Defines the structures used to track abstract kernel-space io buffers.
   5  *
   6  */
   7
   8 #ifndef __LINUX_IOBUF_H
   9 #define __LINUX_IOBUF_H
  10
  11 #include <linux/mm.h>
  12 #include <linux/init.h>
  13 #include <linux/wait.h>
  14 #include <asm/atomic.h>
  15
  16 /*
  17  * The kiobuf structure describes a physical set of pages reserved
  18  * locked for IO.  The reference counts on each page will have been
  19  * incremented, and the flags field will indicate whether or not we have
  20  * pre-locked all of the pages for IO.
  21  *
  22  * kiobufs may be passed in arrays to form a kiovec, but we must
  23  * preserve the property that no page is present more than once over the
  24  * entire iovec.
  25  */
  26
  27 #define KIO_MAX_ATOMIC_IO       64 /* in kb */
  28 #define KIO_MAX_ATOMIC_BYTES    (64 * 1024)
  29 #define KIO_STATIC_PAGES        (KIO_MAX_ATOMIC_IO / (PAGE_SIZE >> 10) + 1)
  30 #define KIO_MAX_SECTORS         (KIO_MAX_ATOMIC_IO * 2)
  31
  32 /* The main kiobuf struct used for all our IO! */
  33
  34 struct kiobuf
  35 {
  36         int             nr_pages;       /* Pages actually referenced */
  37         int             array_len;      /* Space in the allocated lists */
  38         int             offset;         /* Offset to start of valid data */
  39         int             length;         /* Number of valid bytes of data */
  40
  41         /* Keep separate track of the physical addresses and page
  42          * structs involved.  If we do IO to a memory-mapped device
  43          * region, there won't necessarily be page structs defined for
  44          * every address. */
  45
  46         struct page **  maplist;
  47
  48         unsigned int    locked : 1;     /* If set, pages has been locked */
  49
  50         /* Always embed enough struct pages for 64k of IO */
  51         struct page *   map_array[KIO_STATIC_PAGES];
  52
  53         /* Dynamic state for IO completion: */
  54         atomic_t        io_count;       /* IOs still in progress */
  55         int             errno;          /* Status of completed IO */
  56         void            (*end_io) (struct kiobuf *); /* Completion callback */
  57         wait_queue_head_t wait_queue;
  58 };
  59
  60
  61 /* mm/memory.c */
  62
  63 int     map_user_kiobuf(int rw, struct kiobuf *, unsigned long va, size_t len);
  64 void    unmap_kiobuf(struct kiobuf *iobuf);
  65 int     lock_kiovec(int nr, struct kiobuf *iovec[], int wait);
  66 int     unlock_kiovec(int nr, struct kiobuf *iovec[]);
  67
  68 /* fs/iobuf.c */
  69
  70 void __init kiobuf_setup(void);
  71 void    kiobuf_init(struct kiobuf *);
  72 void    end_kio_request(struct kiobuf *, int);
  73 void    simple_wakeup_kiobuf(struct kiobuf *);
  74 int     alloc_kiovec(int nr, struct kiobuf **);
  75 void    free_kiovec(int nr, struct kiobuf **);
  76 int     expand_kiobuf(struct kiobuf *, int);
  77 void    kiobuf_wait_for_io(struct kiobuf *);
  78
  79 /* fs/buffer.c */
  80
  81 int     brw_kiovec(int rw, int nr, struct kiobuf *iovec[],
  82                    kdev_t dev, unsigned long b[], int size);
  83
  84 #endif /* __LINUX_IOBUF_H */