linux/include/linux/dm-io.h
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   1/*
   2 * Copyright (C) 2003 Sistina Software
   3 * Copyright (C) 2004 - 2008 Red Hat, Inc. All rights reserved.
   4 *
   5 * Device-Mapper low-level I/O.
   6 *
   7 * This file is released under the GPL.
   8 */
   9
  10#ifndef _LINUX_DM_IO_H
  11#define _LINUX_DM_IO_H
  12
  13#ifdef __KERNEL__
  14
  15#include <linux/types.h>
  16
  17struct dm_io_region {
  18        struct block_device *bdev;
  19        sector_t sector;
  20        sector_t count;         /* If this is zero the region is ignored. */
  21};
  22
  23struct page_list {
  24        struct page_list *next;
  25        struct page *page;
  26};
  27
  28typedef void (*io_notify_fn)(unsigned long error, void *context);
  29
  30enum dm_io_mem_type {
  31        DM_IO_PAGE_LIST,/* Page list */
  32        DM_IO_BVEC,     /* Bio vector */
  33        DM_IO_VMA,      /* Virtual memory area */
  34        DM_IO_KMEM,     /* Kernel memory */
  35};
  36
  37struct dm_io_memory {
  38        enum dm_io_mem_type type;
  39
  40        unsigned offset;
  41
  42        union {
  43                struct page_list *pl;
  44                struct bio_vec *bvec;
  45                void *vma;
  46                void *addr;
  47        } ptr;
  48};
  49
  50struct dm_io_notify {
  51        io_notify_fn fn;        /* Callback for asynchronous requests */
  52        void *context;          /* Passed to callback */
  53};
  54
  55/*
  56 * IO request structure
  57 */
  58struct dm_io_client;
  59struct dm_io_request {
  60        int bi_rw;                      /* READ|WRITE - not READA */
  61        struct dm_io_memory mem;        /* Memory to use for io */
  62        struct dm_io_notify notify;     /* Synchronous if notify.fn is NULL */
  63        struct dm_io_client *client;    /* Client memory handler */
  64};
  65
  66/*
  67 * For async io calls, users can alternatively use the dm_io() function below
  68 * and dm_io_client_create() to create private mempools for the client.
  69 *
  70 * Create/destroy may block.
  71 */
  72struct dm_io_client *dm_io_client_create(void);
  73void dm_io_client_destroy(struct dm_io_client *client);
  74
  75/*
  76 * IO interface using private per-client pools.
  77 * Each bit in the optional 'sync_error_bits' bitset indicates whether an
  78 * error occurred doing io to the corresponding region.
  79 */
  80int dm_io(struct dm_io_request *io_req, unsigned num_regions,
  81          struct dm_io_region *region, unsigned long *sync_error_bits);
  82
  83#endif  /* __KERNEL__ */
  84#endif  /* _LINUX_DM_IO_H */
  85
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