include/linux/dm-io.h

   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
  17 struct 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
  23 struct page_list {
  24         struct page_list *next;
  25         struct page *page;
  26 };
  27
  28 typedef void (*io_notify_fn)(unsigned long error, void *context);
  29
  30 enum 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
  37 struct dm_io_memory {
  38         enum dm_io_mem_type type;
  39
  40         union {
  41                 struct page_list *pl;
  42                 struct bio_vec *bvec;
  43                 void *vma;
  44                 void *addr;
  45         } ptr;
  46
  47         unsigned offset;
  48 };
  49
  50 struct 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  */
  58 struct dm_io_client;
  59 struct 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  */
  72 struct dm_io_client *dm_io_client_create(unsigned num_pages);
  73 int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client);
  74 void dm_io_client_destroy(struct dm_io_client *client);
  75
  76 /*
  77  * IO interface using private per-client pools.
  78  * Each bit in the optional 'sync_error_bits' bitset indicates whether an
  79  * error occurred doing io to the corresponding region.
  80  */
  81 int dm_io(struct dm_io_request *io_req, unsigned num_regions,
  82           struct dm_io_region *region, unsigned long *sync_error_bits);
  83
  84 #endif  /* __KERNEL__ */
  85 #endif  /* _LINUX_DM_IO_H */