root/include/linux/dm-io.h

INCLUDED FROM

/*
 * Copyright (C) 2003 Sistina Software
 * Copyright (C) 2004 - 2008 Red Hat, Inc. All rights reserved.
 *
 * Device-Mapper low-level I/O.
 *
 * This file is released under the GPL.
 */

#ifndef _LINUX_DM_IO_H
#define _LINUX_DM_IO_H

#ifdef __KERNEL__

#include <linux/types.h>

struct dm_io_region {
        struct block_device *bdev;
        sector_t sector;
        sector_t count;         /* If this is zero the region is ignored. */
};

struct page_list {
        struct page_list *next;
        struct page *page;
};

typedef void (*io_notify_fn)(unsigned long error, void *context);

enum dm_io_mem_type {
        DM_IO_PAGE_LIST,/* Page list */
        DM_IO_BVEC,     /* Bio vector */
        DM_IO_VMA,      /* Virtual memory area */
        DM_IO_KMEM,     /* Kernel memory */
};

struct dm_io_memory {
        enum dm_io_mem_type type;

        union {
                struct page_list *pl;
                struct bio_vec *bvec;
                void *vma;
                void *addr;
        } ptr;

        unsigned offset;
};

struct dm_io_notify {
        io_notify_fn fn;        /* Callback for asynchronous requests */
        void *context;          /* Passed to callback */
};

/*
 * IO request structure
 */
struct dm_io_client;
struct dm_io_request {
        int bi_rw;                      /* READ|WRITE - not READA */
        struct dm_io_memory mem;        /* Memory to use for io */
        struct dm_io_notify notify;     /* Synchronous if notify.fn is NULL */
        struct dm_io_client *client;    /* Client memory handler */
};

/*
 * For async io calls, users can alternatively use the dm_io() function below
 * and dm_io_client_create() to create private mempools for the client.
 *
 * Create/destroy may block.
 */
struct dm_io_client *dm_io_client_create(unsigned num_pages);
int dm_io_client_resize(unsigned num_pages, struct dm_io_client *client);
void dm_io_client_destroy(struct dm_io_client *client);

/*
 * IO interface using private per-client pools.
 * Each bit in the optional 'sync_error_bits' bitset indicates whether an
 * error occurred doing io to the corresponding region.
 */
int dm_io(struct dm_io_request *io_req, unsigned num_regions,
          struct dm_io_region *region, unsigned long *sync_error_bits);

#endif  /* __KERNEL__ */
#endif  /* _LINUX_DM_IO_H */