dm-io.h

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/*
 * 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;

    unsigned offset;

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

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(void);
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 */