dm-snap-transient.c

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/*
 * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
 * Copyright (C) 2006-2008 Red Hat GmbH
 *
 * This file is released under the GPL.
 */

#include "dm-exception-store.h"

#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/vmalloc.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/dm-io.h>

#define DM_MSG_PREFIX "transient snapshot"

/*-----------------------------------------------------------------
 * Implementation of the store for non-persistent snapshots.
 *---------------------------------------------------------------*/
struct transient_c {
    sector_t next_free;
};

static void transient_dtr(struct dm_exception_store *store)
{
    kfree(store->context);
}

static int transient_read_metadata(struct dm_exception_store *store,
                   int (*callback)(void *callback_context,
                           chunk_t old, chunk_t new),
                   void *callback_context)
{
    return 0;
}

static int transient_prepare_exception(struct dm_exception_store *store,
                       struct dm_exception *e)
{
    struct transient_c *tc = store->context;
    sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);

    if (size < (tc->next_free + store->chunk_size))
        return -1;

    e->new_chunk = sector_to_chunk(store, tc->next_free);
    tc->next_free += store->chunk_size;

    return 0;
}

static void transient_commit_exception(struct dm_exception_store *store,
                       struct dm_exception *e,
                       void (*callback) (void *, int success),
                       void *callback_context)
{
    /* Just succeed */
    callback(callback_context, 1);
}

static void transient_usage(struct dm_exception_store *store,
                sector_t *total_sectors,
                sector_t *sectors_allocated,
                sector_t *metadata_sectors)
{
    *sectors_allocated = ((struct transient_c *) store->context)->next_free;
    *total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
    *metadata_sectors = 0;
}

static int transient_ctr(struct dm_exception_store *store,
             unsigned argc, char **argv)
{
    struct transient_c *tc;

    tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
    if (!tc)
        return -ENOMEM;

    tc->next_free = 0;
    store->context = tc;

    return 0;
}

static unsigned transient_status(struct dm_exception_store *store,
                 status_type_t status, char *result,
                 unsigned maxlen)
{
    unsigned sz = 0;

    switch (status) {
    case STATUSTYPE_INFO:
        break;
    case STATUSTYPE_TABLE:
        DMEMIT(" N %llu", (unsigned long long)store->chunk_size);
    }

    return sz;
}

static struct dm_exception_store_type _transient_type = {
    .name = "transient",
    .module = THIS_MODULE,
    .ctr = transient_ctr,
    .dtr = transient_dtr,
    .read_metadata = transient_read_metadata,
    .prepare_exception = transient_prepare_exception,
    .commit_exception = transient_commit_exception,
    .usage = transient_usage,
    .status = transient_status,
};

static struct dm_exception_store_type _transient_compat_type = {
    .name = "N",
    .module = THIS_MODULE,
    .ctr = transient_ctr,
    .dtr = transient_dtr,
    .read_metadata = transient_read_metadata,
    .prepare_exception = transient_prepare_exception,
    .commit_exception = transient_commit_exception,
    .usage = transient_usage,
    .status = transient_status,
};

int dm_transient_snapshot_init(void)
{
    int r;

    r = dm_exception_store_type_register(&_transient_type);
    if (r) {
        DMWARN("Unable to register transient exception store type");
        return r;
    }

    r = dm_exception_store_type_register(&_transient_compat_type);
    if (r) {
        DMWARN("Unable to register old-style transient "
               "exception store type");
        dm_exception_store_type_unregister(&_transient_type);
        return r;
    }

    return r;
}

void dm_transient_snapshot_exit(void)
{
    dm_exception_store_type_unregister(&_transient_type);
    dm_exception_store_type_unregister(&_transient_compat_type);
}