// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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, int valid,
                                       void (*callback)(void *, int success),
                                       void *callback_context)
{
        /* Just succeed */
        callback(callback_context, valid);
}

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, char *options)
{
        struct transient_c *tc;

        tc = kmalloc_obj(struct transient_c);
        if (!tc)
                return -ENOMEM;

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

        return 0;
}

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

        switch (status) {
        case STATUSTYPE_INFO:
                break;
        case STATUSTYPE_TABLE:
                DMEMIT(" N %llu", (unsigned long long)store->chunk_size);
                break;
        case STATUSTYPE_IMA:
                *result = '\0';
                break;
        }

        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);
}