/*
 * Copyright (C) 2014 Sergey Senozhatsky.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/cpu.h>
#include <linux/crypto.h>

#include "zcomp.h"

static const char * const backends[] = {
        "lzo",
#if IS_ENABLED(CONFIG_CRYPTO_LZ4)
        "lz4",
#endif
#if IS_ENABLED(CONFIG_CRYPTO_DEFLATE)
        "deflate",
#endif
#if IS_ENABLED(CONFIG_CRYPTO_LZ4HC)
        "lz4hc",
#endif
#if IS_ENABLED(CONFIG_CRYPTO_842)
        "842",
#endif
        NULL
};

static void zcomp_strm_free(struct zcomp_strm *zstrm)
{
        if (!IS_ERR_OR_NULL(zstrm->tfm))
                crypto_free_comp(zstrm->tfm);
        free_pages((unsigned long)zstrm->buffer, 1);
        kfree(zstrm);
}

/*
 * allocate new zcomp_strm structure with ->tfm initialized by
 * backend, return NULL on error
 */
static struct zcomp_strm *zcomp_strm_alloc(struct zcomp *comp)
{
        struct zcomp_strm *zstrm = kmalloc(sizeof(*zstrm), GFP_KERNEL);
        if (!zstrm)
                return NULL;

        zstrm->tfm = crypto_alloc_comp(comp->name, 0, 0);
        /*
         * allocate 2 pages. 1 for compressed data, plus 1 extra for the
         * case when compressed size is larger than the original one
         */
        zstrm->buffer = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
        if (IS_ERR_OR_NULL(zstrm->tfm) || !zstrm->buffer) {
                zcomp_strm_free(zstrm);
                zstrm = NULL;
        }
        return zstrm;
}

bool zcomp_available_algorithm(const char *comp)
{
        int i;

        i = __sysfs_match_string(backends, -1, comp);
        if (i >= 0)
                return true;

        /*
         * Crypto does not ignore a trailing new line symbol,
         * so make sure you don't supply a string containing
         * one.
         * This also means that we permit zcomp initialisation
         * with any compressing algorithm known to crypto api.
         */
        return crypto_has_comp(comp, 0, 0) == 1;
}

/* show available compressors */
ssize_t zcomp_available_show(const char *comp, char *buf)
{
        bool known_algorithm = false;
        ssize_t sz = 0;
        int i = 0;

        for (; backends[i]; i++) {
                if (!strcmp(comp, backends[i])) {
                        known_algorithm = true;
                        sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
                                        "[%s] ", backends[i]);
                } else {
                        sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
                                        "%s ", backends[i]);
                }
        }

        /*
         * Out-of-tree module known to crypto api or a missing
         * entry in `backends'.
         */
        if (!known_algorithm && crypto_has_comp(comp, 0, 0) == 1)
                sz += scnprintf(buf + sz, PAGE_SIZE - sz - 2,
                                "[%s] ", comp);

        sz += scnprintf(buf + sz, PAGE_SIZE - sz, "\n");
        return sz;
}

struct zcomp_strm *zcomp_stream_get(struct zcomp *comp)
{
        return *get_cpu_ptr(comp->stream);
}

void zcomp_stream_put(struct zcomp *comp)
{
        put_cpu_ptr(comp->stream);
}

int zcomp_compress(struct zcomp_strm *zstrm,
                const void *src, unsigned int *dst_len)
{
        /*
         * Our dst memory (zstrm->buffer) is always `2 * PAGE_SIZE' sized
         * because sometimes we can endup having a bigger compressed data
         * due to various reasons: for example compression algorithms tend
         * to add some padding to the compressed buffer. Speaking of padding,
         * comp algorithm `842' pads the compressed length to multiple of 8
         * and returns -ENOSP when the dst memory is not big enough, which
         * is not something that ZRAM wants to see. We can handle the
         * `compressed_size > PAGE_SIZE' case easily in ZRAM, but when we
         * receive -ERRNO from the compressing backend we can't help it
         * anymore. To make `842' happy we need to tell the exact size of
         * the dst buffer, zram_drv will take care of the fact that
         * compressed buffer is too big.
         */
        *dst_len = PAGE_SIZE * 2;

        return crypto_comp_compress(zstrm->tfm,
                        src, PAGE_SIZE,
                        zstrm->buffer, dst_len);
}

int zcomp_decompress(struct zcomp_strm *zstrm,
                const void *src, unsigned int src_len, void *dst)
{
        unsigned int dst_len = PAGE_SIZE;

        return crypto_comp_decompress(zstrm->tfm,
                        src, src_len,
                        dst, &dst_len);
}

int zcomp_cpu_up_prepare(unsigned int cpu, struct hlist_node *node)
{
        struct zcomp *comp = hlist_entry(node, struct zcomp, node);
        struct zcomp_strm *zstrm;

        if (WARN_ON(*per_cpu_ptr(comp->stream, cpu)))
                return 0;

        zstrm = zcomp_strm_alloc(comp);
        if (IS_ERR_OR_NULL(zstrm)) {
                pr_err("Can't allocate a compression stream\n");
                return -ENOMEM;
        }
        *per_cpu_ptr(comp->stream, cpu) = zstrm;
        return 0;
}

int zcomp_cpu_dead(unsigned int cpu, struct hlist_node *node)
{
        struct zcomp *comp = hlist_entry(node, struct zcomp, node);
        struct zcomp_strm *zstrm;

        zstrm = *per_cpu_ptr(comp->stream, cpu);
        if (!IS_ERR_OR_NULL(zstrm))
                zcomp_strm_free(zstrm);
        *per_cpu_ptr(comp->stream, cpu) = NULL;
        return 0;
}

static int zcomp_init(struct zcomp *comp)
{
        int ret;

        comp->stream = alloc_percpu(struct zcomp_strm *);
        if (!comp->stream)
                return -ENOMEM;

        ret = cpuhp_state_add_instance(CPUHP_ZCOMP_PREPARE, &comp->node);
        if (ret < 0)
                goto cleanup;
        return 0;

cleanup:
        free_percpu(comp->stream);
        return ret;
}

void zcomp_destroy(struct zcomp *comp)
{
        cpuhp_state_remove_instance(CPUHP_ZCOMP_PREPARE, &comp->node);
        free_percpu(comp->stream);
        kfree(comp);
}

/*
 * search available compressors for requested algorithm.
 * allocate new zcomp and initialize it. return compressing
 * backend pointer or ERR_PTR if things went bad. ERR_PTR(-EINVAL)
 * if requested algorithm is not supported, ERR_PTR(-ENOMEM) in
 * case of allocation error, or any other error potentially
 * returned by zcomp_init().
 */
struct zcomp *zcomp_create(const char *compress)
{
        struct zcomp *comp;
        int error;

        if (!zcomp_available_algorithm(compress))
                return ERR_PTR(-EINVAL);

        comp = kzalloc(sizeof(struct zcomp), GFP_KERNEL);
        if (!comp)
                return ERR_PTR(-ENOMEM);

        comp->name = compress;
        error = zcomp_init(comp);
        if (error) {
                kfree(comp);
                return ERR_PTR(error);
        }
        return comp;
}