/*
 * Copyright (C) 2008 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License v2 as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/sched.h>
#include <linux/pagemap.h>
#include <linux/bio.h>
#include <linux/lzo.h>
#include "compression.h"

#define LZO_LEN 4

struct workspace {
        void *mem;
        void *buf;      /* where decompressed data goes */
        void *cbuf;     /* where compressed data goes */
        struct list_head list;
};

static void lzo_free_workspace(struct list_head *ws)
{
        struct workspace *workspace = list_entry(ws, struct workspace, list);

        vfree(workspace->buf);
        vfree(workspace->cbuf);
        vfree(workspace->mem);
        kfree(workspace);
}

static struct list_head *lzo_alloc_workspace(void)
{
        struct workspace *workspace;

        workspace = kzalloc(sizeof(*workspace), GFP_NOFS);
        if (!workspace)
                return ERR_PTR(-ENOMEM);

        workspace->mem = vmalloc(LZO1X_MEM_COMPRESS);
        workspace->buf = vmalloc(lzo1x_worst_compress(PAGE_CACHE_SIZE));
        workspace->cbuf = vmalloc(lzo1x_worst_compress(PAGE_CACHE_SIZE));
        if (!workspace->mem || !workspace->buf || !workspace->cbuf)
                goto fail;

        INIT_LIST_HEAD(&workspace->list);

        return &workspace->list;
fail:
        lzo_free_workspace(&workspace->list);
        return ERR_PTR(-ENOMEM);
}

static inline void write_compress_length(char *buf, size_t len)
{
        __le32 dlen;

        dlen = cpu_to_le32(len);
        memcpy(buf, &dlen, LZO_LEN);
}

static inline size_t read_compress_length(char *buf)
{
        __le32 dlen;

        memcpy(&dlen, buf, LZO_LEN);
        return le32_to_cpu(dlen);
}

static int lzo_compress_pages(struct list_head *ws,
                              struct address_space *mapping,
                              u64 start, unsigned long len,
                              struct page **pages,
                              unsigned long nr_dest_pages,
                              unsigned long *out_pages,
                              unsigned long *total_in,
                              unsigned long *total_out,
                              unsigned long max_out)
{
        struct workspace *workspace = list_entry(ws, struct workspace, list);
        int ret = 0;
        char *data_in;
        char *cpage_out;
        int nr_pages = 0;
        struct page *in_page = NULL;
        struct page *out_page = NULL;
        unsigned long bytes_left;

        size_t in_len;
        size_t out_len;
        char *buf;
        unsigned long tot_in = 0;
        unsigned long tot_out = 0;
        unsigned long pg_bytes_left;
        unsigned long out_offset;
        unsigned long bytes;

        *out_pages = 0;
        *total_out = 0;
        *total_in = 0;

        in_page = find_get_page(mapping, start >> PAGE_CACHE_SHIFT);
        data_in = kmap(in_page);

        /*
         * store the size of all chunks of compressed data in
         * the first 4 bytes
         */
        out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
        if (out_page == NULL) {
                ret = -ENOMEM;
                goto out;
        }
        cpage_out = kmap(out_page);
        out_offset = LZO_LEN;
        tot_out = LZO_LEN;
        pages[0] = out_page;
        nr_pages = 1;
        pg_bytes_left = PAGE_CACHE_SIZE - LZO_LEN;

        /* compress at most one page of data each time */
        in_len = min(len, PAGE_CACHE_SIZE);
        while (tot_in < len) {
                ret = lzo1x_1_compress(data_in, in_len, workspace->cbuf,
                                       &out_len, workspace->mem);
                if (ret != LZO_E_OK) {
                        printk(KERN_DEBUG "BTRFS: deflate in loop returned %d\n",
                               ret);
                        ret = -EIO;
                        goto out;
                }

                /* store the size of this chunk of compressed data */
                write_compress_length(cpage_out + out_offset, out_len);
                tot_out += LZO_LEN;
                out_offset += LZO_LEN;
                pg_bytes_left -= LZO_LEN;

                tot_in += in_len;
                tot_out += out_len;

                /* copy bytes from the working buffer into the pages */
                buf = workspace->cbuf;
                while (out_len) {
                        bytes = min_t(unsigned long, pg_bytes_left, out_len);

                        memcpy(cpage_out + out_offset, buf, bytes);

                        out_len -= bytes;
                        pg_bytes_left -= bytes;
                        buf += bytes;
                        out_offset += bytes;

                        /*
                         * we need another page for writing out.
                         *
                         * Note if there's less than 4 bytes left, we just
                         * skip to a new page.
                         */
                        if ((out_len == 0 && pg_bytes_left < LZO_LEN) ||
                            pg_bytes_left == 0) {
                                if (pg_bytes_left) {
                                        memset(cpage_out + out_offset, 0,
                                               pg_bytes_left);
                                        tot_out += pg_bytes_left;
                                }

                                /* we're done, don't allocate new page */
                                if (out_len == 0 && tot_in >= len)
                                        break;

                                kunmap(out_page);
                                if (nr_pages == nr_dest_pages) {
                                        out_page = NULL;
                                        ret = -E2BIG;
                                        goto out;
                                }

                                out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
                                if (out_page == NULL) {
                                        ret = -ENOMEM;
                                        goto out;
                                }
                                cpage_out = kmap(out_page);
                                pages[nr_pages++] = out_page;

                                pg_bytes_left = PAGE_CACHE_SIZE;
                                out_offset = 0;
                        }
                }

                /* we're making it bigger, give up */
                if (tot_in > 8192 && tot_in < tot_out) {
                        ret = -E2BIG;
                        goto out;
                }

                /* we're all done */
                if (tot_in >= len)
                        break;

                if (tot_out > max_out)
                        break;

                bytes_left = len - tot_in;
                kunmap(in_page);
                page_cache_release(in_page);

                start += PAGE_CACHE_SIZE;
                in_page = find_get_page(mapping, start >> PAGE_CACHE_SHIFT);
                data_in = kmap(in_page);
                in_len = min(bytes_left, PAGE_CACHE_SIZE);
        }

        if (tot_out > tot_in)
                goto out;

        /* store the size of all chunks of compressed data */
        cpage_out = kmap(pages[0]);
        write_compress_length(cpage_out, tot_out);

        kunmap(pages[0]);

        ret = 0;
        *total_out = tot_out;
        *total_in = tot_in;
out:
        *out_pages = nr_pages;
        if (out_page)
                kunmap(out_page);

        if (in_page) {
                kunmap(in_page);
                page_cache_release(in_page);
        }

        return ret;
}

static int lzo_decompress_biovec(struct list_head *ws,
                                 struct page **pages_in,
                                 u64 disk_start,
                                 struct bio_vec *bvec,
                                 int vcnt,
                                 size_t srclen)
{
        struct workspace *workspace = list_entry(ws, struct workspace, list);
        int ret = 0, ret2;
        char *data_in;
        unsigned long page_in_index = 0;
        unsigned long page_out_index = 0;
        unsigned long total_pages_in = DIV_ROUND_UP(srclen, PAGE_CACHE_SIZE);
        unsigned long buf_start;
        unsigned long buf_offset = 0;
        unsigned long bytes;
        unsigned long working_bytes;
        unsigned long pg_offset;

        size_t in_len;
        size_t out_len;
        unsigned long in_offset;
        unsigned long in_page_bytes_left;
        unsigned long tot_in;
        unsigned long tot_out;
        unsigned long tot_len;
        char *buf;
        bool may_late_unmap, need_unmap;

        data_in = kmap(pages_in[0]);
        tot_len = read_compress_length(data_in);

        tot_in = LZO_LEN;
        in_offset = LZO_LEN;
        tot_len = min_t(size_t, srclen, tot_len);
        in_page_bytes_left = PAGE_CACHE_SIZE - LZO_LEN;

        tot_out = 0;
        pg_offset = 0;

        while (tot_in < tot_len) {
                in_len = read_compress_length(data_in + in_offset);
                in_page_bytes_left -= LZO_LEN;
                in_offset += LZO_LEN;
                tot_in += LZO_LEN;

                tot_in += in_len;
                working_bytes = in_len;
                may_late_unmap = need_unmap = false;

                /* fast path: avoid using the working buffer */
                if (in_page_bytes_left >= in_len) {
                        buf = data_in + in_offset;
                        bytes = in_len;
                        may_late_unmap = true;
                        goto cont;
                }

                /* copy bytes from the pages into the working buffer */
                buf = workspace->cbuf;
                buf_offset = 0;
                while (working_bytes) {
                        bytes = min(working_bytes, in_page_bytes_left);

                        memcpy(buf + buf_offset, data_in + in_offset, bytes);
                        buf_offset += bytes;
cont:
                        working_bytes -= bytes;
                        in_page_bytes_left -= bytes;
                        in_offset += bytes;

                        /* check if we need to pick another page */
                        if ((working_bytes == 0 && in_page_bytes_left < LZO_LEN)
                            || in_page_bytes_left == 0) {
                                tot_in += in_page_bytes_left;

                                if (working_bytes == 0 && tot_in >= tot_len)
                                        break;

                                if (page_in_index + 1 >= total_pages_in) {
                                        ret = -EIO;
                                        goto done;
                                }

                                if (may_late_unmap)
                                        need_unmap = true;
                                else
                                        kunmap(pages_in[page_in_index]);

                                data_in = kmap(pages_in[++page_in_index]);

                                in_page_bytes_left = PAGE_CACHE_SIZE;
                                in_offset = 0;
                        }
                }

                out_len = lzo1x_worst_compress(PAGE_CACHE_SIZE);
                ret = lzo1x_decompress_safe(buf, in_len, workspace->buf,
                                            &out_len);
                if (need_unmap)
                        kunmap(pages_in[page_in_index - 1]);
                if (ret != LZO_E_OK) {
                        printk(KERN_WARNING "BTRFS: decompress failed\n");
                        ret = -EIO;
                        break;
                }

                buf_start = tot_out;
                tot_out += out_len;

                ret2 = btrfs_decompress_buf2page(workspace->buf, buf_start,
                                                 tot_out, disk_start,
                                                 bvec, vcnt,
                                                 &page_out_index, &pg_offset);
                if (ret2 == 0)
                        break;
        }
done:
        kunmap(pages_in[page_in_index]);
        if (!ret)
                btrfs_clear_biovec_end(bvec, vcnt, page_out_index, pg_offset);
        return ret;
}

static int lzo_decompress(struct list_head *ws, unsigned char *data_in,
                          struct page *dest_page,
                          unsigned long start_byte,
                          size_t srclen, size_t destlen)
{
        struct workspace *workspace = list_entry(ws, struct workspace, list);
        size_t in_len;
        size_t out_len;
        size_t tot_len;
        int ret = 0;
        char *kaddr;
        unsigned long bytes;

        BUG_ON(srclen < LZO_LEN);

        tot_len = read_compress_length(data_in);
        data_in += LZO_LEN;

        in_len = read_compress_length(data_in);
        data_in += LZO_LEN;

        out_len = PAGE_CACHE_SIZE;
        ret = lzo1x_decompress_safe(data_in, in_len, workspace->buf, &out_len);
        if (ret != LZO_E_OK) {
                printk(KERN_WARNING "BTRFS: decompress failed!\n");
                ret = -EIO;
                goto out;
        }

        if (out_len < start_byte) {
                ret = -EIO;
                goto out;
        }

        /*
         * the caller is already checking against PAGE_SIZE, but lets
         * move this check closer to the memcpy/memset
         */
        destlen = min_t(unsigned long, destlen, PAGE_SIZE);
        bytes = min_t(unsigned long, destlen, out_len - start_byte);

        kaddr = kmap_atomic(dest_page);
        memcpy(kaddr, workspace->buf + start_byte, bytes);

        /*
         * btrfs_getblock is doing a zero on the tail of the page too,
         * but this will cover anything missing from the decompressed
         * data.
         */
        if (bytes < destlen)
                memset(kaddr+bytes, 0, destlen-bytes);
        kunmap_atomic(kaddr);
out:
        return ret;
}

const struct btrfs_compress_op btrfs_lzo_compress = {
        .alloc_workspace        = lzo_alloc_workspace,
        .free_workspace         = lzo_free_workspace,
        .compress_pages         = lzo_compress_pages,
        .decompress_biovec      = lzo_decompress_biovec,
        .decompress             = lzo_decompress,
};