/*
 * 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.
 *
 * Based on jffs2 zlib code:
 * Copyright © 2001-2007 Red Hat, Inc.
 * Created by David Woodhouse <dwmw2@infradead.org>
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/zlib.h>
#include <linux/zutil.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 "compression.h"

struct workspace {
        z_stream strm;
        char *buf;
        struct list_head list;
};

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

        vfree(workspace->strm.workspace);
        kfree(workspace->buf);
        kfree(workspace);
}

static struct list_head *zlib_alloc_workspace(void)
{
        struct workspace *workspace;
        int workspacesize;

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

        workspacesize = max(zlib_deflate_workspacesize(MAX_WBITS, MAX_MEM_LEVEL),
                        zlib_inflate_workspacesize());
        workspace->strm.workspace = vmalloc(workspacesize);
        workspace->buf = kmalloc(PAGE_CACHE_SIZE, GFP_NOFS);
        if (!workspace->strm.workspace || !workspace->buf)
                goto fail;

        INIT_LIST_HEAD(&workspace->list);

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

static int zlib_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;
        char *data_in;
        char *cpage_out;
        int nr_pages = 0;
        struct page *in_page = NULL;
        struct page *out_page = NULL;
        unsigned long bytes_left;

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

        if (Z_OK != zlib_deflateInit(&workspace->strm, 3)) {
                printk(KERN_WARNING "BTRFS: deflateInit failed\n");
                ret = -EIO;
                goto out;
        }

        workspace->strm.total_in = 0;
        workspace->strm.total_out = 0;

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

        out_page = alloc_page(GFP_NOFS | __GFP_HIGHMEM);
        if (out_page == NULL) {
                ret = -ENOMEM;
                goto out;
        }
        cpage_out = kmap(out_page);
        pages[0] = out_page;
        nr_pages = 1;

        workspace->strm.next_in = data_in;
        workspace->strm.next_out = cpage_out;
        workspace->strm.avail_out = PAGE_CACHE_SIZE;
        workspace->strm.avail_in = min(len, PAGE_CACHE_SIZE);

        while (workspace->strm.total_in < len) {
                ret = zlib_deflate(&workspace->strm, Z_SYNC_FLUSH);
                if (ret != Z_OK) {
                        printk(KERN_DEBUG "BTRFS: deflate in loop returned %d\n",
                               ret);
                        zlib_deflateEnd(&workspace->strm);
                        ret = -EIO;
                        goto out;
                }

                /* we're making it bigger, give up */
                if (workspace->strm.total_in > 8192 &&
                    workspace->strm.total_in <
                    workspace->strm.total_out) {
                        ret = -E2BIG;
                        goto out;
                }
                /* we need another page for writing out.  Test this
                 * before the total_in so we will pull in a new page for
                 * the stream end if required
                 */
                if (workspace->strm.avail_out == 0) {
                        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;
                        nr_pages++;
                        workspace->strm.avail_out = PAGE_CACHE_SIZE;
                        workspace->strm.next_out = cpage_out;
                }
                /* we're all done */
                if (workspace->strm.total_in >= len)
                        break;

                /* we've read in a full page, get a new one */
                if (workspace->strm.avail_in == 0) {
                        if (workspace->strm.total_out > max_out)
                                break;

                        bytes_left = len - workspace->strm.total_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);
                        workspace->strm.avail_in = min(bytes_left,
                                                           PAGE_CACHE_SIZE);
                        workspace->strm.next_in = data_in;
                }
        }
        workspace->strm.avail_in = 0;
        ret = zlib_deflate(&workspace->strm, Z_FINISH);
        zlib_deflateEnd(&workspace->strm);

        if (ret != Z_STREAM_END) {
                ret = -EIO;
                goto out;
        }

        if (workspace->strm.total_out >= workspace->strm.total_in) {
                ret = -E2BIG;
                goto out;
        }

        ret = 0;
        *total_out = workspace->strm.total_out;
        *total_in = workspace->strm.total_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 zlib_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;
        int wbits = MAX_WBITS;
        char *data_in;
        size_t total_out = 0;
        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 pg_offset;

        data_in = kmap(pages_in[page_in_index]);
        workspace->strm.next_in = data_in;
        workspace->strm.avail_in = min_t(size_t, srclen, PAGE_CACHE_SIZE);
        workspace->strm.total_in = 0;

        workspace->strm.total_out = 0;
        workspace->strm.next_out = workspace->buf;
        workspace->strm.avail_out = PAGE_CACHE_SIZE;
        pg_offset = 0;

        /* If it's deflate, and it's got no preset dictionary, then
           we can tell zlib to skip the adler32 check. */
        if (srclen > 2 && !(data_in[1] & PRESET_DICT) &&
            ((data_in[0] & 0x0f) == Z_DEFLATED) &&
            !(((data_in[0]<<8) + data_in[1]) % 31)) {

                wbits = -((data_in[0] >> 4) + 8);
                workspace->strm.next_in += 2;
                workspace->strm.avail_in -= 2;
        }

        if (Z_OK != zlib_inflateInit2(&workspace->strm, wbits)) {
                printk(KERN_WARNING "BTRFS: inflateInit failed\n");
                return -EIO;
        }
        while (workspace->strm.total_in < srclen) {
                ret = zlib_inflate(&workspace->strm, Z_NO_FLUSH);
                if (ret != Z_OK && ret != Z_STREAM_END)
                        break;

                buf_start = total_out;
                total_out = workspace->strm.total_out;

                /* we didn't make progress in this inflate call, we're done */
                if (buf_start == total_out)
                        break;

                ret2 = btrfs_decompress_buf2page(workspace->buf, buf_start,
                                                 total_out, disk_start,
                                                 bvec, vcnt,
                                                 &page_out_index, &pg_offset);
                if (ret2 == 0) {
                        ret = 0;
                        goto done;
                }

                workspace->strm.next_out = workspace->buf;
                workspace->strm.avail_out = PAGE_CACHE_SIZE;

                if (workspace->strm.avail_in == 0) {
                        unsigned long tmp;
                        kunmap(pages_in[page_in_index]);
                        page_in_index++;
                        if (page_in_index >= total_pages_in) {
                                data_in = NULL;
                                break;
                        }
                        data_in = kmap(pages_in[page_in_index]);
                        workspace->strm.next_in = data_in;
                        tmp = srclen - workspace->strm.total_in;
                        workspace->strm.avail_in = min(tmp,
                                                           PAGE_CACHE_SIZE);
                }
        }
        if (ret != Z_STREAM_END)
                ret = -EIO;
        else
                ret = 0;
done:
        zlib_inflateEnd(&workspace->strm);
        if (data_in)
                kunmap(pages_in[page_in_index]);
        if (!ret)
                btrfs_clear_biovec_end(bvec, vcnt, page_out_index, pg_offset);
        return ret;
}

static int zlib_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);
        int ret = 0;
        int wbits = MAX_WBITS;
        unsigned long bytes_left;
        unsigned long total_out = 0;
        unsigned long pg_offset = 0;
        char *kaddr;

        destlen = min_t(unsigned long, destlen, PAGE_SIZE);
        bytes_left = destlen;

        workspace->strm.next_in = data_in;
        workspace->strm.avail_in = srclen;
        workspace->strm.total_in = 0;

        workspace->strm.next_out = workspace->buf;
        workspace->strm.avail_out = PAGE_CACHE_SIZE;
        workspace->strm.total_out = 0;
        /* If it's deflate, and it's got no preset dictionary, then
           we can tell zlib to skip the adler32 check. */
        if (srclen > 2 && !(data_in[1] & PRESET_DICT) &&
            ((data_in[0] & 0x0f) == Z_DEFLATED) &&
            !(((data_in[0]<<8) + data_in[1]) % 31)) {

                wbits = -((data_in[0] >> 4) + 8);
                workspace->strm.next_in += 2;
                workspace->strm.avail_in -= 2;
        }

        if (Z_OK != zlib_inflateInit2(&workspace->strm, wbits)) {
                printk(KERN_WARNING "BTRFS: inflateInit failed\n");
                return -EIO;
        }

        while (bytes_left > 0) {
                unsigned long buf_start;
                unsigned long buf_offset;
                unsigned long bytes;

                ret = zlib_inflate(&workspace->strm, Z_NO_FLUSH);
                if (ret != Z_OK && ret != Z_STREAM_END)
                        break;

                buf_start = total_out;
                total_out = workspace->strm.total_out;

                if (total_out == buf_start) {
                        ret = -EIO;
                        break;
                }

                if (total_out <= start_byte)
                        goto next;

                if (total_out > start_byte && buf_start < start_byte)
                        buf_offset = start_byte - buf_start;
                else
                        buf_offset = 0;

                bytes = min(PAGE_CACHE_SIZE - pg_offset,
                            PAGE_CACHE_SIZE - buf_offset);
                bytes = min(bytes, bytes_left);

                kaddr = kmap_atomic(dest_page);
                memcpy(kaddr + pg_offset, workspace->buf + buf_offset, bytes);
                kunmap_atomic(kaddr);

                pg_offset += bytes;
                bytes_left -= bytes;
next:
                workspace->strm.next_out = workspace->buf;
                workspace->strm.avail_out = PAGE_CACHE_SIZE;
        }

        if (ret != Z_STREAM_END && bytes_left != 0)
                ret = -EIO;
        else
                ret = 0;

        zlib_inflateEnd(&workspace->strm);

        /*
         * this should only happen if zlib returned fewer bytes than we
         * expected.  btrfs_get_block is responsible for zeroing from the
         * end of the inline extent (destlen) to the end of the page
         */
        if (pg_offset < destlen) {
                kaddr = kmap_atomic(dest_page);
                memset(kaddr + pg_offset, 0, destlen - pg_offset);
                kunmap_atomic(kaddr);
        }
        return ret;
}

struct btrfs_compress_op btrfs_zlib_compress = {
        .alloc_workspace        = zlib_alloc_workspace,
        .free_workspace         = zlib_free_workspace,
        .compress_pages         = zlib_compress_pages,
        .decompress_biovec      = zlib_decompress_biovec,
        .decompress             = zlib_decompress,
};