// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2008 Oracle.  All rights reserved.
 */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/mm.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 <linux/refcount.h>
#include "compression.h"

#define LZO_LEN 4

/*
 * Btrfs LZO compression format
 *
 * Regular and inlined LZO compressed data extents consist of:
 *
 * 1.  Header
 *     Fixed size. LZO_LEN (4) bytes long, LE32.
 *     Records the total size (including the header) of compressed data.
 *
 * 2.  Segment(s)
 *     Variable size. Each segment includes one segment header, followd by data
 *     payload.
 *     One regular LZO compressed extent can have one or more segments.
 *     For inlined LZO compressed extent, only one segment is allowed.
 *     One segment represents at most one page of uncompressed data.
 *
 * 2.1 Segment header
 *     Fixed size. LZO_LEN (4) bytes long, LE32.
 *     Records the total size of the segment (not including the header).
 *     Segment header never crosses page boundary, thus it's possible to
 *     have at most 3 padding zeros at the end of the page.
 *
 * 2.2 Data Payload
 *     Variable size. Size up limit should be lzo1x_worst_compress(PAGE_SIZE)
 *     which is 4419 for a 4KiB page.
 *
 * Example:
 * Page 1:
 *          0     0x2   0x4   0x6   0x8   0xa   0xc   0xe     0x10
 * 0x0000   |  Header   | SegHdr 01 | Data payload 01 ...     |
 * ...
 * 0x0ff0   | SegHdr  N | Data payload  N     ...          |00|
 *                                                          ^^ padding zeros
 * Page 2:
 * 0x1000   | SegHdr N+1| Data payload N+1 ...                |
 */

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);

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

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

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

        workspace->mem = kvmalloc(LZO1X_MEM_COMPRESS, GFP_KERNEL);
        workspace->buf = kvmalloc(lzo1x_worst_compress(PAGE_SIZE), GFP_KERNEL);
        workspace->cbuf = kvmalloc(lzo1x_worst_compress(PAGE_SIZE), GFP_KERNEL);
        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(const 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,
                              struct page **pages,
                              unsigned long *out_pages,
                              unsigned long *total_in,
                              unsigned long *total_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;
        unsigned long len = *total_out;
        unsigned long nr_dest_pages = *out_pages;
        const unsigned long max_out = nr_dest_pages * PAGE_SIZE;
        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_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_SIZE - LZO_LEN;

        /* compress at most one page of data each time */
        in_len = min(len, PAGE_SIZE);
        while (tot_in < len) {
                ret = lzo1x_1_compress(data_in, in_len, workspace->cbuf,
                                       &out_len, workspace->mem);
                if (ret != LZO_E_OK) {
                        pr_debug("BTRFS: lzo 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_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);
                put_page(in_page);

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

        if (tot_out >= tot_in) {
                ret = -E2BIG;
                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);
                put_page(in_page);
        }

        return ret;
}

static int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
{
        struct workspace *workspace = list_entry(ws, struct workspace, list);
        int ret = 0, ret2;
        char *data_in;
        unsigned long page_in_index = 0;
        size_t srclen = cb->compressed_len;
        unsigned long total_pages_in = DIV_ROUND_UP(srclen, PAGE_SIZE);
        unsigned long buf_start;
        unsigned long buf_offset = 0;
        unsigned long bytes;
        unsigned long working_bytes;
        size_t in_len;
        size_t out_len;
        const size_t max_segment_len = lzo1x_worst_compress(PAGE_SIZE);
        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;
        struct page **pages_in = cb->compressed_pages;
        u64 disk_start = cb->start;
        struct bio *orig_bio = cb->orig_bio;

        data_in = kmap(pages_in[0]);
        tot_len = read_compress_length(data_in);
        /*
         * Compressed data header check.
         *
         * The real compressed size can't exceed the maximum extent length, and
         * all pages should be used (whole unused page with just the segment
         * header is not possible).  If this happens it means the compressed
         * extent is corrupted.
         */
        if (tot_len > min_t(size_t, BTRFS_MAX_COMPRESSED, srclen) ||
            tot_len < srclen - PAGE_SIZE) {
                ret = -EUCLEAN;
                goto done;
        }

        tot_in = LZO_LEN;
        in_offset = LZO_LEN;
        in_page_bytes_left = PAGE_SIZE - LZO_LEN;

        tot_out = 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;

                /*
                 * Segment header check.
                 *
                 * The segment length must not exceed the maximum LZO
                 * compression size, nor the total compressed size.
                 */
                if (in_len > max_segment_len || tot_in + in_len > tot_len) {
                        ret = -EUCLEAN;
                        goto done;
                }

                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_SIZE;
                                in_offset = 0;
                        }
                }

                out_len = max_segment_len;
                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) {
                        pr_warn("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, orig_bio);
                if (ret2 == 0)
                        break;
        }
done:
        kunmap(pages_in[page_in_index]);
        if (!ret)
                zero_fill_bio(orig_bio);
        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 max_segment_len = lzo1x_worst_compress(PAGE_SIZE);
        int ret = 0;
        char *kaddr;
        unsigned long bytes;

        if (srclen < LZO_LEN || srclen > max_segment_len + LZO_LEN * 2)
                return -EUCLEAN;

        in_len = read_compress_length(data_in);
        if (in_len != srclen)
                return -EUCLEAN;
        data_in += LZO_LEN;

        in_len = read_compress_length(data_in);
        if (in_len != srclen - LZO_LEN * 2) {
                ret = -EUCLEAN;
                goto out;
        }
        data_in += LZO_LEN;

        out_len = PAGE_SIZE;
        ret = lzo1x_decompress_safe(data_in, in_len, workspace->buf, &out_len);
        if (ret != LZO_E_OK) {
                pr_warn("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;
}

static void lzo_set_level(struct list_head *ws, unsigned int type)
{
}

const struct btrfs_compress_op btrfs_lzo_compress = {
        .alloc_workspace        = lzo_alloc_workspace,
        .free_workspace         = lzo_free_workspace,
        .compress_pages         = lzo_compress_pages,
        .decompress_bio         = lzo_decompress_bio,
        .decompress             = lzo_decompress,
        .set_level              = lzo_set_level,
};