// 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"
#include "ctree.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, followed 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 struct workspace_manager wsm;

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);
}

struct list_head *lzo_alloc_workspace(unsigned int level)
{
        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);
}

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, *sizes_ptr;
        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);
        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);
                                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 */
        sizes_ptr = kmap_local_page(pages[0]);
        write_compress_length(sizes_ptr, tot_out);
        kunmap_local(sizes_ptr);

        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;
}

/*
 * Copy the compressed segment payload into @dest.
 *
 * For the payload there will be no padding, just need to do page switching.
 */
static void copy_compressed_segment(struct compressed_bio *cb,
                                    char *dest, u32 len, u32 *cur_in)
{
        u32 orig_in = *cur_in;

        while (*cur_in < orig_in + len) {
                char *kaddr;
                struct page *cur_page;
                u32 copy_len = min_t(u32, PAGE_SIZE - offset_in_page(*cur_in),
                                          orig_in + len - *cur_in);

                ASSERT(copy_len);
                cur_page = cb->compressed_pages[*cur_in / PAGE_SIZE];

                kaddr = kmap(cur_page);
                memcpy(dest + *cur_in - orig_in,
                        kaddr + offset_in_page(*cur_in),
                        copy_len);
                kunmap(cur_page);

                *cur_in += copy_len;
        }
}

int lzo_decompress_bio(struct list_head *ws, struct compressed_bio *cb)
{
        struct workspace *workspace = list_entry(ws, struct workspace, list);
        const struct btrfs_fs_info *fs_info = btrfs_sb(cb->inode->i_sb);
        const u32 sectorsize = fs_info->sectorsize;
        char *kaddr;
        int ret;
        /* Compressed data length, can be unaligned */
        u32 len_in;
        /* Offset inside the compressed data */
        u32 cur_in = 0;
        /* Bytes decompressed so far */
        u32 cur_out = 0;

        kaddr = kmap(cb->compressed_pages[0]);
        len_in = read_compress_length(kaddr);
        kunmap(cb->compressed_pages[0]);
        cur_in += LZO_LEN;

        /*
         * LZO header length check
         *
         * The total length should not exceed the maximum extent length,
         * and all sectors should be used.
         * If this happens, it means the compressed extent is corrupted.
         */
        if (len_in > min_t(size_t, BTRFS_MAX_COMPRESSED, cb->compressed_len) ||
            round_up(len_in, sectorsize) < cb->compressed_len) {
                btrfs_err(fs_info,
                        "invalid lzo header, lzo len %u compressed len %u",
                        len_in, cb->compressed_len);
                return -EUCLEAN;
        }

        /* Go through each lzo segment */
        while (cur_in < len_in) {
                struct page *cur_page;
                /* Length of the compressed segment */
                u32 seg_len;
                u32 sector_bytes_left;
                size_t out_len = lzo1x_worst_compress(sectorsize);

                /*
                 * We should always have enough space for one segment header
                 * inside current sector.
                 */
                ASSERT(cur_in / sectorsize ==
                       (cur_in + LZO_LEN - 1) / sectorsize);
                cur_page = cb->compressed_pages[cur_in / PAGE_SIZE];
                kaddr = kmap(cur_page);
                ASSERT(cur_page);
                seg_len = read_compress_length(kaddr + offset_in_page(cur_in));
                cur_in += LZO_LEN;

                /* Copy the compressed segment payload into workspace */
                copy_compressed_segment(cb, workspace->cbuf, seg_len, &cur_in);

                /* Decompress the data */
                ret = lzo1x_decompress_safe(workspace->cbuf, seg_len,
                                            workspace->buf, &out_len);
                if (ret != LZO_E_OK) {
                        btrfs_err(fs_info, "failed to decompress");
                        ret = -EIO;
                        goto out;
                }

                /* Copy the data into inode pages */
                ret = btrfs_decompress_buf2page(workspace->buf, out_len, cb, cur_out);
                cur_out += out_len;

                /* All data read, exit */
                if (ret == 0)
                        goto out;
                ret = 0;

                /* Check if the sector has enough space for a segment header */
                sector_bytes_left = sectorsize - (cur_in % sectorsize);
                if (sector_bytes_left >= LZO_LEN)
                        continue;

                /* Skip the padding zeros */
                cur_in += sector_bytes_left;
        }
out:
        if (!ret)
                zero_fill_bio(cb->orig_bio);
        return ret;
}

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_local_page(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_local(kaddr);
out:
        return ret;
}

const struct btrfs_compress_op btrfs_lzo_compress = {
        .workspace_manager      = &wsm,
        .max_level              = 1,
        .default_level          = 1,
};