compr.c

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/*
 * JFFS2 -- Journalling Flash File System, Version 2.
 *
 * Copyright © 2001-2007 Red Hat, Inc.
 * Copyright © 2004-2010 David Woodhouse <[email protected]>
 * Copyright © 2004 Ferenc Havasi <[email protected]>,
 *          University of Szeged, Hungary
 *
 * Created by Arjan van de Ven <[email protected]>
 *
 * For licensing information, see the file 'LICENCE' in this directory.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include "compr.h"

static DEFINE_SPINLOCK(jffs2_compressor_list_lock);

/* Available compressors are on this list */
static LIST_HEAD(jffs2_compressor_list);

/* Actual compression mode */
static int jffs2_compression_mode = JFFS2_COMPR_MODE_PRIORITY;

/* Statistics for blocks stored without compression */
static uint32_t none_stat_compr_blocks=0,none_stat_decompr_blocks=0,none_stat_compr_size=0;


/*
 * Return 1 to use this compression
 */
static int jffs2_is_best_compression(struct jffs2_compressor *this,
        struct jffs2_compressor *best, uint32_t size, uint32_t bestsize)
{
    switch (jffs2_compression_mode) {
    case JFFS2_COMPR_MODE_SIZE:
        if (bestsize > size)
            return 1;
        return 0;
    case JFFS2_COMPR_MODE_FAVOURLZO:
        if ((this->compr == JFFS2_COMPR_LZO) && (bestsize > size))
            return 1;
        if ((best->compr != JFFS2_COMPR_LZO) && (bestsize > size))
            return 1;
        if ((this->compr == JFFS2_COMPR_LZO) && (bestsize > (size * FAVOUR_LZO_PERCENT / 100)))
            return 1;
        if ((bestsize * FAVOUR_LZO_PERCENT / 100) > size)
            return 1;

        return 0;
    }
    /* Shouldn't happen */
    return 0;
}

/*
 * jffs2_selected_compress:
 * @compr: Explicit compression type to use (ie, JFFS2_COMPR_ZLIB).
 *  If 0, just take the first available compression mode.
 * @data_in: Pointer to uncompressed data
 * @cpage_out: Pointer to returned pointer to buffer for compressed data
 * @datalen: On entry, holds the amount of data available for compression.
 *  On exit, expected to hold the amount of data actually compressed.
 * @cdatalen: On entry, holds the amount of space available for compressed
 *  data. On exit, expected to hold the actual size of the compressed
 *  data.
 *
 * Returns: the compression type used.  Zero is used to show that the data
 * could not be compressed; probably because we couldn't find the requested
 * compression mode.
 */
static int jffs2_selected_compress(u8 compr, unsigned char *data_in,
        unsigned char **cpage_out, u32 *datalen, u32 *cdatalen)
{
    struct jffs2_compressor *this;
    int err, ret = JFFS2_COMPR_NONE;
    uint32_t orig_slen, orig_dlen;
    char *output_buf;

    output_buf = kmalloc(*cdatalen, GFP_KERNEL);
    if (!output_buf) {
        pr_warn("No memory for compressor allocation. Compression failed.\n");
        return ret;
    }
    orig_slen = *datalen;
    orig_dlen = *cdatalen;
    spin_lock(&jffs2_compressor_list_lock);
    list_for_each_entry(this, &jffs2_compressor_list, list) {
        /* Skip decompress-only and disabled modules */
        if (!this->compress || this->disabled)
            continue;

        /* Skip if not the desired compression type */
        if (compr && (compr != this->compr))
            continue;

        /*
         * Either compression type was unspecified, or we found our
         * compressor; either way, we're good to go.
         */
        this->usecount++;
        spin_unlock(&jffs2_compressor_list_lock);

        *datalen  = orig_slen;
        *cdatalen = orig_dlen;
        err = this->compress(data_in, output_buf, datalen, cdatalen);

        spin_lock(&jffs2_compressor_list_lock);
        this->usecount--;
        if (!err) {
            /* Success */
            ret = this->compr;
            this->stat_compr_blocks++;
            this->stat_compr_orig_size += *datalen;
            this->stat_compr_new_size += *cdatalen;
            break;
        }
    }
    spin_unlock(&jffs2_compressor_list_lock);
    if (ret == JFFS2_COMPR_NONE)
        kfree(output_buf);
    else
        *cpage_out = output_buf;

    return ret;
}

/* jffs2_compress:
 * @data_in: Pointer to uncompressed data
 * @cpage_out: Pointer to returned pointer to buffer for compressed data
 * @datalen: On entry, holds the amount of data available for compression.
 *  On exit, expected to hold the amount of data actually compressed.
 * @cdatalen: On entry, holds the amount of space available for compressed
 *  data. On exit, expected to hold the actual size of the compressed
 *  data.
 *
 * Returns: Lower byte to be stored with data indicating compression type used.
 * Zero is used to show that the data could not be compressed - the
 * compressed version was actually larger than the original.
 * Upper byte will be used later. (soon)
 *
 * If the cdata buffer isn't large enough to hold all the uncompressed data,
 * jffs2_compress should compress as much as will fit, and should set
 * *datalen accordingly to show the amount of data which were compressed.
 */
uint16_t jffs2_compress(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
            unsigned char *data_in, unsigned char **cpage_out,
            uint32_t *datalen, uint32_t *cdatalen)
{
    int ret = JFFS2_COMPR_NONE;
    int mode, compr_ret;
    struct jffs2_compressor *this, *best=NULL;
    unsigned char *output_buf = NULL, *tmp_buf;
    uint32_t orig_slen, orig_dlen;
    uint32_t best_slen=0, best_dlen=0;

    if (c->mount_opts.override_compr)
        mode = c->mount_opts.compr;
    else
        mode = jffs2_compression_mode;

    switch (mode) {
    case JFFS2_COMPR_MODE_NONE:
        break;
    case JFFS2_COMPR_MODE_PRIORITY:
        ret = jffs2_selected_compress(0, data_in, cpage_out, datalen,
                cdatalen);
        break;
    case JFFS2_COMPR_MODE_SIZE:
    case JFFS2_COMPR_MODE_FAVOURLZO:
        orig_slen = *datalen;
        orig_dlen = *cdatalen;
        spin_lock(&jffs2_compressor_list_lock);
        list_for_each_entry(this, &jffs2_compressor_list, list) {
            /* Skip decompress-only backwards-compatibility and disabled modules */
            if ((!this->compress)||(this->disabled))
                continue;
            /* Allocating memory for output buffer if necessary */
            if ((this->compr_buf_size < orig_slen) && (this->compr_buf)) {
                spin_unlock(&jffs2_compressor_list_lock);
                kfree(this->compr_buf);
                spin_lock(&jffs2_compressor_list_lock);
                this->compr_buf_size=0;
                this->compr_buf=NULL;
            }
            if (!this->compr_buf) {
                spin_unlock(&jffs2_compressor_list_lock);
                tmp_buf = kmalloc(orig_slen, GFP_KERNEL);
                spin_lock(&jffs2_compressor_list_lock);
                if (!tmp_buf) {
                    pr_warn("No memory for compressor allocation. (%d bytes)\n",
                        orig_slen);
                    continue;
                }
                else {
                    this->compr_buf = tmp_buf;
                    this->compr_buf_size = orig_slen;
                }
            }
            this->usecount++;
            spin_unlock(&jffs2_compressor_list_lock);
            *datalen  = orig_slen;
            *cdatalen = orig_dlen;
            compr_ret = this->compress(data_in, this->compr_buf, datalen, cdatalen);
            spin_lock(&jffs2_compressor_list_lock);
            this->usecount--;
            if (!compr_ret) {
                if (((!best_dlen) || jffs2_is_best_compression(this, best, *cdatalen, best_dlen))
                        && (*cdatalen < *datalen)) {
                    best_dlen = *cdatalen;
                    best_slen = *datalen;
                    best = this;
                }
            }
        }
        if (best_dlen) {
            *cdatalen = best_dlen;
            *datalen  = best_slen;
            output_buf = best->compr_buf;
            best->compr_buf = NULL;
            best->compr_buf_size = 0;
            best->stat_compr_blocks++;
            best->stat_compr_orig_size += best_slen;
            best->stat_compr_new_size  += best_dlen;
            ret = best->compr;
            *cpage_out = output_buf;
        }
        spin_unlock(&jffs2_compressor_list_lock);
        break;
    case JFFS2_COMPR_MODE_FORCELZO:
        ret = jffs2_selected_compress(JFFS2_COMPR_LZO, data_in,
                cpage_out, datalen, cdatalen);
        break;
    case JFFS2_COMPR_MODE_FORCEZLIB:
        ret = jffs2_selected_compress(JFFS2_COMPR_ZLIB, data_in,
                cpage_out, datalen, cdatalen);
        break;
    default:
        pr_err("unknown compression mode\n");
    }

    if (ret == JFFS2_COMPR_NONE) {
        *cpage_out = data_in;
        *datalen = *cdatalen;
        none_stat_compr_blocks++;
        none_stat_compr_size += *datalen;
    }
    return ret;
}

int jffs2_decompress(struct jffs2_sb_info *c, struct jffs2_inode_info *f,
             uint16_t comprtype, unsigned char *cdata_in,
             unsigned char *data_out, uint32_t cdatalen, uint32_t datalen)
{
    struct jffs2_compressor *this;
    int ret;

    /* Older code had a bug where it would write non-zero 'usercompr'
       fields. Deal with it. */
    if ((comprtype & 0xff) <= JFFS2_COMPR_ZLIB)
        comprtype &= 0xff;

    switch (comprtype & 0xff) {
    case JFFS2_COMPR_NONE:
        /* This should be special-cased elsewhere, but we might as well deal with it */
        memcpy(data_out, cdata_in, datalen);
        none_stat_decompr_blocks++;
        break;
    case JFFS2_COMPR_ZERO:
        memset(data_out, 0, datalen);
        break;
    default:
        spin_lock(&jffs2_compressor_list_lock);
        list_for_each_entry(this, &jffs2_compressor_list, list) {
            if (comprtype == this->compr) {
                this->usecount++;
                spin_unlock(&jffs2_compressor_list_lock);
                ret = this->decompress(cdata_in, data_out, cdatalen, datalen);
                spin_lock(&jffs2_compressor_list_lock);
                if (ret) {
                    pr_warn("Decompressor \"%s\" returned %d\n",
                        this->name, ret);
                }
                else {
                    this->stat_decompr_blocks++;
                }
                this->usecount--;
                spin_unlock(&jffs2_compressor_list_lock);
                return ret;
            }
        }
        pr_warn("compression type 0x%02x not available\n", comprtype);
        spin_unlock(&jffs2_compressor_list_lock);
        return -EIO;
    }
    return 0;
}

int jffs2_register_compressor(struct jffs2_compressor *comp)
{
    struct jffs2_compressor *this;

    if (!comp->name) {
        pr_warn("NULL compressor name at registering JFFS2 compressor. Failed.\n");
        return -1;
    }
    comp->compr_buf_size=0;
    comp->compr_buf=NULL;
    comp->usecount=0;
    comp->stat_compr_orig_size=0;
    comp->stat_compr_new_size=0;
    comp->stat_compr_blocks=0;
    comp->stat_decompr_blocks=0;
    jffs2_dbg(1, "Registering JFFS2 compressor \"%s\"\n", comp->name);

    spin_lock(&jffs2_compressor_list_lock);

    list_for_each_entry(this, &jffs2_compressor_list, list) {
        if (this->priority < comp->priority) {
            list_add(&comp->list, this->list.prev);
            goto out;
        }
    }
    list_add_tail(&comp->list, &jffs2_compressor_list);
out:
    D2(list_for_each_entry(this, &jffs2_compressor_list, list) {
        printk(KERN_DEBUG "Compressor \"%s\", prio %d\n", this->name, this->priority);
    })

    spin_unlock(&jffs2_compressor_list_lock);

    return 0;
}

int jffs2_unregister_compressor(struct jffs2_compressor *comp)
{
    D2(struct jffs2_compressor *this);

    jffs2_dbg(1, "Unregistering JFFS2 compressor \"%s\"\n", comp->name);

    spin_lock(&jffs2_compressor_list_lock);

    if (comp->usecount) {
        spin_unlock(&jffs2_compressor_list_lock);
        pr_warn("Compressor module is in use. Unregister failed.\n");
        return -1;
    }
    list_del(&comp->list);

    D2(list_for_each_entry(this, &jffs2_compressor_list, list) {
        printk(KERN_DEBUG "Compressor \"%s\", prio %d\n", this->name, this->priority);
    })
    spin_unlock(&jffs2_compressor_list_lock);
    return 0;
}

void jffs2_free_comprbuf(unsigned char *comprbuf, unsigned char *orig)
{
    if (orig != comprbuf)
        kfree(comprbuf);
}

int __init jffs2_compressors_init(void)
{
/* Registering compressors */
#ifdef CONFIG_JFFS2_ZLIB
    jffs2_zlib_init();
#endif
#ifdef CONFIG_JFFS2_RTIME
    jffs2_rtime_init();
#endif
#ifdef CONFIG_JFFS2_RUBIN
    jffs2_rubinmips_init();
    jffs2_dynrubin_init();
#endif
#ifdef CONFIG_JFFS2_LZO
    jffs2_lzo_init();
#endif
/* Setting default compression mode */
#ifdef CONFIG_JFFS2_CMODE_NONE
    jffs2_compression_mode = JFFS2_COMPR_MODE_NONE;
    jffs2_dbg(1, "default compression mode: none\n");
#else
#ifdef CONFIG_JFFS2_CMODE_SIZE
    jffs2_compression_mode = JFFS2_COMPR_MODE_SIZE;
    jffs2_dbg(1, "default compression mode: size\n");
#else
#ifdef CONFIG_JFFS2_CMODE_FAVOURLZO
    jffs2_compression_mode = JFFS2_COMPR_MODE_FAVOURLZO;
    jffs2_dbg(1, "default compression mode: favourlzo\n");
#else
    jffs2_dbg(1, "default compression mode: priority\n");
#endif
#endif
#endif
    return 0;
}

int jffs2_compressors_exit(void)
{
/* Unregistering compressors */
#ifdef CONFIG_JFFS2_LZO
    jffs2_lzo_exit();
#endif
#ifdef CONFIG_JFFS2_RUBIN
    jffs2_dynrubin_exit();
    jffs2_rubinmips_exit();
#endif
#ifdef CONFIG_JFFS2_RTIME
    jffs2_rtime_exit();
#endif
#ifdef CONFIG_JFFS2_ZLIB
    jffs2_zlib_exit();
#endif
    return 0;
}