compr.c

jffs2源代码基于2。6内核

/*
 * JFFS2 -- Journalling Flash File System, Version 2.
 *
 * Copyright (C) 2001-2003 Red Hat, Inc.
 * Created by Arjan van de Ven <[e-mail]>
 *
 * Copyright (C) 2004 Ferenc Havasi <[e-mail]>,
 *                    University of Szeged, Hungary
 *
 * For licensing information, see the file 'LICENCE' in this directory.
 *
 * $Id: compr.c,v 1.42 2004/08/07 21:56:08 dwmw2 Exp $
 *
 */

#include "compr.h"

static spinlock_t jffs2_compressor_list_lock = SPIN_LOCK_UNLOCKED;

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

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

void jffs2_set_compression_mode(int mode) 
{
        jffs2_compression_mode = mode;
}

int jffs2_get_compression_mode(void)
{
        return jffs2_compression_mode;
}

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

/* jffs2_compress:
 * @data: Pointer to uncompressed data
 * @cdata: 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 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;

        switch (jffs2_compression_mode) {
        case JFFS2_COMPR_MODE_NONE:
                break;
        case JFFS2_COMPR_MODE_PRIORITY:
                output_buf = kmalloc(*cdatalen,GFP_KERNEL);
                if (!output_buf) {
                        printk(KERN_WARNING "JFFS2: No memory for compressor allocation. Compression failed.\n");
                        goto out;
                }
                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;

                        this->usecount++;
                        spin_unlock(&jffs2_compressor_list_lock);
                        *datalen  = orig_slen;
                        *cdatalen = orig_dlen;
                        compr_ret = this->compress(data_in, output_buf, datalen, cdatalen, NULL);
                        spin_lock(&jffs2_compressor_list_lock);
                        this->usecount--;
                        if (!compr_ret) {
                                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);
                break;
        case JFFS2_COMPR_MODE_SIZE:
                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_dlen)&&(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_dlen,GFP_KERNEL);
                                spin_lock(&jffs2_compressor_list_lock);
                                if (!tmp_buf) {
                                        printk(KERN_WARNING "JFFS2: No memory for compressor allocation. (%d bytes)\n",orig_dlen);
                                        continue;
                                }
                                else {
                                        this->compr_buf = tmp_buf;
                                        this->compr_buf_size = orig_dlen;
                                }
                        }
                        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, NULL);
                        spin_lock(&jffs2_compressor_list_lock);
                        this->usecount--;
                        if (!compr_ret) {
                                if ((!best_dlen)||(best_dlen>*cdatalen)) {
                                        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;
                }
                spin_unlock(&jffs2_compressor_list_lock);
                break;
        default:
                printk(KERN_ERR "JFFS2: unknow compression mode.\n");
        }
 out:
        if (ret == JFFS2_COMPR_NONE) {
	        *cpage_out = data_in;
	        *datalen = *cdatalen;
                none_stat_compr_blocks++;
                none_stat_compr_size += *datalen;
        }
        else {
                *cpage_out = output_buf;
        }
	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, NULL);
                                spin_lock(&jffs2_compressor_list_lock);
                                if (ret) {
                                        printk(KERN_WARNING "Decompressor \"%s\" returned %d\n", this->name, ret);
                                }
                                else {
                                        this->stat_decompr_blocks++;
                                }
                                this->usecount--;
                                spin_unlock(&jffs2_compressor_list_lock);
                                return ret;
                        }
                }
		printk(KERN_WARNING "JFFS2 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) {
                printk(KERN_WARNING "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;
        D1(printk(KERN_DEBUG "Registering JFFS2 compressor \"%s\"\n", comp->name));

        spin_lock(&jffs2_compressor_list_lock);