fs/jffs2/compr.c - maze/linux - Git at Google

 /*
  * JFFS2 -- Journalling Flash File System, Version 2.
  *
  * Copyright © 2001-2007 Red Hat, Inc.
  * Copyright © 2004-2010 David Woodhouse <dwmw2@infradead.org>
  * Copyright © 2004 Ferenc Havasi <havasi@inf.u-szeged.hu>,
  *		    University of Szeged, Hungary
  *
  * Created by Arjan van de Ven <arjan@infradead.org>
  *
  * For licensing information, see the file 'LICENCE' in this directory.
  *
  */

 #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("JFFS2: 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("JFFS2: 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("JFFS2: 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("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) {
 		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("JFFS2: 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, "JFFS2: default compression mode: none\n");
 #else
 #ifdef CONFIG_JFFS2_CMODE_SIZE
 	jffs2_compression_mode = JFFS2_COMPR_MODE_SIZE;
 	jffs2_dbg(1, "JFFS2: default compression mode: size\n");
 #else
 #ifdef CONFIG_JFFS2_CMODE_FAVOURLZO
 	jffs2_compression_mode = JFFS2_COMPR_MODE_FAVOURLZO;
 	jffs2_dbg(1, "JFFS2: default compression mode: favourlzo\n");
 #else
 	jffs2_dbg(1, "JFFS2: 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;
 }
	/*
	* JFFS2 -- Journalling Flash File System, Version 2.
	*
	* Copyright © 2001-2007 Red Hat, Inc.
	* Copyright © 2004-2010 David Woodhouse <dwmw2@infradead.org>
	* Copyright © 2004 Ferenc Havasi <havasi@inf.u-szeged.hu>,
	* University of Szeged, Hungary
	*
	* Created by Arjan van de Ven <arjan@infradead.org>
	*
	* For licensing information, see the file 'LICENCE' in this directory.
	*
	*/

	#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("JFFS2: 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("JFFS2: 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("JFFS2: 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("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) {
	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("JFFS2: 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, "JFFS2: default compression mode: none\n");
	#else
	#ifdef CONFIG_JFFS2_CMODE_SIZE
	jffs2_compression_mode = JFFS2_COMPR_MODE_SIZE;
	jffs2_dbg(1, "JFFS2: default compression mode: size\n");
	#else
	#ifdef CONFIG_JFFS2_CMODE_FAVOURLZO
	jffs2_compression_mode = JFFS2_COMPR_MODE_FAVOURLZO;
	jffs2_dbg(1, "JFFS2: default compression mode: favourlzo\n");
	#else
	jffs2_dbg(1, "JFFS2: 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;
	}