Commit 3b23c1f5 authored by Richard Purdie's avatar Richard Purdie Committed by David Woodhouse
Browse files

[JFFS2] Add a "favourlzo" compression mode 



Add a "favourlzo" compression mode to jffs2 which tries to
optimise by size but gives lzo an advantage when comparing sizes.
This means the faster lzo algorithm can be preferred when there
isn't much difference in compressed size (the exact threshold can
be changed).

Signed-off-by: default avatarRichard Purdie <rpurdie@openedhand.com>
Signed-off-by: default avatarDavid Woodhouse <dwmw2@infradead.org>
parent c799aca3

fs/Kconfig

+7 −0
Original line number Diff line number Diff line
@@ -1364,6 +1364,13 @@ config JFFS2_CMODE_SIZE 
	  Tries all compressors and chooses the one which has the smallest

	  result.



config JFFS2_CMODE_FAVOURLZO

	bool "Favour LZO"

	help

	  Tries all compressors and chooses the one which has the smallest

	  result but gives some preference to LZO (which has faster

	  decompression) at the expense of size.



endchoice



config CRAMFS

fs/jffs2/compr.c

+40 −5
Original line number Diff line number Diff line
@@ -24,6 +24,34 @@ 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_compress:

 * @data: Pointer to uncompressed data

 * @cdata: Pointer to returned pointer to buffer for compressed data
@@ -90,6 +118,7 @@ uint16_t jffs2_compress(struct jffs2_sb_info *c, struct jffs2_inode_info *f, 
			kfree(output_buf);

		break;

	case JFFS2_COMPR_MODE_SIZE:

	case JFFS2_COMPR_MODE_FAVOURLZO:

		orig_slen = *datalen;

		orig_dlen = *cdatalen;

		spin_lock(&jffs2_compressor_list_lock);
@@ -98,7 +127,7 @@ uint16_t jffs2_compress(struct jffs2_sb_info *c, struct jffs2_inode_info *f, 
			if ((!this->compress)||(this->disabled))

				continue;

			/* Allocating memory for output buffer if necessary */

			if ((this->compr_buf_size<orig_dlen)&&(this->compr_buf)) {

			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);
@@ -107,15 +136,15 @@ uint16_t jffs2_compress(struct jffs2_sb_info *c, struct jffs2_inode_info *f, 
			}

			if (!this->compr_buf) {

				spin_unlock(&jffs2_compressor_list_lock);

				tmp_buf = kmalloc(orig_dlen,GFP_KERNEL);

				tmp_buf = kmalloc(orig_slen, 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);

					printk(KERN_WARNING "JFFS2: No memory for compressor allocation. (%d bytes)\n", orig_slen);

					continue;

				}

				else {

					this->compr_buf = tmp_buf;

					this->compr_buf_size = orig_dlen;

					this->compr_buf_size = orig_slen;

				}

			}

			this->usecount++;
@@ -126,7 +155,8 @@ uint16_t jffs2_compress(struct jffs2_sb_info *c, struct jffs2_inode_info *f, 
			spin_lock(&jffs2_compressor_list_lock);

			this->usecount--;

			if (!compr_ret) {

				if ((!best_dlen)||(best_dlen>*cdatalen)) {

				if (((!best_dlen) || jffs2_is_best_compression(this, best, *cdatalen, best_dlen))

						&& (*cdatalen < *datalen)) {

					best_dlen = *cdatalen;

					best_slen = *datalen;

					best = this;
@@ -297,9 +327,14 @@ int __init jffs2_compressors_init(void) 
#ifdef CONFIG_JFFS2_CMODE_SIZE

	jffs2_compression_mode = JFFS2_COMPR_MODE_SIZE;

	D1(printk(KERN_INFO "JFFS2: default compression mode: size\n");)

#else

#ifdef CONFIG_JFFS2_CMODE_FAVOURLZO

	jffs2_compression_mode = JFFS2_COMPR_MODE_FAVOURLZO;

	D1(printk(KERN_INFO "JFFS2: default compression mode: favourlzo\n");)

#else

	D1(printk(KERN_INFO "JFFS2: default compression mode: priority\n");)

#endif

#endif

#endif

	return 0;

}

fs/jffs2/compr.h

+3 −0
Original line number Diff line number Diff line
@@ -38,6 +38,9 @@ 
#define JFFS2_COMPR_MODE_NONE       0

#define JFFS2_COMPR_MODE_PRIORITY   1

#define JFFS2_COMPR_MODE_SIZE       2

#define JFFS2_COMPR_MODE_FAVOURLZO  3



#define FAVOUR_LZO_PERCENT 80



struct jffs2_compressor {

	struct list_head list;

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