[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: Richard Purdie <rpurdie@openedhand.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/fs/jffs2/compr.c b/fs/jffs2/compr.c
index bcc28d2..86739ee 100644
--- a/fs/jffs2/compr.c
+++ b/fs/jffs2/compr.c
@@ -24,6 +24,34 @@
/* 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 @@
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 @@
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 @@
}
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 @@
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;
@@ -298,9 +328,14 @@
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;
}