Re: [PATCH 3/5] jffs2: Add a "favourlzo" compression mode to jffs2

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 <redacted>
---
 fs/Kconfig       |    7 +++++++
 fs/jffs2/compr.c |   45 ++++++++++++++++++++++++++++++++++++++++-----
 fs/jffs2/compr.h |    3 +++
 3 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/fs/Kconfig b/fs/Kconfig
index 1645dfa..328a62f 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig

@@ -1359,6 +1359,13 @@ 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

diff --git a/fs/jffs2/compr.c b/fs/jffs2/compr.c
index 6a23408..fdb0efd 100644
--- a/fs/jffs2/compr.c
+++ b/fs/jffs2/compr.c

@@ -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) {

+				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

@@ -106,15 +135,15 @@ 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);

                                         continue;
                                 }
                                 else {
                                         this->compr_buf = tmp_buf;
-                                        this->compr_buf_size = orig_dlen;
+                                        this->compr_buf_size = orig_slen;
                                 }
                         }
                         this->usecount++;

@@ -125,7 +154,8 @@ 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))