jffs2: Reduce excessive scan of empty blocks

Scanning 1024 bytes to see if an EB is empty is a bit much.
Lower it to 256 bytes and make sure the while loop is
optimized.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

diff --git a/fs/jffs2/scan.c b/fs/jffs2/scan.c
index 46f870d1cc36ffaca178be3e62c600186e23d7f6..b632dddcb482821122918bd1673391ff34d51e4c 100644 (file)
--- a/fs/jffs2/scan.c
+++ b/fs/jffs2/scan.c
@@ -20,7 +20,7 @@
 #include "summary.h"
 #include "debug.h"
 
-#define DEFAULT_EMPTY_SCAN_SIZE 1024
+#define DEFAULT_EMPTY_SCAN_SIZE 256
 
 #define noisy_printk(noise, args...) do { \
        if (*(noise)) { \
@@ -435,7 +435,7 @@ static int jffs2_scan_eraseblock (struct jffs2_sb_info *c, struct jffs2_eraseblo
                                  unsigned char *buf, uint32_t buf_size, struct jffs2_summary *s) {
        struct jffs2_unknown_node *node;
        struct jffs2_unknown_node crcnode;
-       uint32_t ofs, prevofs;
+       uint32_t ofs, prevofs, max_ofs;
        uint32_t hdr_crc, buf_ofs, buf_len;
        int err;
        int noise = 0;
@@ -550,12 +550,12 @@ static int jffs2_scan_eraseblock (struct jffs2_sb_info *c, struct jffs2_eraseblo
 
        /* We temporarily use 'ofs' as a pointer into the buffer/jeb */
        ofs = 0;
-
-       /* Scan only 4KiB of 0xFF before declaring it's empty */
-       while(ofs < EMPTY_SCAN_SIZE(c->sector_size) && *(uint32_t *)(&buf[ofs]) == 0xFFFFFFFF)
+       max_ofs = EMPTY_SCAN_SIZE(c->sector_size);
+       /* Scan only EMPTY_SCAN_SIZE of 0xFF before declaring it's empty */
+       while(ofs < max_ofs && *(uint32_t *)(&buf[ofs]) == 0xFFFFFFFF)
                ofs += 4;
 
-       if (ofs == EMPTY_SCAN_SIZE(c->sector_size)) {
+       if (ofs == max_ofs) {
 #ifdef CONFIG_JFFS2_FS_WRITEBUFFER
                if (jffs2_cleanmarker_oob(c)) {
                        /* scan oob, take care of cleanmarker */