Re: [U-Boot] [PATCH] JFFS2: accelerate scanning.

Hi Leo,

This patch make the JFFS2 scanning faster in U-Boot. 1). if we find 1KB 0xFF data from the beginning of the erase block,skip it. 2). if the 1KB data is 0xFF after the cleanmarker, ship this erase block.

Ship it to where? ;) Typo, should be skip.

For the 16MB nor flash, the scanning time is changed from about 9s to 1s.

Signed-off-by: Leo Liu liucai.lfn@gmail.com

checkpatch says:

total: 7 errors, 9 warnings, 103 lines checked

NOTE: whitespace errors detected, you may wish to use scripts/cleanpatch or scripts/cleanfile

Is there a corresponding thing in the Linux kernel?

---

fs/jffs2/jffs2_1pass.c | 31 +++++++++++++++++++++---------- fs/jffs2/jffs2_nand_1pass.c | 2 +- 2 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/fs/jffs2/jffs2_1pass.c b/fs/jffs2/jffs2_1pass.c index dfb1745..f38f755 100644 --- a/fs/jffs2/jffs2_1pass.c +++ b/fs/jffs2/jffs2_1pass.c @@ -1441,7 +1441,7 @@ dump_dirents(struct b_lists *pL) } #endif

-#define DEFAULT_EMPTY_SCAN_SIZE 4096 +#define DEFAULT_EMPTY_SCAN_SIZE 1024

Hm, this is not mentioned in the commit log. So is this detection already there and you simply decrease the amount of empty space you are looking for?

static inline uint32_t EMPTY_SCAN_SIZE(uint32_t sector_size) { @@ -1461,7 +1461,7 @@ jffs2_1pass_build_lists(struct part_info * part) u32 counter4 = 0; u32 counterF = 0; u32 counterN = 0;

• u32 buf_size = DEFAULT_EMPTY_SCAN_SIZE;

• u32 buf_size = 128*1024;;

This is a 128k buffer size which previously was a 4k buffer. Why is this change needed? Where does the size come from?

char *buf;

/* turn off the lcd. Refreshing the lcd adds 50% overhead to the */ @@ -1559,14 +1559,17 @@ jffs2_1pass_build_lists(struct part_info * part) /* We temporarily use 'ofs' as a pointer into the buffer/jeb */ ofs = 0;

• /* Scan only 4KiB of 0xFF before declaring it's empty */
  

• /* Scan only 1KiB of 0xFF before declaring it's empty */
  

Change the comment to refer to the macro so we don't need to change it every time the macro changes.

while (ofs < EMPTY_SCAN_SIZE(part->sector_size) &&
		*(uint32_t *)(&buf[ofs]) == 0xFFFFFFFF)
	ofs += 4;

• if (ofs == EMPTY_SCAN_SIZE(part->sector_size))
  

• if (ofs == EMPTY_SCAN_SIZE(part->sector_size)) {
  

• 	printf("Block at 0x%08x is empty (erased)\n", sector_ofs);
  

Hm, you add this output so lets consider what it says - wouldn't it be better to say "is considered to be empty"? After all, we only infer the emptiness in the code.

	continue;

• }
  
  

• /* Now ofs is a complete physical flash offset as it always was... */
  

  ofs += sector_ofs; prevofs = ofs - 1;

@@ -1594,16 +1597,14 @@ jffs2_1pass_build_lists(struct part_info * part)

	if (*(uint32_t *)(&buf[ofs-buf_ofs]) == 0xffffffff) {
		uint32_t inbuf_ofs;

• 		uint32_t empty_start, scan_end;
  

• 		uint32_t empty_start;
  
  	empty_start = ofs;
  	ofs += 4;
  

• 		scan_end = min_t(uint32_t, EMPTY_SCAN_SIZE(
  

• 					part->sector_size)/8,
  

• 					buf_len);
  

• 		
  more_empty:
  	inbuf_ofs = ofs - buf_ofs;
  

• 		while (inbuf_ofs < scan_end) {
  

• 		while (inbuf_ofs < buf_len) {
  		if (*(uint32_t *)(&buf[inbuf_ofs]) !=
  				0xffffffff)
  			goto scan_more;
  

@@ -1613,6 +1614,12 @@ jffs2_1pass_build_lists(struct part_info * part) } /* Ran off end. */

• 		/* If we're only checking the beginning of a block with a cleanmarker,
  

• 		   bail now */
  

• 		if((buf_ofs == sector_ofs) && 
  

• 			(node ==(struct jffs2_unknown_node *)&buf[ofs-buf_ofs])) 
  

• 			break;
  

• 	/* See how much more there is to read in this
  	 * eraseblock...
  	 */
  

@@ -1627,12 +1634,12 @@ jffs2_1pass_build_lists(struct part_info * part) */ break; }

• 		scan_end = buf_len;
  	get_fl_mem((u32)part->offset + ofs, buf_len,
  		   buf);
  	buf_ofs = ofs;
  	goto more_empty;
  }
  

• 	
  if (node->magic != JFFS2_MAGIC_BITMASK ||
  		!hdr_crc(node)) {
  	ofs += 4;
  

@@ -1650,6 +1657,8 @@ jffs2_1pass_build_lists(struct part_info * part) case JFFS2_NODETYPE_INODE: if (buf_ofs + buf_len < ofs + sizeof(struct jffs2_raw_inode)) {

• 			buf_len = min_t(uint32_t, buf_size, sector_ofs
  

• 					+ part->sector_size - ofs);
  
  		get_fl_mem((u32)part->offset + ofs,
  			   buf_len, buf);
  		buf_ofs = ofs;
  

@@ -1671,6 +1680,8 @@ jffs2_1pass_build_lists(struct part_info * part) ((struct jffs2_raw_dirent *) node)->nsize) {

• 			buf_len = min_t(uint32_t, buf_size, sector_ofs
  

• 					+ part->sector_size - ofs);
  
  		get_fl_mem((u32)part->offset + ofs,
  			   buf_len, buf);
  		buf_ofs = ofs;
  

diff --git a/fs/jffs2/jffs2_nand_1pass.c b/fs/jffs2/jffs2_nand_1pass.c index e3bc536..16bb2e9 100644 --- a/fs/jffs2/jffs2_nand_1pass.c +++ b/fs/jffs2/jffs2_nand_1pass.c @@ -833,7 +833,7 @@ jffs2_1pass_build_lists(struct part_info * part) return 0;

ofs = 0;

• /* Scan only 4KiB of 0xFF before declaring it's empty */
  

• /* Scan only 1KiB of 0xFF before declaring it's empty */
  

  while (ofs < EMPTY_SCAN_SIZE && *(uint32_t *)(&buf[ofs]) == 0xFFFFFFFF) ofs += 4; if (ofs == EMPTY_SCAN_SIZE)

On a whole - is this optimization safe with regard to uncompressed files containing only 0xFFs?

Cheers Detlev