[JFFS2] Speed up mount for directly-mapped NOR flash

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=c2aecda79cd872679b9b11f9e59d797fb4c7d677
Commit:     c2aecda79cd872679b9b11f9e59d797fb4c7d677
Parent:     10731f83009e2556f98ffa5c7c2cbffe66dacfb3
Author:     Joakim Tjernlund <Joakim.Tjernlund at transmode.se>
AuthorDate: Tue Mar 27 13:32:09 2007 +0200
Committer:  David Woodhouse <dwmw2 at infradead.org>
CommitDate: Tue Apr 17 14:07:34 2007 -0400

    [JFFS2] Speed up mount for directly-mapped NOR flash
    
    Remove excessive scanning of empty flash after a clean
    marker for users of the point/unpoint method. cfi_cmdset_0001
    uses point/unpoint by default iff flash mapping is linear.
    The speedup is several orders of magnitude if FS is less than
    half full.
    
    Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund at transmode.se>
    Signed-off-by: David Woodhouse <dwmw2 at infradead.org>
---
 fs/jffs2/scan.c |   15 +++++++++++----
 1 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/fs/jffs2/scan.c b/fs/jffs2/scan.c
index a5103df..7a46a43 100644
--- a/fs/jffs2/scan.c
+++ b/fs/jffs2/scan.c
@@ -636,16 +636,17 @@ scan_more:
 
 		if (*(uint32_t *)(&buf[ofs-buf_ofs]) == 0xffffffff) {
 			uint32_t inbuf_ofs;
-			uint32_t empty_start;
+			uint32_t empty_start, scan_end;
 
 			empty_start = ofs;
 			ofs += 4;
+			scan_end = min_t(uint32_t, EMPTY_SCAN_SIZE(c->sector_size)/8, buf_len);
 
 			D1(printk(KERN_DEBUG "Found empty flash at 0x%08x\n", ofs));
 		more_empty:
 			inbuf_ofs = ofs - buf_ofs;
-			while (inbuf_ofs < buf_len) {
-				if (*(uint32_t *)(&buf[inbuf_ofs]) != 0xffffffff) {
+			while (inbuf_ofs < scan_end) {
+				if (unlikely(*(uint32_t *)(&buf[inbuf_ofs]) != 0xffffffff)) {
 					printk(KERN_WARNING "Empty flash at 0x%08x ends at 0x%08x\n",
 					       empty_start, ofs);
 					if ((err = jffs2_scan_dirty_space(c, jeb, ofs-empty_start)))
@@ -666,7 +667,11 @@ scan_more:
 				D1(printk(KERN_DEBUG "%d bytes at start of block seems clean... assuming all clean\n", EMPTY_SCAN_SIZE(c->sector_size)));
 				return BLK_STATE_CLEANMARKER;
 			}
-
+			if (!buf_size && (scan_end != buf_len)) {/* XIP/point case */
+				scan_end = buf_len;
+				goto more_empty;
+			}
+			
 			/* See how much more there is to read in this eraseblock... */
 			buf_len = min_t(uint32_t, buf_size, jeb->offset + c->sector_size - ofs);
 			if (!buf_len) {
@@ -676,6 +681,8 @@ scan_more:
 					  empty_start));
 				break;
 			}
+			/* point never reaches here */
+			scan_end = buf_len;
 			D1(printk(KERN_DEBUG "Reading another 0x%x at 0x%08x\n", buf_len, ofs));
 			err = jffs2_fill_scan_buf(c, buf, ofs, buf_len);
 			if (err)