Re: [PATCH Linux 2.6.12-rc2 01/04] blk: use find_first_zero_bit() in blk_queue_start_tag()

[Tejun Heo]

01_blk_tag_map_use_find_first_zero_bit.patch

	blk_queue_start_tag() hand-coded searching for the first zero
	bit in the tag map.  Replace it with find_first_zero_bit().
	With this patch, blk_queue_star_tag() doesn't need to fill
	remains of tag map with 1, thus allowing it to work properly
	with the next remove_real_max_depth patch.

Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>

 ll_rw_blk.c |   13 ++++---------
 1 files changed, 4 insertions(+), 9 deletions(-)

Index: blk-fixes/drivers/block/ll_rw_blk.c
===================================================================
--- blk-fixes.orig/drivers/block/ll_rw_blk.c	2005-04-20 20:36:35.000000000 +0900
+++ blk-fixes/drivers/block/ll_rw_blk.c	2005-04-20 20:36:36.000000000 +0900
@@ -967,8 +967,7 @@ EXPORT_SYMBOL(blk_queue_end_tag);
 int blk_queue_start_tag(request_queue_t *q, struct request *rq)
 {
 	struct blk_queue_tag *bqt = q->queue_tags;
-	unsigned long *map = bqt->tag_map;
-	int tag = 0;
+	int tag;
 
 	if (unlikely((rq->flags & REQ_QUEUED))) {
 		printk(KERN_ERR 
@@ -977,14 +976,10 @@ int blk_queue_start_tag(request_queue_t 
 		BUG();
 	}
 
-	for (map = bqt->tag_map; *map == -1UL; map++) {
-		tag += BLK_TAGS_PER_LONG;
-
-		if (tag >= bqt->max_depth)
-			return 1;
-	}
+	tag = find_first_zero_bit(bqt->tag_map, bqt->max_depth);
+	if (tag >= bqt->max_depth)
+		return 1;
 
-	tag += ffz(*map);
 	__set_bit(tag, bqt->tag_map);
 
 	rq->flags |= REQ_QUEUED;

-
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