[PATCH] blk: use find_first_zero_bit() in blk_queue_start_tag()

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@gmail.com>
Acked-by: Jens Axboe <axboe@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 9 deletions

diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c
index cd8cf302068c..808390c74200 100644
--- a/drivers/block/ll_rw_blk.c
+++ b/drivers/block/ll_rw_blk.c
@@ -968,8 +968,7 @@ 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 
@@ -978,14 +977,10 @@ int blk_queue_start_tag(request_queue_t *q, struct request *rq)
                 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;