[PATCH] [BLOCK] Allow tag 0 to be generated

From: Luben Tuikov
Date: Mon Jan 10 2011 - 12:26:22 EST


Commit 67869fb9fdfa04503b250d59e086c15f1698aea0
skipped tag 0 by virtue of setting last_tag to
0. This commit sets it to -1, in order to start
and loop over from 0, thus generating tags
[0,max_tag-1], instead of [1,max_tag-1].

Signed-off-by: Luben Tuikov <ltuikov@xxxxxxxxx>
---
For a reference to the original patch see here:
git://github.com/ltuikov/linux-2.6.git

block/blk-tag.c | 8 ++++----
1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/block/blk-tag.c b/block/blk-tag.c
index f792e98..744cea6 100644
--- a/block/blk-tag.c
+++ b/block/blk-tag.c
@@ -130,7 +130,7 @@ init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth)
tags->max_depth = depth;
tags->tag_index = tag_index;
tags->tag_map = tag_map;
- tags->last_tag = 0;
+ tags->last_tag = -1;

return 0;
fail:
@@ -340,7 +340,7 @@ EXPORT_SYMBOL(blk_queue_end_tag);
int blk_queue_start_tag(struct request_queue *q, struct request *rq)
{
struct blk_queue_tag *bqt = q->queue_tags;
- unsigned max_depth;
+ int max_depth;
int tag;

if (unlikely((rq->cmd_flags & REQ_QUEUED))) {
@@ -361,14 +361,14 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq)
max_depth = bqt->max_depth;
if (!rq_is_sync(rq) && max_depth > 1) {
max_depth -= 2;
- if (!max_depth)
+ if (max_depth <= 0)
max_depth = 1;
if (q->in_flight[BLK_RW_ASYNC] > max_depth)
return 1;
}

if (bqt->last_tag == bqt->max_depth-1)
- bqt->last_tag = 0;
+ bqt->last_tag = -1;

do {
tag = find_next_zero_bit(bqt->tag_map,
--
1.7.2.2.165.gbc382

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