[RFC][PATCH] blk-tag: Use atomic_t type for bqt->busy.

Abhijeet Joglekar
2008-08-26T01:54:32Z

blk-tag: Use atomic_t type for bqt->busy.

bqt->busy is an integer that keeps count of number of outstanding tags. For
host-wide shared tag map, busy is accessed in a queue lock (not host lock)
which corrupts the busy value. Change busy to atomic_t and use atomic
macros to access it.

Signed-off-by: Abhijeet Joglekar <abjoglek@cisco.com>
---
block/blk-tag.c | 8 ++++----
include/linux/blkdev.h | 2 +-
2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/block/blk-tag.c b/block/blk-tag.c
index 32667be..8f37d08 100644
--- a/block/blk-tag.c
+++ b/block/blk-tag.c
@@ -38,7 +38,7 @@ static int __blk_free_tags(struct blk_queue_tag *bqt)

retval = atomic_dec_and_test(&bqt->refcnt);
if (retval) {
- BUG_ON(bqt->busy);
+ BUG_ON(atomic_read(&bqt->busy));

kfree(bqt->tag_index);
bqt->tag_index = NULL;
@@ -147,7 +147,7 @@ static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q,
if (init_tag_map(q, tags, depth))
goto fail;

- tags->busy = 0;
+ atomic_set(&tags->busy, 0);
atomic_set(&tags->refcnt, 1);
return tags;
fail:
@@ -313,7 +313,7 @@ void blk_queue_end_tag(struct request_queue *q, struct request *rq)
* unlock memory barrier semantics.
*/
clear_bit_unlock(tag, bqt->tag_map);
- bqt->busy--;
+ atomic_dec(&bqt->busy);
}
EXPORT_SYMBOL(blk_queue_end_tag);

@@ -368,7 +368,7 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq)
bqt->tag_index[tag] = rq;
blkdev_dequeue_request(rq);
list_add(&rq->queuelist, &q->tag_busy_list);
- bqt->busy++;
+ atomic_inc(&bqt->busy);
return 0;
}
EXPORT_SYMBOL(blk_queue_start_tag);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 88d6808..106531e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -274,7 +274,7 @@ enum blk_queue_state {
struct blk_queue_tag {
struct request **tag_index; /* map of busy tags */
unsigned long *tag_map; /* bit map of free/busy tags */
- int busy; /* current depth */
+ atomic_t busy; /* current depth */
int max_depth; /* what we will send to device */
int real_max_depth; /* what the array can hold */
atomic_t refcnt; /* map can be shared */