From adb4ddbbfb90c302e78da68b3f015588ca45d7f3 Mon Sep 17 00:00:00 2001
From: Nick Piggin <npiggin@suse.de>
Date: Wed, 24 Oct 2007 10:54:38 +0200
Subject: [PATCH] block: use lock bitops for the tag map.
The block queue tag map can use lock bitops.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
block/ll_rw_blk.c | 20 +++++++++-----------
1 file changed, 9 insertions(+), 11 deletions(-)
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index d8616e6ebd92..a8a181072bf8 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -1057,18 +1057,16 @@ void blk_queue_end_tag(struct request_queue *q, struct request *rq)
bqt->tag_index[tag] = NULL;
- /*
- * We use test_and_clear_bit's memory ordering properties here.
- * The tag_map bit acts as a lock for tag_index[bit], so we need
- * a barrer before clearing the bit (precisely: release semantics).
- * Could use clear_bit_unlock when it is merged.
- */
- if (unlikely(!test_and_clear_bit(tag, bqt->tag_map))) {
+ if (unlikely(!test_bit(tag, bqt->tag_map))) {
printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n",
__FUNCTION__, tag);
return;
}
-
+ /*
+ * The tag_map bit acts as a lock for tag_index[bit], so we need
+ * unlock memory barrier semantics.
+ */
+ clear_bit_unlock(tag, bqt->tag_map);
bqt->busy--;
}
@@ -1114,10 +1112,10 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq)
if (tag >= bqt->max_depth)
return 1;
- } while (test_and_set_bit(tag, bqt->tag_map));
+ } while (test_and_set_bit_lock(tag, bqt->tag_map));
/*
- * We rely on test_and_set_bit providing lock memory ordering semantics
- * (could use test_and_set_bit_lock when it is merged).
+ * We need lock ordering semantics given by test_and_set_bit_lock.
+ * See blk_queue_end_tag for details.
*/
rq->cmd_flags |= REQ_QUEUED;
--
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