[PATCH 3.15 09/37] block: dont assume last put of shared tags is for the host

Greg Kroah-Hartman
2014-07-30T01:48:45Z

From: Christoph Hellwig <hch@lst.de>

commit d45b3279a5a2252cafcd665bbf2db8c9b31ef783 upstream.

There is no inherent reason why the last put of a tag structure must be
the one for the Scsi_Host, as device model objects can be held for
arbitrary periods. Merge blk_free_tags and __blk_free_tags into a single
funtion that just release a references and get rid of the BUG() when the
host reference wasn't the last.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
block/blk-tag.c | 33 +++++++--------------------------
1 file changed, 7 insertions(+), 26 deletions(-)

--- a/block/blk-tag.c
+++ b/block/blk-tag.c
@@ -27,18 +27,15 @@ struct request *blk_queue_find_tag(struc
EXPORT_SYMBOL(blk_queue_find_tag);

/**
- * __blk_free_tags - release a given set of tag maintenance info
+ * blk_free_tags - release a given set of tag maintenance info
* @bqt: the tag map to free
*
- * Tries to free the specified @bqt. Returns true if it was
- * actually freed and false if there are still references using it
+ * Drop the reference count on @bqt and frees it when the last reference
+ * is dropped.
*/
-static int __blk_free_tags(struct blk_queue_tag *bqt)
+void blk_free_tags(struct blk_queue_tag *bqt)
{
- int retval;
-
- retval = atomic_dec_and_test(&bqt->refcnt);
- if (retval) {
+ if (atomic_dec_and_test(&bqt->refcnt)) {
BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) <
bqt->max_depth);

@@ -50,9 +47,8 @@ static int __blk_free_tags(struct blk_qu

kfree(bqt);
}
-
- return retval;
}
+EXPORT_SYMBOL(blk_free_tags);

/**
* __blk_queue_free_tags - release tag maintenance info
@@ -69,28 +65,13 @@ void __blk_queue_free_tags(struct reques
if (!bqt)
return;

- __blk_free_tags(bqt);
+ blk_free_tags(bqt);

q->queue_tags = NULL;
queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q);
}

/**
- * blk_free_tags - release a given set of tag maintenance info
- * @bqt: the tag map to free
- *
- * For externally managed @bqt frees the map. Callers of this
- * function must guarantee to have released all the queues that
- * might have been using this tag map.
- */
-void blk_free_tags(struct blk_queue_tag *bqt)
-{
- if (unlikely(!__blk_free_tags(bqt)))
- BUG();
-}
-EXPORT_SYMBOL(blk_free_tags);
-
-/**
* blk_queue_free_tags - release tag maintenance info
* @q: the request queue for the device
*