[3.11.y.z extended stable] Patch "block: don't assume last put of shared tags is for the host" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    block: don't assume last put of shared tags is for the host

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 4a5e15f23bb6b4f484615934cb77d7747abe9f53 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch at lst.de>
Date: Tue, 8 Jul 2014 12:25:28 +0200
Subject: block: don't assume last put of shared tags is for the host

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 at lst.de>
Signed-off-by: Jens Axboe <axboe at fb.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 block/blk-tag.c | 33 +++++++--------------------------
 1 file changed, 7 insertions(+), 26 deletions(-)

diff --git a/block/blk-tag.c b/block/blk-tag.c
index 3f33d8672268..a185b86741e5 100644
--- a/block/blk-tag.c
+++ b/block/blk-tag.c
@@ -27,18 +27,15 @@ struct request *blk_queue_find_tag(struct request_queue *q, int tag)
 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_queue_tag *bqt)

 		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 request_queue *q)
 	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
  *
--
1.9.1