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Commit 6eca9004 authored by Jens Axboe's avatar Jens Axboe
Browse files

[BLOCK] Fix bad sharing of tag busy list on queues with shared tag maps 



For the locking to work, only the tag map and tag bit map may be shared
(incidentally, I was just explaining this to Nick yesterday, but I
apparently didn't review the code well enough myself). But we also share
the busy list!  The busy_list must be queue private, or we need a
block_queue_tag covering lock as well.

So we have to move the busy_list to the queue. This'll work fine, and
it'll actually also fix a problem with blk_queue_invalidate_tags() which
will invalidate tags across all shared queues. This is a bit confusing,
the low level driver should call it for each queue seperately since
otherwise you cannot kill tags on just a single queue for eg a hard
drive that stops responding. Since the function has no callers
currently, it's not an issue.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 3a424f2d

block/ll_rw_blk.c

+3 −5
Original line number Diff line number Diff line
@@ -791,7 +791,6 @@ 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(!list_empty(&bqt->busy_list));



		kfree(bqt->tag_index);

		bqt->tag_index = NULL;
@@ -903,7 +902,6 @@ static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q, 
	if (init_tag_map(q, tags, depth))

		goto fail;



	INIT_LIST_HEAD(&tags->busy_list);

	tags->busy = 0;

	atomic_set(&tags->refcnt, 1);

	return tags;
@@ -954,6 +952,7 @@ int blk_queue_init_tags(struct request_queue *q, int depth, 
	 */

	q->queue_tags = tags;

	q->queue_flags |= (1 << QUEUE_FLAG_QUEUED);

	INIT_LIST_HEAD(&q->tag_busy_list);

	return 0;

fail:

	kfree(tags);
@@ -1122,7 +1121,7 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq) 
	rq->tag = tag;

	bqt->tag_index[tag] = rq;

	blkdev_dequeue_request(rq);

	list_add(&rq->queuelist, &bqt->busy_list);

	list_add(&rq->queuelist, &q->tag_busy_list);

	bqt->busy++;

	return 0;

}
@@ -1143,11 +1142,10 @@ EXPORT_SYMBOL(blk_queue_start_tag); 
 **/

void blk_queue_invalidate_tags(struct request_queue *q)

{

	struct blk_queue_tag *bqt = q->queue_tags;

	struct list_head *tmp, *n;

	struct request *rq;



	list_for_each_safe(tmp, n, &bqt->busy_list) {

	list_for_each_safe(tmp, n, &q->tag_busy_list) {

		rq = list_entry_rq(tmp);



		if (rq->tag == -1) {

include/linux/blkdev.h

+1 −1
Original line number Diff line number Diff line
@@ -341,7 +341,6 @@ 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 */

	struct list_head busy_list;	/* fifo list of busy tags */

	int busy;			/* current depth */

	int max_depth;			/* what we will send to device */

	int real_max_depth;		/* what the array can hold */
@@ -435,6 +434,7 @@ struct request_queue 
	unsigned int		dma_alignment;



	struct blk_queue_tag	*queue_tags;

	struct list_head	tag_busy_list;



	unsigned int		nr_sorted;

	unsigned int		in_flight;