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From: Ming Lei <ming.lei@redhat.com>
To: John Garry <john.garry@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	James Bottomley <James.Bottomley@hansenpartnership.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Hannes Reinecke <hare@suse.com>,
	Don Brace <don.brace@microsemi.com>,
	Kashyap Desai <kashyap.desai@broadcom.com>,
	Sathya Prakash <sathya.prakash@broadcom.com>,
	Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/9] blk-mq: allow hw queues to share hostwide tags
Date: Mon, 24 Jun 2019 16:46:15 +0800
Message-ID: <20190624084614.GC10941@ming.t460p> (raw)
In-Reply-To: <0f1773af-170a-a6b5-54ce-274dacb2b63a@huawei.com>

On Wed, Jun 05, 2019 at 03:10:51PM +0100, John Garry wrote:
> On 31/05/2019 03:27, Ming Lei wrote:
> > index 32b8ad3d341b..49d73d979cb3 100644
> > --- a/block/blk-mq.c
> > +++ b/block/blk-mq.c
> > @@ -2433,6 +2433,11 @@ static bool __blk_mq_alloc_rq_map(struct blk_mq_tag_set *set, int hctx_idx)
> >  {
> >  	int ret = 0;
> > 
> 
> Hi Ming,
> 
> > +	if ((set->flags & BLK_MQ_F_HOST_TAGS) && hctx_idx) {
> > +		set->tags[hctx_idx] = set->tags[0];
> 
> Here we set all tags same as that of hctx index 0.
> 
> > +		return true;
> 
> 
> As such, I think that the error handling in __blk_mq_alloc_rq_maps() is made
> a little fragile:
> 
> __blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
> {
> 	int i;
> 
> 	for (i = 0; i < set->nr_hw_queues; i++)
> 		if (!__blk_mq_alloc_rq_map(set, i))
> 			goto out_unwind;
> 
> 	return 0;
> 
> out_unwind:
> 	while (--i >= 0)
> 		blk_mq_free_rq_map(set->tags[i]);
> 
> 	return -ENOMEM;
> }
> 
> If __blk_mq_alloc_rq_map(, i > 1) fails for when BLK_MQ_F_HOST_TAGS FLAG is
> set (even though today it can't), then we would try to free set->tags[0]
> multiple times.

Good catch, and the issue can be addressed easily by setting set->hctx[i] as
NULL, then check 'tags' in blk_mq_free_rq_map().

Thanks,
Ming

  reply index

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-31  2:27 [PATCH 0/9] blk-mq/scsi: convert private reply queue into blk_mq hw queue Ming Lei
2019-05-31  2:27 ` [PATCH 1/9] blk-mq: allow hw queues to share hostwide tags Ming Lei
2019-05-31  6:07   ` Hannes Reinecke
2019-05-31 15:37   ` Bart Van Assche
2019-06-24  8:44     ` Ming Lei
2019-06-05 14:10   ` John Garry
2019-06-24  8:46     ` Ming Lei [this message]
2019-06-24 13:14       ` John Garry
2019-05-31  2:27 ` [PATCH 2/9] block: null_blk: introduce module parameter of 'g_host_tags' Ming Lei
2019-05-31  6:08   ` Hannes Reinecke
2019-05-31 15:39   ` Bart Van Assche
2019-06-24  8:43     ` Ming Lei
2019-06-02  1:56   ` Minwoo Im
2019-05-31  2:27 ` [PATCH 3/9] scsi: Add template flag 'host_tagset' Ming Lei
2019-05-31  6:08   ` Hannes Reinecke
2019-05-31  2:27 ` [PATCH 4/9] scsi_debug: support host tagset Ming Lei
2019-05-31  6:09   ` Hannes Reinecke
2019-06-02  2:03   ` Minwoo Im
2019-06-02 17:01   ` Douglas Gilbert
2019-05-31  2:27 ` [PATCH 5/9] scsi: introduce scsi_cmnd_hctx_index() Ming Lei
2019-05-31  6:10   ` Hannes Reinecke
2019-05-31  2:27 ` [PATCH 6/9] scsi: hpsa: convert private reply queue to blk-mq hw queue Ming Lei
2019-05-31  6:15   ` Hannes Reinecke
2019-05-31  6:30     ` Ming Lei
2019-05-31  6:40       ` Hannes Reinecke
2019-05-31  2:27 ` [PATCH 7/9] scsi: hisi_sas_v3: " Ming Lei
2019-05-31  6:20   ` Hannes Reinecke
2019-05-31  6:34     ` Ming Lei
2019-05-31  6:42       ` Hannes Reinecke
2019-05-31  7:14         ` Ming Lei
2019-05-31 11:38       ` John Garry
2019-06-03 11:00         ` Ming Lei
2019-06-03 13:00           ` John Garry
2019-06-04 13:37             ` Ming Lei
2019-05-31  2:28 ` [PATCH 8/9] scsi: megaraid: " Ming Lei
2019-05-31  6:22   ` Hannes Reinecke
2019-06-01 21:41   ` Kashyap Desai
2019-06-02  6:42     ` Ming Lei
2019-06-02  7:48       ` Ming Lei
2019-06-02 16:34         ` Kashyap Desai
2019-06-03  3:56           ` Ming Lei
2019-06-03 10:00             ` Kashyap Desai
2019-06-07  9:45             ` Kashyap Desai
2019-05-31  2:28 ` [PATCH 9/9] scsi: mp3sas: " Ming Lei
2019-05-31  6:23   ` Hannes Reinecke
2019-06-06 11:58   ` Sreekanth Reddy
2019-06-04  8:49 ` [PATCH 0/9] blk-mq/scsi: convert private reply queue into blk_mq " John Garry
2019-08-13  8:30   ` John Garry

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