linux-kernel - Re: [PATCH v6 08/14] nvmet-fcloop: prevent double port deletion

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Message-ID: <8ce7f125-66b3-4c8c-8c99-77d129adb1a8@suse.de>
Date: Wed, 7 May 2025 15:59:02 +0200
From: Hannes Reinecke <hare@...e.de>
To: Daniel Wagner <wagi@...nel.org>, James Smart <james.smart@...adcom.com>,
 Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
 Chaitanya Kulkarni <kch@...dia.com>
Cc: Keith Busch <kbusch@...nel.org>, linux-nvme@...ts.infradead.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 08/14] nvmet-fcloop: prevent double port deletion

On 5/7/25 14:23, Daniel Wagner wrote:
> The delete callback can be called either via the unregister function or
> from the transport directly. Thus it is necessary ensure resources are
> not freed multiple times.
> 
> Signed-off-by: Daniel Wagner <wagi@...nel.org>
> ---
>   drivers/nvme/target/fcloop.c | 19 +++++++++++++++++--
>   1 file changed, 17 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/target/fcloop.c b/drivers/nvme/target/fcloop.c
> index 9adaee3c7129f7e270842c5d09f78de2e108479a..c74baa7f6e43c8bddd9e6948f806f27b032b1d4d 100644
> --- a/drivers/nvme/target/fcloop.c
> +++ b/drivers/nvme/target/fcloop.c
> @@ -215,6 +215,9 @@ struct fcloop_lport_priv {
>   	struct fcloop_lport *lport;
>   };
>   
> +/* The port is already being removed, avoid double free */
> +#define PORT_DELETED	0
> +
>   struct fcloop_rport {
>   	struct nvme_fc_remote_port	*remoteport;
>   	struct nvmet_fc_target_port	*targetport;
> @@ -223,6 +226,7 @@ struct fcloop_rport {
>   	spinlock_t			lock;
>   	struct list_head		ls_list;
>   	struct work_struct		ls_work;
> +	unsigned long			flags;
>   };
>   
>   struct fcloop_tport {
> @@ -233,6 +237,7 @@ struct fcloop_tport {
>   	spinlock_t			lock;
>   	struct list_head		ls_list;
>   	struct work_struct		ls_work;
> +	unsigned long			flags;
>   };
>   
>   struct fcloop_nport {
> @@ -1067,30 +1072,38 @@ static void
>   fcloop_remoteport_delete(struct nvme_fc_remote_port *remoteport)
>   {
>   	struct fcloop_rport *rport = remoteport->private;
> +	bool put_port = false;
>   	unsigned long flags;
>   
>   	flush_work(&rport->ls_work);
>   
>   	spin_lock_irqsave(&fcloop_lock, flags);
> +	if (!test_and_set_bit(PORT_DELETED, &rport->flags))
> +		put_port = true;
>   	rport->nport->rport = NULL;

Can't we set '->nport' to NULL here (and save it in a temporary
variable)?
Then it's quite obvious if we need to call nport_put(),
and we would do away with the 'flags' field ...

>   	spin_unlock_irqrestore(&fcloop_lock, flags);
>   
> -	fcloop_nport_put(rport->nport);
> +	if (put_port)
> +		fcloop_nport_put(rport->nport);
>   }
>   
>   static void
>   fcloop_targetport_delete(struct nvmet_fc_target_port *targetport)
>   {
>   	struct fcloop_tport *tport = targetport->private;
> +	bool put_port = false;
>   	unsigned long flags;
>   
>   	flush_work(&tport->ls_work);
>   
>   	spin_lock_irqsave(&fcloop_lock, flags);
> +	if (!test_and_set_bit(PORT_DELETED, &tport->flags))
> +		put_port = true;
>   	tport->nport->tport = NULL;

Similar here.

>   	spin_unlock_irqrestore(&fcloop_lock, flags);
>   
> -	fcloop_nport_put(tport->nport);
> +	if (put_port)
> +		fcloop_nport_put(tport->nport);
>   }
>   
>   #define	FCLOOP_HW_QUEUES		4
> @@ -1433,6 +1446,7 @@ fcloop_create_remote_port(struct device *dev, struct device_attribute *attr,
>   	rport->nport = nport;
>   	rport->lport = nport->lport;
>   	nport->rport = rport;
> +	rport->flags = 0;
>   	spin_lock_init(&rport->lock);
>   	INIT_WORK(&rport->ls_work, fcloop_rport_lsrqst_work);
>   	INIT_LIST_HEAD(&rport->ls_list);
> @@ -1530,6 +1544,7 @@ fcloop_create_target_port(struct device *dev, struct device_attribute *attr,
>   	tport->nport = nport;
>   	tport->lport = nport->lport;
>   	nport->tport = tport;
> +	tport->flags = 0;
>   	spin_lock_init(&tport->lock);
>   	INIT_WORK(&tport->ls_work, fcloop_tport_lsrqst_work);
>   	INIT_LIST_HEAD(&tport->ls_list);
> 

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                  Kernel Storage Architect
hare@...e.de                                +49 911 74053 688
SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg
HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich