Re: [PATCH] scsi: rescan VPD attributes

[Johannes Thumshirn <jthumshirn@suse.com>]

On Mon, 2015-11-09 at 13:24 +0100, Hannes Reinecke wrote:
> The VPD page information might change, so we need to be able to
> update it. This patch implements a VPD page rescan whenever
> the 'rescan' sysfs attribute is triggered.
> 
> Signed-off-by: Hannes Reinecke <hare@suse.de>
> ---
>  drivers/scsi/scsi.c        | 20 +++++++++++++++++---
>  drivers/scsi/scsi_scan.c   |  4 ++++
>  drivers/scsi/scsi_sysfs.c  |  8 ++++++--
>  drivers/scsi/ses.c         | 12 +++++++++---
>  include/scsi/scsi_device.h |  5 +++--
>  5 files changed, 39 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
> index 207d6a7..2e4ef56 100644
> --- a/drivers/scsi/scsi.c
> +++ b/drivers/scsi/scsi.c
> @@ -803,7 +803,7 @@ void scsi_attach_vpd(struct scsi_device *sdev)
>  	int vpd_len = SCSI_VPD_PG_LEN;
>  	int pg80_supported = 0;
>  	int pg83_supported = 0;
> -	unsigned char *vpd_buf;
> +	unsigned char __rcu *vpd_buf, *orig_vpd_buf = NULL;
>  
>  	if (sdev->skip_vpd_pages)
>  		return;
> @@ -849,8 +849,16 @@ retry_pg80:
>  			kfree(vpd_buf);
>  			goto retry_pg80;
>  		}
> +		mutex_lock(&sdev->inquiry_mutex);
> +		orig_vpd_buf = sdev->vpd_pg80;
>  		sdev->vpd_pg80_len = result;
> -		sdev->vpd_pg80 = vpd_buf;
> +		rcu_assign_pointer(sdev->vpd_pg80, vpd_buf);
> +		mutex_unlock(&sdev->inquiry_mutex);
> +		synchronize_rcu();
> +		if (orig_vpd_buf) {
> +			kfree(orig_vpd_buf);
> +			orig_vpd_buf = NULL;
> +		}
>  		vpd_len = SCSI_VPD_PG_LEN;
>  	}
>  
> @@ -870,8 +878,14 @@ retry_pg83:
>  			kfree(vpd_buf);
>  			goto retry_pg83;
>  		}
> +		mutex_lock(&sdev->inquiry_mutex);
> +		orig_vpd_buf = sdev->vpd_pg83;
>  		sdev->vpd_pg83_len = result;
> -		sdev->vpd_pg83 = vpd_buf;
> +		rcu_assign_pointer(sdev->vpd_pg83, vpd_buf);
> +		mutex_unlock(&sdev->inquiry_mutex);
> +		synchronize_rcu();
> +		if (orig_vpd_buf)
> +			kfree(orig_vpd_buf);
>  	}
>  }
>  
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index 3b3dfef..7e0820f 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -236,6 +236,7 @@ static struct scsi_device *scsi_alloc_sdev(struct
> scsi_target *starget,
>  	INIT_LIST_HEAD(&sdev->starved_entry);
>  	INIT_LIST_HEAD(&sdev->event_list);
>  	spin_lock_init(&sdev->list_lock);
> +	mutex_init(&sdev->inquiry_mutex);
>  	INIT_WORK(&sdev->event_work, scsi_evt_thread);
>  	INIT_WORK(&sdev->requeue_work, scsi_requeue_run_queue);
>  
> @@ -1517,6 +1518,9 @@ EXPORT_SYMBOL(scsi_add_device);
>  void scsi_rescan_device(struct device *dev)
>  {
>  	device_lock(dev);
> +
> +	scsi_attach_vpd(to_scsi_device(dev));
> +
>  	if (dev->driver && try_module_get(dev->driver->owner)) {
>  		struct scsi_driver *drv = to_scsi_driver(dev->driver);
>  
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index fdcf0ab..f021423 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -758,11 +758,15 @@ show_vpd_##_page(struct file *filp, struct kobject
> *kobj,	\
>  {									\
>  	struct device *dev = container_of(kobj, struct device, kobj);	
> \
>  	struct scsi_device *sdev = to_scsi_device(dev);			
> \
> +	int ret;							\
>  	if (!sdev->vpd_##_page)						
> \
>  		return -EINVAL;						
> \
> -	return memory_read_from_buffer(buf, count, &off,		\
> -				       sdev->vpd_##_page,		\
> +	rcu_read_lock();						\
> +	ret = memory_read_from_buffer(buf, count, &off,			
> \
> +				      rcu_dereference(sdev->vpd_##_page), \
>  				       sdev->vpd_##_page##_len);	\
> +	rcu_read_unlock();						\
> +	return ret;						\
>  }									\
>  static struct bin_attribute dev_attr_vpd_##_page = {		\
>  	.attr =	{.name = __stringify(vpd_##_page), .mode = S_IRUGO },
> 	\
> diff --git a/drivers/scsi/ses.c b/drivers/scsi/ses.c
> index dcb0d76..e234da7 100644
> --- a/drivers/scsi/ses.c
> +++ b/drivers/scsi/ses.c
> @@ -554,17 +554,22 @@ static void ses_match_to_enclosure(struct
> enclosure_device *edev,
>  				   struct scsi_device *sdev)
>  {
>  	unsigned char *desc;
> +	unsigned char __rcu *vpd_pg83;
>  	struct efd efd = {
>  		.addr = 0,
>  	};
>  
>  	ses_enclosure_data_process(edev, to_scsi_device(edev->edev.parent),
> 0);
>  
> -	if (!sdev->vpd_pg83_len)
> +	rcu_read_lock();
> +	vpd_pg83 = rcu_dereference(sdev->vpd_pg83);
> +	if (!vpd_pg83) {
> +		rcu_read_unlock();
>  		return;
> +	}
>  
> -	desc = sdev->vpd_pg83 + 4;
> -	while (desc < sdev->vpd_pg83 + sdev->vpd_pg83_len) {
> +	desc = vpd_pg83 + 4;
> +	while (desc < vpd_pg83 + sdev->vpd_pg83_len) {
>  		enum scsi_protocol proto = desc[0] >> 4;
>  		u8 code_set = desc[0] & 0x0f;
>  		u8 piv = desc[1] & 0x80;
> @@ -578,6 +583,7 @@ static void ses_match_to_enclosure(struct
> enclosure_device *edev,
>  
>  		desc += len + 4;
>  	}
> +	rcu_read_unlock();
>  	if (efd.addr) {
>  		efd.dev = &sdev->sdev_gendev;
>  
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index fe89d7c..bde4077 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -109,6 +109,7 @@ struct scsi_device {
>  	char type;
>  	char scsi_level;
>  	char inq_periph_qual;	/* PQ from INQUIRY data */	
> +	struct mutex inquiry_mutex;
>  	unsigned char inquiry_len;	/* valid bytes in 'inquiry' */
>  	unsigned char * inquiry;	/* INQUIRY response data */
>  	const char * vendor;		/* [back_compat] point into
> 'inquiry' ... */
> @@ -117,9 +118,9 @@ struct scsi_device {
>  
>  #define SCSI_VPD_PG_LEN                255
>  	int vpd_pg83_len;
> -	unsigned char *vpd_pg83;
> +	unsigned char __rcu *vpd_pg83;
>  	int vpd_pg80_len;
> -	unsigned char *vpd_pg80;
> +	unsigned char __rcu *vpd_pg80;
>  	unsigned char current_tag;	/* current tag */
>  	struct scsi_target      *sdev_target;   /* used only for single_lun
> */
>  

Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
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