linux-kernel - Re: [PATCHv4 1/1] SCSI: hosts: update to use ida_simple for host

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Date:	Wed, 14 Oct 2015 14:22:42 +0200
From:	Johannes Thumshirn <jthumshirn@...e.de>
To:	Lee Duncan <lduncan@...e.com>, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Tejun Heo <tj@...nel.org>, Hannes Reinecke <hare@...e.com>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCHv4 1/1] SCSI: hosts: update to use ida_simple for host_no
 management

On Wed, 2015-10-07 at 16:51 -0700, Lee Duncan wrote:
> Update the SCSI hosts module to use the ida_simple*() routines
> to manage its host_no index instead of an ATOMIC integer. This
> means that the SCSI host number will now be reclaimable.
> 
> Signed-off-by: Lee Duncan <lduncan@...e.com>
> ---
>  drivers/scsi/hosts.c | 22 ++++++++++++++--------
>  1 file changed, 14 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
> index 8bb173e01084..b6a5ffa886b7 100644
> --- a/drivers/scsi/hosts.c
> +++ b/drivers/scsi/hosts.c
> @@ -33,7 +33,7 @@
>  #include <linux/transport_class.h>
>  #include <linux/platform_device.h>
>  #include <linux/pm_runtime.h>
> -
> +#include <linux/idr.h>
>  #include <scsi/scsi_device.h>
>  #include <scsi/scsi_host.h>
>  #include <scsi/scsi_transport.h>
> @@ -42,7 +42,7 @@
>  #include "scsi_logging.h"
>  
>  
> -static atomic_t scsi_host_next_hn = ATOMIC_INIT(0);	/*
> host_no for next new host */
> +static DEFINE_IDA(host_index_ida);
>  
>  
>  static void scsi_host_cls_release(struct device *dev)
> @@ -337,6 +337,8 @@ static void scsi_host_dev_release(struct device
> *dev)
>  
>  	kfree(shost->shost_data);
>  
> +	ida_simple_remove(&host_index_ida, shost->host_no);
> +
>  	if (parent)
>  		put_device(parent);
>  	kfree(shost);
> @@ -370,6 +372,7 @@ struct Scsi_Host *scsi_host_alloc(struct
> scsi_host_template *sht, int privsize)
>  {
>  	struct Scsi_Host *shost;
>  	gfp_t gfp_mask = GFP_KERNEL;
> +	int index;
>  
>  	if (sht->unchecked_isa_dma && privsize)
>  		gfp_mask |= __GFP_DMA;
> @@ -388,11 +391,11 @@ struct Scsi_Host *scsi_host_alloc(struct
> scsi_host_template *sht, int privsize)
>  	init_waitqueue_head(&shost->host_wait);
>  	mutex_init(&shost->scan_mutex);
>  
> -	/*
> -	 * subtract one because we increment first then return, but
> we need to
> -	 * know what the next host number was before increment
> -	 */
> -	shost->host_no = atomic_inc_return(&scsi_host_next_hn) - 1;
> +	index = ida_simple_get(&host_index_ida, 0, 0, GFP_KERNEL);
> +	if (index < 0)
> +		goto fail_kfree;
> +	shost->host_no = index;
> +
>  	shost->dma_channel = 0xff;
>  
>  	/* These three are default values which can be overridden */
> @@ -477,7 +480,7 @@ struct Scsi_Host *scsi_host_alloc(struct
> scsi_host_template *sht, int privsize)
>  		shost_printk(KERN_WARNING, shost,
>  			"error handler thread failed to spawn, error
> = %ld\n",
>  			PTR_ERR(shost->ehandler));
> -		goto fail_kfree;
> +		goto fail_index_remove;
>  	}
>  
>  	shost->tmf_work_q = alloc_workqueue("scsi_tmf_%d",
> @@ -493,6 +496,8 @@ struct Scsi_Host *scsi_host_alloc(struct
> scsi_host_template *sht, int privsize)
>  
>   fail_kthread:
>  	kthread_stop(shost->ehandler);
> + fail_index_remove:
> +	ida_simple_remove(&host_index_ida, shost->host_no);
>   fail_kfree:
>  	kfree(shost);
>  	return NULL;
> @@ -588,6 +593,7 @@ int scsi_init_hosts(void)
>  void scsi_exit_hosts(void)
>  {
>  	class_unregister(&shost_class);
> +	ida_destroy(&host_index_ida);
>  }
>  
>  int scsi_is_host_device(const struct device *dev)

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

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