[PATCHv2] Update scsi host to use ida for host number

[PATCHv2] Update scsi host to use ida for host number

[lduncan]

From: Lee Duncan <lduncan@suse.com>

Each Scsi_host instance gets a host number starting
at 0, but this is implemented with an atomic integer,
and rollover doesn't seem to have been considered.
Another side-effect of this design is that scsi host
numbers used by iscsi are never reused, thereby  making
rollover more likely. This patch converts Scsi_host
instances to use ida to manage their instance
numbers.

This also means that host instance numbers will be
reused, when available.

Changes from v1:
* Added inline host_put_index() and its use

Signed-off-by: Lee Duncan <lduncan@suse.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 drivers/scsi/hosts.c | 47 +++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 39 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index 8bb173e01084..36cb65612821 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 +42,8 @@
 #include "scsi_logging.h"
 
 
-static atomic_t scsi_host_next_hn = ATOMIC_INIT(0);	/* host_no for next new host */
+static DEFINE_SPINLOCK(host_index_lock);
+static DEFINE_IDA(host_index_ida);
 
 
 static void scsi_host_cls_release(struct device *dev)
@@ -337,6 +338,10 @@ static void scsi_host_dev_release(struct device *dev)
 
 	kfree(shost->shost_data);
 
+	spin_lock(&host_index_lock);
+	ida_remove(&host_index_ida, shost->host_no);
+	spin_unlock(&host_index_lock);
+
 	if (parent)
 		put_device(parent);
 	kfree(shost);
@@ -353,6 +358,28 @@ static struct device_type scsi_host_type = {
 	.release =	scsi_host_dev_release,
 };
 
+static int host_get_index(int *index)
+{
+	int error = -ENOMEM;
+
+	do {
+		if (!ida_pre_get(&host_index_ida, GFP_KERNEL))
+			break;
+		spin_lock(&host_index_lock);
+		error = ida_get_new(&host_index_ida, index);
+		spin_unlock(&host_index_lock);
+	} while (error == -EAGAIN);
+
+	return error;
+}
+
+static inline void host_put_index(int index)
+{
+	spin_lock(&host_index_lock);
+	ida_remove(&host_index_ida, index);
+	spin_unlock(&host_index_lock);
+}
+
 /**
  * scsi_host_alloc - register a scsi host adapter instance.
  * @sht:	pointer to scsi host template
@@ -370,6 +397,8 @@ 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;
+	int error;
 
 	if (sht->unchecked_isa_dma && privsize)
 		gfp_mask |= __GFP_DMA;
@@ -388,11 +417,11 @@ 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;
+	error = host_get_index(&index);
+	if (error < 0)
+		goto fail_kfree;
+	shost->host_no = index;
+
 	shost->dma_channel = 0xff;
 
 	/* These three are default values which can be overridden */
@@ -477,7 +506,7 @@ 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_free_index;
 	}
 
 	shost->tmf_work_q = alloc_workqueue("scsi_tmf_%d",
@@ -493,6 +522,8 @@ struct Scsi_Host *scsi_host_alloc(struct scsi_host_template *sht, int privsize)
 
  fail_kthread:
 	kthread_stop(shost->ehandler);
+ fail_free_index:
+	host_put_index(index);
  fail_kfree:
 	kfree(shost);
 	return NULL;
-- 
2.1.4

Re: [PATCHv2] Update scsi host to use ida for host number

[Sagi Grimberg]

On 9/1/2015 8:38 PM, lduncan@suse.com wrote:
> From: Lee Duncan <lduncan@suse.com>
>
> Each Scsi_host instance gets a host number starting
> at 0, but this is implemented with an atomic integer,
> and rollover doesn't seem to have been considered.
> Another side-effect of this design is that scsi host
> numbers used by iscsi are never reused, thereby  making
> rollover more likely. This patch converts Scsi_host
> instances to use ida to manage their instance
> numbers.
>
> This also means that host instance numbers will be
> reused, when available.
>
> Changes from v1:
> * Added inline host_put_index() and its use
>
> Signed-off-by: Lee Duncan <lduncan@suse.com>
> Reviewed-by: Hannes Reinecke <hare@suse.com>
> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
> ---
>   drivers/scsi/hosts.c | 47 +++++++++++++++++++++++++++++++++++++++--------
>   1 file changed, 39 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
> index 8bb173e01084..36cb65612821 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 +42,8 @@
>   #include "scsi_logging.h"
>
>
> -static atomic_t scsi_host_next_hn = ATOMIC_INIT(0);	/* host_no for next new host */
> +static DEFINE_SPINLOCK(host_index_lock);
> +static DEFINE_IDA(host_index_ida);
>
>
>   static void scsi_host_cls_release(struct device *dev)
> @@ -337,6 +338,10 @@ static void scsi_host_dev_release(struct device *dev)
>
>   	kfree(shost->shost_data);
>
> +	spin_lock(&host_index_lock);
> +	ida_remove(&host_index_ida, shost->host_no);
> +	spin_unlock(&host_index_lock);

Why not host_put_index(index)?

Re: [PATCHv2] Update scsi host to use ida for host number

[Lee Duncan]

On 09/01/2015 10:49 AM, Sagi Grimberg wrote:
> On 9/1/2015 8:38 PM, lduncan@suse.com wrote:
>> From: Lee Duncan <lduncan@suse.com>
>>
>> Each Scsi_host instance gets a host number starting
>> at 0, but this is implemented with an atomic integer,
>> and rollover doesn't seem to have been considered.
>> Another side-effect of this design is that scsi host
>> numbers used by iscsi are never reused, thereby  making
>> rollover more likely. This patch converts Scsi_host
>> instances to use ida to manage their instance
>> numbers.
>>
>> This also means that host instance numbers will be
>> reused, when available.
>>
>> Changes from v1:
>> * Added inline host_put_index() and its use
>>
>> Signed-off-by: Lee Duncan <lduncan@suse.com>
>> Reviewed-by: Hannes Reinecke <hare@suse.com>
>> Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
>> ---
>>   drivers/scsi/hosts.c | 47
>> +++++++++++++++++++++++++++++++++++++++--------
>>   1 file changed, 39 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
>> index 8bb173e01084..36cb65612821 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 +42,8 @@
>>   #include "scsi_logging.h"
>>
>>
>> -static atomic_t scsi_host_next_hn = ATOMIC_INIT(0);    /* host_no for
>> next new host */
>> +static DEFINE_SPINLOCK(host_index_lock);
>> +static DEFINE_IDA(host_index_ida);
>>
>>
>>   static void scsi_host_cls_release(struct device *dev)
>> @@ -337,6 +338,10 @@ static void scsi_host_dev_release(struct device
>> *dev)
>>
>>       kfree(shost->shost_data);
>>
>> +    spin_lock(&host_index_lock);
>> +    ida_remove(&host_index_ida, shost->host_no);
>> +    spin_unlock(&host_index_lock);
> 
> Why not host_put_index(index)?
> 

Doh! I'll fix that in both places.
-- 
Lee Duncan