[PATCH 1/2] xen/scsiback: correct frontend counting

[PATCH 1/2] xen/scsiback: correct frontend counting

[Juergen Gross]

When adding a new frontend to xen-scsiback don't decrement the number
of active frontends in case of no error. Not doing so results in a
failure when trying to remove the xen-pvscsi nexus even if no domain
is using it.

Signed-off-by: Juergen Gross <jgross@suse.com>
Cc: stable@vger.kernel.org
---
 drivers/xen/xen-scsiback.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
index ad4eb10..51387d7 100644
--- a/drivers/xen/xen-scsiback.c
+++ b/drivers/xen/xen-scsiback.c
@@ -939,12 +939,12 @@ out:
 	spin_unlock_irqrestore(&info->v2p_lock, flags);
 
 out_free:
-	mutex_lock(&tpg->tv_tpg_mutex);
-	tpg->tv_tpg_fe_count--;
-	mutex_unlock(&tpg->tv_tpg_mutex);
-
-	if (err)
+	if (err) {
+		mutex_lock(&tpg->tv_tpg_mutex);
+		tpg->tv_tpg_fe_count--;
+		mutex_unlock(&tpg->tv_tpg_mutex);
 		kfree(new);
+	}
 
 	return err;
 }
-- 
2.6.2

[PATCH 2/2] xen/scsiback: avoid warnings when adding multiple LUNs to a domain

[Juergen Gross]

When adding more than one LUN to a frontend a warning for a failed
assignment is issued in dom0 for each already existing LUN. Avoid this
warning.

Signed-off-by: Juergen Gross <jgross@suse.com>
Cc: stable@vger.kernel.org
---
 drivers/xen/xen-scsiback.c | 65 ++++++++++++++++++++++++++--------------------
 1 file changed, 37 insertions(+), 28 deletions(-)

diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
index 51387d7..69de879 100644
--- a/drivers/xen/xen-scsiback.c
+++ b/drivers/xen/xen-scsiback.c
@@ -849,15 +849,31 @@ static int scsiback_map(struct vscsibk_info *info)
 }
 
 /*
+  Check for a translation entry being present
+*/
+static struct v2p_entry *scsiback_chk_translation_entry(
+	struct vscsibk_info *info, struct ids_tuple *v)
+{
+	struct list_head *head = &(info->v2p_entry_lists);
+	struct v2p_entry *entry;
+
+	list_for_each_entry(entry, head, l)
+		if ((entry->v.chn == v->chn) &&
+		    (entry->v.tgt == v->tgt) &&
+		    (entry->v.lun == v->lun))
+			return entry;
+
+	return NULL;
+}
+
+/*
   Add a new translation entry
 */
 static int scsiback_add_translation_entry(struct vscsibk_info *info,
 					  char *phy, struct ids_tuple *v)
 {
 	int err = 0;
-	struct v2p_entry *entry;
 	struct v2p_entry *new;
-	struct list_head *head = &(info->v2p_entry_lists);
 	unsigned long flags;
 	char *lunp;
 	unsigned long long unpacked_lun;
@@ -917,15 +933,10 @@ static int scsiback_add_translation_entry(struct vscsibk_info *info,
 	spin_lock_irqsave(&info->v2p_lock, flags);
 
 	/* Check double assignment to identical virtual ID */
-	list_for_each_entry(entry, head, l) {
-		if ((entry->v.chn == v->chn) &&
-		    (entry->v.tgt == v->tgt) &&
-		    (entry->v.lun == v->lun)) {
-			pr_warn("Virtual ID is already used. Assignment was not performed.\n");
-			err = -EEXIST;
-			goto out;
-		}
-
+	if (scsiback_chk_translation_entry(info, v)) {
+		pr_warn("Virtual ID is already used. Assignment was not performed.\n");
+		err = -EEXIST;
+		goto out;
 	}
 
 	/* Create a new translation entry and add to the list */
@@ -933,7 +944,7 @@ static int scsiback_add_translation_entry(struct vscsibk_info *info,
 	new->v = *v;
 	new->tpg = tpg;
 	new->lun = unpacked_lun;
-	list_add_tail(&new->l, head);
+	list_add_tail(&new->l, &info->v2p_entry_lists);
 
 out:
 	spin_unlock_irqrestore(&info->v2p_lock, flags);
@@ -962,33 +973,31 @@ static int scsiback_del_translation_entry(struct vscsibk_info *info,
 					  struct ids_tuple *v)
 {
 	struct v2p_entry *entry;
-	struct list_head *head = &(info->v2p_entry_lists);
 	unsigned long flags;
 
 	spin_lock_irqsave(&info->v2p_lock, flags);
 	/* Find out the translation entry specified */
-	list_for_each_entry(entry, head, l) {
-		if ((entry->v.chn == v->chn) &&
-		    (entry->v.tgt == v->tgt) &&
-		    (entry->v.lun == v->lun)) {
-			goto found;
-		}
-	}
-
-	spin_unlock_irqrestore(&info->v2p_lock, flags);
-	return 1;
-
-found:
-	/* Delete the translation entry specfied */
-	__scsiback_del_translation_entry(entry);
+	entry = scsiback_chk_translation_entry(info, v);
+	if (entry)
+		__scsiback_del_translation_entry(entry);
 
 	spin_unlock_irqrestore(&info->v2p_lock, flags);
-	return 0;
+	return entry == NULL;
 }
 
 static void scsiback_do_add_lun(struct vscsibk_info *info, const char *state,
 				char *phy, struct ids_tuple *vir, int try)
 {
+	struct v2p_entry *entry;
+	unsigned long flags;
+
+	if (try) {
+		spin_lock_irqsave(&info->v2p_lock, flags);
+		entry = scsiback_chk_translation_entry(info, vir);
+		spin_unlock_irqrestore(&info->v2p_lock, flags);
+		if (entry)
+			return;
+	}
 	if (!scsiback_add_translation_entry(info, phy, vir)) {
 		if (xenbus_printf(XBT_NIL, info->dev->nodename, state,
 				  "%d", XenbusStateInitialised)) {
-- 
2.6.2

Re: [PATCH 2/2] xen/scsiback: avoid warnings when adding multiple LUNs to a domain

[Boris Ostrovsky]

On 02/05/2016 08:21 AM, Juergen Gross wrote:
> When adding more than one LUN to a frontend a warning for a failed
> assignment is issued in dom0 for each already existing LUN. Avoid this
> warning.

Aren't you just factoring out the check? The warning is still printed 
for each scsiback_add_translation_entry() invocation, no?


>
> Signed-off-by: Juergen Gross <jgross@suse.com>
> Cc: stable@vger.kernel.org
> ---
>   drivers/xen/xen-scsiback.c | 65 ++++++++++++++++++++++++++--------------------
>   1 file changed, 37 insertions(+), 28 deletions(-)
>
> diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
> index 51387d7..69de879 100644
> --- a/drivers/xen/xen-scsiback.c
> +++ b/drivers/xen/xen-scsiback.c
> @@ -849,15 +849,31 @@ static int scsiback_map(struct vscsibk_info *info)
>   }
>   
>   /*
> +  Check for a translation entry being present
> +*/
> +static struct v2p_entry *scsiback_chk_translation_entry(
> +	struct vscsibk_info *info, struct ids_tuple *v)
> +{
> +	struct list_head *head = &(info->v2p_entry_lists);
> +	struct v2p_entry *entry;
> +
> +	list_for_each_entry(entry, head, l)
> +		if ((entry->v.chn == v->chn) &&
> +		    (entry->v.tgt == v->tgt) &&
> +		    (entry->v.lun == v->lun))
> +			return entry;
> +
> +	return NULL;
> +}
> +
> +/*
>     Add a new translation entry
>   */
>   static int scsiback_add_translation_entry(struct vscsibk_info *info,
>   					  char *phy, struct ids_tuple *v)
>   {
>   	int err = 0;
> -	struct v2p_entry *entry;
>   	struct v2p_entry *new;
> -	struct list_head *head = &(info->v2p_entry_lists);
>   	unsigned long flags;
>   	char *lunp;
>   	unsigned long long unpacked_lun;
> @@ -917,15 +933,10 @@ static int scsiback_add_translation_entry(struct vscsibk_info *info,
>   	spin_lock_irqsave(&info->v2p_lock, flags);
>   
>   	/* Check double assignment to identical virtual ID */
> -	list_for_each_entry(entry, head, l) {
> -		if ((entry->v.chn == v->chn) &&
> -		    (entry->v.tgt == v->tgt) &&
> -		    (entry->v.lun == v->lun)) {
> -			pr_warn("Virtual ID is already used. Assignment was not performed.\n");
> -			err = -EEXIST;
> -			goto out;
> -		}
> -
> +	if (scsiback_chk_translation_entry(info, v)) {
> +		pr_warn("Virtual ID is already used. Assignment was not performed.\n");
> +		err = -EEXIST;
> +		goto out;
>   	}
>   
>   	/* Create a new translation entry and add to the list */
> @@ -933,7 +944,7 @@ static int scsiback_add_translation_entry(struct vscsibk_info *info,
>   	new->v = *v;
>   	new->tpg = tpg;
>   	new->lun = unpacked_lun;
> -	list_add_tail(&new->l, head);
> +	list_add_tail(&new->l, &info->v2p_entry_lists);
>   
>   out:
>   	spin_unlock_irqrestore(&info->v2p_lock, flags);
> @@ -962,33 +973,31 @@ static int scsiback_del_translation_entry(struct vscsibk_info *info,
>   					  struct ids_tuple *v)
>   {
>   	struct v2p_entry *entry;
> -	struct list_head *head = &(info->v2p_entry_lists);
>   	unsigned long flags;
>   
>   	spin_lock_irqsave(&info->v2p_lock, flags);
>   	/* Find out the translation entry specified */
> -	list_for_each_entry(entry, head, l) {
> -		if ((entry->v.chn == v->chn) &&
> -		    (entry->v.tgt == v->tgt) &&
> -		    (entry->v.lun == v->lun)) {
> -			goto found;
> -		}
> -	}
> -
> -	spin_unlock_irqrestore(&info->v2p_lock, flags);
> -	return 1;
> -
> -found:
> -	/* Delete the translation entry specfied */
> -	__scsiback_del_translation_entry(entry);
> +	entry = scsiback_chk_translation_entry(info, v);
> +	if (entry)
> +		__scsiback_del_translation_entry(entry);
>   
>   	spin_unlock_irqrestore(&info->v2p_lock, flags);
> -	return 0;
> +	return entry == NULL;

Might be better to return -ENOENT instead of 1 above and -EEXISTS if 
entry!=NULL, given that this returns an int.

-boris

>   }
>   
>   static void scsiback_do_add_lun(struct vscsibk_info *info, const char *state,
>   				char *phy, struct ids_tuple *vir, int try)
>   {
> +	struct v2p_entry *entry;
> +	unsigned long flags;
> +
> +	if (try) {
> +		spin_lock_irqsave(&info->v2p_lock, flags);
> +		entry = scsiback_chk_translation_entry(info, vir);
> +		spin_unlock_irqrestore(&info->v2p_lock, flags);
> +		if (entry)
> +			return;
> +	}
>   	if (!scsiback_add_translation_entry(info, phy, vir)) {
>   		if (xenbus_printf(XBT_NIL, info->dev->nodename, state,
>   				  "%d", XenbusStateInitialised)) {

Re: [PATCH 2/2] xen/scsiback: avoid warnings when adding multiple LUNs to a domain

[Boris Ostrovsky]

On 02/05/2016 10:50 AM, Boris Ostrovsky wrote:
>
>
>> @@ -962,33 +973,31 @@ static int 
>> scsiback_del_translation_entry(struct vscsibk_info *info,
>>                         struct ids_tuple *v)
>>   {
>>       struct v2p_entry *entry;
>> -    struct list_head *head = &(info->v2p_entry_lists);
>>       unsigned long flags;
>>         spin_lock_irqsave(&info->v2p_lock, flags);
>>       /* Find out the translation entry specified */
>> -    list_for_each_entry(entry, head, l) {
>> -        if ((entry->v.chn == v->chn) &&
>> -            (entry->v.tgt == v->tgt) &&
>> -            (entry->v.lun == v->lun)) {
>> -            goto found;
>> -        }
>> -    }
>> -
>> -    spin_unlock_irqrestore(&info->v2p_lock, flags);
>> -    return 1;
>> -
>> -found:
>> -    /* Delete the translation entry specfied */
>> -    __scsiback_del_translation_entry(entry);
>> +    entry = scsiback_chk_translation_entry(info, v);
>> +    if (entry)
>> +        __scsiback_del_translation_entry(entry);
>>         spin_unlock_irqrestore(&info->v2p_lock, flags);
>> -    return 0;
>> +    return entry == NULL;
>
> Might be better to return -ENOENT instead of 1 above and -EEXISTS if 
> entry!=NULL, given that this returns an int.

Nevermind reference to 1, it's removed. But returning an error code 
instead of a bool is still better I think.

-boris

Re: [PATCH 2/2] xen/scsiback: avoid warnings when adding multiple LUNs to a domain

[Juergen Gross]

On 05/02/16 16:50, Boris Ostrovsky wrote:
> 
> 
> On 02/05/2016 08:21 AM, Juergen Gross wrote:
>> When adding more than one LUN to a frontend a warning for a failed
>> assignment is issued in dom0 for each already existing LUN. Avoid this
>> warning.
> 
> Aren't you just factoring out the check? The warning is still printed
> for each scsiback_add_translation_entry() invocation, no?

I don't call scsiback_add_translation_entry() in the critical case.

> 
> 
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> Cc: stable@vger.kernel.org
>> ---
>>   drivers/xen/xen-scsiback.c | 65
>> ++++++++++++++++++++++++++--------------------
>>   1 file changed, 37 insertions(+), 28 deletions(-)
>>
>> diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
>> index 51387d7..69de879 100644
>> --- a/drivers/xen/xen-scsiback.c
>> +++ b/drivers/xen/xen-scsiback.c
>> @@ -849,15 +849,31 @@ static int scsiback_map(struct vscsibk_info *info)
>>   }
>>     /*
>> +  Check for a translation entry being present
>> +*/
>> +static struct v2p_entry *scsiback_chk_translation_entry(
>> +    struct vscsibk_info *info, struct ids_tuple *v)
>> +{
>> +    struct list_head *head = &(info->v2p_entry_lists);
>> +    struct v2p_entry *entry;
>> +
>> +    list_for_each_entry(entry, head, l)
>> +        if ((entry->v.chn == v->chn) &&
>> +            (entry->v.tgt == v->tgt) &&
>> +            (entry->v.lun == v->lun))
>> +            return entry;
>> +
>> +    return NULL;
>> +}
>> +
>> +/*
>>     Add a new translation entry
>>   */
>>   static int scsiback_add_translation_entry(struct vscsibk_info *info,
>>                         char *phy, struct ids_tuple *v)
>>   {
>>       int err = 0;
>> -    struct v2p_entry *entry;
>>       struct v2p_entry *new;
>> -    struct list_head *head = &(info->v2p_entry_lists);
>>       unsigned long flags;
>>       char *lunp;
>>       unsigned long long unpacked_lun;
>> @@ -917,15 +933,10 @@ static int scsiback_add_translation_entry(struct
>> vscsibk_info *info,
>>       spin_lock_irqsave(&info->v2p_lock, flags);
>>         /* Check double assignment to identical virtual ID */
>> -    list_for_each_entry(entry, head, l) {
>> -        if ((entry->v.chn == v->chn) &&
>> -            (entry->v.tgt == v->tgt) &&
>> -            (entry->v.lun == v->lun)) {
>> -            pr_warn("Virtual ID is already used. Assignment was not
>> performed.\n");
>> -            err = -EEXIST;
>> -            goto out;
>> -        }
>> -
>> +    if (scsiback_chk_translation_entry(info, v)) {
>> +        pr_warn("Virtual ID is already used. Assignment was not
>> performed.\n");
>> +        err = -EEXIST;
>> +        goto out;
>>       }
>>         /* Create a new translation entry and add to the list */
>> @@ -933,7 +944,7 @@ static int scsiback_add_translation_entry(struct
>> vscsibk_info *info,
>>       new->v = *v;
>>       new->tpg = tpg;
>>       new->lun = unpacked_lun;
>> -    list_add_tail(&new->l, head);
>> +    list_add_tail(&new->l, &info->v2p_entry_lists);
>>     out:
>>       spin_unlock_irqrestore(&info->v2p_lock, flags);
>> @@ -962,33 +973,31 @@ static int scsiback_del_translation_entry(struct
>> vscsibk_info *info,
>>                         struct ids_tuple *v)
>>   {
>>       struct v2p_entry *entry;
>> -    struct list_head *head = &(info->v2p_entry_lists);
>>       unsigned long flags;
>>         spin_lock_irqsave(&info->v2p_lock, flags);
>>       /* Find out the translation entry specified */
>> -    list_for_each_entry(entry, head, l) {
>> -        if ((entry->v.chn == v->chn) &&
>> -            (entry->v.tgt == v->tgt) &&
>> -            (entry->v.lun == v->lun)) {
>> -            goto found;
>> -        }
>> -    }
>> -
>> -    spin_unlock_irqrestore(&info->v2p_lock, flags);
>> -    return 1;
>> -
>> -found:
>> -    /* Delete the translation entry specfied */
>> -    __scsiback_del_translation_entry(entry);
>> +    entry = scsiback_chk_translation_entry(info, v);
>> +    if (entry)
>> +        __scsiback_del_translation_entry(entry);
>>         spin_unlock_irqrestore(&info->v2p_lock, flags);
>> -    return 0;
>> +    return entry == NULL;
> 
> Might be better to return -ENOENT instead of 1 above and -EEXISTS if
> entry!=NULL, given that this returns an int.

I just didn't want to change more than necessary. In case it is
okay to do some cleanup as well I'd rather change the return type
to "bool".


Juergen

> 
> -boris
> 
>>   }
>>     static void scsiback_do_add_lun(struct vscsibk_info *info, const
>> char *state,
>>                   char *phy, struct ids_tuple *vir, int try)
>>   {
>> +    struct v2p_entry *entry;
>> +    unsigned long flags;
>> +
>> +    if (try) {
>> +        spin_lock_irqsave(&info->v2p_lock, flags);
>> +        entry = scsiback_chk_translation_entry(info, vir);
>> +        spin_unlock_irqrestore(&info->v2p_lock, flags);
>> +        if (entry)
>> +            return;
>> +    }
>>       if (!scsiback_add_translation_entry(info, phy, vir)) {
>>           if (xenbus_printf(XBT_NIL, info->dev->nodename, state,
>>                     "%d", XenbusStateInitialised)) {
> 
> 

Re: [PATCH 2/2] xen/scsiback: avoid warnings when adding multiple LUNs to a domain

[Boris Ostrovsky]

On 02/05/2016 11:59 AM, Juergen Gross wrote:
> On 05/02/16 16:50, Boris Ostrovsky wrote:
>>
>> On 02/05/2016 08:21 AM, Juergen Gross wrote:
>>> When adding more than one LUN to a frontend a warning for a failed
>>> assignment is issued in dom0 for each already existing LUN. Avoid this
>>> warning.
>> Aren't you just factoring out the check? The warning is still printed
>> for each scsiback_add_translation_entry() invocation, no?
> I don't call scsiback_add_translation_entry() in the critical case.

Which is scsiback_do_add_lun()? If yes then perhaps you could mention it 
in the commit message since there are few changes that this patch 
provides and it's not clear which is the one that prevents the warning.

>
> @@ -962,33 +973,31 @@ static int scsiback_del_translation_entry(struct
> vscsibk_info *info,
>                          struct ids_tuple *v)
>    {
>        struct v2p_entry *entry;
> -    struct list_head *head = &(info->v2p_entry_lists);
>        unsigned long flags;
>          spin_lock_irqsave(&info->v2p_lock, flags);
>        /* Find out the translation entry specified */
> -    list_for_each_entry(entry, head, l) {
> -        if ((entry->v.chn == v->chn) &&
> -            (entry->v.tgt == v->tgt) &&
> -            (entry->v.lun == v->lun)) {
> -            goto found;
> -        }
> -    }
> -
> -    spin_unlock_irqrestore(&info->v2p_lock, flags);
> -    return 1;
> -
> -found:
> -    /* Delete the translation entry specfied */
> -    __scsiback_del_translation_entry(entry);
> +    entry = scsiback_chk_translation_entry(info, v);
> +    if (entry)
> +        __scsiback_del_translation_entry(entry);
>          spin_unlock_irqrestore(&info->v2p_lock, flags);
> -    return 0;
> +    return entry == NULL;
>> Might be better to return -ENOENT instead of 1 above and -EEXISTS if
>> entry!=NULL, given that this returns an int.
> I just didn't want to change more than necessary. In case it is
> okay to do some cleanup as well I'd rather change the return type
> to "bool".

I don't think using error code will require changing anything except the 
last line above (which is already a change anyway)

But using a bool is OK too.

-boris

Re: [PATCH 2/2] xen/scsiback: avoid warnings when adding multiple LUNs to a domain

[Juergen Gross]

On 05/02/16 18:24, Boris Ostrovsky wrote:
> 
> 
> On 02/05/2016 11:59 AM, Juergen Gross wrote:
>> On 05/02/16 16:50, Boris Ostrovsky wrote:
>>>
>>> On 02/05/2016 08:21 AM, Juergen Gross wrote:
>>>> When adding more than one LUN to a frontend a warning for a failed
>>>> assignment is issued in dom0 for each already existing LUN. Avoid this
>>>> warning.
>>> Aren't you just factoring out the check? The warning is still printed
>>> for each scsiback_add_translation_entry() invocation, no?
>> I don't call scsiback_add_translation_entry() in the critical case.
> 
> Which is scsiback_do_add_lun()? If yes then perhaps you could mention it
> in the commit message since there are few changes that this patch
> provides and it's not clear which is the one that prevents the warning.
> 
>>
>> @@ -962,33 +973,31 @@ static int scsiback_del_translation_entry(struct
>> vscsibk_info *info,
>>                          struct ids_tuple *v)
>>    {
>>        struct v2p_entry *entry;
>> -    struct list_head *head = &(info->v2p_entry_lists);
>>        unsigned long flags;
>>          spin_lock_irqsave(&info->v2p_lock, flags);
>>        /* Find out the translation entry specified */
>> -    list_for_each_entry(entry, head, l) {
>> -        if ((entry->v.chn == v->chn) &&
>> -            (entry->v.tgt == v->tgt) &&
>> -            (entry->v.lun == v->lun)) {
>> -            goto found;
>> -        }
>> -    }
>> -
>> -    spin_unlock_irqrestore(&info->v2p_lock, flags);
>> -    return 1;
>> -
>> -found:
>> -    /* Delete the translation entry specfied */
>> -    __scsiback_del_translation_entry(entry);
>> +    entry = scsiback_chk_translation_entry(info, v);
>> +    if (entry)
>> +        __scsiback_del_translation_entry(entry);
>>          spin_unlock_irqrestore(&info->v2p_lock, flags);
>> -    return 0;
>> +    return entry == NULL;
>>> Might be better to return -ENOENT instead of 1 above and -EEXISTS if
>>> entry!=NULL, given that this returns an int.
>> I just didn't want to change more than necessary. In case it is
>> okay to do some cleanup as well I'd rather change the return type
>> to "bool".
> 
> I don't think using error code will require changing anything except the
> last line above (which is already a change anyway)

And returning -ENOENT or 0 will be even better, I guess.


Juergen

Re: [PATCH 1/2] xen/scsiback: correct frontend counting

[Boris Ostrovsky]

On 02/05/2016 08:21 AM, Juergen Gross wrote:
> When adding a new frontend to xen-scsiback don't decrement the number
> of active frontends in case of no error. Not doing so results in a

I think you meant "Doing so".

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>


> failure when trying to remove the xen-pvscsi nexus even if no domain
> is using it.
>
> Signed-off-by: Juergen Gross <jgross@suse.com>
> Cc: stable@vger.kernel.org
> ---
>   drivers/xen/xen-scsiback.c | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
> index ad4eb10..51387d7 100644
> --- a/drivers/xen/xen-scsiback.c
> +++ b/drivers/xen/xen-scsiback.c
> @@ -939,12 +939,12 @@ out:
>   	spin_unlock_irqrestore(&info->v2p_lock, flags);
>   
>   out_free:
> -	mutex_lock(&tpg->tv_tpg_mutex);
> -	tpg->tv_tpg_fe_count--;
> -	mutex_unlock(&tpg->tv_tpg_mutex);
> -
> -	if (err)
> +	if (err) {
> +		mutex_lock(&tpg->tv_tpg_mutex);
> +		tpg->tv_tpg_fe_count--;
> +		mutex_unlock(&tpg->tv_tpg_mutex);
>   		kfree(new);
> +	}
>   
>   	return err;
>   }

Re: [PATCH 1/2] xen/scsiback: correct frontend counting

[Juergen Gross]

On 05/02/16 16:42, Boris Ostrovsky wrote:
> 
> 
> On 02/05/2016 08:21 AM, Juergen Gross wrote:
>> When adding a new frontend to xen-scsiback don't decrement the number
>> of active frontends in case of no error. Not doing so results in a
> 
> I think you meant "Doing so".

I think so, too.

> 
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>

Thanks, Juergen

> 
> 
>> failure when trying to remove the xen-pvscsi nexus even if no domain
>> is using it.
>>
>> Signed-off-by: Juergen Gross <jgross@suse.com>
>> Cc: stable@vger.kernel.org
>> ---
>>   drivers/xen/xen-scsiback.c | 10 +++++-----
>>   1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
>> index ad4eb10..51387d7 100644
>> --- a/drivers/xen/xen-scsiback.c
>> +++ b/drivers/xen/xen-scsiback.c
>> @@ -939,12 +939,12 @@ out:
>>       spin_unlock_irqrestore(&info->v2p_lock, flags);
>>     out_free:
>> -    mutex_lock(&tpg->tv_tpg_mutex);
>> -    tpg->tv_tpg_fe_count--;
>> -    mutex_unlock(&tpg->tv_tpg_mutex);
>> -
>> -    if (err)
>> +    if (err) {
>> +        mutex_lock(&tpg->tv_tpg_mutex);
>> +        tpg->tv_tpg_fe_count--;
>> +        mutex_unlock(&tpg->tv_tpg_mutex);
>>           kfree(new);
>> +    }
>>         return err;
>>   }
> 
>