[PATCH v3 0/2] Update SCSI target removal path

[PATCH v3 0/2] Update SCSI target removal path

[Johannes Thumshirn]

This is a follow up to "scsi: Add intermediate STARGET_REMOVE state to 
scsi_target_state".

If anyone has an idea how to create a regression test suite for the target
removal path I'd be all ears, given the fact that this is the 3rd or 4th patch
targeting it.

Changes to v2:
* Reverse the order of patches as pointed out by James

Changes to v1:
* Fix error (hit BUG_ON()) discovered by the 0-Day bot.
* Revert "scsi: fix soft lockup in scsi_remove_target() on module removal"

Johannes Thumshirn (2):
  scsi: Add intermediate STARGET_REMOVE state to scsi_target_state
  Revert "scsi: fix soft lockup in scsi_remove_target() on module
    removal"

 drivers/scsi/scsi_scan.c   | 2 ++
 drivers/scsi/scsi_sysfs.c  | 6 +++---
 include/scsi/scsi_device.h | 1 +
 3 files changed, 6 insertions(+), 3 deletions(-)

-- 
1.8.5.6

[PATCH v3 1/2] scsi: Add intermediate STARGET_REMOVE state to scsi_target_state

[Johannes Thumshirn]

Add intermediate STARGET_REMOVE state to scsi_target_state to avoid running
into the BUG_ON() in scsi_target_reap().

This intermediate state is only valid in the path from scsi_remove_target() to
scsi_target_destroy() indicating this target is going to be removed.

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Fixes: 40998193560dab6c3ce8d25f4fa58a23e252ef38
---
 drivers/scsi/scsi_scan.c   | 2 ++
 drivers/scsi/scsi_sysfs.c  | 2 ++
 include/scsi/scsi_device.h | 1 +
 3 files changed, 5 insertions(+)

diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 6a82066..63b8bca 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -315,6 +315,8 @@ static void scsi_target_destroy(struct scsi_target *starget)
 	struct Scsi_Host *shost = dev_to_shost(dev->parent);
 	unsigned long flags;
 
+	BUG_ON(starget->state != STARGET_REMOVE &&
+	       starget->state != STARGET_CREATED);
 	starget->state = STARGET_DEL;
 	transport_destroy_device(dev);
 	spin_lock_irqsave(shost->host_lock, flags);
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 00bc721..0df82e8 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1279,11 +1279,13 @@ restart:
 	spin_lock_irqsave(shost->host_lock, flags);
 	list_for_each_entry(starget, &shost->__targets, siblings) {
 		if (starget->state == STARGET_DEL ||
+		    starget->state == STARGET_REMOVE ||
 		    starget == last_target)
 			continue;
 		if (starget->dev.parent == dev || &starget->dev == dev) {
 			kref_get(&starget->reap_ref);
 			last_target = starget;
+			starget->state = STARGET_REMOVE;
 			spin_unlock_irqrestore(shost->host_lock, flags);
 			__scsi_remove_target(starget);
 			scsi_target_reap(starget);
diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
index f63a167..2bffaa6 100644
--- a/include/scsi/scsi_device.h
+++ b/include/scsi/scsi_device.h
@@ -240,6 +240,7 @@ scmd_printk(const char *, const struct scsi_cmnd *, const char *, ...);
 enum scsi_target_state {
 	STARGET_CREATED = 1,
 	STARGET_RUNNING,
+	STARGET_REMOVE,
 	STARGET_DEL,
 };
 
-- 
1.8.5.6

[PATCH v3 2/2] Revert "scsi: fix soft lockup in scsi_remove_target() on module removal"

[Johannes Thumshirn]

This reverts commit 90a88d6ef88edcfc4f644dddc7eef4ea41bccf8b.

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 drivers/scsi/scsi_sysfs.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 0df82e8..9e5f893 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1272,19 +1272,17 @@ static void __scsi_remove_target(struct scsi_target *starget)
 void scsi_remove_target(struct device *dev)
 {
 	struct Scsi_Host *shost = dev_to_shost(dev->parent);
-	struct scsi_target *starget, *last_target = NULL;
+	struct scsi_target *starget;
 	unsigned long flags;
 
 restart:
 	spin_lock_irqsave(shost->host_lock, flags);
 	list_for_each_entry(starget, &shost->__targets, siblings) {
 		if (starget->state == STARGET_DEL ||
-		    starget->state == STARGET_REMOVE ||
-		    starget == last_target)
+		    starget->state == STARGET_REMOVE)
 			continue;
 		if (starget->dev.parent == dev || &starget->dev == dev) {
 			kref_get(&starget->reap_ref);
-			last_target = starget;
 			starget->state = STARGET_REMOVE;
 			spin_unlock_irqrestore(shost->host_lock, flags);
 			__scsi_remove_target(starget);
-- 
1.8.5.6

Re: [PATCH v3 1/2] scsi: Add intermediate STARGET_REMOVE state to scsi_target_state

[Hannes Reinecke]

On 03/31/2016 02:53 PM, Johannes Thumshirn wrote:
> Add intermediate STARGET_REMOVE state to scsi_target_state to avoid running
> into the BUG_ON() in scsi_target_reap().
> 
> This intermediate state is only valid in the path from scsi_remove_target() to
> scsi_target_destroy() indicating this target is going to be removed.
> 
> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
> Fixes: 40998193560dab6c3ce8d25f4fa58a23e252ef38
> ---
>  drivers/scsi/scsi_scan.c   | 2 ++
>  drivers/scsi/scsi_sysfs.c  | 2 ++
>  include/scsi/scsi_device.h | 1 +
>  3 files changed, 5 insertions(+)
> 
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index 6a82066..63b8bca 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -315,6 +315,8 @@ static void scsi_target_destroy(struct scsi_target *starget)
>  	struct Scsi_Host *shost = dev_to_shost(dev->parent);
>  	unsigned long flags;
>  
> +	BUG_ON(starget->state != STARGET_REMOVE &&
> +	       starget->state != STARGET_CREATED);
>  	starget->state = STARGET_DEL;
>  	transport_destroy_device(dev);
>  	spin_lock_irqsave(shost->host_lock, flags);
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 00bc721..0df82e8 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -1279,11 +1279,13 @@ restart:
>  	spin_lock_irqsave(shost->host_lock, flags);
>  	list_for_each_entry(starget, &shost->__targets, siblings) {
>  		if (starget->state == STARGET_DEL ||
> +		    starget->state == STARGET_REMOVE ||
>  		    starget == last_target)
>  			continue;
>  		if (starget->dev.parent == dev || &starget->dev == dev) {
>  			kref_get(&starget->reap_ref);
>  			last_target = starget;
> +			starget->state = STARGET_REMOVE;
>  			spin_unlock_irqrestore(shost->host_lock, flags);
>  			__scsi_remove_target(starget);
>  			scsi_target_reap(starget);
> diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h
> index f63a167..2bffaa6 100644
> --- a/include/scsi/scsi_device.h
> +++ b/include/scsi/scsi_device.h
> @@ -240,6 +240,7 @@ scmd_printk(const char *, const struct scsi_cmnd *, const char *, ...);
>  enum scsi_target_state {
>  	STARGET_CREATED = 1,
>  	STARGET_RUNNING,
> +	STARGET_REMOVE,
>  	STARGET_DEL,
>  };
>  
> 
Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)

Re: [PATCH v3 2/2] Revert "scsi: fix soft lockup in scsi_remove_target() on module removal"

[Hannes Reinecke]

On 03/31/2016 02:53 PM, Johannes Thumshirn wrote:
> This reverts commit 90a88d6ef88edcfc4f644dddc7eef4ea41bccf8b.
> 
> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
> ---
>  drivers/scsi/scsi_sysfs.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.com>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)

Re: [PATCH v3 1/2] scsi: Add intermediate STARGET_REMOVE state to scsi_target_state

[James Bottomley]

On Thu, 2016-03-31 at 14:53 +0200, Johannes Thumshirn wrote:
> Add intermediate STARGET_REMOVE state to scsi_target_state to avoid
> running
> into the BUG_ON() in scsi_target_reap().
> 
> This intermediate state is only valid in the path from
> scsi_remove_target() to
> scsi_target_destroy() indicating this target is going to be removed.
> 
> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
> Fixes: 40998193560dab6c3ce8d25f4fa58a23e252ef38

The code and ordering is fine with me, so you can add

Reviewed-by: James Bottomley <jejb@linux.vnet.ibm.com>

However, I'd really appreciate it if the description of what was going
on was clearer for a non-SUSE distro maintainer.  What we're doing is
applying a more comprehensive fix for a previously hack fixed problem
and then reverting the hack.  I think message 1 should say "this
refixes the problem introduced by commit X in a more comprehensive way"

and message 2 "Now that we've done a more comprehensive fix with the
intermediate target state in patch Y, we can remove the previous hack"

James

Re: [PATCH v3 1/2] scsi: Add intermediate STARGET_REMOVE state to scsi_target_state

[Johannes Thumshirn]

On 2016-04-02 18:36, James Bottomley wrote:
> On Thu, 2016-03-31 at 14:53 +0200, Johannes Thumshirn wrote:
>> Add intermediate STARGET_REMOVE state to scsi_target_state to avoid
>> running
>> into the BUG_ON() in scsi_target_reap().
>> 
>> This intermediate state is only valid in the path from
>> scsi_remove_target() to
>> scsi_target_destroy() indicating this target is going to be removed.
>> 
>> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
>> Fixes: 40998193560dab6c3ce8d25f4fa58a23e252ef38
> 
> The code and ordering is fine with me, so you can add
> 
> Reviewed-by: James Bottomley <jejb@linux.vnet.ibm.com>
> 
> However, I'd really appreciate it if the description of what was going
> on was clearer for a non-SUSE distro maintainer.  What we're doing is
> applying a more comprehensive fix for a previously hack fixed problem
> and then reverting the hack.  I think message 1 should say "this
> refixes the problem introduced by commit X in a more comprehensive way"
> 
> and message 2 "Now that we've done a more comprehensive fix with the
> intermediate target state in patch Y, we can remove the previous hack"
> 
> James

OK, I'll try my very best. Thanks for the review.