[PATCH v2 0/1] concurrency handling for zoned null-blk

[PATCH v2 0/1] concurrency handling for zoned null-blk

[Kanchan Joshi]

Changes since v1:
- applied the refactoring suggested by Damien

Kanchan Joshi (1):
  null_blk: synchronization fix for zoned device

 drivers/block/null_blk.h       |  1 +
 drivers/block/null_blk_zoned.c | 22 ++++++++++++++++++----
 2 files changed, 19 insertions(+), 4 deletions(-)

-- 
2.25.1

[PATCH v2 1/1] null_blk: synchronization fix for zoned device

[Kanchan Joshi]

Parallel write,read,zone-mgmt operations accessing/altering zone state
and write-pointer may get into race. Avoid the situation by using a new
spinlock for zoned device.
Concurrent zone-appends (on a zone) returning same write-pointer issue
is also avoided using this lock.

Fixes: e0489ed5daeb ("null_blk: Support REQ_OP_ZONE_APPEND")
Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
---
 drivers/block/null_blk.h       |  1 +
 drivers/block/null_blk_zoned.c | 22 ++++++++++++++++++----
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/block/null_blk.h b/drivers/block/null_blk.h
index daed4a9c3436..28099be50395 100644
--- a/drivers/block/null_blk.h
+++ b/drivers/block/null_blk.h
@@ -44,6 +44,7 @@ struct nullb_device {
 	unsigned int nr_zones;
 	struct blk_zone *zones;
 	sector_t zone_size_sects;
+	spinlock_t zone_lock;
 
 	unsigned long size; /* device size in MB */
 	unsigned long completion_nsec; /* time in ns to complete a request */
diff --git a/drivers/block/null_blk_zoned.c b/drivers/block/null_blk_zoned.c
index 3d25c9ad2383..e8d8b13aaa5a 100644
--- a/drivers/block/null_blk_zoned.c
+++ b/drivers/block/null_blk_zoned.c
@@ -45,6 +45,7 @@ int null_init_zoned_dev(struct nullb_device *dev, struct request_queue *q)
 	if (!dev->zones)
 		return -ENOMEM;
 
+	spin_lock_init(&dev->zone_lock);
 	if (dev->zone_nr_conv >= dev->nr_zones) {
 		dev->zone_nr_conv = dev->nr_zones - 1;
 		pr_info("changed the number of conventional zones to %u",
@@ -131,8 +132,11 @@ int null_report_zones(struct gendisk *disk, sector_t sector,
 		 * So use a local copy to avoid corruption of the device zone
 		 * array.
 		 */
+		spin_lock_irq(&dev->zone_lock);
 		memcpy(&zone, &dev->zones[first_zone + i],
 		       sizeof(struct blk_zone));
+		spin_unlock_irq(&dev->zone_lock);
+
 		error = cb(&zone, i, data);
 		if (error)
 			return error;
@@ -277,18 +281,28 @@ static blk_status_t null_zone_mgmt(struct nullb_cmd *cmd, enum req_opf op,
 blk_status_t null_process_zoned_cmd(struct nullb_cmd *cmd, enum req_opf op,
 				    sector_t sector, sector_t nr_sectors)
 {
+	blk_status_t sts;
+	struct nullb_device *dev = cmd->nq->dev;
+
+	spin_lock_irq(&dev->zone_lock);
 	switch (op) {
 	case REQ_OP_WRITE:
-		return null_zone_write(cmd, sector, nr_sectors, false);
+		sts = null_zone_write(cmd, sector, nr_sectors, false);
+		break;
 	case REQ_OP_ZONE_APPEND:
-		return null_zone_write(cmd, sector, nr_sectors, true);
+		sts = null_zone_write(cmd, sector, nr_sectors, true);
+		break;
 	case REQ_OP_ZONE_RESET:
 	case REQ_OP_ZONE_RESET_ALL:
 	case REQ_OP_ZONE_OPEN:
 	case REQ_OP_ZONE_CLOSE:
 	case REQ_OP_ZONE_FINISH:
-		return null_zone_mgmt(cmd, op, sector);
+		sts = null_zone_mgmt(cmd, op, sector);
+		break;
 	default:
-		return null_process_cmd(cmd, op, sector, nr_sectors);
+		sts = null_process_cmd(cmd, op, sector, nr_sectors);
 	}
+	spin_unlock_irq(&dev->zone_lock);
+
+	return sts;
 }
-- 
2.25.1

Re: [PATCH v2 1/1] null_blk: synchronization fix for zoned device

[Damien Le Moal]

On 2020/09/28 18:59, Kanchan Joshi wrote:
> Parallel write,read,zone-mgmt operations accessing/altering zone state
> and write-pointer may get into race. Avoid the situation by using a new
> spinlock for zoned device.
> Concurrent zone-appends (on a zone) returning same write-pointer issue
> is also avoided using this lock.
> 
> Fixes: e0489ed5daeb ("null_blk: Support REQ_OP_ZONE_APPEND")
> Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
> ---
>  drivers/block/null_blk.h       |  1 +
>  drivers/block/null_blk_zoned.c | 22 ++++++++++++++++++----
>  2 files changed, 19 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/block/null_blk.h b/drivers/block/null_blk.h
> index daed4a9c3436..28099be50395 100644
> --- a/drivers/block/null_blk.h
> +++ b/drivers/block/null_blk.h
> @@ -44,6 +44,7 @@ struct nullb_device {
>  	unsigned int nr_zones;
>  	struct blk_zone *zones;
>  	sector_t zone_size_sects;
> +	spinlock_t zone_lock;
>  
>  	unsigned long size; /* device size in MB */
>  	unsigned long completion_nsec; /* time in ns to complete a request */
> diff --git a/drivers/block/null_blk_zoned.c b/drivers/block/null_blk_zoned.c
> index 3d25c9ad2383..e8d8b13aaa5a 100644
> --- a/drivers/block/null_blk_zoned.c
> +++ b/drivers/block/null_blk_zoned.c
> @@ -45,6 +45,7 @@ int null_init_zoned_dev(struct nullb_device *dev, struct request_queue *q)
>  	if (!dev->zones)
>  		return -ENOMEM;
>  
> +	spin_lock_init(&dev->zone_lock);
>  	if (dev->zone_nr_conv >= dev->nr_zones) {
>  		dev->zone_nr_conv = dev->nr_zones - 1;
>  		pr_info("changed the number of conventional zones to %u",
> @@ -131,8 +132,11 @@ int null_report_zones(struct gendisk *disk, sector_t sector,
>  		 * So use a local copy to avoid corruption of the device zone
>  		 * array.
>  		 */
> +		spin_lock_irq(&dev->zone_lock);
>  		memcpy(&zone, &dev->zones[first_zone + i],
>  		       sizeof(struct blk_zone));
> +		spin_unlock_irq(&dev->zone_lock);
> +
>  		error = cb(&zone, i, data);
>  		if (error)
>  			return error;
> @@ -277,18 +281,28 @@ static blk_status_t null_zone_mgmt(struct nullb_cmd *cmd, enum req_opf op,
>  blk_status_t null_process_zoned_cmd(struct nullb_cmd *cmd, enum req_opf op,
>  				    sector_t sector, sector_t nr_sectors)
>  {
> +	blk_status_t sts;
> +	struct nullb_device *dev = cmd->nq->dev;
> +
> +	spin_lock_irq(&dev->zone_lock);
>  	switch (op) {
>  	case REQ_OP_WRITE:
> -		return null_zone_write(cmd, sector, nr_sectors, false);
> +		sts = null_zone_write(cmd, sector, nr_sectors, false);
> +		break;
>  	case REQ_OP_ZONE_APPEND:
> -		return null_zone_write(cmd, sector, nr_sectors, true);
> +		sts = null_zone_write(cmd, sector, nr_sectors, true);
> +		break;
>  	case REQ_OP_ZONE_RESET:
>  	case REQ_OP_ZONE_RESET_ALL:
>  	case REQ_OP_ZONE_OPEN:
>  	case REQ_OP_ZONE_CLOSE:
>  	case REQ_OP_ZONE_FINISH:
> -		return null_zone_mgmt(cmd, op, sector);
> +		sts = null_zone_mgmt(cmd, op, sector);
> +		break;
>  	default:
> -		return null_process_cmd(cmd, op, sector, nr_sectors);
> +		sts = null_process_cmd(cmd, op, sector, nr_sectors);
>  	}
> +	spin_unlock_irq(&dev->zone_lock);
> +
> +	return sts;
>  }
> 

Looks good.

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH v2 1/1] null_blk: synchronization fix for zoned device

[Jens Axboe]

On 9/28/20 3:55 AM, Kanchan Joshi wrote:
> Parallel write,read,zone-mgmt operations accessing/altering zone state
> and write-pointer may get into race. Avoid the situation by using a new
> spinlock for zoned device.
> Concurrent zone-appends (on a zone) returning same write-pointer issue
> is also avoided using this lock.

Applied, thanks.

-- 
Jens Axboe

Re: [PATCH v2 0/1] concurrency handling for zoned null-blk

[Damien Le Moal]

On 2020/09/28 18:59, Kanchan Joshi wrote:
> Changes since v1:
> - applied the refactoring suggested by Damien
> 
> Kanchan Joshi (1):
>   null_blk: synchronization fix for zoned device
> 
>  drivers/block/null_blk.h       |  1 +
>  drivers/block/null_blk_zoned.c | 22 ++++++++++++++++++----
>  2 files changed, 19 insertions(+), 4 deletions(-)
> 

For single patches, you should add this after the "---" in the patch file, above
the patch stats. This is ignores by git when the patch is applied (the patch
starts at the first "diff" entry).


-- 
Damien Le Moal
Western Digital Research

Re: [PATCH v2 0/1] concurrency handling for zoned null-blk

[Greg KH]

On Mon, Sep 28, 2020 at 03:25:48PM +0530, Kanchan Joshi wrote:
> Changes since v1:
> - applied the refactoring suggested by Damien
> 
> Kanchan Joshi (1):
>   null_blk: synchronization fix for zoned device
> 
>  drivers/block/null_blk.h       |  1 +
>  drivers/block/null_blk_zoned.c | 22 ++++++++++++++++++----
>  2 files changed, 19 insertions(+), 4 deletions(-)
> 
> -- 
> 2.25.1
> 


<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>

Re: [PATCH v2 0/1] concurrency handling for zoned null-blk

[Kanchan Joshi]

On Mon, Sep 28, 2020 at 5:42 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Mon, Sep 28, 2020 at 03:25:48PM +0530, Kanchan Joshi wrote:
> > Changes since v1:
> > - applied the refactoring suggested by Damien
> >
> > Kanchan Joshi (1):
> >   null_blk: synchronization fix for zoned device
> >
> >  drivers/block/null_blk.h       |  1 +
> >  drivers/block/null_blk_zoned.c | 22 ++++++++++++++++++----
> >  2 files changed, 19 insertions(+), 4 deletions(-)
> >
> > --
> > 2.25.1
> >
>
>
> <formletter>
>
> This is not the correct way to submit patches for inclusion in the
> stable kernel tree.  Please read:
>     https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
> for how to do this properly.
>
> </formletter>
I'm sorry for the goof-up, Greg.



--
Joshi