2020-09-28 10:00:59

by Kanchan Joshi

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

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 <[email protected]>
---
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

2020-09-28 10:13:59

by Damien Le Moal

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

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 <[email protected]>
> ---
> 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 <[email protected]>


--
Damien Le Moal
Western Digital Research

2020-10-28 23:48:22

by Jens Axboe

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

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