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

On 2020/09/28 19:12, Damien Le Moal wrote:

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

Jens,

Could you queue this patch for rc2 please ? We are seeing some issues with zone append in btrfs testing without it.