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Subject[PATCH] null_blk: synchronization fix for zoned device
Date
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.

Signed-off-by: Kanchan Joshi <joshi.k@samsung.com>
---
drivers/block/null_blk.h | 1 +
drivers/block/null_blk_zoned.c | 84 +++++++++++++++++++++++-----------
2 files changed, 58 insertions(+), 27 deletions(-)

diff --git a/drivers/block/null_blk.h b/drivers/block/null_blk.h
index daed4a9c3436..b3f4d62e7c38 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 zlock;

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..04fbf267703a 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->zlock);
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",
@@ -124,6 +125,7 @@ int null_report_zones(struct gendisk *disk, sector_t sector,
nr_zones = min(nr_zones, dev->nr_zones - first_zone);
trace_nullb_report_zones(nullb, nr_zones);

+ spin_lock_irq(&dev->zlock);
for (i = 0; i < nr_zones; i++) {
/*
* Stacked DM target drivers will remap the zone information by
@@ -134,10 +136,13 @@ int null_report_zones(struct gendisk *disk, sector_t sector,
memcpy(&zone, &dev->zones[first_zone + i],
sizeof(struct blk_zone));
error = cb(&zone, i, data);
- if (error)
+ if (error) {
+ spin_unlock_irq(&dev->zlock);
return error;
+ }
}

+ spin_unlock_irq(&dev->zlock);
return nr_zones;
}

@@ -147,16 +152,24 @@ size_t null_zone_valid_read_len(struct nullb *nullb,
struct nullb_device *dev = nullb->dev;
struct blk_zone *zone = &dev->zones[null_zone_no(dev, sector)];
unsigned int nr_sectors = len >> SECTOR_SHIFT;
+ size_t ret = 0;

+ spin_lock_irq(&dev->zlock);
/* Read must be below the write pointer position */
if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL ||
- sector + nr_sectors <= zone->wp)
- return len;
+ sector + nr_sectors <= zone->wp) {
+ ret = len;
+ goto out_unlock;
+ }

if (sector > zone->wp)
- return 0;
+ goto out_unlock;
+
+ ret = (zone->wp - sector) << SECTOR_SHIFT;

- return (zone->wp - sector) << SECTOR_SHIFT;
+out_unlock:
+ spin_unlock_irq(&dev->zlock);
+ return ret;
}

static blk_status_t null_zone_write(struct nullb_cmd *cmd, sector_t sector,
@@ -165,17 +178,19 @@ static blk_status_t null_zone_write(struct nullb_cmd *cmd, sector_t sector,
struct nullb_device *dev = cmd->nq->dev;
unsigned int zno = null_zone_no(dev, sector);
struct blk_zone *zone = &dev->zones[zno];
- blk_status_t ret;
+ blk_status_t ret = BLK_STS_OK;

trace_nullb_zone_op(cmd, zno, zone->cond);

if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL)
return null_process_cmd(cmd, REQ_OP_WRITE, sector, nr_sectors);

+ spin_lock_irq(&dev->zlock);
switch (zone->cond) {
case BLK_ZONE_COND_FULL:
/* Cannot write to a full zone */
- return BLK_STS_IOERR;
+ ret = BLK_STS_IOERR;
+ break;
case BLK_ZONE_COND_EMPTY:
case BLK_ZONE_COND_IMP_OPEN:
case BLK_ZONE_COND_EXP_OPEN:
@@ -193,27 +208,33 @@ static blk_status_t null_zone_write(struct nullb_cmd *cmd, sector_t sector,
else
cmd->rq->__sector = sector;
} else if (sector != zone->wp) {
- return BLK_STS_IOERR;
+ ret = BLK_STS_IOERR;
+ break;
}

- if (zone->wp + nr_sectors > zone->start + zone->capacity)
- return BLK_STS_IOERR;
+ if (zone->wp + nr_sectors > zone->start + zone->capacity) {
+ ret = BLK_STS_IOERR;
+ break;
+ }

if (zone->cond != BLK_ZONE_COND_EXP_OPEN)
zone->cond = BLK_ZONE_COND_IMP_OPEN;

ret = null_process_cmd(cmd, REQ_OP_WRITE, sector, nr_sectors);
if (ret != BLK_STS_OK)
- return ret;
+ break;

zone->wp += nr_sectors;
if (zone->wp == zone->start + zone->capacity)
zone->cond = BLK_ZONE_COND_FULL;
- return BLK_STS_OK;
+ break;
default:
/* Invalid zone condition */
- return BLK_STS_IOERR;
+ ret = BLK_STS_IOERR;
}
+
+ spin_unlock_irq(&dev->zlock);
+ return ret;
}

static blk_status_t null_zone_mgmt(struct nullb_cmd *cmd, enum req_opf op,
@@ -223,7 +244,9 @@ static blk_status_t null_zone_mgmt(struct nullb_cmd *cmd, enum req_opf op,
unsigned int zone_no = null_zone_no(dev, sector);
struct blk_zone *zone = &dev->zones[zone_no];
size_t i;
+ blk_status_t ret = BLK_STS_OK;

+ spin_lock_irq(&dev->zlock);
switch (op) {
case REQ_OP_ZONE_RESET_ALL:
for (i = 0; i < dev->nr_zones; i++) {
@@ -234,25 +257,29 @@ static blk_status_t null_zone_mgmt(struct nullb_cmd *cmd, enum req_opf op,
}
break;
case REQ_OP_ZONE_RESET:
- if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL)
- return BLK_STS_IOERR;
+ if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL) {
+ ret = BLK_STS_IOERR;
+ break;
+ }

zone->cond = BLK_ZONE_COND_EMPTY;
zone->wp = zone->start;
break;
case REQ_OP_ZONE_OPEN:
- if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL)
- return BLK_STS_IOERR;
- if (zone->cond == BLK_ZONE_COND_FULL)
- return BLK_STS_IOERR;
+ if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL ||
+ zone->cond == BLK_ZONE_COND_FULL) {
+ ret = BLK_STS_IOERR;
+ break;
+ }

zone->cond = BLK_ZONE_COND_EXP_OPEN;
break;
case REQ_OP_ZONE_CLOSE:
- if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL)
- return BLK_STS_IOERR;
- if (zone->cond == BLK_ZONE_COND_FULL)
- return BLK_STS_IOERR;
+ if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL ||
+ zone->cond == BLK_ZONE_COND_FULL) {
+ ret = BLK_STS_IOERR;
+ break;
+ }

if (zone->wp == zone->start)
zone->cond = BLK_ZONE_COND_EMPTY;
@@ -260,18 +287,21 @@ static blk_status_t null_zone_mgmt(struct nullb_cmd *cmd, enum req_opf op,
zone->cond = BLK_ZONE_COND_CLOSED;
break;
case REQ_OP_ZONE_FINISH:
- if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL)
- return BLK_STS_IOERR;
+ if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL) {
+ ret = BLK_STS_IOERR;
+ break;
+ }

zone->cond = BLK_ZONE_COND_FULL;
zone->wp = zone->start + zone->len;
break;
default:
- return BLK_STS_NOTSUPP;
+ ret = BLK_STS_NOTSUPP;
}

+ spin_unlock_irq(&dev->zlock);
trace_nullb_zone_op(cmd, zone_no, zone->cond);
- return BLK_STS_OK;
+ return ret;
}

blk_status_t null_process_zoned_cmd(struct nullb_cmd *cmd, enum req_opf op,
--
2.25.1
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