linux/drivers/block/null_blk_zoned.c
Damien Le Moal e1777d0997 null_blk: Fix scheduling in atomic with zoned mode
Commit aa1c09cb65 ("null_blk: Fix locking in zoned mode") changed
zone locking to using the potentially sleeping wait_on_bit_io()
function. This is acceptable when memory backing is enabled as the
device queue is in that case marked as blocking, but this triggers a
scheduling while in atomic context with memory backing disabled.

Fix this by relying solely on the device zone spinlock for zone
information protection without temporarily releasing this lock around
null_process_cmd() execution in null_zone_write(). This is OK to do
since when memory backing is disabled, command processing does not
block and the memory backing lock nullb->lock is unused. This solution
avoids the overhead of having to mark a zoned null_blk device queue as
blocking when memory backing is unused.

This patch also adds comments to the zone locking code to explain the
unusual locking scheme.

Fixes: aa1c09cb65 ("null_blk: Fix locking in zoned mode")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2020-11-06 09:36:42 -07:00

607 lines
15 KiB
C

// SPDX-License-Identifier: GPL-2.0
#include <linux/vmalloc.h>
#include <linux/bitmap.h>
#include "null_blk.h"
#define CREATE_TRACE_POINTS
#include "null_blk_trace.h"
/* zone_size in MBs to sectors. */
#define ZONE_SIZE_SHIFT 11
static inline unsigned int null_zone_no(struct nullb_device *dev, sector_t sect)
{
return sect >> ilog2(dev->zone_size_sects);
}
int null_init_zoned_dev(struct nullb_device *dev, struct request_queue *q)
{
sector_t dev_size = (sector_t)dev->size * 1024 * 1024;
sector_t sector = 0;
unsigned int i;
if (!is_power_of_2(dev->zone_size)) {
pr_err("zone_size must be power-of-two\n");
return -EINVAL;
}
if (dev->zone_size > dev->size) {
pr_err("Zone size larger than device capacity\n");
return -EINVAL;
}
if (!dev->zone_capacity)
dev->zone_capacity = dev->zone_size;
if (dev->zone_capacity > dev->zone_size) {
pr_err("null_blk: zone capacity (%lu MB) larger than zone size (%lu MB)\n",
dev->zone_capacity, dev->zone_size);
return -EINVAL;
}
dev->zone_size_sects = dev->zone_size << ZONE_SIZE_SHIFT;
dev->nr_zones = dev_size >>
(SECTOR_SHIFT + ilog2(dev->zone_size_sects));
dev->zones = kvmalloc_array(dev->nr_zones, sizeof(struct blk_zone),
GFP_KERNEL | __GFP_ZERO);
if (!dev->zones)
return -ENOMEM;
/*
* With memory backing, the zone_lock spinlock needs to be temporarily
* released to avoid scheduling in atomic context. To guarantee zone
* information protection, use a bitmap to lock zones with
* wait_on_bit_lock_io(). Sleeping on the lock is OK as memory backing
* implies that the queue is marked with BLK_MQ_F_BLOCKING.
*/
spin_lock_init(&dev->zone_lock);
if (dev->memory_backed) {
dev->zone_locks = bitmap_zalloc(dev->nr_zones, GFP_KERNEL);
if (!dev->zone_locks) {
kvfree(dev->zones);
return -ENOMEM;
}
}
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",
dev->zone_nr_conv);
}
/* Max active zones has to be < nbr of seq zones in order to be enforceable */
if (dev->zone_max_active >= dev->nr_zones - dev->zone_nr_conv) {
dev->zone_max_active = 0;
pr_info("zone_max_active limit disabled, limit >= zone count\n");
}
/* Max open zones has to be <= max active zones */
if (dev->zone_max_active && dev->zone_max_open > dev->zone_max_active) {
dev->zone_max_open = dev->zone_max_active;
pr_info("changed the maximum number of open zones to %u\n",
dev->nr_zones);
} else if (dev->zone_max_open >= dev->nr_zones - dev->zone_nr_conv) {
dev->zone_max_open = 0;
pr_info("zone_max_open limit disabled, limit >= zone count\n");
}
for (i = 0; i < dev->zone_nr_conv; i++) {
struct blk_zone *zone = &dev->zones[i];
zone->start = sector;
zone->len = dev->zone_size_sects;
zone->capacity = zone->len;
zone->wp = zone->start + zone->len;
zone->type = BLK_ZONE_TYPE_CONVENTIONAL;
zone->cond = BLK_ZONE_COND_NOT_WP;
sector += dev->zone_size_sects;
}
for (i = dev->zone_nr_conv; i < dev->nr_zones; i++) {
struct blk_zone *zone = &dev->zones[i];
zone->start = zone->wp = sector;
zone->len = dev->zone_size_sects;
zone->capacity = dev->zone_capacity << ZONE_SIZE_SHIFT;
zone->type = BLK_ZONE_TYPE_SEQWRITE_REQ;
zone->cond = BLK_ZONE_COND_EMPTY;
sector += dev->zone_size_sects;
}
q->limits.zoned = BLK_ZONED_HM;
blk_queue_flag_set(QUEUE_FLAG_ZONE_RESETALL, q);
blk_queue_required_elevator_features(q, ELEVATOR_F_ZBD_SEQ_WRITE);
return 0;
}
int null_register_zoned_dev(struct nullb *nullb)
{
struct nullb_device *dev = nullb->dev;
struct request_queue *q = nullb->q;
if (queue_is_mq(q)) {
int ret = blk_revalidate_disk_zones(nullb->disk, NULL);
if (ret)
return ret;
} else {
blk_queue_chunk_sectors(q, dev->zone_size_sects);
q->nr_zones = blkdev_nr_zones(nullb->disk);
}
blk_queue_max_zone_append_sectors(q, dev->zone_size_sects);
blk_queue_max_open_zones(q, dev->zone_max_open);
blk_queue_max_active_zones(q, dev->zone_max_active);
return 0;
}
void null_free_zoned_dev(struct nullb_device *dev)
{
bitmap_free(dev->zone_locks);
kvfree(dev->zones);
}
static inline void null_lock_zone(struct nullb_device *dev, unsigned int zno)
{
if (dev->memory_backed)
wait_on_bit_lock_io(dev->zone_locks, zno, TASK_UNINTERRUPTIBLE);
spin_lock_irq(&dev->zone_lock);
}
static inline void null_unlock_zone(struct nullb_device *dev, unsigned int zno)
{
spin_unlock_irq(&dev->zone_lock);
if (dev->memory_backed)
clear_and_wake_up_bit(zno, dev->zone_locks);
}
int null_report_zones(struct gendisk *disk, sector_t sector,
unsigned int nr_zones, report_zones_cb cb, void *data)
{
struct nullb *nullb = disk->private_data;
struct nullb_device *dev = nullb->dev;
unsigned int first_zone, i, zno;
struct blk_zone zone;
int error;
first_zone = null_zone_no(dev, sector);
if (first_zone >= dev->nr_zones)
return 0;
nr_zones = min(nr_zones, dev->nr_zones - first_zone);
trace_nullb_report_zones(nullb, nr_zones);
zno = first_zone;
for (i = 0; i < nr_zones; i++, zno++) {
/*
* Stacked DM target drivers will remap the zone information by
* modifying the zone information passed to the report callback.
* So use a local copy to avoid corruption of the device zone
* array.
*/
null_lock_zone(dev, zno);
memcpy(&zone, &dev->zones[zno], sizeof(struct blk_zone));
null_unlock_zone(dev, zno);
error = cb(&zone, i, data);
if (error)
return error;
}
return nr_zones;
}
/*
* This is called in the case of memory backing from null_process_cmd()
* with the target zone already locked.
*/
size_t null_zone_valid_read_len(struct nullb *nullb,
sector_t sector, unsigned int len)
{
struct nullb_device *dev = nullb->dev;
struct blk_zone *zone = &dev->zones[null_zone_no(dev, sector)];
unsigned int nr_sectors = len >> SECTOR_SHIFT;
/* Read must be below the write pointer position */
if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL ||
sector + nr_sectors <= zone->wp)
return len;
if (sector > zone->wp)
return 0;
return (zone->wp - sector) << SECTOR_SHIFT;
}
static blk_status_t null_close_zone(struct nullb_device *dev, struct blk_zone *zone)
{
if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL)
return BLK_STS_IOERR;
switch (zone->cond) {
case BLK_ZONE_COND_CLOSED:
/* close operation on closed is not an error */
return BLK_STS_OK;
case BLK_ZONE_COND_IMP_OPEN:
dev->nr_zones_imp_open--;
break;
case BLK_ZONE_COND_EXP_OPEN:
dev->nr_zones_exp_open--;
break;
case BLK_ZONE_COND_EMPTY:
case BLK_ZONE_COND_FULL:
default:
return BLK_STS_IOERR;
}
if (zone->wp == zone->start) {
zone->cond = BLK_ZONE_COND_EMPTY;
} else {
zone->cond = BLK_ZONE_COND_CLOSED;
dev->nr_zones_closed++;
}
return BLK_STS_OK;
}
static void null_close_first_imp_zone(struct nullb_device *dev)
{
unsigned int i;
for (i = dev->zone_nr_conv; i < dev->nr_zones; i++) {
if (dev->zones[i].cond == BLK_ZONE_COND_IMP_OPEN) {
null_close_zone(dev, &dev->zones[i]);
return;
}
}
}
static blk_status_t null_check_active(struct nullb_device *dev)
{
if (!dev->zone_max_active)
return BLK_STS_OK;
if (dev->nr_zones_exp_open + dev->nr_zones_imp_open +
dev->nr_zones_closed < dev->zone_max_active)
return BLK_STS_OK;
return BLK_STS_ZONE_ACTIVE_RESOURCE;
}
static blk_status_t null_check_open(struct nullb_device *dev)
{
if (!dev->zone_max_open)
return BLK_STS_OK;
if (dev->nr_zones_exp_open + dev->nr_zones_imp_open < dev->zone_max_open)
return BLK_STS_OK;
if (dev->nr_zones_imp_open) {
if (null_check_active(dev) == BLK_STS_OK) {
null_close_first_imp_zone(dev);
return BLK_STS_OK;
}
}
return BLK_STS_ZONE_OPEN_RESOURCE;
}
/*
* This function matches the manage open zone resources function in the ZBC standard,
* with the addition of max active zones support (added in the ZNS standard).
*
* The function determines if a zone can transition to implicit open or explicit open,
* while maintaining the max open zone (and max active zone) limit(s). It may close an
* implicit open zone in order to make additional zone resources available.
*
* ZBC states that an implicit open zone shall be closed only if there is not
* room within the open limit. However, with the addition of an active limit,
* it is not certain that closing an implicit open zone will allow a new zone
* to be opened, since we might already be at the active limit capacity.
*/
static blk_status_t null_check_zone_resources(struct nullb_device *dev, struct blk_zone *zone)
{
blk_status_t ret;
switch (zone->cond) {
case BLK_ZONE_COND_EMPTY:
ret = null_check_active(dev);
if (ret != BLK_STS_OK)
return ret;
fallthrough;
case BLK_ZONE_COND_CLOSED:
return null_check_open(dev);
default:
/* Should never be called for other states */
WARN_ON(1);
return BLK_STS_IOERR;
}
}
static blk_status_t null_zone_write(struct nullb_cmd *cmd, sector_t sector,
unsigned int nr_sectors, bool append)
{
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;
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);
null_lock_zone(dev, zno);
switch (zone->cond) {
case BLK_ZONE_COND_FULL:
/* Cannot write to a full zone */
ret = BLK_STS_IOERR;
goto unlock;
case BLK_ZONE_COND_EMPTY:
case BLK_ZONE_COND_CLOSED:
ret = null_check_zone_resources(dev, zone);
if (ret != BLK_STS_OK)
goto unlock;
break;
case BLK_ZONE_COND_IMP_OPEN:
case BLK_ZONE_COND_EXP_OPEN:
break;
default:
/* Invalid zone condition */
ret = BLK_STS_IOERR;
goto unlock;
}
/*
* Regular writes must be at the write pointer position.
* Zone append writes are automatically issued at the write
* pointer and the position returned using the request or BIO
* sector.
*/
if (append) {
sector = zone->wp;
if (cmd->bio)
cmd->bio->bi_iter.bi_sector = sector;
else
cmd->rq->__sector = sector;
} else if (sector != zone->wp) {
ret = BLK_STS_IOERR;
goto unlock;
}
if (zone->wp + nr_sectors > zone->start + zone->capacity) {
ret = BLK_STS_IOERR;
goto unlock;
}
if (zone->cond == BLK_ZONE_COND_CLOSED) {
dev->nr_zones_closed--;
dev->nr_zones_imp_open++;
} else if (zone->cond == BLK_ZONE_COND_EMPTY) {
dev->nr_zones_imp_open++;
}
if (zone->cond != BLK_ZONE_COND_EXP_OPEN)
zone->cond = BLK_ZONE_COND_IMP_OPEN;
/*
* Memory backing allocation may sleep: release the zone_lock spinlock
* to avoid scheduling in atomic context. Zone operation atomicity is
* still guaranteed through the zone_locks bitmap.
*/
if (dev->memory_backed)
spin_unlock_irq(&dev->zone_lock);
ret = null_process_cmd(cmd, REQ_OP_WRITE, sector, nr_sectors);
if (dev->memory_backed)
spin_lock_irq(&dev->zone_lock);
if (ret != BLK_STS_OK)
goto unlock;
zone->wp += nr_sectors;
if (zone->wp == zone->start + zone->capacity) {
if (zone->cond == BLK_ZONE_COND_EXP_OPEN)
dev->nr_zones_exp_open--;
else if (zone->cond == BLK_ZONE_COND_IMP_OPEN)
dev->nr_zones_imp_open--;
zone->cond = BLK_ZONE_COND_FULL;
}
ret = BLK_STS_OK;
unlock:
null_unlock_zone(dev, zno);
return ret;
}
static blk_status_t null_open_zone(struct nullb_device *dev, struct blk_zone *zone)
{
blk_status_t ret;
if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL)
return BLK_STS_IOERR;
switch (zone->cond) {
case BLK_ZONE_COND_EXP_OPEN:
/* open operation on exp open is not an error */
return BLK_STS_OK;
case BLK_ZONE_COND_EMPTY:
ret = null_check_zone_resources(dev, zone);
if (ret != BLK_STS_OK)
return ret;
break;
case BLK_ZONE_COND_IMP_OPEN:
dev->nr_zones_imp_open--;
break;
case BLK_ZONE_COND_CLOSED:
ret = null_check_zone_resources(dev, zone);
if (ret != BLK_STS_OK)
return ret;
dev->nr_zones_closed--;
break;
case BLK_ZONE_COND_FULL:
default:
return BLK_STS_IOERR;
}
zone->cond = BLK_ZONE_COND_EXP_OPEN;
dev->nr_zones_exp_open++;
return BLK_STS_OK;
}
static blk_status_t null_finish_zone(struct nullb_device *dev, struct blk_zone *zone)
{
blk_status_t ret;
if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL)
return BLK_STS_IOERR;
switch (zone->cond) {
case BLK_ZONE_COND_FULL:
/* finish operation on full is not an error */
return BLK_STS_OK;
case BLK_ZONE_COND_EMPTY:
ret = null_check_zone_resources(dev, zone);
if (ret != BLK_STS_OK)
return ret;
break;
case BLK_ZONE_COND_IMP_OPEN:
dev->nr_zones_imp_open--;
break;
case BLK_ZONE_COND_EXP_OPEN:
dev->nr_zones_exp_open--;
break;
case BLK_ZONE_COND_CLOSED:
ret = null_check_zone_resources(dev, zone);
if (ret != BLK_STS_OK)
return ret;
dev->nr_zones_closed--;
break;
default:
return BLK_STS_IOERR;
}
zone->cond = BLK_ZONE_COND_FULL;
zone->wp = zone->start + zone->len;
return BLK_STS_OK;
}
static blk_status_t null_reset_zone(struct nullb_device *dev, struct blk_zone *zone)
{
if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL)
return BLK_STS_IOERR;
switch (zone->cond) {
case BLK_ZONE_COND_EMPTY:
/* reset operation on empty is not an error */
return BLK_STS_OK;
case BLK_ZONE_COND_IMP_OPEN:
dev->nr_zones_imp_open--;
break;
case BLK_ZONE_COND_EXP_OPEN:
dev->nr_zones_exp_open--;
break;
case BLK_ZONE_COND_CLOSED:
dev->nr_zones_closed--;
break;
case BLK_ZONE_COND_FULL:
break;
default:
return BLK_STS_IOERR;
}
zone->cond = BLK_ZONE_COND_EMPTY;
zone->wp = zone->start;
return BLK_STS_OK;
}
static blk_status_t null_zone_mgmt(struct nullb_cmd *cmd, enum req_opf op,
sector_t sector)
{
struct nullb_device *dev = cmd->nq->dev;
unsigned int zone_no;
struct blk_zone *zone;
blk_status_t ret;
size_t i;
if (op == REQ_OP_ZONE_RESET_ALL) {
for (i = dev->zone_nr_conv; i < dev->nr_zones; i++) {
null_lock_zone(dev, i);
zone = &dev->zones[i];
if (zone->cond != BLK_ZONE_COND_EMPTY) {
null_reset_zone(dev, zone);
trace_nullb_zone_op(cmd, i, zone->cond);
}
null_unlock_zone(dev, i);
}
return BLK_STS_OK;
}
zone_no = null_zone_no(dev, sector);
zone = &dev->zones[zone_no];
null_lock_zone(dev, zone_no);
switch (op) {
case REQ_OP_ZONE_RESET:
ret = null_reset_zone(dev, zone);
break;
case REQ_OP_ZONE_OPEN:
ret = null_open_zone(dev, zone);
break;
case REQ_OP_ZONE_CLOSE:
ret = null_close_zone(dev, zone);
break;
case REQ_OP_ZONE_FINISH:
ret = null_finish_zone(dev, zone);
break;
default:
ret = BLK_STS_NOTSUPP;
break;
}
if (ret == BLK_STS_OK)
trace_nullb_zone_op(cmd, zone_no, zone->cond);
null_unlock_zone(dev, zone_no);
return ret;
}
blk_status_t null_process_zoned_cmd(struct nullb_cmd *cmd, enum req_opf op,
sector_t sector, sector_t nr_sectors)
{
struct nullb_device *dev = cmd->nq->dev;
unsigned int zno = null_zone_no(dev, sector);
blk_status_t sts;
switch (op) {
case REQ_OP_WRITE:
sts = null_zone_write(cmd, sector, nr_sectors, false);
break;
case REQ_OP_ZONE_APPEND:
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:
sts = null_zone_mgmt(cmd, op, sector);
break;
default:
null_lock_zone(dev, zno);
sts = null_process_cmd(cmd, op, sector, nr_sectors);
null_unlock_zone(dev, zno);
}
return sts;
}