block: introduce zoned block devices zone write locking

Components relying only on the request_queue structure for accessing
block devices (e.g. I/O schedulers) have a limited knowledged of the
device characteristics. In particular, the device capacity cannot be
easily discovered, which for a zoned block device also result in the
inability to easily know the number of zones of the device (the zone
size is indicated by the chunk_sectors field of the queue limits).

Introduce the nr_zones field to the request_queue structure to simplify
access to this information. Also, add the bitmap seq_zone_bitmap which
indicates which zones of the device are sequential zones (write
preferred or write required) and the bitmap seq_zones_wlock which
indicates if a zone is write locked, that is, if a write request
targeting a zone was dispatched to the device. These fields are
initialized by the low level block device driver (sd.c for ZBC/ZAC
disks). They are not initialized by stacking drivers (device mappers)
handling zoned block devices (e.g. dm-linear).

Using this, I/O schedulers can introduce zone write locking to control
request dispatching to a zoned block device and avoid write request
reordering by limiting to at most a single write request per zone
outside of the scheduler at any time.

Based on previous patches from Damien Le Moal.

Signed-off-by: Christoph Hellwig <hch@lst.de>
[Damien]
* Fixed comments and identation in blkdev.h
* Changed helper functions
* Fixed this commit message
Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2017-12-21 15:43:38 +09:00 committed by Jens Axboe
parent 882d4171a8
commit 6cc77e9cb0
3 changed files with 154 additions and 0 deletions

View file

@ -1641,6 +1641,7 @@ void __blk_put_request(struct request_queue *q, struct request *req)
lockdep_assert_held(q->queue_lock);
blk_req_zone_write_unlock(req);
blk_pm_put_request(req);
elv_completed_request(q, req);

View file

@ -21,6 +21,48 @@ static inline sector_t blk_zone_start(struct request_queue *q,
return sector & ~zone_mask;
}
/*
* Return true if a request is a write requests that needs zone write locking.
*/
bool blk_req_needs_zone_write_lock(struct request *rq)
{
if (!rq->q->seq_zones_wlock)
return false;
if (blk_rq_is_passthrough(rq))
return false;
switch (req_op(rq)) {
case REQ_OP_WRITE_ZEROES:
case REQ_OP_WRITE_SAME:
case REQ_OP_WRITE:
return blk_rq_zone_is_seq(rq);
default:
return false;
}
}
EXPORT_SYMBOL_GPL(blk_req_needs_zone_write_lock);
void __blk_req_zone_write_lock(struct request *rq)
{
if (WARN_ON_ONCE(test_and_set_bit(blk_rq_zone_no(rq),
rq->q->seq_zones_wlock)))
return;
WARN_ON_ONCE(rq->rq_flags & RQF_ZONE_WRITE_LOCKED);
rq->rq_flags |= RQF_ZONE_WRITE_LOCKED;
}
EXPORT_SYMBOL_GPL(__blk_req_zone_write_lock);
void __blk_req_zone_write_unlock(struct request *rq)
{
rq->rq_flags &= ~RQF_ZONE_WRITE_LOCKED;
if (rq->q->seq_zones_wlock)
WARN_ON_ONCE(!test_and_clear_bit(blk_rq_zone_no(rq),
rq->q->seq_zones_wlock));
}
EXPORT_SYMBOL_GPL(__blk_req_zone_write_unlock);
/*
* Check that a zone report belongs to the partition.
* If yes, fix its start sector and write pointer, copy it in the

View file

@ -121,6 +121,8 @@ typedef __u32 __bitwise req_flags_t;
/* Look at ->special_vec for the actual data payload instead of the
bio chain. */
#define RQF_SPECIAL_PAYLOAD ((__force req_flags_t)(1 << 18))
/* The per-zone write lock is held for this request */
#define RQF_ZONE_WRITE_LOCKED ((__force req_flags_t)(1 << 19))
/* flags that prevent us from merging requests: */
#define RQF_NOMERGE_FLAGS \
@ -546,6 +548,22 @@ struct request_queue {
struct queue_limits limits;
/*
* Zoned block device information for request dispatch control.
* nr_zones is the total number of zones of the device. This is always
* 0 for regular block devices. seq_zones_bitmap is a bitmap of nr_zones
* bits which indicates if a zone is conventional (bit clear) or
* sequential (bit set). seq_zones_wlock is a bitmap of nr_zones
* bits which indicates if a zone is write locked, that is, if a write
* request targeting the zone was dispatched. All three fields are
* initialized by the low level device driver (e.g. scsi/sd.c).
* Stacking drivers (device mappers) may or may not initialize
* these fields.
*/
unsigned int nr_zones;
unsigned long *seq_zones_bitmap;
unsigned long *seq_zones_wlock;
/*
* sg stuff
*/
@ -790,6 +808,27 @@ static inline unsigned int blk_queue_zone_sectors(struct request_queue *q)
return blk_queue_is_zoned(q) ? q->limits.chunk_sectors : 0;
}
static inline unsigned int blk_queue_nr_zones(struct request_queue *q)
{
return q->nr_zones;
}
static inline unsigned int blk_queue_zone_no(struct request_queue *q,
sector_t sector)
{
if (!blk_queue_is_zoned(q))
return 0;
return sector >> ilog2(q->limits.chunk_sectors);
}
static inline bool blk_queue_zone_is_seq(struct request_queue *q,
sector_t sector)
{
if (!blk_queue_is_zoned(q) || !q->seq_zones_bitmap)
return false;
return test_bit(blk_queue_zone_no(q, sector), q->seq_zones_bitmap);
}
static inline bool rq_is_sync(struct request *rq)
{
return op_is_sync(rq->cmd_flags);
@ -1029,6 +1068,16 @@ static inline unsigned int blk_rq_cur_sectors(const struct request *rq)
return blk_rq_cur_bytes(rq) >> 9;
}
static inline unsigned int blk_rq_zone_no(struct request *rq)
{
return blk_queue_zone_no(rq->q, blk_rq_pos(rq));
}
static inline unsigned int blk_rq_zone_is_seq(struct request *rq)
{
return blk_queue_zone_is_seq(rq->q, blk_rq_pos(rq));
}
/*
* Some commands like WRITE SAME have a payload or data transfer size which
* is different from the size of the request. Any driver that supports such
@ -1578,7 +1627,15 @@ static inline unsigned int bdev_zone_sectors(struct block_device *bdev)
if (q)
return blk_queue_zone_sectors(q);
return 0;
}
static inline unsigned int bdev_nr_zones(struct block_device *bdev)
{
struct request_queue *q = bdev_get_queue(bdev);
if (q)
return blk_queue_nr_zones(q);
return 0;
}
@ -1954,6 +2011,60 @@ extern int __blkdev_driver_ioctl(struct block_device *, fmode_t, unsigned int,
extern int bdev_read_page(struct block_device *, sector_t, struct page *);
extern int bdev_write_page(struct block_device *, sector_t, struct page *,
struct writeback_control *);
#ifdef CONFIG_BLK_DEV_ZONED
bool blk_req_needs_zone_write_lock(struct request *rq);
void __blk_req_zone_write_lock(struct request *rq);
void __blk_req_zone_write_unlock(struct request *rq);
static inline void blk_req_zone_write_lock(struct request *rq)
{
if (blk_req_needs_zone_write_lock(rq))
__blk_req_zone_write_lock(rq);
}
static inline void blk_req_zone_write_unlock(struct request *rq)
{
if (rq->rq_flags & RQF_ZONE_WRITE_LOCKED)
__blk_req_zone_write_unlock(rq);
}
static inline bool blk_req_zone_is_write_locked(struct request *rq)
{
return rq->q->seq_zones_wlock &&
test_bit(blk_rq_zone_no(rq), rq->q->seq_zones_wlock);
}
static inline bool blk_req_can_dispatch_to_zone(struct request *rq)
{
if (!blk_req_needs_zone_write_lock(rq))
return true;
return !blk_req_zone_is_write_locked(rq);
}
#else
static inline bool blk_req_needs_zone_write_lock(struct request *rq)
{
return false;
}
static inline void blk_req_zone_write_lock(struct request *rq)
{
}
static inline void blk_req_zone_write_unlock(struct request *rq)
{
}
static inline bool blk_req_zone_is_write_locked(struct request *rq)
{
return false;
}
static inline bool blk_req_can_dispatch_to_zone(struct request *rq)
{
return true;
}
#endif /* CONFIG_BLK_DEV_ZONED */
#else /* CONFIG_BLOCK */
struct block_device;