new file mode 100644
@@ -0,0 +1,48 @@
+Zoned I/O scheduler
+===================
+
+The Zoned I/O scheduler solves zoned block devices write ordering problems
+inherent to the absence of a global request queue lock in the blk-mq
+infrastructure. Multiple contexts may try to dispatch simultaneously write
+requests to the same sequential zone of a zoned block device, doing so
+potentially breaking the sequential write order imposed by the device.
+
+The Zoned I/O scheduler is based on the mq-deadline scheduler. It shares the
+same tunables and behaves in a comparable manner. The main difference introduced
+with the zoned scheduler is handling of write batches. Whereas mq-deadline will
+keep dispatching write requests to the device as long as the batching size
+allows and reads are not starved, the zoned scheduler introduces additional
+constraints:
+1) At most only one write request can be issued to a sequential zone of the
+device. This ensures that no reordering of sequential writes to a sequential
+zone can happen once the write request leaves the scheduler internal queue (rb
+tree).
+2) The number of sequential zones that can be simultaneously written is limited
+to the device advertized maximum number of open zones. This additional condition
+avoids performance degradation due to excessive open zone resource use at the
+device level.
+
+These conditions do not apply to write requests targeting conventional zones.
+For these, the zoned scheduler behaves exactly like the mq-deadline scheduler.
+
+The zoned I/O scheduler cannot be used with regular block devices. It can only
+be used with host-managed or host-aware zoned block devices.
+Using the zoned I/O scheduler is mandatory with host-managed disks unless the
+disk user tightly controls itself write sequencing to sequential zones. The
+zoned scheduler will treat host-aware disks exactly the same way as host-managed
+devices. That is, eventhough host aware disks can be randomly written, the zoned
+scheduler will still impose the limit to one write per zone so that sequential
+writes sequences are preserved.
+
+For host-managed disks, automating the used of the zoned scheduler can be done
+simply with a udev rule. An example of such rule is shown below.
+
+# Set zoned scheduler for host-managed zoned block devices
+ACTION=="add|change", KERNEL=="sd[a-z]", ATTR{queue/zoned}=="host-managed", \
+ ATTR{queue/scheduler}="zoned"
+
+Zoned I/O scheduler tunables
+============================
+
+Tunables of the Zoned I/O scheduler are identical to those of the deadline
+I/O scheduler. See Documentation/block/deadline-iosched.txt for details.
@@ -70,6 +70,18 @@ config MQ_IOSCHED_DEADLINE
---help---
MQ version of the deadline IO scheduler.
+config MQ_IOSCHED_ZONED
+ tristate "Zoned I/O scheduler"
+ depends on BLK_DEV_ZONED
+ depends on SCSI_MOD
+ depends on BLK_DEV_SD
+ default y
+ ---help---
+ MQ deadline IO scheduler with support for zoned block devices.
+
+ This should be set as the default I/O scheduler for host-managed
+ zoned block devices. It is optional for host-aware block devices.
+
config MQ_IOSCHED_KYBER
tristate "Kyber I/O scheduler"
default y
@@ -176,6 +176,7 @@ hv_storvsc-y := storvsc_drv.o
sd_mod-objs := sd.o
sd_mod-$(CONFIG_BLK_DEV_INTEGRITY) += sd_dif.o
sd_mod-$(CONFIG_BLK_DEV_ZONED) += sd_zbc.o
+obj-$(CONFIG_MQ_IOSCHED_ZONED) += sd_zbc_iosched.o
sr_mod-objs := sr.o sr_ioctl.o sr_vendor.o
ncr53c8xx-flags-$(CONFIG_SCSI_ZALON) \
@@ -75,7 +75,8 @@ struct scsi_disk {
#ifdef CONFIG_BLK_DEV_ZONED
unsigned int nr_zones;
unsigned int zone_blocks;
- unsigned int zone_shift;
+ unsigned int zone_sectors;
+ unsigned int zone_sectors_shift;
unsigned long *zones_wlock;
unsigned long *seq_zones;
unsigned int zones_optimal_open;
@@ -217,7 +217,7 @@ int sd_zbc_setup_reset_cmnd(struct scsi_cmnd *cmd)
if (sdkp->device->changed)
return BLKPREP_KILL;
- if (sector & (sd_zbc_zone_sectors(sdkp) - 1))
+ if (sector & (sdkp->zone_sectors - 1))
/* Unaligned request */
return BLKPREP_KILL;
@@ -245,7 +245,7 @@ int sd_zbc_write_lock_zone(struct scsi_cmnd *cmd)
struct request *rq = cmd->request;
struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);
sector_t sector = blk_rq_pos(rq);
- sector_t zone_sectors = sd_zbc_zone_sectors(sdkp);
+ sector_t zone_sectors = sdkp->zone_sectors;
unsigned int zno;
/*
@@ -268,7 +268,7 @@ int sd_zbc_write_lock_zone(struct scsi_cmnd *cmd)
* ordering problems due to the unlocking of the request queue in the
* dispatch path of the non scsi-mq (legacy) case.
*/
- zno = sd_zbc_zone_no(sdkp, sector);
+ zno = sd_zbc_rq_zone_no(sdkp, rq);
if (!test_bit(zno, sdkp->seq_zones))
return BLKPREP_OK;
if (test_and_set_bit(zno, sdkp->zones_wlock))
@@ -290,7 +290,7 @@ void sd_zbc_write_unlock_zone(struct scsi_cmnd *cmd)
struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);
if (cmd->flags & SCMD_ZONE_WRITE_LOCK) {
- unsigned int zno = sd_zbc_zone_no(sdkp, blk_rq_pos(rq));
+ unsigned int zno = sd_zbc_rq_zone_no(sdkp, rq);
WARN_ON_ONCE(!test_bit(zno, sdkp->zones_wlock));
cmd->flags &= ~SCMD_ZONE_WRITE_LOCK;
@@ -509,7 +509,8 @@ static int sd_zbc_check_zone_size(struct scsi_disk *sdkp)
}
sdkp->zone_blocks = zone_blocks;
- sdkp->zone_shift = ilog2(zone_blocks);
+ sdkp->zone_sectors = logical_to_sectors(sdkp->device, zone_blocks);
+ sdkp->zone_sectors_shift = ilog2(sdkp->zone_sectors);
return 0;
}
@@ -574,6 +575,7 @@ static int sd_zbc_setup_seq_zones(struct scsi_disk *sdkp)
static int sd_zbc_setup(struct scsi_disk *sdkp)
{
+ sector_t zone_blocks = sdkp->zone_blocks;
int ret;
/* READ16/WRITE16 is mandatory for ZBC disks */
@@ -582,9 +584,9 @@ static int sd_zbc_setup(struct scsi_disk *sdkp)
/* chunk_sectors indicates the zone size */
blk_queue_chunk_sectors(sdkp->disk->queue,
- logical_to_sectors(sdkp->device, sdkp->zone_blocks));
+ logical_to_sectors(sdkp->device, zone_blocks));
sdkp->nr_zones =
- round_up(sdkp->capacity, sdkp->zone_blocks) >> sdkp->zone_shift;
+ round_up(sdkp->capacity, zone_blocks) >> ilog2(zone_blocks);
/*
* Wait for the disk capacity to stabilize before
@@ -13,15 +13,10 @@ static inline int sd_is_zoned(struct scsi_disk *sdkp)
#ifdef CONFIG_BLK_DEV_ZONED
-static inline sector_t sd_zbc_zone_sectors(struct scsi_disk *sdkp)
+static inline unsigned int sd_zbc_rq_zone_no(struct scsi_disk *sdkp,
+ struct request *rq)
{
- return logical_to_sectors(sdkp->device, sdkp->zone_blocks);
-}
-
-static inline unsigned int sd_zbc_zone_no(struct scsi_disk *sdkp,
- sector_t sector)
-{
- return sectors_to_logical(sdkp->device, sector) >> sdkp->zone_shift;
+ return blk_rq_pos(rq) >> sdkp->zone_sectors_shift;
}
static inline unsigned long *sd_zbc_alloc_zone_bitmap(struct scsi_disk *sdkp)
new file mode 100644
@@ -0,0 +1,934 @@
+/*
+ * Zoned MQ Deadline i/o scheduler - adaptation of the MQ deadline scheduler,
+ * for zoned block devices used with the blk-mq scheduling framework
+ *
+ * Copyright (C) 2016 Jens Axboe <axboe@kernel.dk>
+ * Copyright (C) 2017 Damien Le Moal <damien.lemoal@wdc.com>
+ */
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/blkdev.h>
+#include <linux/blk-mq.h>
+#include <linux/elevator.h>
+#include <linux/bio.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/compiler.h>
+#include <linux/rbtree.h>
+#include <linux/sbitmap.h>
+#include <linux/seq_file.h>
+
+#include "sd_zbc.h"
+
+/*
+ * See Documentation/block/deadline-iosched.txt
+ */
+
+/* max time before a read is submitted. */
+static const int read_expire = HZ / 2;
+
+/* ditto for writes, these limits are SOFT! */
+static const int write_expire = 5 * HZ;
+
+/* max times reads can starve a write */
+static const int writes_starved = 2;
+
+/*
+ * Number of sequential requests treated as one by the above parameters.
+ * For throughput.
+ */
+static const int fifo_batch = 16;
+
+/*
+ * Run time data.
+ */
+struct zoned_data {
+ /*
+ * requests (zoned_rq s) are present on both sort_list and fifo_list
+ */
+ struct rb_root sort_list[2];
+ struct list_head fifo_list[2];
+
+ /*
+ * next in sort order. read, write or both are NULL
+ */
+ struct request *next_rq[2];
+ unsigned int batching; /* number of sequential requests made */
+ unsigned int starved; /* times reads have starved writes */
+
+ /*
+ * settings that change how the i/o scheduler behaves
+ */
+ int fifo_expire[2];
+ int fifo_batch;
+ int writes_starved;
+ int front_merges;
+
+ spinlock_t lock;
+ struct list_head dispatch;
+
+ struct scsi_disk *sdkp;
+
+ spinlock_t zones_lock;
+ unsigned long *zones_wlock;
+ unsigned long *seq_zones;
+};
+
+static inline struct rb_root *
+zoned_rb_root(struct zoned_data *zd, struct request *rq)
+{
+ return &zd->sort_list[rq_data_dir(rq)];
+}
+
+/*
+ * get the request after `rq' in sector-sorted order
+ */
+static inline struct request *
+zoned_latter_request(struct request *rq)
+{
+ struct rb_node *node = rb_next(&rq->rb_node);
+
+ if (node)
+ return rb_entry_rq(node);
+
+ return NULL;
+}
+
+static void
+zoned_add_rq_rb(struct zoned_data *zd, struct request *rq)
+{
+ struct rb_root *root = zoned_rb_root(zd, rq);
+
+ elv_rb_add(root, rq);
+}
+
+static inline void
+zoned_del_rq_rb(struct zoned_data *zd, struct request *rq)
+{
+ const int data_dir = rq_data_dir(rq);
+
+ if (zd->next_rq[data_dir] == rq)
+ zd->next_rq[data_dir] = zoned_latter_request(rq);
+
+ elv_rb_del(zoned_rb_root(zd, rq), rq);
+}
+
+/*
+ * remove rq from rbtree and fifo.
+ */
+static void zoned_remove_request(struct request_queue *q, struct request *rq)
+{
+ struct zoned_data *zd = q->elevator->elevator_data;
+
+ list_del_init(&rq->queuelist);
+
+ /*
+ * We might not be on the rbtree, if we are doing an insert merge
+ */
+ if (!RB_EMPTY_NODE(&rq->rb_node))
+ zoned_del_rq_rb(zd, rq);
+
+ elv_rqhash_del(q, rq);
+ if (q->last_merge == rq)
+ q->last_merge = NULL;
+}
+
+static void zd_request_merged(struct request_queue *q, struct request *req,
+ enum elv_merge type)
+{
+ struct zoned_data *zd = q->elevator->elevator_data;
+
+ /*
+ * if the merge was a front merge, we need to reposition request
+ */
+ if (type == ELEVATOR_FRONT_MERGE) {
+ elv_rb_del(zoned_rb_root(zd, req), req);
+ zoned_add_rq_rb(zd, req);
+ }
+}
+
+static void zd_merged_requests(struct request_queue *q, struct request *req,
+ struct request *next)
+{
+ /*
+ * if next expires before rq, assign its expire time to rq
+ * and move into next position (next will be deleted) in fifo
+ */
+ if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
+ if (time_before((unsigned long)next->fifo_time,
+ (unsigned long)req->fifo_time)) {
+ list_move(&req->queuelist, &next->queuelist);
+ req->fifo_time = next->fifo_time;
+ }
+ }
+
+ /*
+ * kill knowledge of next, this one is a goner
+ */
+ zoned_remove_request(q, next);
+}
+
+/*
+ * Return true if a request is a write requests that needs zone
+ * write locking.
+ */
+static inline bool zoned_request_needs_wlock(struct zoned_data *zd,
+ struct request *rq)
+{
+ unsigned int zno = sd_zbc_rq_zone_no(zd->sdkp, rq);
+
+ if (blk_rq_is_passthrough(rq))
+ return false;
+
+ if (!test_bit(zno, zd->seq_zones))
+ return false;
+
+ switch (req_op(rq)) {
+ case REQ_OP_WRITE_ZEROES:
+ case REQ_OP_WRITE_SAME:
+ case REQ_OP_WRITE:
+ return true;
+ default:
+ return false;
+ }
+}
+
+/*
+ * Abuse the elv.priv[0] pointer to indicate if a request
+ * has locked its target zone.
+ */
+#define RQ_LOCKED_ZONE ((void *)1UL)
+static inline void zoned_set_request_lock(struct request *rq)
+{
+ rq->elv.priv[0] = RQ_LOCKED_ZONE;
+}
+
+#define RQ_ZONE_NO_LOCK ((void *)0UL)
+static inline void zoned_clear_request_lock(struct request *rq)
+{
+ rq->elv.priv[0] = RQ_ZONE_NO_LOCK;
+}
+
+static inline bool zoned_request_has_lock(struct request *rq)
+{
+ return rq->elv.priv[0] == RQ_LOCKED_ZONE;
+}
+
+/*
+ * Write lock the target zone of a write request.
+ */
+static void zoned_wlock_request_zone(struct zoned_data *zd, struct request *rq)
+{
+ unsigned int zno = sd_zbc_rq_zone_no(zd->sdkp, rq);
+
+ WARN_ON_ONCE(zoned_request_has_lock(rq));
+ WARN_ON_ONCE(test_and_set_bit(zno, zd->zones_wlock));
+ zoned_set_request_lock(rq);
+}
+
+/*
+ * Write unlock the target zone of a write request.
+ */
+static void zoned_wunlock_request_zone(struct zoned_data *zd,
+ struct request *rq)
+{
+ unsigned int zno = sd_zbc_rq_zone_no(zd->sdkp, rq);
+ unsigned long flags;
+
+ /*
+ * Dispatch may be running on a different CPU.
+ * So do not unlock the zone until it is done or
+ * a write request in the middle of a sequence may end up
+ * being dispatched.
+ */
+ spin_lock_irqsave(&zd->zones_lock, flags);
+
+ WARN_ON_ONCE(!test_and_clear_bit(zno, zd->zones_wlock));
+ zoned_clear_request_lock(rq);
+
+ spin_unlock_irqrestore(&zd->zones_lock, flags);
+}
+
+/*
+ * Test the write lock state of the target zone of a write request.
+ */
+static inline bool zoned_request_zone_is_wlocked(struct zoned_data *zd,
+ struct request *rq)
+{
+ unsigned int zno = sd_zbc_rq_zone_no(zd->sdkp, rq);
+
+ return test_bit(zno, zd->zones_wlock);
+}
+
+/*
+ * move an entry to dispatch queue
+ */
+static void zoned_move_request(struct zoned_data *zd, struct request *rq)
+{
+ const int data_dir = rq_data_dir(rq);
+
+ zd->next_rq[READ] = NULL;
+ zd->next_rq[WRITE] = NULL;
+ zd->next_rq[data_dir] = zoned_latter_request(rq);
+
+ /*
+ * take it off the sort and fifo list
+ */
+ zoned_remove_request(rq->q, rq);
+}
+
+/*
+ * zoned_check_fifo returns 0 if there are no expired requests on the fifo,
+ * 1 otherwise. Requires !list_empty(&zd->fifo_list[data_dir])
+ */
+static inline int zoned_check_fifo(struct zoned_data *zd, int ddir)
+{
+ struct request *rq = rq_entry_fifo(zd->fifo_list[ddir].next);
+
+ /*
+ * rq is expired!
+ */
+ if (time_after_eq(jiffies, (unsigned long)rq->fifo_time))
+ return 1;
+
+ return 0;
+}
+
+/*
+ * Test if a request can be dispatched.
+ */
+static inline bool zoned_can_dispatch_request(struct zoned_data *zd,
+ struct request *rq)
+{
+ return !zoned_request_needs_wlock(zd, rq) ||
+ !zoned_request_zone_is_wlocked(zd, rq);
+}
+
+/*
+ * For the specified data direction, find the next request that can be
+ * dispatched. Search in increasing sector position.
+ */
+static struct request *
+zoned_next_request(struct zoned_data *zd, int data_dir)
+{
+ struct request *rq = zd->next_rq[data_dir];
+ unsigned long flags;
+
+ if (data_dir == READ)
+ return rq;
+
+ spin_lock_irqsave(&zd->zones_lock, flags);
+ while (rq) {
+ if (zoned_can_dispatch_request(zd, rq))
+ break;
+ rq = zoned_latter_request(rq);
+ }
+ spin_unlock_irqrestore(&zd->zones_lock, flags);
+
+ return rq;
+}
+
+/*
+ * For the specified data direction, find the next request that can be
+ * dispatched. Search in arrival order from the oldest request.
+ */
+static struct request *
+zoned_fifo_request(struct zoned_data *zd, int data_dir)
+{
+ struct request *rq;
+ unsigned long flags;
+
+ if (list_empty(&zd->fifo_list[data_dir]))
+ return NULL;
+
+ if (data_dir == READ)
+ return rq_entry_fifo(zd->fifo_list[READ].next);
+
+ spin_lock_irqsave(&zd->zones_lock, flags);
+
+ list_for_each_entry(rq, &zd->fifo_list[WRITE], queuelist) {
+ if (zoned_can_dispatch_request(zd, rq))
+ goto out;
+ }
+ rq = NULL;
+
+out:
+ spin_unlock_irqrestore(&zd->zones_lock, flags);
+
+ return rq;
+}
+
+/*
+ * __zd_dispatch_request selects the best request according to
+ * read/write batch expiration, fifo_batch, target zone lock state, etc
+ */
+static struct request *__zd_dispatch_request(struct blk_mq_hw_ctx *hctx)
+{
+ struct zoned_data *zd = hctx->queue->elevator->elevator_data;
+ struct request *rq = NULL, *next_rq;
+ bool reads, writes;
+ int data_dir;
+
+ if (!list_empty(&zd->dispatch)) {
+ rq = list_first_entry(&zd->dispatch, struct request, queuelist);
+ list_del_init(&rq->queuelist);
+ goto done;
+ }
+
+ reads = !list_empty(&zd->fifo_list[READ]);
+ writes = !list_empty(&zd->fifo_list[WRITE]);
+
+ /*
+ * batches are currently reads XOR writes
+ */
+ rq = zoned_next_request(zd, WRITE);
+ if (!rq)
+ rq = zoned_next_request(zd, READ);
+ if (rq && zd->batching < zd->fifo_batch)
+ /* we have a next request are still entitled to batch */
+ goto dispatch_request;
+
+ /*
+ * at this point we are not running a batch. select the appropriate
+ * data direction (read / write)
+ */
+
+ if (reads) {
+ if (writes && (zd->starved++ >= zd->writes_starved))
+ goto dispatch_writes;
+
+ data_dir = READ;
+
+ goto dispatch_find_request;
+ }
+
+ /*
+ * there are either no reads or writes have been starved
+ */
+
+ if (writes) {
+dispatch_writes:
+ zd->starved = 0;
+
+ /* Really select writes if at least one can be dispatched */
+ if (zoned_fifo_request(zd, WRITE))
+ data_dir = WRITE;
+ else
+ data_dir = READ;
+
+ goto dispatch_find_request;
+ }
+
+ return NULL;
+
+dispatch_find_request:
+ /*
+ * we are not running a batch, find best request for selected data_dir
+ */
+ next_rq = zoned_next_request(zd, data_dir);
+ if (zoned_check_fifo(zd, data_dir) || !next_rq) {
+ /*
+ * A deadline has expired, the last request was in the other
+ * direction, or we have run out of higher-sectored requests.
+ * Start again from the request with the earliest expiry time.
+ */
+ rq = zoned_fifo_request(zd, data_dir);
+ } else {
+ /*
+ * The last req was the same dir and we have a next request in
+ * sort order. No expired requests so continue on from here.
+ */
+ rq = next_rq;
+ }
+
+ if (!rq)
+ return NULL;
+
+ zd->batching = 0;
+
+dispatch_request:
+ /*
+ * rq is the selected appropriate request.
+ */
+ zd->batching++;
+ zoned_move_request(zd, rq);
+
+done:
+ /*
+ * If the request needs its target zone locked, do it.
+ */
+ if (zoned_request_needs_wlock(zd, rq))
+ zoned_wlock_request_zone(zd, rq);
+ rq->rq_flags |= RQF_STARTED;
+ return rq;
+}
+
+static struct request *zd_dispatch_request(struct blk_mq_hw_ctx *hctx)
+{
+ struct zoned_data *zd = hctx->queue->elevator->elevator_data;
+ struct request *rq;
+
+ spin_lock(&zd->lock);
+ rq = __zd_dispatch_request(hctx);
+ spin_unlock(&zd->lock);
+
+ return rq;
+}
+
+static int zd_request_merge(struct request_queue *q, struct request **rq,
+ struct bio *bio)
+{
+ struct zoned_data *zd = q->elevator->elevator_data;
+ sector_t sector = bio_end_sector(bio);
+ struct request *__rq;
+
+ if (!zd->front_merges)
+ return ELEVATOR_NO_MERGE;
+
+ __rq = elv_rb_find(&zd->sort_list[bio_data_dir(bio)], sector);
+ if (__rq) {
+ if (WARN_ON(sector != blk_rq_pos(__rq)))
+ return ELEVATOR_NO_MERGE;
+
+ if (elv_bio_merge_ok(__rq, bio)) {
+ *rq = __rq;
+ return ELEVATOR_FRONT_MERGE;
+ }
+ }
+
+ return ELEVATOR_NO_MERGE;
+}
+
+static bool zd_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
+{
+ struct request_queue *q = hctx->queue;
+ struct zoned_data *zd = q->elevator->elevator_data;
+ struct request *free = NULL;
+ bool ret;
+
+ spin_lock(&zd->lock);
+ ret = blk_mq_sched_try_merge(q, bio, &free);
+ spin_unlock(&zd->lock);
+
+ if (free)
+ blk_mq_free_request(free);
+
+ return ret;
+}
+
+/*
+ * add rq to rbtree and fifo
+ */
+static void __zd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
+ bool at_head)
+{
+ struct request_queue *q = hctx->queue;
+ struct zoned_data *zd = q->elevator->elevator_data;
+ const int data_dir = rq_data_dir(rq);
+
+ if (blk_mq_sched_try_insert_merge(q, rq))
+ return;
+
+ blk_mq_sched_request_inserted(rq);
+
+ if (at_head || blk_rq_is_passthrough(rq)) {
+ if (at_head)
+ list_add(&rq->queuelist, &zd->dispatch);
+ else
+ list_add_tail(&rq->queuelist, &zd->dispatch);
+ } else {
+ zoned_add_rq_rb(zd, rq);
+
+ if (rq_mergeable(rq)) {
+ elv_rqhash_add(q, rq);
+ if (!q->last_merge)
+ q->last_merge = rq;
+ }
+
+ /*
+ * set expire time and add to fifo list
+ */
+ rq->fifo_time = jiffies + zd->fifo_expire[data_dir];
+ list_add_tail(&rq->queuelist, &zd->fifo_list[data_dir]);
+ }
+}
+
+static void zd_insert_requests(struct blk_mq_hw_ctx *hctx,
+ struct list_head *list, bool at_head)
+{
+ struct request_queue *q = hctx->queue;
+ struct zoned_data *zd = q->elevator->elevator_data;
+
+ spin_lock(&zd->lock);
+ while (!list_empty(list)) {
+ struct request *rq;
+
+ rq = list_first_entry(list, struct request, queuelist);
+ list_del_init(&rq->queuelist);
+
+ /*
+ * This may be a requeue of a request that has locked its
+ * target zone. If this is the case, release the zone lock.
+ */
+ if (zoned_request_has_lock(rq))
+ zoned_wunlock_request_zone(zd, rq);
+
+ __zd_insert_request(hctx, rq, at_head);
+ }
+ spin_unlock(&zd->lock);
+}
+
+/*
+ * Write unlock the target zone of a completed write request.
+ */
+static void zd_completed_request(struct request *rq)
+{
+
+ if (zoned_request_has_lock(rq)) {
+ struct zoned_data *zd = rq->q->elevator->elevator_data;
+
+ zoned_wunlock_request_zone(zd, rq);
+ }
+}
+
+static bool zd_has_work(struct blk_mq_hw_ctx *hctx)
+{
+ struct zoned_data *zd = hctx->queue->elevator->elevator_data;
+
+ return !list_empty_careful(&zd->dispatch) ||
+ !list_empty_careful(&zd->fifo_list[0]) ||
+ !list_empty_careful(&zd->fifo_list[1]);
+}
+
+static struct scsi_disk *__zoned_scsi_disk(struct request_queue *q)
+{
+ struct scsi_device *sdp;
+ struct scsi_disk *sdkp;
+
+ if (!blk_queue_is_zoned(q)) {
+ pr_err("zoned: Not a zoned block device\n");
+ return NULL;
+ }
+
+ sdp = scsi_device_from_queue(q);
+ if (!sdp) {
+ pr_err("zoned: Not a SCSI device\n");
+ return NULL;
+ }
+
+ sdkp = dev_get_drvdata(&sdp->sdev_gendev);
+ if (WARN_ON(sdkp->disk->queue != q))
+ return NULL;
+
+ return sdkp;
+}
+
+/*
+ * Initialize elevator private data (zoned_data).
+ */
+static int zd_init_queue(struct request_queue *q, struct elevator_type *e)
+{
+ struct scsi_disk *sdkp;
+ struct zoned_data *zd;
+ struct elevator_queue *eq;
+ int ret;
+
+ sdkp = __zoned_scsi_disk(q);
+ if (!sdkp)
+ return -ENODEV;
+
+ eq = elevator_alloc(q, e);
+ if (!eq)
+ return -ENOMEM;
+
+ zd = kzalloc_node(sizeof(*zd), GFP_KERNEL, q->node);
+ if (!zd) {
+ kobject_put(&eq->kobj);
+ return -ENOMEM;
+ }
+
+ INIT_LIST_HEAD(&zd->fifo_list[READ]);
+ INIT_LIST_HEAD(&zd->fifo_list[WRITE]);
+ zd->sort_list[READ] = RB_ROOT;
+ zd->sort_list[WRITE] = RB_ROOT;
+ zd->fifo_expire[READ] = read_expire;
+ zd->fifo_expire[WRITE] = write_expire;
+ zd->writes_starved = writes_starved;
+ zd->front_merges = 1;
+ zd->fifo_batch = fifo_batch;
+ spin_lock_init(&zd->lock);
+ INIT_LIST_HEAD(&zd->dispatch);
+
+ zd->sdkp = sdkp;
+ spin_lock_init(&zd->zones_lock);
+
+ zd->zones_wlock = sdkp->zones_wlock;
+ zd->seq_zones = sdkp->seq_zones;
+ if (!zd->zones_wlock || !zd->seq_zones) {
+ ret = -ENOMEM;
+ goto err;
+ }
+
+ eq->elevator_data = zd;
+ q->elevator = eq;
+
+ return 0;
+
+err:
+ kfree(zd);
+ kobject_put(&eq->kobj);
+
+ return ret;
+}
+
+static void zd_exit_queue(struct elevator_queue *e)
+{
+ struct zoned_data *zd = e->elevator_data;
+
+ WARN_ON(!list_empty(&zd->fifo_list[READ]));
+ WARN_ON(!list_empty(&zd->fifo_list[WRITE]));
+
+ kfree(zd);
+}
+
+/*
+ * sysfs parts below
+ */
+static ssize_t
+zoned_var_show(int var, char *page)
+{
+ return sprintf(page, "%d\n", var);
+}
+
+static ssize_t
+zoned_var_store(int *var, const char *page, size_t count)
+{
+ char *p = (char *) page;
+ int ret;
+
+ ret = kstrtoint(p, 10, var);
+ if (ret)
+ return ret;
+
+ return count;
+}
+
+#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
+static ssize_t __FUNC(struct elevator_queue *e, char *page) \
+{ \
+ struct zoned_data *zd = e->elevator_data; \
+ int __data = __VAR; \
+ if (__CONV) \
+ __data = jiffies_to_msecs(__data); \
+ return zoned_var_show(__data, (page)); \
+}
+SHOW_FUNCTION(zoned_read_expire_show, zd->fifo_expire[READ], 1);
+SHOW_FUNCTION(zoned_write_expire_show, zd->fifo_expire[WRITE], 1);
+SHOW_FUNCTION(zoned_writes_starved_show, zd->writes_starved, 0);
+SHOW_FUNCTION(zoned_front_merges_show, zd->front_merges, 0);
+SHOW_FUNCTION(zoned_fifo_batch_show, zd->fifo_batch, 0);
+#undef SHOW_FUNCTION
+
+#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
+static ssize_t __FUNC(struct elevator_queue *e, \
+ const char *page, size_t count) \
+{ \
+ struct zoned_data *zd = e->elevator_data; \
+ int __data; \
+ int ret = zoned_var_store(&__data, (page), count); \
+ if (__data < (MIN)) \
+ __data = (MIN); \
+ else if (__data > (MAX)) \
+ __data = (MAX); \
+ if (__CONV) \
+ *(__PTR) = msecs_to_jiffies(__data); \
+ else \
+ *(__PTR) = __data; \
+ return ret; \
+}
+STORE_FUNCTION(zoned_read_expire_store, &zd->fifo_expire[READ],
+ 0, INT_MAX, 1);
+STORE_FUNCTION(zoned_write_expire_store, &zd->fifo_expire[WRITE],
+ 0, INT_MAX, 1);
+STORE_FUNCTION(zoned_writes_starved_store, &zd->writes_starved,
+ INT_MIN, INT_MAX, 0);
+STORE_FUNCTION(zoned_front_merges_store, &zd->front_merges,
+ 0, 1, 0);
+STORE_FUNCTION(zoned_fifo_batch_store, &zd->fifo_batch,
+ 0, INT_MAX, 0);
+#undef STORE_FUNCTION
+
+#define DD_ATTR(name) \
+ __ATTR(name, S_IRUGO|S_IWUSR, zoned_##name##_show, \
+ zoned_##name##_store)
+
+static struct elv_fs_entry zoned_attrs[] = {
+ DD_ATTR(read_expire),
+ DD_ATTR(write_expire),
+ DD_ATTR(writes_starved),
+ DD_ATTR(front_merges),
+ DD_ATTR(fifo_batch),
+ __ATTR_NULL
+};
+
+#ifdef CONFIG_BLK_DEBUG_FS
+#define ZONED_DEBUGFS_DDIR_ATTRS(ddir, name) \
+static void *zoned_##name##_fifo_start(struct seq_file *m, \
+ loff_t *pos) \
+ __acquires(&zd->lock) \
+{ \
+ struct request_queue *q = m->private; \
+ struct zoned_data *zd = q->elevator->elevator_data; \
+ \
+ spin_lock(&zd->lock); \
+ return seq_list_start(&zd->fifo_list[ddir], *pos); \
+} \
+ \
+static void *zoned_##name##_fifo_next(struct seq_file *m, void *v, \
+ loff_t *pos) \
+{ \
+ struct request_queue *q = m->private; \
+ struct zoned_data *zd = q->elevator->elevator_data; \
+ \
+ return seq_list_next(v, &zd->fifo_list[ddir], pos); \
+} \
+ \
+static void zoned_##name##_fifo_stop(struct seq_file *m, void *v) \
+ __releases(&zd->lock) \
+{ \
+ struct request_queue *q = m->private; \
+ struct zoned_data *zd = q->elevator->elevator_data; \
+ \
+ spin_unlock(&zd->lock); \
+} \
+ \
+static const struct seq_operations zoned_##name##_fifo_seq_ops = { \
+ .start = zoned_##name##_fifo_start, \
+ .next = zoned_##name##_fifo_next, \
+ .stop = zoned_##name##_fifo_stop, \
+ .show = blk_mq_debugfs_rq_show, \
+}; \
+ \
+static int zoned_##name##_next_rq_show(void *data, \
+ struct seq_file *m) \
+{ \
+ struct request_queue *q = data; \
+ struct zoned_data *zd = q->elevator->elevator_data; \
+ struct request *rq = zd->next_rq[ddir]; \
+ \
+ if (rq) \
+ __blk_mq_debugfs_rq_show(m, rq); \
+ return 0; \
+}
+ZONED_DEBUGFS_DDIR_ATTRS(READ, read)
+ZONED_DEBUGFS_DDIR_ATTRS(WRITE, write)
+#undef ZONED_DEBUGFS_DDIR_ATTRS
+
+static int zoned_batching_show(void *data, struct seq_file *m)
+{
+ struct request_queue *q = data;
+ struct zoned_data *zd = q->elevator->elevator_data;
+
+ seq_printf(m, "%u\n", zd->batching);
+ return 0;
+}
+
+static int zoned_starved_show(void *data, struct seq_file *m)
+{
+ struct request_queue *q = data;
+ struct zoned_data *zd = q->elevator->elevator_data;
+
+ seq_printf(m, "%u\n", zd->starved);
+ return 0;
+}
+
+static void *zoned_dispatch_start(struct seq_file *m, loff_t *pos)
+ __acquires(&zd->lock)
+{
+ struct request_queue *q = m->private;
+ struct zoned_data *zd = q->elevator->elevator_data;
+
+ spin_lock(&zd->lock);
+ return seq_list_start(&zd->dispatch, *pos);
+}
+
+static void *zoned_dispatch_next(struct seq_file *m, void *v, loff_t *pos)
+{
+ struct request_queue *q = m->private;
+ struct zoned_data *zd = q->elevator->elevator_data;
+
+ return seq_list_next(v, &zd->dispatch, pos);
+}
+
+static void zoned_dispatch_stop(struct seq_file *m, void *v)
+ __releases(&zd->lock)
+{
+ struct request_queue *q = m->private;
+ struct zoned_data *zd = q->elevator->elevator_data;
+
+ spin_unlock(&zd->lock);
+}
+
+static const struct seq_operations zoned_dispatch_seq_ops = {
+ .start = zoned_dispatch_start,
+ .next = zoned_dispatch_next,
+ .stop = zoned_dispatch_stop,
+ .show = blk_mq_debugfs_rq_show,
+};
+
+#define ZONED_QUEUE_DDIR_ATTRS(name) \
+ {#name "_fifo_list", 0400, .seq_ops = &zoned_##name##_fifo_seq_ops}, \
+ {#name "_next_rq", 0400, zoned_##name##_next_rq_show}
+static const struct blk_mq_debugfs_attr zoned_queue_debugfs_attrs[] = {
+ ZONED_QUEUE_DDIR_ATTRS(read),
+ ZONED_QUEUE_DDIR_ATTRS(write),
+ {"batching", 0400, zoned_batching_show},
+ {"starved", 0400, zoned_starved_show},
+ {"dispatch", 0400, .seq_ops = &zoned_dispatch_seq_ops},
+ {},
+};
+#undef ZONED_QUEUE_DDIR_ATTRS
+#endif
+
+static struct elevator_type zoned_elv = {
+ .ops.mq = {
+ .insert_requests = zd_insert_requests,
+ .dispatch_request = zd_dispatch_request,
+ .completed_request = zd_completed_request,
+ .next_request = elv_rb_latter_request,
+ .former_request = elv_rb_former_request,
+ .bio_merge = zd_bio_merge,
+ .request_merge = zd_request_merge,
+ .requests_merged = zd_merged_requests,
+ .request_merged = zd_request_merged,
+ .has_work = zd_has_work,
+ .init_sched = zd_init_queue,
+ .exit_sched = zd_exit_queue,
+ },
+
+ .uses_mq = true,
+#ifdef CONFIG_BLK_DEBUG_FS
+ .queue_debugfs_attrs = zoned_queue_debugfs_attrs,
+#endif
+ .elevator_attrs = zoned_attrs,
+ .elevator_name = "zoned",
+ .elevator_owner = THIS_MODULE,
+};
+
+static int __init zoned_init(void)
+{
+ return elv_register(&zoned_elv);
+}
+
+static void __exit zoned_exit(void)
+{
+ elv_unregister(&zoned_elv);
+}
+
+module_init(zoned_init);
+module_exit(zoned_exit);
+
+MODULE_AUTHOR("Damien Le Moal");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Zoned MQ deadline IO scheduler");
The zoned I/O scheduler is mostly identical to mq-deadline and retains the same configuration attributes. The main difference is that the zoned scheduler will ensure that at any time at most only one write request (command) per sequential zone is in flight (has been issued to the disk) in order to protect against sequential write reordering potentially resulting from the concurrent execution of request dispatch by multiple contexts. This is achieved similarly to the legacy SCSI I/O path by write locking zones when a write requests is issued. Subsequent writes to the same zone have to wait for the completion of the previously issued write before being in turn dispatched to the disk. This ensures that sequential writes are processed in the correct order without needing any modification to the execution model of blk-mq. In addition, this also protects against write reordering at the HBA level (e.g. AHCI). This zoned scheduler code is added under the drivers/scsi directory so that information managed using the scsi_disk structure can be directly referenced. Doing so, cluttering the block layer with device type specific code is avoided. Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com> --- Documentation/block/zoned-iosched.txt | 48 ++ block/Kconfig.iosched | 12 + drivers/scsi/Makefile | 1 + drivers/scsi/sd.h | 3 +- drivers/scsi/sd_zbc.c | 16 +- drivers/scsi/sd_zbc.h | 11 +- drivers/scsi/sd_zbc_iosched.c | 934 ++++++++++++++++++++++++++++++++++ 7 files changed, 1009 insertions(+), 16 deletions(-) create mode 100644 Documentation/block/zoned-iosched.txt create mode 100644 drivers/scsi/sd_zbc_iosched.c