scsi: sd_zbc: emulate ZONE_APPEND commands

Emulate ZONE_APPEND for SCSI disks using a regular WRITE(16) command
with a start LBA set to the target zone write pointer position.

In order to always know the write pointer position of a sequential write
zone, the write pointer of all zones is tracked using an array of 32bits
zone write pointer offset attached to the scsi disk structure. Each
entry of the array indicate a zone write pointer position relative to
the zone start sector. The write pointer offsets are maintained in sync
with the device as follows:
1) the write pointer offset of a zone is reset to 0 when a
   REQ_OP_ZONE_RESET command completes.
2) the write pointer offset of a zone is set to the zone size when a
   REQ_OP_ZONE_FINISH command completes.
3) the write pointer offset of a zone is incremented by the number of
   512B sectors written when a write, write same or a zone append
   command completes.
4) the write pointer offset of all zones is reset to 0 when a
   REQ_OP_ZONE_RESET_ALL command completes.

Since the block layer does not write lock zones for zone append
commands, to ensure a sequential ordering of the regular write commands
used for the emulation, the target zone of a zone append command is
locked when the function sd_zbc_prepare_zone_append() is called from
sd_setup_read_write_cmnd(). If the zone write lock cannot be obtained
(e.g. a zone append is in-flight or a regular write has already locked
the zone), the zone append command dispatching is delayed by returning
BLK_STS_ZONE_RESOURCE.

To avoid the need for write locking all zones for REQ_OP_ZONE_RESET_ALL
requests, use a spinlock to protect accesses and modifications of the
zone write pointer offsets. This spinlock is initialized from sd_probe()
using the new function sd_zbc_init().

Co-developed-by: Damien Le Moal <Damien.LeMoal@wdc.com>
Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 339 insertions, 24 deletions

diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
index ee156fbf3780..bb87fbba2a09 100644
--- a/drivers/scsi/sd_zbc.c
+++ b/drivers/scsi/sd_zbc.c
@@ -11,6 +11,7 @@
 #include <linux/blkdev.h>
 #include <linux/vmalloc.h>
 #include <linux/sched/mm.h>
+#include <linux/mutex.h>
 
 #include <asm/unaligned.h>
 
@@ -19,11 +20,36 @@
 
 #include "sd.h"
 
+static unsigned int sd_zbc_get_zone_wp_offset(struct blk_zone *zone)
+{
+	if (zone->type == ZBC_ZONE_TYPE_CONV)
+		return 0;
+
+	switch (zone->cond) {
+	case BLK_ZONE_COND_IMP_OPEN:
+	case BLK_ZONE_COND_EXP_OPEN:
+	case BLK_ZONE_COND_CLOSED:
+		return zone->wp - zone->start;
+	case BLK_ZONE_COND_FULL:
+		return zone->len;
+	case BLK_ZONE_COND_EMPTY:
+	case BLK_ZONE_COND_OFFLINE:
+	case BLK_ZONE_COND_READONLY:
+	default:
+		/*
+		 * Offline and read-only zones do not have a valid
+		 * write pointer. Use 0 as for an empty zone.
+		 */
+		return 0;
+	}
+}
+
 static int sd_zbc_parse_report(struct scsi_disk *sdkp, u8 *buf,
 			       unsigned int idx, report_zones_cb cb, void *data)
 {
 	struct scsi_device *sdp = sdkp->device;
 	struct blk_zone zone = { 0 };
+	int ret;
 
 	zone.type = buf[0] & 0x0f;
 	zone.cond = (buf[1] >> 4) & 0xf;
@@ -39,7 +65,14 @@ static int sd_zbc_parse_report(struct scsi_disk *sdkp, u8 *buf,
 	    zone.cond == ZBC_ZONE_COND_FULL)
 		zone.wp = zone.start + zone.len;
 
-	return cb(&zone, idx, data);
+	ret = cb(&zone, idx, data);
+	if (ret)
+		return ret;
+
+	if (sdkp->rev_wp_offset)
+		sdkp->rev_wp_offset[idx] = sd_zbc_get_zone_wp_offset(&zone);
+
+	return 0;
 }
 
 /**
@@ -229,6 +262,116 @@ static blk_status_t sd_zbc_cmnd_checks(struct scsi_cmnd *cmd)
 	return BLK_STS_OK;
 }
 
+#define SD_ZBC_INVALID_WP_OFST	(~0u)
+#define SD_ZBC_UPDATING_WP_OFST	(SD_ZBC_INVALID_WP_OFST - 1)
+
+static int sd_zbc_update_wp_offset_cb(struct blk_zone *zone, unsigned int idx,
+				    void *data)
+{
+	struct scsi_disk *sdkp = data;
+
+	lockdep_assert_held(&sdkp->zones_wp_offset_lock);
+
+	sdkp->zones_wp_offset[idx] = sd_zbc_get_zone_wp_offset(zone);
+
+	return 0;
+}
+
+static void sd_zbc_update_wp_offset_workfn(struct work_struct *work)
+{
+	struct scsi_disk *sdkp;
+	unsigned int zno;
+	int ret;
+
+	sdkp = container_of(work, struct scsi_disk, zone_wp_offset_work);
+
+	spin_lock_bh(&sdkp->zones_wp_offset_lock);
+	for (zno = 0; zno < sdkp->nr_zones; zno++) {
+		if (sdkp->zones_wp_offset[zno] != SD_ZBC_UPDATING_WP_OFST)
+			continue;
+
+		spin_unlock_bh(&sdkp->zones_wp_offset_lock);
+		ret = sd_zbc_do_report_zones(sdkp, sdkp->zone_wp_update_buf,
+					     SD_BUF_SIZE,
+					     zno * sdkp->zone_blocks, true);
+		spin_lock_bh(&sdkp->zones_wp_offset_lock);
+		if (!ret)
+			sd_zbc_parse_report(sdkp, sdkp->zone_wp_update_buf + 64,
+					    zno, sd_zbc_update_wp_offset_cb,
+					    sdkp);
+	}
+	spin_unlock_bh(&sdkp->zones_wp_offset_lock);
+
+	scsi_device_put(sdkp->device);
+}
+
+/**
+ * sd_zbc_prepare_zone_append() - Prepare an emulated ZONE_APPEND command.
+ * @cmd: the command to setup
+ * @lba: the LBA to patch
+ * @nr_blocks: the number of LBAs to be written
+ *
+ * Called from sd_setup_read_write_cmnd() for REQ_OP_ZONE_APPEND.
+ * @sd_zbc_prepare_zone_append() handles the necessary zone wrote locking and
+ * patching of the lba for an emulated ZONE_APPEND command.
+ *
+ * In case the cached write pointer offset is %SD_ZBC_INVALID_WP_OFST it will
+ * schedule a REPORT ZONES command and return BLK_STS_IOERR.
+ */
+blk_status_t sd_zbc_prepare_zone_append(struct scsi_cmnd *cmd, sector_t *lba,
+					unsigned int nr_blocks)
+{
+	struct request *rq = cmd->request;
+	struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);
+	unsigned int wp_offset, zno = blk_rq_zone_no(rq);
+	blk_status_t ret;
+
+	ret = sd_zbc_cmnd_checks(cmd);
+	if (ret != BLK_STS_OK)
+		return ret;
+
+	if (!blk_rq_zone_is_seq(rq))
+		return BLK_STS_IOERR;
+
+	/* Unlock of the write lock will happen in sd_zbc_complete() */
+	if (!blk_req_zone_write_trylock(rq))
+		return BLK_STS_ZONE_RESOURCE;
+
+	spin_lock_bh(&sdkp->zones_wp_offset_lock);
+	wp_offset = sdkp->zones_wp_offset[zno];
+	switch (wp_offset) {
+	case SD_ZBC_INVALID_WP_OFST:
+		/*
+		 * We are about to schedule work to update a zone write pointer
+		 * offset, which will cause the zone append command to be
+		 * requeued. So make sure that the scsi device does not go away
+		 * while the work is being processed.
+		 */
+		if (scsi_device_get(sdkp->device)) {
+			ret = BLK_STS_IOERR;
+			break;
+		}
+		sdkp->zones_wp_offset[zno] = SD_ZBC_UPDATING_WP_OFST;
+		schedule_work(&sdkp->zone_wp_offset_work);
+		fallthrough;
+	case SD_ZBC_UPDATING_WP_OFST:
+		ret = BLK_STS_DEV_RESOURCE;
+		break;
+	default:
+		wp_offset = sectors_to_logical(sdkp->device, wp_offset);
+		if (wp_offset + nr_blocks > sdkp->zone_blocks) {
+			ret = BLK_STS_IOERR;
+			break;
+		}
+
+		*lba += wp_offset;
+	}
+	spin_unlock_bh(&sdkp->zones_wp_offset_lock);
+	if (ret)
+		blk_req_zone_write_unlock(rq);
+	return ret;
+}
+
 /**
  * sd_zbc_setup_zone_mgmt_cmnd - Prepare a zone ZBC_OUT command. The operations
  *			can be RESET WRITE POINTER, OPEN, CLOSE or FINISH.
@@ -269,16 +412,105 @@ blk_status_t sd_zbc_setup_zone_mgmt_cmnd(struct scsi_cmnd *cmd,
 	return BLK_STS_OK;
 }
 
+static bool sd_zbc_need_zone_wp_update(struct request *rq)
+{
+	switch (req_op(rq)) {
+	case REQ_OP_ZONE_APPEND:
+	case REQ_OP_ZONE_FINISH:
+	case REQ_OP_ZONE_RESET:
+	case REQ_OP_ZONE_RESET_ALL:
+		return true;
+	case REQ_OP_WRITE:
+	case REQ_OP_WRITE_ZEROES:
+	case REQ_OP_WRITE_SAME:
+		return blk_rq_zone_is_seq(rq);
+	default:
+		return false;
+	}
+}
+
+/**
+ * sd_zbc_zone_wp_update - Update cached zone write pointer upon cmd completion
+ * @cmd: Completed command
+ * @good_bytes: Command reply bytes
+ *
+ * Called from sd_zbc_complete() to handle the update of the cached zone write
+ * pointer value in case an update is needed.
+ */
+static unsigned int sd_zbc_zone_wp_update(struct scsi_cmnd *cmd,
+					  unsigned int good_bytes)
+{
+	int result = cmd->result;
+	struct request *rq = cmd->request;
+	struct scsi_disk *sdkp = scsi_disk(rq->rq_disk);
+	unsigned int zno = blk_rq_zone_no(rq);
+	enum req_opf op = req_op(rq);
+
+	/*
+	 * If we got an error for a command that needs updating the write
+	 * pointer offset cache, we must mark the zone wp offset entry as
+	 * invalid to force an update from disk the next time a zone append
+	 * command is issued.
+	 */
+	spin_lock_bh(&sdkp->zones_wp_offset_lock);
+
+	if (result && op != REQ_OP_ZONE_RESET_ALL) {
+		if (op == REQ_OP_ZONE_APPEND) {
+			/* Force complete completion (no retry) */
+			good_bytes = 0;
+			scsi_set_resid(cmd, blk_rq_bytes(rq));
+		}
+
+		/*
+		 * Force an update of the zone write pointer offset on
+		 * the next zone append access.
+		 */
+		if (sdkp->zones_wp_offset[zno] != SD_ZBC_UPDATING_WP_OFST)
+			sdkp->zones_wp_offset[zno] = SD_ZBC_INVALID_WP_OFST;
+		goto unlock_wp_offset;
+	}
+
+	switch (op) {
+	case REQ_OP_ZONE_APPEND:
+		rq->__sector += sdkp->zones_wp_offset[zno];
+		fallthrough;
+	case REQ_OP_WRITE_ZEROES:
+	case REQ_OP_WRITE_SAME:
+	case REQ_OP_WRITE:
+		if (sdkp->zones_wp_offset[zno] < sd_zbc_zone_sectors(sdkp))
+			sdkp->zones_wp_offset[zno] +=
+						good_bytes >> SECTOR_SHIFT;
+		break;
+	case REQ_OP_ZONE_RESET:
+		sdkp->zones_wp_offset[zno] = 0;
+		break;
+	case REQ_OP_ZONE_FINISH:
+		sdkp->zones_wp_offset[zno] = sd_zbc_zone_sectors(sdkp);
+		break;
+	case REQ_OP_ZONE_RESET_ALL:
+		memset(sdkp->zones_wp_offset, 0,
+		       sdkp->nr_zones * sizeof(unsigned int));
+		break;
+	default:
+		break;
+	}
+
+unlock_wp_offset:
+	spin_unlock_bh(&sdkp->zones_wp_offset_lock);
+
+	return good_bytes;
+}
+
 /**
  * sd_zbc_complete - ZBC command post processing.
  * @cmd: Completed command
  * @good_bytes: Command reply bytes
  * @sshdr: command sense header
  *
- * Called from sd_done(). Process report zones reply and handle reset zone
- * and write commands errors.
+ * Called from sd_done() to handle zone commands errors and updates to the
+ * device queue zone write pointer offset cahce.
  */
-void sd_zbc_complete(struct scsi_cmnd *cmd, unsigned int good_bytes,
+unsigned int sd_zbc_complete(struct scsi_cmnd *cmd, unsigned int good_bytes,
 		     struct scsi_sense_hdr *sshdr)
 {
 	int result = cmd->result;
@@ -294,7 +526,13 @@ void sd_zbc_complete(struct scsi_cmnd *cmd, unsigned int good_bytes,
 		 * so be quiet about the error.
 		 */
 		rq->rq_flags |= RQF_QUIET;
-	}
+	} else if (sd_zbc_need_zone_wp_update(rq))
+		good_bytes = sd_zbc_zone_wp_update(cmd, good_bytes);
+
+	if (req_op(rq) == REQ_OP_ZONE_APPEND)
+		blk_req_zone_write_unlock(rq);
+
+	return good_bytes;
 }
 
 /**
@@ -396,11 +634,67 @@ static int sd_zbc_check_capacity(struct scsi_disk *sdkp, unsigned char *buf,
 	return 0;
 }
 
+static void sd_zbc_revalidate_zones_cb(struct gendisk *disk)
+{
+	struct scsi_disk *sdkp = scsi_disk(disk);
+
+	swap(sdkp->zones_wp_offset, sdkp->rev_wp_offset);
+}
+
+static int sd_zbc_revalidate_zones(struct scsi_disk *sdkp,
+				   u32 zone_blocks,
+				   unsigned int nr_zones)
+{
+	struct gendisk *disk = sdkp->disk;
+	int ret = 0;
+
+	/*
+	 * Make sure revalidate zones are serialized to ensure exclusive
+	 * updates of the scsi disk data.
+	 */
+	mutex_lock(&sdkp->rev_mutex);
+
+	/*
+	 * Revalidate the disk zones to update the device request queue zone
+	 * bitmaps and the zone write pointer offset array. Do this only once
+	 * the device capacity is set on the second revalidate execution for
+	 * disk scan or if something changed when executing a normal revalidate.
+	 */
+	if (sdkp->first_scan) {
+		sdkp->zone_blocks = zone_blocks;
+		sdkp->nr_zones = nr_zones;
+		goto unlock;
+	}
+
+	if (sdkp->zone_blocks == zone_blocks &&
+	    sdkp->nr_zones == nr_zones &&
+	    disk->queue->nr_zones == nr_zones)
+		goto unlock;
+
+	sdkp->rev_wp_offset = kvcalloc(nr_zones, sizeof(u32), GFP_NOIO);
+	if (!sdkp->rev_wp_offset) {
+		ret = -ENOMEM;
+		goto unlock;
+	}
+
+	ret = blk_revalidate_disk_zones(disk, sd_zbc_revalidate_zones_cb);
+
+	kvfree(sdkp->rev_wp_offset);
+	sdkp->rev_wp_offset = NULL;
+
+unlock:
+	mutex_unlock(&sdkp->rev_mutex);
+
+	return ret;
+}
+
 int sd_zbc_read_zones(struct scsi_disk *sdkp, unsigned char *buf)
 {
 	struct gendisk *disk = sdkp->disk;
+	struct request_queue *q = disk->queue;
 	unsigned int nr_zones;
 	u32 zone_blocks = 0;
+	u32 max_append;
 	int ret;
 
 	if (!sd_is_zoned(sdkp))
@@ -421,35 +715,31 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, unsigned char *buf)
 		goto err;
 
 	/* The drive satisfies the kernel restrictions: set it up */
-	blk_queue_flag_set(QUEUE_FLAG_ZONE_RESETALL, sdkp->disk->queue);
-	blk_queue_required_elevator_features(sdkp->disk->queue,
-					     ELEVATOR_F_ZBD_SEQ_WRITE);
+	blk_queue_flag_set(QUEUE_FLAG_ZONE_RESETALL, q);
+	blk_queue_required_elevator_features(q, ELEVATOR_F_ZBD_SEQ_WRITE);
 	nr_zones = round_up(sdkp->capacity, zone_blocks) >> ilog2(zone_blocks);
 
 	/* READ16/WRITE16 is mandatory for ZBC disks */
 	sdkp->device->use_16_for_rw = 1;
 	sdkp->device->use_10_for_rw = 0;
 
+	ret = sd_zbc_revalidate_zones(sdkp, zone_blocks, nr_zones);
+	if (ret)
+		goto err;
+
 	/*
-	 * Revalidate the disk zone bitmaps once the block device capacity is
-	 * set on the second revalidate execution during disk scan and if
-	 * something changed when executing a normal revalidate.
+	 * On the first scan 'chunk_sectors' isn't setup yet, so calling
+	 * blk_queue_max_zone_append_sectors() will result in a WARN(). Defer
+	 * this setting to the second scan.
 	 */
-	if (sdkp->first_scan) {
-		sdkp->zone_blocks = zone_blocks;
-		sdkp->nr_zones = nr_zones;
+	if (sdkp->first_scan)
 		return 0;
-	}
 
-	if (sdkp->zone_blocks != zone_blocks ||
-	    sdkp->nr_zones != nr_zones ||
-	    disk->queue->nr_zones != nr_zones) {
-		ret = blk_revalidate_disk_zones(disk);
-		if (ret != 0)
-			goto err;
-		sdkp->zone_blocks = zone_blocks;
-		sdkp->nr_zones = nr_zones;
-	}
+	max_append = min_t(u32, logical_to_sectors(sdkp->device, zone_blocks),
+			   q->limits.max_segments << (PAGE_SHIFT - 9));
+	max_append = min_t(u32, max_append, queue_max_hw_sectors(q));
+
+	blk_queue_max_zone_append_sectors(q, max_append);
 
 	return 0;
 
@@ -475,3 +765,28 @@ void sd_zbc_print_zones(struct scsi_disk *sdkp)
 			  sdkp->nr_zones,
 			  sdkp->zone_blocks);
 }
+
+int sd_zbc_init_disk(struct scsi_disk *sdkp)
+{
+	if (!sd_is_zoned(sdkp))
+		return 0;
+
+	sdkp->zones_wp_offset = NULL;
+	spin_lock_init(&sdkp->zones_wp_offset_lock);
+	sdkp->rev_wp_offset = NULL;
+	mutex_init(&sdkp->rev_mutex);
+	INIT_WORK(&sdkp->zone_wp_offset_work, sd_zbc_update_wp_offset_workfn);
+	sdkp->zone_wp_update_buf = kzalloc(SD_BUF_SIZE, GFP_KERNEL);
+	if (!sdkp->zone_wp_update_buf)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void sd_zbc_release_disk(struct scsi_disk *sdkp)
+{
+	kvfree(sdkp->zones_wp_offset);
+	sdkp->zones_wp_offset = NULL;
+	kfree(sdkp->zone_wp_update_buf);
+	sdkp->zone_wp_update_buf = NULL;
+}