[RFC PATCH 02/17] btrfs: Get zone information of zoned block devices

[Naohiro Aota]

If a zoned block device is found, get its zone information (number of zones
and zone size) using the new helper function btrfs_get_dev_zone().  To
avoid costly run-time zone reports commands to test the device zones type
during block allocation, attach the seqzones bitmap to the device structure
to indicate if a zone is sequential or accept random writes.

This patch also introduces the helper function btrfs_dev_is_sequential() to
test if the zone storing a block is a sequential write required zone.

Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
Signed-off-by: Naohiro Aota <naota@xxxxxxxxx>
---
 fs/btrfs/volumes.c | 146 +++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/volumes.h |  32 ++++++++++
 2 files changed, 178 insertions(+)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index da86706123ff..35b3a2187653 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -677,6 +677,134 @@ static void btrfs_free_stale_devices(const char *path,
 	}
 }
 
+static int __btrfs_get_dev_zones(struct btrfs_device *device, u64 pos,
+				 struct blk_zone **zones,
+				 unsigned int *nr_zones, gfp_t gfp_mask)
+{
+	struct blk_zone *z = *zones;
+	int ret;
+
+	if (!z) {
+		z = kcalloc(*nr_zones, sizeof(struct blk_zone), GFP_KERNEL);
+		if (!z)
+			return -ENOMEM;
+	}
+
+	ret = blkdev_report_zones(device->bdev, pos >> 9,
+				  z, nr_zones, gfp_mask);
+	if (ret != 0) {
+		pr_err("BTRFS: Get zone at %llu failed %d\n",
+		       pos, ret);
+		return ret;
+	}
+
+	*zones = z;
+
+	return 0;
+}
+
+static void btrfs_drop_dev_zonetypes(struct btrfs_device *device)
+{
+	kfree(device->seq_zones);
+	kfree(device->empty_zones);
+	device->seq_zones = NULL;
+	device->empty_zones = NULL;
+	device->nr_zones = 0;
+	device->zone_size = 0;
+	device->zone_size_shift = 0;
+}
+
+int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
+		       struct blk_zone *zone, gfp_t gfp_mask)
+{
+	unsigned int nr_zones = 1;
+	int ret;
+
+	ret = __btrfs_get_dev_zones(device, pos, &zone, &nr_zones, gfp_mask);
+	if (ret != 0 || !nr_zones)
+		return ret ? ret : -EIO;
+
+	return 0;
+}
+
+static int btrfs_get_dev_zonetypes(struct btrfs_device *device)
+{
+	struct block_device *bdev = device->bdev;
+	sector_t nr_sectors = bdev->bd_part->nr_sects;
+	sector_t sector = 0;
+	struct blk_zone *zones = NULL;
+	unsigned int i, n = 0, nr_zones;
+	int ret;
+
+	device->zone_size = 0;
+	device->zone_size_shift = 0;
+	device->nr_zones = 0;
+	device->seq_zones = NULL;
+	device->empty_zones = NULL;
+
+	if (!bdev_is_zoned(bdev))
+		return 0;
+
+	device->zone_size = (u64)bdev_zone_sectors(bdev) << 9;
+	device->zone_size_shift = ilog2(device->zone_size);
+	device->nr_zones = nr_sectors >> ilog2(bdev_zone_sectors(bdev));
+	if (nr_sectors & (bdev_zone_sectors(bdev) - 1))
+		device->nr_zones++;
+
+	device->seq_zones = kcalloc(BITS_TO_LONGS(device->nr_zones),
+				    sizeof(*device->seq_zones), GFP_KERNEL);
+	if (!device->seq_zones)
+		return -ENOMEM;
+
+	device->empty_zones = kcalloc(BITS_TO_LONGS(device->nr_zones),
+				      sizeof(*device->empty_zones), GFP_KERNEL);
+	if (!device->empty_zones)
+		return -ENOMEM;
+
+#define BTRFS_REPORT_NR_ZONES   4096
+
+	/* Get zones type */
+	while (sector < nr_sectors) {
+		nr_zones = BTRFS_REPORT_NR_ZONES;
+		ret = __btrfs_get_dev_zones(device, sector << 9,
+					    &zones, &nr_zones, GFP_KERNEL);
+		if (ret != 0 || !nr_zones) {
+			if (!ret)
+				ret = -EIO;
+			goto out;
+		}
+
+		for (i = 0; i < nr_zones; i++) {
+			if (zones[i].type == BLK_ZONE_TYPE_SEQWRITE_REQ)
+				set_bit(n, device->seq_zones);
+			if (zones[i].cond == BLK_ZONE_COND_EMPTY)
+				set_bit(n, device->empty_zones);
+			sector = zones[i].start + zones[i].len;
+			n++;
+		}
+	}
+
+	if (n != device->nr_zones) {
+		pr_err("BTRFS: Inconsistent number of zones (%u / %u)\n",
+		       n, device->nr_zones);
+		ret = -EIO;
+		goto out;
+	}
+
+	pr_info("BTRFS: host-%s zoned block device, %u zones of %llu sectors\n",
+		bdev_zoned_model(bdev) == BLK_ZONED_HM ? "managed" : "aware",
+		device->nr_zones, device->zone_size >> 9);
+
+out:
+	kfree(zones);
+
+	if (ret)
+		btrfs_drop_dev_zonetypes(device);
+
+	return ret;
+}
+
+
 static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
 			struct btrfs_device *device, fmode_t flags,
 			void *holder)
@@ -726,6 +854,13 @@ static int btrfs_open_one_device(struct btrfs_fs_devices *fs_devices,
 	clear_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
 	device->mode = flags;
 
+	/* Get zone type information of zoned block devices */
+	if (bdev_is_zoned(bdev)) {
+		ret = btrfs_get_dev_zonetypes(device);
+		if (ret != 0)
+			goto error_brelse;
+	}
+
 	fs_devices->open_devices++;
 	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
 	    device->devid != BTRFS_DEV_REPLACE_DEVID) {
@@ -1012,6 +1147,7 @@ static void btrfs_close_bdev(struct btrfs_device *device)
 	}
 
 	blkdev_put(device->bdev, device->mode);
+	btrfs_drop_dev_zonetypes(device);
 }
 
 static void btrfs_close_one_device(struct btrfs_device *device)
@@ -2439,6 +2575,15 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	mutex_unlock(&fs_info->chunk_mutex);
 	mutex_unlock(&fs_devices->device_list_mutex);
 
+	/* Get zone type information of zoned block devices */
+	if (bdev_is_zoned(bdev)) {
+		ret = btrfs_get_dev_zonetypes(device);
+		if (ret) {
+			btrfs_abort_transaction(trans, ret);
+			goto error_sysfs;
+		}
+	}
+
 	if (seeding_dev) {
 		mutex_lock(&fs_info->chunk_mutex);
 		ret = init_first_rw_device(trans, fs_info);
@@ -2504,6 +2649,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	return ret;
 
 error_sysfs:
+	btrfs_drop_dev_zonetypes(device);
 	btrfs_sysfs_rm_device_link(fs_devices, device);
 	mutex_lock(&fs_info->fs_devices->device_list_mutex);
 	mutex_lock(&fs_info->chunk_mutex);
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 23e9285d88de..13d59bff204f 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -61,6 +61,16 @@ struct btrfs_device {
 
 	struct block_device *bdev;
 
+	/*
+	 * Number of zones, zone size and types of zones if bdev is a
+	 * zoned block device.
+	 */
+	u64 zone_size;
+	u8  zone_size_shift;
+	u32 nr_zones;
+	unsigned long *seq_zones;
+	unsigned long *empty_zones;
+
 	/* the mode sent to blkdev_get */
 	fmode_t mode;
 
@@ -404,6 +414,8 @@ blk_status_t btrfs_map_bio(struct btrfs_fs_info *fs_info, struct bio *bio,
 			   int mirror_num, int async_submit);
 int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 		       fmode_t flags, void *holder);
+int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
+		       struct blk_zone *zone, gfp_t gfp_mask);
 struct btrfs_device *btrfs_scan_one_device(const char *path,
 					   fmode_t flags, void *holder);
 int btrfs_close_devices(struct btrfs_fs_devices *fs_devices);
@@ -466,6 +478,26 @@ int btrfs_finish_chunk_alloc(struct btrfs_trans_handle *trans,
 			     u64 chunk_offset, u64 chunk_size);
 int btrfs_remove_chunk(struct btrfs_trans_handle *trans, u64 chunk_offset);
 
+static inline int btrfs_dev_is_sequential(struct btrfs_device *device, u64 pos)
+{
+	unsigned int zno = pos >> device->zone_size_shift;
+
+	if (!device->seq_zones)
+		return 1;
+
+	return test_bit(zno, device->seq_zones);
+}
+
+static inline int btrfs_dev_is_empty_zone(struct btrfs_device *device, u64 pos)
+{
+	unsigned int zno = pos >> device->zone_size_shift;
+
+	if (!device->empty_zones)
+		return 0;
+
+	return test_bit(zno, device->empty_zones);
+}
+
 static inline void btrfs_dev_stat_inc(struct btrfs_device *dev,
 				      int index)
 {
-- 
2.18.0