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_zonetypes().  To
avoid costly run-time zone report commands to test the device zones type
during block allocation, attach the seq_zones bitmap to the device
structure to indicate if a zone is sequential or accept random writes. Also
it attaches the empty_zones bitmap to indicate if a zone is empty or not.

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 and
btrfs_dev_is_empty_zone() to test if the zone is a empty zone.

Signed-off-by: Damien Le Moal <damien.lem...@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.a...@wdc.com>
---
 fs/btrfs/Makefile  |   2 +-
 fs/btrfs/hmzoned.c | 162 +++++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/hmzoned.h |  79 ++++++++++++++++++++++
 fs/btrfs/volumes.c |  18 ++++-
 fs/btrfs/volumes.h |   4 ++
 5 files changed, 262 insertions(+), 3 deletions(-)
 create mode 100644 fs/btrfs/hmzoned.c
 create mode 100644 fs/btrfs/hmzoned.h

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index 76a843198bcb..8d93abb31074 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -11,7 +11,7 @@ btrfs-y += super.o ctree.o extent-tree.o print-tree.o 
root-tree.o dir-item.o \
           compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \
           reada.o backref.o ulist.o qgroup.o send.o dev-replace.o raid56.o \
           uuid-tree.o props.o free-space-tree.o tree-checker.o space-info.o \
-          block-rsv.o delalloc-space.o
+          block-rsv.o delalloc-space.o hmzoned.o
 
 btrfs-$(CONFIG_BTRFS_FS_POSIX_ACL) += acl.o
 btrfs-$(CONFIG_BTRFS_FS_CHECK_INTEGRITY) += check-integrity.o
diff --git a/fs/btrfs/hmzoned.c b/fs/btrfs/hmzoned.c
new file mode 100644
index 000000000000..bfd04792dd62
--- /dev/null
+++ b/fs/btrfs/hmzoned.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ * Authors:
+ *     Naohiro Aota    <naohiro.a...@wdc.com>
+ *     Damien Le Moal  <damien.lem...@wdc.com>
+ */
+
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+#include "ctree.h"
+#include "volumes.h"
+#include "hmzoned.h"
+#include "rcu-string.h"
+
+/* Maximum number of zones to report per blkdev_report_zones() call */
+#define BTRFS_REPORT_NR_ZONES   4096
+
+static int btrfs_get_dev_zones(struct btrfs_device *device, u64 pos,
+                              struct blk_zone **zones_ret,
+                              unsigned int *nr_zones, gfp_t gfp_mask)
+{
+       struct blk_zone *zones = *zones_ret;
+       int ret;
+
+       if (!zones) {
+               zones = kcalloc(*nr_zones, sizeof(struct blk_zone), GFP_KERNEL);
+               if (!zones)
+                       return -ENOMEM;
+       }
+
+       ret = blkdev_report_zones(device->bdev, pos >> SECTOR_SHIFT,
+                                 zones, nr_zones, gfp_mask);
+       if (ret != 0) {
+               btrfs_err_in_rcu(device->fs_info,
+                                "get zone at %llu on %s failed %d", pos,
+                                rcu_str_deref(device->name), ret);
+               return ret;
+       }
+       if (!*nr_zones)
+               return -EIO;
+
+       *zones_ret = zones;
+
+       return 0;
+}
+
+int btrfs_get_dev_zone_info(struct btrfs_device *device)
+{
+       struct btrfs_zoned_device_info *zone_info = NULL;
+       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, nreported = 0, nr_zones;
+       unsigned int zone_sectors;
+       int ret;
+
+       if (!bdev_is_zoned(bdev))
+               return 0;
+
+       zone_info = kzalloc(sizeof(*zone_info), GFP_KERNEL);
+       if (!zone_info)
+               return -ENOMEM;
+
+       zone_sectors = bdev_zone_sectors(bdev);
+       ASSERT(is_power_of_2(zone_sectors));
+       zone_info->zone_size = (u64)zone_sectors << SECTOR_SHIFT;
+       zone_info->zone_size_shift = ilog2(zone_info->zone_size);
+       zone_info->nr_zones = nr_sectors >> ilog2(bdev_zone_sectors(bdev));
+       if (nr_sectors & (bdev_zone_sectors(bdev) - 1))
+               zone_info->nr_zones++;
+
+       zone_info->seq_zones = kcalloc(BITS_TO_LONGS(zone_info->nr_zones),
+                                      sizeof(*zone_info->seq_zones),
+                                      GFP_KERNEL);
+       if (!zone_info->seq_zones) {
+               ret = -ENOMEM;
+               goto out;
+       }
+
+       zone_info->empty_zones = kcalloc(BITS_TO_LONGS(zone_info->nr_zones),
+                                        sizeof(*zone_info->empty_zones),
+                                        GFP_KERNEL);
+       if (!zone_info->empty_zones) {
+               ret = -ENOMEM;
+               goto out;
+       }
+
+       /* Get zones type */
+       while (sector < nr_sectors) {
+               nr_zones = BTRFS_REPORT_NR_ZONES;
+               ret = btrfs_get_dev_zones(device, sector << SECTOR_SHIFT,
+                                         &zones, &nr_zones, GFP_KERNEL);
+               if (ret)
+                       goto out;
+
+               for (i = 0; i < nr_zones; i++) {
+                       if (zones[i].type == BLK_ZONE_TYPE_SEQWRITE_REQ)
+                               set_bit(nreported, zone_info->seq_zones);
+                       if (zones[i].cond == BLK_ZONE_COND_EMPTY)
+                               set_bit(nreported, zone_info->empty_zones);
+                       nreported++;
+               }
+               sector = zones[nr_zones - 1].start + zones[nr_zones - 1].len;
+       }
+
+       if (nreported != zone_info->nr_zones) {
+               btrfs_err_in_rcu(device->fs_info,
+                                "inconsistent number of zones on %s (%u / %u)",
+                                rcu_str_deref(device->name), nreported,
+                                zone_info->nr_zones);
+               ret = -EIO;
+               goto out;
+       }
+
+       device->zone_info = zone_info;
+
+       btrfs_info_in_rcu(
+               device->fs_info,
+               "host-%s zoned block device %s, %u zones of %llu sectors",
+               bdev_zoned_model(bdev) == BLK_ZONED_HM ? "managed" : "aware",
+               rcu_str_deref(device->name), zone_info->nr_zones,
+               zone_info->zone_size >> SECTOR_SHIFT);
+
+out:
+       kfree(zones);
+
+       if (ret) {
+               kfree(zone_info->seq_zones);
+               kfree(zone_info->empty_zones);
+               kfree(zone_info);
+       }
+
+       return ret;
+}
+
+void btrfs_destroy_dev_zone_info(struct btrfs_device *device)
+{
+       struct btrfs_zoned_device_info *zone_info = device->zone_info;
+
+       if (!zone_info)
+               return;
+
+       kfree(zone_info->seq_zones);
+       kfree(zone_info->empty_zones);
+       kfree(zone_info);
+       device->zone_info = NULL;
+}
+
+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;
+}
diff --git a/fs/btrfs/hmzoned.h b/fs/btrfs/hmzoned.h
new file mode 100644
index 000000000000..ffc70842135e
--- /dev/null
+++ b/fs/btrfs/hmzoned.h
@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019 Western Digital Corporation or its affiliates.
+ * Authors:
+ *     Naohiro Aota    <naohiro.a...@wdc.com>
+ *     Damien Le Moal  <damien.lem...@wdc.com>
+ */
+
+#ifndef BTRFS_HMZONED_H
+#define BTRFS_HMZONED_H
+
+struct btrfs_zoned_device_info {
+       /*
+        * 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;
+};
+
+int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
+                      struct blk_zone *zone, gfp_t gfp_mask);
+int btrfs_get_dev_zone_info(struct btrfs_device *device);
+void btrfs_destroy_dev_zone_info(struct btrfs_device *device);
+
+static inline bool btrfs_dev_is_sequential(struct btrfs_device *device, u64 
pos)
+{
+       struct btrfs_zoned_device_info *zone_info = device->zone_info;
+
+       if (!zone_info)
+               return false;
+
+       return test_bit(pos >> zone_info->zone_size_shift,
+                       zone_info->seq_zones);
+}
+
+static inline bool btrfs_dev_is_empty_zone(struct btrfs_device *device, u64 
pos)
+{
+       struct btrfs_zoned_device_info *zone_info = device->zone_info;
+
+       if (!zone_info)
+               return true;
+
+       return test_bit(pos >> zone_info->zone_size_shift,
+                       zone_info->empty_zones);
+}
+
+static inline void btrfs_dev_set_empty_zone_bit(struct btrfs_device *device,
+                                               u64 pos, bool set)
+{
+       struct btrfs_zoned_device_info *zone_info = device->zone_info;
+       unsigned int zno;
+
+       if (!zone_info)
+               return;
+
+       zno = pos >> zone_info->zone_size_shift;
+       if (set)
+               set_bit(zno, zone_info->empty_zones);
+       else
+               clear_bit(zno, zone_info->empty_zones);
+}
+
+static inline void btrfs_dev_set_zone_empty(struct btrfs_device *device,
+                                           u64 pos)
+{
+       btrfs_dev_set_empty_zone_bit(device, pos, true);
+}
+
+static inline void btrfs_dev_clear_zone_empty(struct btrfs_device *device,
+                                             u64 pos)
+{
+       btrfs_dev_set_empty_zone_bit(device, pos, false);
+}
+
+#endif
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index d74b74ca07af..8e5a894e7bde 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -29,6 +29,7 @@
 #include "sysfs.h"
 #include "tree-checker.h"
 #include "space-info.h"
+#include "hmzoned.h"
 
 const struct btrfs_raid_attr btrfs_raid_array[BTRFS_NR_RAID_TYPES] = {
        [BTRFS_RAID_RAID10] = {
@@ -342,6 +343,7 @@ void btrfs_free_device(struct btrfs_device *device)
        rcu_string_free(device->name);
        extent_io_tree_release(&device->alloc_state);
        bio_put(device->flush_bio);
+       btrfs_destroy_dev_zone_info(device);
        kfree(device);
 }
 
@@ -847,6 +849,11 @@ 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 */
+       ret = btrfs_get_dev_zone_info(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) {
@@ -2598,6 +2605,14 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, 
const char *device_path
        }
        rcu_assign_pointer(device->name, name);
 
+       device->fs_info = fs_info;
+       device->bdev = bdev;
+
+       /* Get zone type information of zoned block devices */
+       ret = btrfs_get_dev_zone_info(device);
+       if (ret)
+               goto error_free_device;
+
        trans = btrfs_start_transaction(root, 0);
        if (IS_ERR(trans)) {
                ret = PTR_ERR(trans);
@@ -2614,8 +2629,6 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, 
const char *device_path
                                         fs_info->sectorsize);
        device->disk_total_bytes = device->total_bytes;
        device->commit_total_bytes = device->total_bytes;
-       device->fs_info = fs_info;
-       device->bdev = bdev;
        set_bit(BTRFS_DEV_STATE_IN_FS_METADATA, &device->dev_state);
        clear_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state);
        device->mode = FMODE_EXCL;
@@ -2756,6 +2769,7 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, 
const char *device_path
                sb->s_flags |= SB_RDONLY;
        if (trans)
                btrfs_end_transaction(trans);
+       btrfs_destroy_dev_zone_info(device);
 error_free_device:
        btrfs_free_device(device);
 error:
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 7f6aa1816409..5da1f354db93 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -57,6 +57,8 @@ struct btrfs_io_geometry {
 #define BTRFS_DEV_STATE_REPLACE_TGT    (3)
 #define BTRFS_DEV_STATE_FLUSH_SENT     (4)
 
+struct btrfs_zoned_device_info;
+
 struct btrfs_device {
        struct list_head dev_list; /* device_list_mutex */
        struct list_head dev_alloc_list; /* chunk mutex */
@@ -77,6 +79,8 @@ struct btrfs_device {
 
        struct block_device *bdev;
 
+       struct btrfs_zoned_device_info *zone_info;
+
        /* the mode sent to blkdev_get */
        fmode_t mode;
 
-- 
2.22.0

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