[PATCH v14 03/42] btrfs: defer loading zone info after opening trees

[Naohiro Aota <naohiro.aota@wdc.com>]

This is preparation patch to implement zone emulation on a regular device.

To emulate zoned mode on a regular (non-zoned) device, we need to decide an
emulating zone size. Instead of making it compile-time static value, we'll
make it configurable at mkfs time. Since we have one zone == one device
extent restriction, we can determine the emulated zone size from the size
of a device extent. We can extend btrfs_get_dev_zone_info() to show a
regular device filled with conventional zones once the zone size is
decided.

The current call site of btrfs_get_dev_zone_info() during the mount process
is earlier than reading the trees, so we can't slice a regular device to
conventional zones. This patch defers the loading of zone info to
open_ctree() to load the emulated zone size from a device extent.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
---
 fs/btrfs/disk-io.c | 13 +++++++++++++
 fs/btrfs/volumes.c |  4 ----
 fs/btrfs/zoned.c   | 24 ++++++++++++++++++++++++
 fs/btrfs/zoned.h   |  7 +++++++
 4 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 5473bed6a7e8..39cbe10a81b6 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3257,6 +3257,19 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
 	if (ret)
 		goto fail_tree_roots;
 
+	/*
+	 * Get zone type information of zoned block devices. This will also
+	 * handle emulation of the zoned mode for btrfs if a regular device has
+	 * the zoned incompat feature flag set.
+	 */
+	ret = btrfs_get_dev_zone_info_all_devices(fs_info);
+	if (ret) {
+		btrfs_err(fs_info,
+			  "failed to read device zone info: %d",
+			  ret);
+		goto fail_block_groups;
+	}
+
 	/*
 	 * If we have a uuid root and we're not being told to rescan we need to
 	 * check the generation here so we can set the
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index badb972919eb..bb3f341f6a22 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -669,10 +669,6 @@ 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;
 
-	ret = btrfs_get_dev_zone_info(device);
-	if (ret != 0)
-		goto error_free_page;
-
 	fs_devices->open_devices++;
 	if (test_bit(BTRFS_DEV_STATE_WRITEABLE, &device->dev_state) &&
 	    device->devid != BTRFS_DEV_REPLACE_DEVID) {
diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index c38846659019..bcabdb2c97f1 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -143,6 +143,30 @@ static int btrfs_get_dev_zones(struct btrfs_device *device, u64 pos,
 	return 0;
 }
 
+int btrfs_get_dev_zone_info_all_devices(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	struct btrfs_device *device;
+	int ret = 0;
+
+	if (!btrfs_fs_incompat(fs_info, ZONED))
+		return 0;
+
+	mutex_lock(&fs_devices->device_list_mutex);
+	list_for_each_entry(device, &fs_devices->devices, dev_list) {
+		/* We can skip reading of zone info for missing devices */
+		if (!device->bdev)
+			continue;
+
+		ret = btrfs_get_dev_zone_info(device);
+		if (ret)
+			break;
+	}
+	mutex_unlock(&fs_devices->device_list_mutex);
+
+	return ret;
+}
+
 int btrfs_get_dev_zone_info(struct btrfs_device *device)
 {
 	struct btrfs_zoned_device_info *zone_info = NULL;
diff --git a/fs/btrfs/zoned.h b/fs/btrfs/zoned.h
index 8abe2f83272b..5e0e7de84a82 100644
--- a/fs/btrfs/zoned.h
+++ b/fs/btrfs/zoned.h
@@ -25,6 +25,7 @@ struct btrfs_zoned_device_info {
 #ifdef CONFIG_BLK_DEV_ZONED
 int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
 		       struct blk_zone *zone);
+int btrfs_get_dev_zone_info_all_devices(struct btrfs_fs_info *fs_info);
 int btrfs_get_dev_zone_info(struct btrfs_device *device);
 void btrfs_destroy_dev_zone_info(struct btrfs_device *device);
 int btrfs_check_zoned_mode(struct btrfs_fs_info *fs_info);
@@ -42,6 +43,12 @@ static inline int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
 	return 0;
 }
 
+static inline int btrfs_get_dev_zone_info_all_devices(
+	struct btrfs_fs_info *fs_info)
+{
+	return 0;
+}
+
 static inline int btrfs_get_dev_zone_info(struct btrfs_device *device)
 {
 	return 0;
-- 
2.27.0