[RFC PATCH 03/17] btrfs: Check and enable HMZONED mode

[Naohiro Aota <naota@elisp.net>]

HMZONED mode cannot be used together with the RAID5/6 profile. Introduce
the function btrfs_check_hmzoned_mode() to check this. This function will
also check if HMZONED flag is enabled on the file system and if the file
system consists of zoned devices with equal zone size.

Additionally, as updates to the space cache are in-place, the space cache
cannot be located over sequential zones and there is no guarantees that the
device will have enough conventional zones to store this cache. Resolve
this problem by disabling completely the space cache.  This does not
introduces any problems with sequential block groups: all the free space is
located after the allocation pointer and no free space before the pointer.
There is no need to have such cache.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Naohiro Aota <naota@elisp.net>
---
 fs/btrfs/ctree.h       |  3 ++
 fs/btrfs/dev-replace.c |  7 ++++
 fs/btrfs/disk-io.c     |  7 ++++
 fs/btrfs/super.c       | 12 +++---
 fs/btrfs/volumes.c     | 87 ++++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/volumes.h     |  1 +
 6 files changed, 112 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 66f1d3895bca..14f880126532 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -763,6 +763,9 @@ struct btrfs_fs_info {
 	struct btrfs_root *uuid_root;
 	struct btrfs_root *free_space_root;
 
+	/* Zone size when in HMZONED mode */
+	u64 zone_size;
+
 	/* the log root tree is a directory of all the other log roots */
 	struct btrfs_root *log_root_tree;
 
diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index dec01970d8c5..839a35008fd8 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -202,6 +202,13 @@ static int btrfs_init_dev_replace_tgtdev(struct btrfs_fs_info *fs_info,
 		return PTR_ERR(bdev);
 	}
 
+	if ((bdev_zoned_model(bdev) == BLK_ZONED_HM &&
+	     !btrfs_fs_incompat(fs_info, HMZONED)) ||
+	    (!bdev_is_zoned(bdev) && btrfs_fs_incompat(fs_info, HMZONED))) {
+		ret = -EINVAL;
+		goto error;
+	}
+
 	filemap_write_and_wait(bdev->bd_inode->i_mapping);
 
 	devices = &fs_info->fs_devices->devices;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 5124c15705ce..14f284382ba7 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3057,6 +3057,13 @@ int open_ctree(struct super_block *sb,
 
 	btrfs_free_extra_devids(fs_devices, 1);
 
+	ret = btrfs_check_hmzoned_mode(fs_info);
+	if (ret) {
+		btrfs_err(fs_info, "failed to init hmzoned mode: %d",
+				ret);
+		goto fail_block_groups;
+	}
+
 	ret = btrfs_sysfs_add_fsid(fs_devices, NULL);
 	if (ret) {
 		btrfs_err(fs_info, "failed to init sysfs fsid interface: %d",
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 5fdd95e3de05..cc812e459197 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -435,11 +435,13 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 	bool saved_compress_force;
 	int no_compress = 0;
 
-	cache_gen = btrfs_super_cache_generation(info->super_copy);
-	if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
-		btrfs_set_opt(info->mount_opt, FREE_SPACE_TREE);
-	else if (cache_gen)
-		btrfs_set_opt(info->mount_opt, SPACE_CACHE);
+	if (!btrfs_fs_incompat(info, HMZONED)) {
+		cache_gen = btrfs_super_cache_generation(info->super_copy);
+		if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE))
+			btrfs_set_opt(info->mount_opt, FREE_SPACE_TREE);
+		else if (cache_gen)
+			btrfs_set_opt(info->mount_opt, SPACE_CACHE);
+	}
 
 	/*
 	 * Even the options are empty, we still need to do extra check
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 35b3a2187653..ba7ebb80de4d 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1293,6 +1293,80 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 	return ret;
 }
 
+int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info)
+{
+	struct btrfs_fs_devices *fs_devices = fs_info->fs_devices;
+	struct btrfs_device *device;
+	u64 hmzoned_devices = 0;
+	u64 nr_devices = 0;
+	u64 zone_size = 0;
+	int incompat_hmzoned = btrfs_fs_incompat(fs_info, HMZONED);
+	int ret = 0;
+
+	/* Count zoned devices */
+	list_for_each_entry(device, &fs_devices->devices, dev_list) {
+		if (!device->bdev)
+			continue;
+		if (bdev_zoned_model(device->bdev) == BLK_ZONED_HM ||
+		    (bdev_zoned_model(device->bdev) == BLK_ZONED_HA &&
+		     incompat_hmzoned)) {
+			hmzoned_devices++;
+			if (!zone_size) {
+				zone_size = device->zone_size;
+			} else if (device->zone_size != zone_size) {
+				btrfs_err(fs_info,
+					  "Zoned block devices must have equal zone sizes");
+				ret = -EINVAL;
+				goto out;
+			}
+		}
+		nr_devices++;
+	}
+
+	if (!hmzoned_devices && incompat_hmzoned) {
+		/* No zoned block device, disable HMZONED */
+		btrfs_err(fs_info, "HMZONED enabled file system should have zoned devices");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	fs_info->zone_size = zone_size;
+
+	if (hmzoned_devices != nr_devices) {
+		btrfs_err(fs_info,
+			  "zoned devices mixed with regular devices");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* RAID56 is not allowed */
+	if (btrfs_fs_incompat(fs_info, RAID56)) {
+		btrfs_err(fs_info, "HMZONED mode does not support RAID56");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/*
+	 * SPACE CACHE writing is not cowed. Disable that to avoid
+	 * write errors in sequential zones.
+	 */
+	if (btrfs_test_opt(fs_info, SPACE_CACHE)) {
+		btrfs_info(fs_info,
+			   "disabling disk space caching with HMZONED mode");
+		btrfs_clear_opt(fs_info->mount_opt, SPACE_CACHE);
+	}
+
+	btrfs_set_and_info(fs_info, NOTREELOG,
+			   "disabling tree log with HMZONED  mode");
+
+	btrfs_info(fs_info, "HMZONED mode enabled, zone size %llu B",
+		   fs_info->zone_size);
+
+out:
+
+	return ret;
+}
+
 static void btrfs_release_disk_super(struct page *page)
 {
 	kunmap(page);
@@ -2471,6 +2545,13 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 	if (IS_ERR(bdev))
 		return PTR_ERR(bdev);
 
+	if ((bdev_zoned_model(bdev) == BLK_ZONED_HM &&
+	     !btrfs_fs_incompat(fs_info, HMZONED)) ||
+	    (!bdev_is_zoned(bdev) && btrfs_fs_incompat(fs_info, HMZONED))) {
+		ret = -EINVAL;
+		goto error;
+	}
+
 	if (fs_devices->seeding) {
 		seeding_dev = 1;
 		down_write(&sb->s_umount);
@@ -2584,6 +2665,12 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 		}
 	}
 
+	ret = btrfs_check_hmzoned_mode(fs_info);
+	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);
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 13d59bff204f..58053d2e24aa 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -416,6 +416,7 @@ 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);
+int btrfs_check_hmzoned_mode(struct btrfs_fs_info *fs_info);
 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);
-- 
2.18.0