btrfs: disallow space_cache in ZONED mode (5d1ab66c) · Commits · 戴 / test

As updates to the space cache v1 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 v1. This does not introduce 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. Note: we can technically use free-space-tree (space cache v2) on ZONED mode. But, since ZONED mode now always allocates extents in a block group sequentially regardless of underlying device zone type, it's no use to enable and maintain the tree. For the same reason, NODATACOW is also disabled. In summary, ZONED will disable: | Disabled features | Reason | |-------------------+-----------------------------------------------------| | RAID/DUP | Cannot handle two zone append writes to different | | | zones | |-------------------+-----------------------------------------------------| | space_cache (v1) | In-place updating | | NODATACOW | In-place updating | |-------------------+-----------------------------------------------------| | fallocate | Reserved extent will be a write hole | |-------------------+-----------------------------------------------------| | MIXED_BG | Allocated metadata region will be write holes for | | | data writes | Reviewed-by:

Josef Bacik <josef@toxicpanda.com> Signed-off-by:

Naohiro Aota <naohiro.aota@wdc.com> Reviewed-by:

David Sterba <dsterba@suse.com> Signed-off-by:

David Sterba <dsterba@suse.com>

fs/btrfs/super.c

+11 −2

Original line number	Diff line number	Diff line
		@@ -565,8 +565,15 @@ int btrfs_parse_options(struct btrfs_fs_info info, char options,
		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)
		else if (cache_gen) {
		if (btrfs_is_zoned(info)) {
		btrfs_info(info,
		"zoned: clearing existing space cache");
		btrfs_set_super_cache_generation(info->super_copy, 0);
		} else {
		btrfs_set_opt(info->mount_opt, SPACE_CACHE);
		}
		}

		/*
		* Even the options are empty, we still need to do extra check
		@@ -1025,6 +1032,8 @@ out:
		ret = -EINVAL;

		}
		if (!ret)
		ret = btrfs_check_mountopts_zoned(info);
		if (!ret && btrfs_test_opt(info, SPACE_CACHE))
		btrfs_info(info, "disk space caching is enabled");
		if (!ret && btrfs_test_opt(info, FREE_SPACE_TREE))

fs/btrfs/zoned.c

+17 −0

Original line number	Diff line number	Diff line
		@@ -259,3 +259,20 @@ int btrfs_check_zoned_mode(struct btrfs_fs_info *fs_info)
		out:
		return ret;
		}

		int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info)
		{
		if (!btrfs_is_zoned(info))
		return 0;

		/*
		* Space cache writing is not COWed. Disable that to avoid write errors
		* in sequential zones.
		*/
		if (btrfs_test_opt(info, SPACE_CACHE)) {
		btrfs_err(info, "zoned: space cache v1 is not supported");
		return -EINVAL;
		}

		return 0;
		}

fs/btrfs/zoned.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -25,6 +25,7 @@ int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
		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);
		int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info);
		#else /* CONFIG_BLK_DEV_ZONED */
		static inline int btrfs_get_dev_zone(struct btrfs_device *device, u64 pos,
		struct blk_zone *zone)
		@@ -48,6 +49,11 @@ static inline int btrfs_check_zoned_mode(const struct btrfs_fs_info *fs_info)
		return -EOPNOTSUPP;
		}

		static inline int btrfs_check_mountopts_zoned(struct btrfs_fs_info *info)
		{
		return 0;
		}

		#endif

		static inline bool btrfs_dev_is_sequential(struct btrfs_device *device, u64 pos)

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