From ef6a31d035a1000071dc4846aebd02ad081db9e4 Mon Sep 17 00:00:00 2001 From: Mark Harmstone Date: Wed, 7 Jan 2026 14:09:01 +0000 Subject: btrfs: add definitions and constants for remap-tree Add an incompat flag for the new remap-tree feature, and the constants and definitions needed to support it. Reviewed-by: Boris Burkov Signed-off-by: Mark Harmstone Reviewed-by: David Sterba Signed-off-by: David Sterba --- include/uapi/linux/btrfs.h | 1 + include/uapi/linux/btrfs_tree.h | 17 +++++++++++++++++ 2 files changed, 18 insertions(+) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h index e8fd92789423..9165154a274d 100644 --- a/include/uapi/linux/btrfs.h +++ b/include/uapi/linux/btrfs.h @@ -336,6 +336,7 @@ struct btrfs_ioctl_fs_info_args { #define BTRFS_FEATURE_INCOMPAT_EXTENT_TREE_V2 (1ULL << 13) #define BTRFS_FEATURE_INCOMPAT_RAID_STRIPE_TREE (1ULL << 14) #define BTRFS_FEATURE_INCOMPAT_SIMPLE_QUOTA (1ULL << 16) +#define BTRFS_FEATURE_INCOMPAT_REMAP_TREE (1ULL << 17) struct btrfs_ioctl_feature_flags { __u64 compat_flags; diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h index fc29d273845d..f011d34cb699 100644 --- a/include/uapi/linux/btrfs_tree.h +++ b/include/uapi/linux/btrfs_tree.h @@ -76,6 +76,9 @@ /* Tracks RAID stripes in block groups. */ #define BTRFS_RAID_STRIPE_TREE_OBJECTID 12ULL +/* Holds details of remapped addresses after relocation. */ +#define BTRFS_REMAP_TREE_OBJECTID 13ULL + /* device stats in the device tree */ #define BTRFS_DEV_STATS_OBJECTID 0ULL @@ -282,6 +285,10 @@ #define BTRFS_RAID_STRIPE_KEY 230 +#define BTRFS_IDENTITY_REMAP_KEY 234 +#define BTRFS_REMAP_KEY 235 +#define BTRFS_REMAP_BACKREF_KEY 236 + /* * Records the overall state of the qgroups. * There's only one instance of this key present, @@ -1161,6 +1168,7 @@ struct btrfs_dev_replace_item { #define BTRFS_BLOCK_GROUP_RAID6 (1ULL << 8) #define BTRFS_BLOCK_GROUP_RAID1C3 (1ULL << 9) #define BTRFS_BLOCK_GROUP_RAID1C4 (1ULL << 10) +#define BTRFS_BLOCK_GROUP_REMAPPED (1ULL << 11) #define BTRFS_BLOCK_GROUP_RESERVED (BTRFS_AVAIL_ALLOC_BIT_SINGLE | \ BTRFS_SPACE_INFO_GLOBAL_RSV) @@ -1323,4 +1331,13 @@ struct btrfs_verity_descriptor_item { __u8 encryption; } __attribute__ ((__packed__)); +/* + * For a range identified by a BTRFS_REMAP_KEY item in the remap tree, gives + * the address that the start of the range will get remapped to. This + * structure is also shared by BTRFS_REMAP_BACKREF_KEY. + */ +struct btrfs_remap_item { + __le64 address; +} __attribute__ ((__packed__)); + #endif /* _BTRFS_CTREE_H_ */ -- cgit v1.2.3 From 0b4d29fa98ca1a49c4498353253f857573871ba0 Mon Sep 17 00:00:00 2001 From: Mark Harmstone Date: Wed, 7 Jan 2026 14:09:02 +0000 Subject: btrfs: add METADATA_REMAP chunk type Add a new METADATA_REMAP chunk type, which is a metadata chunk that holds the remap tree. This is needed for bootstrapping purposes: the remap tree can't itself be remapped, and must be relocated the existing way, by COWing every leaf. The remap tree can't go in the SYSTEM chunk as space there is limited, because a copy of the chunk item gets placed in the superblock. The changes in fs/btrfs/volumes.h are because we're adding a new block group type bit after the profile bits, and so can no longer rely on the const_ilog2 trick. The sizing to 32MB per chunk, matching the SYSTEM chunk, is an estimate here, we can adjust it later if it proves to be too big or too small. This works out to be ~500,000 remap items, which for a 4KB block size covers ~2GB of remapped data in the worst case and ~500TB in the best case. Reviewed-by: Boris Burkov Signed-off-by: Mark Harmstone Reviewed-by: David Sterba Signed-off-by: David Sterba --- include/uapi/linux/btrfs_tree.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h index f011d34cb699..76578426671c 100644 --- a/include/uapi/linux/btrfs_tree.h +++ b/include/uapi/linux/btrfs_tree.h @@ -1169,12 +1169,14 @@ struct btrfs_dev_replace_item { #define BTRFS_BLOCK_GROUP_RAID1C3 (1ULL << 9) #define BTRFS_BLOCK_GROUP_RAID1C4 (1ULL << 10) #define BTRFS_BLOCK_GROUP_REMAPPED (1ULL << 11) +#define BTRFS_BLOCK_GROUP_METADATA_REMAP (1ULL << 12) #define BTRFS_BLOCK_GROUP_RESERVED (BTRFS_AVAIL_ALLOC_BIT_SINGLE | \ BTRFS_SPACE_INFO_GLOBAL_RSV) #define BTRFS_BLOCK_GROUP_TYPE_MASK (BTRFS_BLOCK_GROUP_DATA | \ BTRFS_BLOCK_GROUP_SYSTEM | \ - BTRFS_BLOCK_GROUP_METADATA) + BTRFS_BLOCK_GROUP_METADATA | \ + BTRFS_BLOCK_GROUP_METADATA_REMAP) #define BTRFS_BLOCK_GROUP_PROFILE_MASK (BTRFS_BLOCK_GROUP_RAID0 | \ BTRFS_BLOCK_GROUP_RAID1 | \ -- cgit v1.2.3 From 7977011460cffc6f5a0cd830584c832c4aa07076 Mon Sep 17 00:00:00 2001 From: Mark Harmstone Date: Wed, 7 Jan 2026 14:09:07 +0000 Subject: btrfs: add extended version of struct block_group_item Add a struct btrfs_block_group_item_v2, which is used in the block group tree if the remap-tree incompat flag is set. This adds two new fields to the block group item: `remap_bytes` and `identity_remap_count`. `remap_bytes` records the amount of data that's physically within this block group, but nominally in another, remapped block group. This is necessary because this data will need to be moved first if this block group is itself relocated. If `remap_bytes` > 0, this is an indicator to the relocation thread that it will need to search the remap-tree for backrefs. A block group must also have `remap_bytes` == 0 before it can be dropped. `identity_remap_count` records how many identity remap items are located in the remap tree for this block group. When relocation is begun for this block group, this is set to the number of holes in the free-space tree for this range. As identity remaps are converted into actual remaps by the relocation process, this number is decreased. Once it reaches 0, either because of relocation or because extents have been deleted, the block group has been fully remapped and its chunk's device extents are removed. Reviewed-by: Boris Burkov Signed-off-by: Mark Harmstone Signed-off-by: David Sterba --- include/uapi/linux/btrfs_tree.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h index 76578426671c..86820a9644e8 100644 --- a/include/uapi/linux/btrfs_tree.h +++ b/include/uapi/linux/btrfs_tree.h @@ -1229,6 +1229,14 @@ struct btrfs_block_group_item { __le64 flags; } __attribute__ ((__packed__)); +struct btrfs_block_group_item_v2 { + __le64 used; + __le64 chunk_objectid; + __le64 flags; + __le64 remap_bytes; + __le32 identity_remap_count; +} __attribute__ ((__packed__)); + struct btrfs_free_space_info { __le32 extent_count; __le32 flags; -- cgit v1.2.3 From 8620da16fb6be1fd9906374fa1c763a10c6918df Mon Sep 17 00:00:00 2001 From: Mark Harmstone Date: Wed, 7 Jan 2026 14:09:08 +0000 Subject: btrfs: allow mounting filesystems with remap-tree incompat flag If we encounter a filesystem with the remap-tree incompat flag set, validate its compatibility with the other flags, and load the remap tree using the values that have been added to the superblock. The remap-tree feature depends on the free-space-tree, but no-holes and block-group-tree have been made dependencies to reduce the testing matrix. Similarly I'm not aware of any reason why mixed-bg and zoned would be incompatible with remap-tree, but this is blocked for the time being until it can be fully tested. Reviewed-by: Boris Burkov Signed-off-by: Mark Harmstone Signed-off-by: David Sterba --- include/uapi/linux/btrfs_tree.h | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h index 86820a9644e8..f7843e6bb978 100644 --- a/include/uapi/linux/btrfs_tree.h +++ b/include/uapi/linux/btrfs_tree.h @@ -721,9 +721,12 @@ struct btrfs_super_block { __u8 metadata_uuid[BTRFS_FSID_SIZE]; __u64 nr_global_roots; + __le64 remap_root; + __le64 remap_root_generation; + __u8 remap_root_level; /* Future expansion */ - __le64 reserved[27]; + __u8 reserved[199]; __u8 sys_chunk_array[BTRFS_SYSTEM_CHUNK_ARRAY_SIZE]; struct btrfs_root_backup super_roots[BTRFS_NUM_BACKUP_ROOTS]; -- cgit v1.2.3