[PATCH v2 02/16] btrfs: add REMAP chunk type

[Mark Harmstone <mark@harmstone.com>]

Add a new 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.

Signed-off-by: Mark Harmstone <mark@harmstone.com>
---
 fs/btrfs/block-rsv.c            |  8 ++++++++
 fs/btrfs/block-rsv.h            |  1 +
 fs/btrfs/disk-io.c              |  1 +
 fs/btrfs/fs.h                   |  2 ++
 fs/btrfs/space-info.c           | 13 ++++++++++++-
 fs/btrfs/sysfs.c                |  2 ++
 fs/btrfs/tree-checker.c         | 13 +++++++++++--
 fs/btrfs/volumes.c              |  3 +++
 fs/btrfs/volumes.h              | 11 +++++++++--
 include/uapi/linux/btrfs_tree.h |  4 +++-
 10 files changed, 52 insertions(+), 6 deletions(-)

diff --git a/fs/btrfs/block-rsv.c b/fs/btrfs/block-rsv.c
index 5ad6de738aee..2678cd3bed29 100644
--- a/fs/btrfs/block-rsv.c
+++ b/fs/btrfs/block-rsv.c
@@ -421,6 +421,9 @@ void btrfs_init_root_block_rsv(struct btrfs_root *root)
 	case BTRFS_TREE_LOG_OBJECTID:
 		root->block_rsv = &fs_info->treelog_rsv;
 		break;
+	case BTRFS_REMAP_TREE_OBJECTID:
+		root->block_rsv = &fs_info->remap_block_rsv;
+		break;
 	default:
 		root->block_rsv = NULL;
 		break;
@@ -434,6 +437,9 @@ void btrfs_init_global_block_rsv(struct btrfs_fs_info *fs_info)
 	space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_SYSTEM);
 	fs_info->chunk_block_rsv.space_info = space_info;
 
+	space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_REMAP);
+	fs_info->remap_block_rsv.space_info = space_info;
+
 	space_info = btrfs_find_space_info(fs_info, BTRFS_BLOCK_GROUP_METADATA);
 	fs_info->global_block_rsv.space_info = space_info;
 	fs_info->trans_block_rsv.space_info = space_info;
@@ -460,6 +466,8 @@ void btrfs_release_global_block_rsv(struct btrfs_fs_info *fs_info)
 	WARN_ON(fs_info->trans_block_rsv.reserved > 0);
 	WARN_ON(fs_info->chunk_block_rsv.size > 0);
 	WARN_ON(fs_info->chunk_block_rsv.reserved > 0);
+	WARN_ON(fs_info->remap_block_rsv.size > 0);
+	WARN_ON(fs_info->remap_block_rsv.reserved > 0);
 	WARN_ON(fs_info->delayed_block_rsv.size > 0);
 	WARN_ON(fs_info->delayed_block_rsv.reserved > 0);
 	WARN_ON(fs_info->delayed_refs_rsv.reserved > 0);
diff --git a/fs/btrfs/block-rsv.h b/fs/btrfs/block-rsv.h
index 79ae9d05cd91..8359fb96bc3c 100644
--- a/fs/btrfs/block-rsv.h
+++ b/fs/btrfs/block-rsv.h
@@ -22,6 +22,7 @@ enum btrfs_rsv_type {
 	BTRFS_BLOCK_RSV_DELALLOC,
 	BTRFS_BLOCK_RSV_TRANS,
 	BTRFS_BLOCK_RSV_CHUNK,
+	BTRFS_BLOCK_RSV_REMAP,
 	BTRFS_BLOCK_RSV_DELOPS,
 	BTRFS_BLOCK_RSV_DELREFS,
 	BTRFS_BLOCK_RSV_TREELOG,
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 123c397ca8f8..7e60097b2a96 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2815,6 +2815,7 @@ void btrfs_init_fs_info(struct btrfs_fs_info *fs_info)
 			     BTRFS_BLOCK_RSV_GLOBAL);
 	btrfs_init_block_rsv(&fs_info->trans_block_rsv, BTRFS_BLOCK_RSV_TRANS);
 	btrfs_init_block_rsv(&fs_info->chunk_block_rsv, BTRFS_BLOCK_RSV_CHUNK);
+	btrfs_init_block_rsv(&fs_info->remap_block_rsv, BTRFS_BLOCK_RSV_REMAP);
 	btrfs_init_block_rsv(&fs_info->treelog_rsv, BTRFS_BLOCK_RSV_TREELOG);
 	btrfs_init_block_rsv(&fs_info->empty_block_rsv, BTRFS_BLOCK_RSV_EMPTY);
 	btrfs_init_block_rsv(&fs_info->delayed_block_rsv,
diff --git a/fs/btrfs/fs.h b/fs/btrfs/fs.h
index f0b090d4ac04..9ce75843b578 100644
--- a/fs/btrfs/fs.h
+++ b/fs/btrfs/fs.h
@@ -472,6 +472,8 @@ struct btrfs_fs_info {
 	struct btrfs_block_rsv trans_block_rsv;
 	/* Block reservation for chunk tree */
 	struct btrfs_block_rsv chunk_block_rsv;
+	/* Block reservation for remap tree */
+	struct btrfs_block_rsv remap_block_rsv;
 	/* Block reservation for delayed operations */
 	struct btrfs_block_rsv delayed_block_rsv;
 	/* Block reservation for delayed refs */
diff --git a/fs/btrfs/space-info.c b/fs/btrfs/space-info.c
index 0481c693ac2e..278034a22dbf 100644
--- a/fs/btrfs/space-info.c
+++ b/fs/btrfs/space-info.c
@@ -215,7 +215,7 @@ static u64 calc_chunk_size(const struct btrfs_fs_info *fs_info, u64 flags)
 
 	if (flags & BTRFS_BLOCK_GROUP_DATA)
 		return BTRFS_MAX_DATA_CHUNK_SIZE;
-	else if (flags & BTRFS_BLOCK_GROUP_SYSTEM)
+	else if (flags & (BTRFS_BLOCK_GROUP_SYSTEM | BTRFS_BLOCK_GROUP_REMAP))
 		return SZ_32M;
 
 	/* Handle BTRFS_BLOCK_GROUP_METADATA */
@@ -343,6 +343,8 @@ int btrfs_init_space_info(struct btrfs_fs_info *fs_info)
 	if (mixed) {
 		flags = BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_DATA;
 		ret = create_space_info(fs_info, flags);
+		if (ret)
+			goto out;
 	} else {
 		flags = BTRFS_BLOCK_GROUP_METADATA;
 		ret = create_space_info(fs_info, flags);
@@ -351,7 +353,15 @@ int btrfs_init_space_info(struct btrfs_fs_info *fs_info)
 
 		flags = BTRFS_BLOCK_GROUP_DATA;
 		ret = create_space_info(fs_info, flags);
+		if (ret)
+			goto out;
+	}
+
+	if (features & BTRFS_FEATURE_INCOMPAT_REMAP_TREE) {
+		flags = BTRFS_BLOCK_GROUP_REMAP;
+		ret = create_space_info(fs_info, flags);
 	}
+
 out:
 	return ret;
 }
@@ -590,6 +600,7 @@ static void dump_global_block_rsv(struct btrfs_fs_info *fs_info)
 	DUMP_BLOCK_RSV(fs_info, global_block_rsv);
 	DUMP_BLOCK_RSV(fs_info, trans_block_rsv);
 	DUMP_BLOCK_RSV(fs_info, chunk_block_rsv);
+	DUMP_BLOCK_RSV(fs_info, remap_block_rsv);
 	DUMP_BLOCK_RSV(fs_info, delayed_block_rsv);
 	DUMP_BLOCK_RSV(fs_info, delayed_refs_rsv);
 }
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 857d2772db1c..f942fde1d936 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -1973,6 +1973,8 @@ static const char *alloc_name(struct btrfs_space_info *space_info)
 	case BTRFS_BLOCK_GROUP_SYSTEM:
 		ASSERT(space_info->subgroup_id == BTRFS_SUB_GROUP_PRIMARY);
 		return "system";
+	case BTRFS_BLOCK_GROUP_REMAP:
+		return "remap";
 	default:
 		WARN_ON(1);
 		return "invalid-combination";
diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index 76ec3698f197..ca898b1f12f1 100644
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -747,17 +747,26 @@ static int check_block_group_item(struct extent_buffer *leaf,
 		return -EUCLEAN;
 	}
 
+	if (flags & BTRFS_BLOCK_GROUP_REMAP &&
+		!btrfs_fs_incompat(fs_info, REMAP_TREE)) {
+		block_group_err(leaf, slot,
+"invalid flags, have 0x%llx (REMAP flag set) but no remap-tree incompat flag",
+				flags);
+		return -EUCLEAN;
+	}
+
 	type = flags & BTRFS_BLOCK_GROUP_TYPE_MASK;
 	if (unlikely(type != BTRFS_BLOCK_GROUP_DATA &&
 		     type != BTRFS_BLOCK_GROUP_METADATA &&
 		     type != BTRFS_BLOCK_GROUP_SYSTEM &&
+		     type != BTRFS_BLOCK_GROUP_REMAP &&
 		     type != (BTRFS_BLOCK_GROUP_METADATA |
 			      BTRFS_BLOCK_GROUP_DATA))) {
 		block_group_err(leaf, slot,
-"invalid type, have 0x%llx (%lu bits set) expect either 0x%llx, 0x%llx, 0x%llx or 0x%llx",
+"invalid type, have 0x%llx (%lu bits set) expect either 0x%llx, 0x%llx, 0x%llx, 0x%llx or 0x%llx",
 			type, hweight64(type),
 			BTRFS_BLOCK_GROUP_DATA, BTRFS_BLOCK_GROUP_METADATA,
-			BTRFS_BLOCK_GROUP_SYSTEM,
+			BTRFS_BLOCK_GROUP_SYSTEM, BTRFS_BLOCK_GROUP_REMAP,
 			BTRFS_BLOCK_GROUP_METADATA | BTRFS_BLOCK_GROUP_DATA);
 		return -EUCLEAN;
 	}
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index e067e9cd68a5..f4d1527f265e 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -231,6 +231,9 @@ void btrfs_describe_block_groups(u64 bg_flags, char *buf, u32 size_buf)
 	DESCRIBE_FLAG(BTRFS_BLOCK_GROUP_DATA, "data");
 	DESCRIBE_FLAG(BTRFS_BLOCK_GROUP_SYSTEM, "system");
 	DESCRIBE_FLAG(BTRFS_BLOCK_GROUP_METADATA, "metadata");
+	/* block groups containing the remap tree */
+	DESCRIBE_FLAG(BTRFS_BLOCK_GROUP_REMAP, "remap");
+	/* block group that has been remapped */
 	DESCRIBE_FLAG(BTRFS_BLOCK_GROUP_REMAPPED, "remapped");
 
 	DESCRIBE_FLAG(BTRFS_AVAIL_ALLOC_BIT_SINGLE, "single");
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index a56e873a3029..430be12fd5e7 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -58,8 +58,6 @@ static_assert(const_ilog2(BTRFS_STRIPE_LEN) == BTRFS_STRIPE_LEN_SHIFT);
  */
 static_assert(const_ffs(BTRFS_BLOCK_GROUP_RAID0) <
 	      const_ffs(BTRFS_BLOCK_GROUP_PROFILE_MASK & ~BTRFS_BLOCK_GROUP_RAID0));
-static_assert(const_ilog2(BTRFS_BLOCK_GROUP_RAID0) >
-	      ilog2(BTRFS_BLOCK_GROUP_TYPE_MASK));
 
 /* ilog2() can handle both constants and variables */
 #define BTRFS_BG_FLAG_TO_INDEX(profile)					\
@@ -81,6 +79,15 @@ enum btrfs_raid_types {
 	BTRFS_NR_RAID_TYPES
 };
 
+static_assert(BTRFS_RAID_RAID0 == 1);
+static_assert(BTRFS_RAID_RAID1 == 2);
+static_assert(BTRFS_RAID_DUP == 3);
+static_assert(BTRFS_RAID_RAID10 == 4);
+static_assert(BTRFS_RAID_RAID5 == 5);
+static_assert(BTRFS_RAID_RAID6 == 6);
+static_assert(BTRFS_RAID_RAID1C3 == 7);
+static_assert(BTRFS_RAID_RAID1C4 == 8);
+
 /*
  * Use sequence counter to get consistent device stat data on
  * 32-bit processors.
diff --git a/include/uapi/linux/btrfs_tree.h b/include/uapi/linux/btrfs_tree.h
index 4439d77a7252..9a36f0206d90 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_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_REMAP)
 
 #define BTRFS_BLOCK_GROUP_PROFILE_MASK	(BTRFS_BLOCK_GROUP_RAID0 |   \
 					 BTRFS_BLOCK_GROUP_RAID1 |   \
-- 
2.49.1