[PATCH RFC 2/7] btrfs-progs: Enable read-write ability for 'skinny_bg_tree' feature

Qu Wenruo
2019-11-04T12:04:22Z

Allow btrfs-progs to open, read and write 'skinny_bg_tree' enabled fs.

The modification itself is not large, as block groups items are only
used at 4 timing:

1) open_ctree()
We only need to populate fs_info->bg_root and read block group items
from fs_info->bg_root.
The obvious change is, we don't need to do btrfs_search_slot() for
each block group item, but btrfs_next_item() is enough.

This should hugely reduce open_ctree() execution duration.

2) btrfs_commit_transaction()
We need to write back dirty block group items back to bg_root.

The modification here is to insert new block group item if we can't
find one existing in bg_root, and delete the old one in extent tree
if we're converting to skinny_bg_tree feature.

3) btrfs_make_block_group()
For skinny_bg_tree feature, we insert key only, with key.offset ==
used.

This modification needs extra handling for converting case, where
block group items can be either in extent tree or bg tree.

4) free_block_group_item()
Just delete the block group item in extent tree or bg tree.

Signed-off-by: Qu Wenruo <wqu@suse.com>
---
ctree.h | 17 +++-
disk-io.c | 21 ++++-
extent-tree.c | 230 ++++++++++++++++++++++++++++++++++++++++++++++----
3 files changed, 251 insertions(+), 17 deletions(-)

diff --git a/ctree.h b/ctree.h
index ec57f113839f..a93e1d5d202d 100644
--- a/ctree.h
+++ b/ctree.h
@@ -89,6 +89,9 @@ struct btrfs_free_space_ctl;
/* tracks free space in block groups. */
#define BTRFS_FREE_SPACE_TREE_OBJECTID 10ULL

+/* store BLOCK_GROUP_ITEMS in a seperate tree */
+#define BTRFS_BLOCK_GROUP_TREE_OBJECTID 11ULL
+
/* device stats in the device tree */
#define BTRFS_DEV_STATS_OBJECTID 0ULL

@@ -492,6 +495,7 @@ struct btrfs_super_block {
#define BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA (1ULL << 8)
#define BTRFS_FEATURE_INCOMPAT_NO_HOLES (1ULL << 9)
#define BTRFS_FEATURE_INCOMPAT_METADATA_UUID (1ULL << 10)
+#define BTRFS_FEATURE_INCOMPAT_SKINNY_BG_TREE (1ULL << 11)

#define BTRFS_FEATURE_COMPAT_SUPP 0ULL

@@ -515,7 +519,8 @@ struct btrfs_super_block {
BTRFS_FEATURE_INCOMPAT_MIXED_GROUPS | \
BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA | \
BTRFS_FEATURE_INCOMPAT_NO_HOLES | \
- BTRFS_FEATURE_INCOMPAT_METADATA_UUID)
+ BTRFS_FEATURE_INCOMPAT_METADATA_UUID | \
+ BTRFS_FEATURE_INCOMPAT_SKINNY_BG_TREE)

/*
* A leaf is full of items. offset and size tell us where to find
@@ -1125,6 +1130,7 @@ struct btrfs_fs_info {
struct btrfs_root *quota_root;
struct btrfs_root *free_space_root;
struct btrfs_root *uuid_root;
+ struct btrfs_root *bg_root;

struct rb_root fs_root_tree;

@@ -1176,6 +1182,8 @@ struct btrfs_fs_info {
unsigned int avoid_meta_chunk_alloc:1;
unsigned int avoid_sys_chunk_alloc:1;
unsigned int finalize_on_close:1;
+ /* Converting from bg in extent tree to skinny bg tree */
+ unsigned int convert_to_bg_tree:1;

int transaction_aborted;

@@ -1332,6 +1340,13 @@ static inline u32 BTRFS_MAX_XATTR_SIZE(const struct btrfs_fs_info *info)
*/
#define BTRFS_BLOCK_GROUP_ITEM_KEY 192

+/*
+ * More optimized block group item, use key.objectid for block group bytenr,
+ * key.offset for used bytes.
+ * No item data needed.
+ */
+#define BTRFS_SKINNY_BLOCK_GROUP_ITEM_KEY 193
+
/*
* Every block group is represented in the free space tree by a free space info
* item, which stores some accounting information. It is keyed on
diff --git a/disk-io.c b/disk-io.c
index a5b47b0ef16c..1cb62511f4ad 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -731,6 +731,8 @@ struct btrfs_root *btrfs_read_fs_root(struct btrfs_fs_info *fs_info,
if (location->objectid == BTRFS_FREE_SPACE_TREE_OBJECTID)
return fs_info->free_space_root ? fs_info->free_space_root :
ERR_PTR(-ENOENT);
+ if (location->objectid == BTRFS_BLOCK_GROUP_TREE_OBJECTID)
+ return fs_info->bg_root ? fs_info->bg_root : ERR_PTR(-ENOENT);

BUG_ON(location->objectid == BTRFS_TREE_RELOC_OBJECTID ||
location->offset != (u64)-1);
@@ -783,6 +785,7 @@ struct btrfs_fs_info *btrfs_new_fs_info(int writable, u64 sb_bytenr)
fs_info->quota_root = calloc(1, sizeof(struct btrfs_root));
fs_info->free_space_root = calloc(1, sizeof(struct btrfs_root));
fs_info->uuid_root = calloc(1, sizeof(struct btrfs_root));
+ fs_info->bg_root = calloc(1, sizeof(struct btrfs_root));
fs_info->super_copy = calloc(1, BTRFS_SUPER_INFO_SIZE);

if (!fs_info->tree_root || !fs_info->extent_root ||
@@ -932,7 +935,6 @@ int btrfs_setup_all_roots(struct btrfs_fs_info *fs_info, u64 root_tree_bytenr,
root_tree_bytenr = btrfs_backup_tree_root(backup);
generation = btrfs_backup_tree_root_gen(backup);
}
-
root->node = read_tree_block(fs_info, root_tree_bytenr, generation);
if (!extent_buffer_uptodate(root->node)) {
fprintf(stderr, "Couldn't read tree root\n");
@@ -945,6 +947,21 @@ int btrfs_setup_all_roots(struct btrfs_fs_info *fs_info, u64 root_tree_bytenr,
return ret;
fs_info->extent_root->track_dirty = 1;

+ if (btrfs_fs_incompat(fs_info, SKINNY_BG_TREE)) {
+ ret = setup_root_or_create_block(fs_info, flags,
+ fs_info->bg_root,
+ BTRFS_BLOCK_GROUP_TREE_OBJECTID, "bg");
+ if (ret < 0) {
+ error("Couldn't setup bg tree");
+ return ret;
+ }
+ fs_info->bg_root->track_dirty = 1;
+ fs_info->bg_root->ref_cows = 0;
+ } else {
+ free(fs_info->bg_root);
+ fs_info->bg_root = NULL;
+ }
+
ret = find_and_setup_root(root, fs_info, BTRFS_DEV_TREE_OBJECTID,
fs_info->dev_root);
if (ret) {
@@ -1035,6 +1052,8 @@ void btrfs_release_all_roots(struct btrfs_fs_info *fs_info)
free_extent_buffer(fs_info->extent_root->node);
if (fs_info->tree_root)
free_extent_buffer(fs_info->tree_root->node);
+ if (fs_info->bg_root)
+ free_extent_buffer(fs_info->bg_root->node);
if (fs_info->log_root_tree)
free_extent_buffer(fs_info->log_root_tree->node);
if (fs_info->chunk_root)
diff --git a/extent-tree.c b/extent-tree.c
index d67e4098351f..7c68508de2ac 100644
--- a/extent-tree.c
+++ b/extent-tree.c
@@ -1524,6 +1524,67 @@ int btrfs_dec_ref(struct btrfs_trans_handle *trans, struct btrfs_root *root,
return __btrfs_mod_ref(trans, root, buf, record_parent, 0);
}

+static int write_one_skinny_block_group(struct btrfs_trans_handle *trans,
+ struct btrfs_path *path,
+ struct btrfs_block_group_cache *cache)
+{
+ struct btrfs_fs_info *fs_info = trans->fs_info;
+ struct btrfs_root *bg_root = fs_info->bg_root;
+ struct btrfs_key key;
+ int ret;
+
+ ASSERT(bg_root && btrfs_fs_incompat(fs_info, SKINNY_BG_TREE));
+ key.objectid = cache->key.objectid;
+ key.type = BTRFS_SKINNY_BLOCK_GROUP_ITEM_KEY;
+ key.offset = (u64)-1;
+
+ ret = btrfs_search_slot(trans, bg_root, &key, path, 0, 1);
+ if (ret < 0)
+ return ret;
+ if (ret == 0) {
+ error("invalid skinny bg found, start=%llu", key.objectid);
+ ret = -EUCLEAN;
+ goto out;
+ }
+ ret = btrfs_previous_item(bg_root, path, key.objectid, key.type);
+ if (ret < 0)
+ goto out;
+ if (ret > 0 && fs_info->convert_to_bg_tree) {
+ btrfs_release_path(path);
+
+ /* We are doing convert, insert new one for it */
+ key.offset = cache->used;
+ ret = btrfs_insert_item(trans, bg_root, &key, NULL, 0);
+ if (ret < 0)
+ goto out;
+
+ /* Also delete the existing one in extent tree */
+ key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
+ key.offset = cache->key.offset;
+
+ ret = btrfs_search_slot(trans, fs_info->extent_root, &key,
+ path, -1, 1);
+ if (ret < 0)
+ goto out;
+ if (ret > 0) {
+ ret = 0;
+ goto out;
+ }
+ ret = btrfs_del_item(trans, fs_info->extent_root, path);
+ goto out;
+ }
+ if (ret > 0) {
+ ret = -ENOENT;
+ goto out;
+ }
+ key.offset = cache->used;
+ btrfs_set_item_key_safe(bg_root, path, &key);
+ btrfs_mark_buffer_dirty(path->nodes[0]);
+out:
+ btrfs_release_path(path);
+ return ret;
+}
+
static int write_one_cache_group(struct btrfs_trans_handle *trans,
struct btrfs_path *path,
struct btrfs_block_group_cache *cache)
@@ -1534,6 +1595,9 @@ static int write_one_cache_group(struct btrfs_trans_handle *trans,
struct btrfs_block_group_item bgi;
struct extent_buffer *leaf;

+ if (btrfs_fs_incompat(trans->fs_info, SKINNY_BG_TREE))
+ return write_one_skinny_block_group(trans, path, cache);
+
ret = btrfs_search_slot(trans, extent_root, &cache->key, path, 0, 1);
if (ret < 0)
goto fail;
@@ -2665,32 +2729,63 @@ static int read_one_block_group(struct btrfs_fs_info *fs_info,
struct extent_buffer *leaf = path->nodes[0];
struct btrfs_space_info *space_info;
struct btrfs_block_group_cache *cache;
- struct btrfs_block_group_item bgi;
struct btrfs_key key;
+ u64 bg_len;
+ u64 flags;
+ u64 used;
int slot = path->slots[0];
int bit = 0;
int ret;

btrfs_item_key_to_cpu(leaf, &key, slot);
- ASSERT(key.type == BTRFS_BLOCK_GROUP_ITEM_KEY);
+ ASSERT((!btrfs_fs_incompat(fs_info, SKINNY_BG_TREE) &&
+ key.type == BTRFS_BLOCK_GROUP_ITEM_KEY) ||
+ (btrfs_fs_incompat(fs_info, SKINNY_BG_TREE) &&
+ key.type == BTRFS_SKINNY_BLOCK_GROUP_ITEM_KEY));

/*
* Skip 0 sized block group, don't insert them into block group cache
* tree, as its length is 0, it won't get freed at close_ctree() time.
*/
- if (key.offset == 0)
+ if (key.type == BTRFS_BLOCK_GROUP_ITEM_KEY && key.offset == 0)
return 0;

+ if (key.type == BTRFS_SKINNY_BLOCK_GROUP_ITEM_KEY) {
+ struct btrfs_mapping_tree *map_tree = &fs_info->mapping_tree;
+ struct map_lookup *map;
+ struct cache_extent *ce;
+
+ ce = search_cache_extent(&map_tree->cache_tree, key.objectid);
+ if (!ce || ce->start != key.objectid) {
+ error(
+ "invalid skinny block group %llu: no corresponding chunk",
+ key.objectid);
+ return -ENOENT;
+ }
+ bg_len = ce->size;
+ map = container_of(ce, struct map_lookup, ce);
+ flags = map->type;
+ used = key.offset;
+ } else {
+ struct btrfs_block_group_item bgi;
+
+ bg_len = key.offset;
+ read_extent_buffer(leaf, &bgi,
+ btrfs_item_ptr_offset(leaf, slot),
+ sizeof(bgi));
+ flags = btrfs_block_group_flags(&bgi);
+ used = btrfs_block_group_used(&bgi);
+ }
cache = kzalloc(sizeof(*cache), GFP_NOFS);
if (!cache)
return -ENOMEM;
- read_extent_buffer(leaf, &bgi, btrfs_item_ptr_offset(leaf, slot),
- sizeof(bgi));
- memcpy(&cache->key, &key, sizeof(key));
cache->cached = 0;
cache->pinned = 0;
- cache->flags = btrfs_block_group_flags(&bgi);
- cache->used = btrfs_block_group_used(&bgi);
+ cache->flags = flags;
+ cache->used = used;
+ cache->key.objectid = key.objectid;
+ cache->key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
+ cache->key.offset = bg_len;
if (cache->flags & BTRFS_BLOCK_GROUP_DATA) {
bit = BLOCK_GROUP_DATA;
} else if (cache->flags & BTRFS_BLOCK_GROUP_SYSTEM) {
@@ -2719,6 +2814,55 @@ static int read_one_block_group(struct btrfs_fs_info *fs_info,
return 0;
}

+static int read_skinny_bg_tree(struct btrfs_fs_info *fs_info)
+{
+ struct btrfs_root *bg_root = fs_info->bg_root;
+ struct btrfs_path path;
+ struct btrfs_key key;
+ int ret;
+
+ btrfs_init_path(&path);
+ key.objectid = 0;
+ key.offset = 0;
+ key.type = 0;
+
+ ret = btrfs_search_slot(NULL, bg_root, &key, &path, 0, 0);
+ if (ret < 0)
+ goto out;
+ if (ret == 0) {
+ error("invalid key found in skinny bg tree: (0, 0, 0)");
+ ret = -EUCLEAN;
+ goto out;
+ }
+
+ while (1) {
+ btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+ if (key.type != BTRFS_SKINNY_BLOCK_GROUP_ITEM_KEY) {
+ error(
+ "invalid key found in skinny bg tree: (%llu, %u, %llu)",
+ key.objectid, key.type, key.offset);
+ ret = -EUCLEAN;
+ goto out;
+ }
+ ret = read_one_block_group(fs_info, &path);
+ if (ret < 0) {
+ errno = -ret;
+ error("failed to read one block group: %m");
+ goto out;
+ }
+ ret = btrfs_next_item(bg_root, &path);
+ if (ret < 0)
+ goto out;
+ if (ret > 0) {
+ ret = 0;
+ goto out;
+ }
+ }
+out:
+ btrfs_release_path(&path);
+ return ret;
+}
+
int btrfs_read_block_groups(struct btrfs_fs_info *fs_info)
{
struct btrfs_path path;
@@ -2726,6 +2870,9 @@ int btrfs_read_block_groups(struct btrfs_fs_info *fs_info)
int ret;
struct btrfs_key key;

+ if (btrfs_fs_incompat(fs_info, SKINNY_BG_TREE))
+ return read_skinny_bg_tree(fs_info);
+
root = fs_info->extent_root;
key.objectid = 0;
key.offset = 0;
@@ -2806,16 +2953,25 @@ int btrfs_make_block_group(struct btrfs_trans_handle *trans,
int ret;
struct btrfs_root *extent_root = fs_info->extent_root;
struct btrfs_block_group_cache *cache;
- struct btrfs_block_group_item bgi;

cache = btrfs_add_block_group(fs_info, bytes_used, type, chunk_offset,
size);
- btrfs_set_block_group_used(&bgi, cache->used);
- btrfs_set_block_group_flags(&bgi, cache->flags);
- btrfs_set_block_group_chunk_objectid(&bgi,
- BTRFS_FIRST_CHUNK_TREE_OBJECTID);
- ret = btrfs_insert_item(trans, extent_root, &cache->key, &bgi,
+ if (btrfs_fs_incompat(fs_info, SKINNY_BG_TREE)) {
+ struct btrfs_key key;
+
+ key.objectid = cache->key.objectid;
+ key.type = BTRFS_SKINNY_BLOCK_GROUP_ITEM_KEY;
+ key.offset = bytes_used;
+ ret = btrfs_insert_item(trans, fs_info->bg_root, &key, NULL, 0);
+ } else {
+ struct btrfs_block_group_item bgi;
+ btrfs_set_block_group_used(&bgi, cache->used);
+ btrfs_set_block_group_flags(&bgi, cache->flags);
+ btrfs_set_block_group_chunk_objectid(&bgi,
+ BTRFS_FIRST_CHUNK_TREE_OBJECTID);
+ ret = btrfs_insert_item(trans, extent_root, &cache->key, &bgi,
sizeof(bgi));
+ }
BUG_ON(ret);

return 0;
@@ -2925,6 +3081,41 @@ int btrfs_update_block_group(struct btrfs_root *root,
alloc, mark_free);
}

+static int free_skinny_block_group_item(struct btrfs_trans_handle *trans,
+ struct btrfs_fs_info *fs_info,
+ u64 bytenr)
+{
+ struct btrfs_path path;
+ struct btrfs_key key;
+ struct btrfs_root *bg_root = fs_info->bg_root;
+ int ret;
+
+ btrfs_init_path(&path);
+ key.objectid = bytenr;
+ key.type = BTRFS_SKINNY_BLOCK_GROUP_ITEM_KEY;
+ key.offset = (u64)-1;
+
+ ret = btrfs_search_slot(trans, bg_root, &key, &path, -1, 1);
+ if (ret < 0)
+ return ret;
+ if (ret == 0) {
+ error("invalid skinny block group item found");
+ ret = -EUCLEAN;
+ goto out;
+ }
+ ret = btrfs_previous_item(bg_root, &path, key.objectid, key.type);
+ if (ret < 0)
+ goto out;
+ if (ret > 0) {
+ ret = -ENOENT;
+ goto out;
+ }
+ ret = btrfs_del_item(trans, bg_root, &path);
+out:
+ btrfs_release_path(&path);
+ return ret;
+}
+
/*
* Just remove a block group item in extent tree
* Caller should ensure the block group is empty and all space is pinned.
@@ -2939,6 +3130,12 @@ static int free_block_group_item(struct btrfs_trans_handle *trans,
struct btrfs_root *root = fs_info->extent_root;
int ret = 0;

+ if (btrfs_fs_incompat(fs_info, SKINNY_BG_TREE)) {
+ ret = free_skinny_block_group_item(trans, fs_info, bytenr);
+ if (!fs_info->convert_to_bg_tree)
+ return ret;
+ }
+
key.objectid = bytenr;
key.offset = len;
key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
@@ -2949,7 +3146,10 @@ static int free_block_group_item(struct btrfs_trans_handle *trans,

ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
if (ret > 0) {
- ret = -ENOENT;
+ if (fs_info->convert_to_bg_tree)
+ ret = 0;
+ else
+ ret = -ENOENT;
goto out;
}
if (ret < 0)
--
2.23.0