btrfs: don't save block group root into super block
authorQu Wenruo <wqu@suse.com>
Tue, 9 Aug 2022 05:02:17 +0000 (13:02 +0800)
committerDavid Sterba <dsterba@suse.com>
Mon, 26 Sep 2022 10:28:00 +0000 (12:28 +0200)
The extent tree v2 needs a new root for storing all block group items,
the whole feature hasn't been finished yet so we can afford to do some
changes.

My initial proposal years ago just added a new tree rootid, and load it
from tree root, just like what we did for quota/free space tree/uuid/extent
roots.

But the extent tree v2 patches introduced a completely new way to store
block group tree root into super block which is arguably wasteful.

Currently there are only 3 trees stored in super blocks, and they all
have their valid reasons:

- Chunk root
  Needed for bootstrap.

- Tree root
  Really the entry point for all trees.

- Log root
  This is special as log root has to be updated out of existing
  transaction mechanism.

There is not even any reason to put block group root into super blocks,
the block group tree is updated at the same time as the old extent tree,
no need for extra bootstrap/out-of-transaction update.

So just move block group root from super block into tree root.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
fs/btrfs/block-rsv.c
fs/btrfs/ctree.h
fs/btrfs/disk-io.c
fs/btrfs/transaction.c

index 06be0644dd37651ca3afcfe93d7586f4bfc094ae..6ce704d3bdd27db2b2f375976a862f651c2387b8 100644 (file)
@@ -424,6 +424,7 @@ void btrfs_init_root_block_rsv(struct btrfs_root *root)
        case BTRFS_CSUM_TREE_OBJECTID:
        case BTRFS_EXTENT_TREE_OBJECTID:
        case BTRFS_FREE_SPACE_TREE_OBJECTID:
+       case BTRFS_BLOCK_GROUP_TREE_OBJECTID:
                root->block_rsv = &fs_info->delayed_refs_rsv;
                break;
        case BTRFS_ROOT_TREE_OBJECTID:
index b38cd6e2eb5d6f050b53d1c970f1e0ac5b6cdb8a..2c38daa822efdd71a2a4336a985bbf7f74115764 100644 (file)
@@ -280,14 +280,9 @@ struct btrfs_super_block {
        /* the UUID written into btree blocks */
        u8 metadata_uuid[BTRFS_FSID_SIZE];
 
-       /* Extent tree v2 */
-       __le64 block_group_root;
-       __le64 block_group_root_generation;
-       u8 block_group_root_level;
-
        /* future expansion */
-       u8 reserved8[7];
-       __le64 reserved[25];
+       u8 reserved8[8];
+       __le64 reserved[27];
        u8 sys_chunk_array[BTRFS_SYSTEM_CHUNK_ARRAY_SIZE];
        struct btrfs_root_backup super_roots[BTRFS_NUM_BACKUP_ROOTS];
 
@@ -2477,17 +2472,6 @@ BTRFS_SETGET_STACK_FUNCS(backup_bytes_used, struct btrfs_root_backup,
 BTRFS_SETGET_STACK_FUNCS(backup_num_devices, struct btrfs_root_backup,
                   num_devices, 64);
 
-/*
- * For extent tree v2 we overload the extent root with the block group root, as
- * we will have multiple extent roots.
- */
-BTRFS_SETGET_STACK_FUNCS(backup_block_group_root, struct btrfs_root_backup,
-                        extent_root, 64);
-BTRFS_SETGET_STACK_FUNCS(backup_block_group_root_gen, struct btrfs_root_backup,
-                        extent_root_gen, 64);
-BTRFS_SETGET_STACK_FUNCS(backup_block_group_root_level,
-                        struct btrfs_root_backup, extent_root_level, 8);
-
 /* struct btrfs_balance_item */
 BTRFS_SETGET_FUNCS(balance_flags, struct btrfs_balance_item, flags, 64);
 
@@ -2620,13 +2604,6 @@ BTRFS_SETGET_STACK_FUNCS(super_cache_generation, struct btrfs_super_block,
 BTRFS_SETGET_STACK_FUNCS(super_magic, struct btrfs_super_block, magic, 64);
 BTRFS_SETGET_STACK_FUNCS(super_uuid_tree_generation, struct btrfs_super_block,
                         uuid_tree_generation, 64);
-BTRFS_SETGET_STACK_FUNCS(super_block_group_root, struct btrfs_super_block,
-                        block_group_root, 64);
-BTRFS_SETGET_STACK_FUNCS(super_block_group_root_generation,
-                        struct btrfs_super_block,
-                        block_group_root_generation, 64);
-BTRFS_SETGET_STACK_FUNCS(super_block_group_root_level, struct btrfs_super_block,
-                        block_group_root_level, 8);
 
 int btrfs_super_csum_size(const struct btrfs_super_block *s);
 const char *btrfs_super_csum_name(u16 csum_type);
index bb87b5697affa2d901dc4f52d3db4ad2dafa2483..dfc9b3aea76a7c9528c5f801e6e029fa2e87f762 100644 (file)
@@ -1522,6 +1522,9 @@ static struct btrfs_root *btrfs_get_global_root(struct btrfs_fs_info *fs_info,
        if (objectid == BTRFS_UUID_TREE_OBJECTID)
                return btrfs_grab_root(fs_info->uuid_root) ?
                        fs_info->uuid_root : ERR_PTR(-ENOENT);
+       if (objectid == BTRFS_BLOCK_GROUP_TREE_OBJECTID)
+               return btrfs_grab_root(fs_info->block_group_root) ?
+                       fs_info->block_group_root : ERR_PTR(-ENOENT);
        if (objectid == BTRFS_FREE_SPACE_TREE_OBJECTID) {
                struct btrfs_root *root = btrfs_global_root(fs_info, &key);
 
@@ -1978,14 +1981,7 @@ static void backup_super_roots(struct btrfs_fs_info *info)
        btrfs_set_backup_chunk_root_level(root_backup,
                               btrfs_header_level(info->chunk_root->node));
 
-       if (btrfs_fs_incompat(info, EXTENT_TREE_V2)) {
-               btrfs_set_backup_block_group_root(root_backup,
-                                       info->block_group_root->node->start);
-               btrfs_set_backup_block_group_root_gen(root_backup,
-                       btrfs_header_generation(info->block_group_root->node));
-               btrfs_set_backup_block_group_root_level(root_backup,
-                       btrfs_header_level(info->block_group_root->node));
-       } else {
+       if (!btrfs_fs_incompat(info, EXTENT_TREE_V2)) {
                struct btrfs_root *extent_root = btrfs_extent_root(info, 0);
                struct btrfs_root *csum_root = btrfs_csum_root(info, 0);
 
@@ -2527,10 +2523,24 @@ static int btrfs_read_roots(struct btrfs_fs_info *fs_info)
        if (ret)
                return ret;
 
-       location.objectid = BTRFS_DEV_TREE_OBJECTID;
        location.type = BTRFS_ROOT_ITEM_KEY;
        location.offset = 0;
 
+       if (btrfs_fs_incompat(fs_info, EXTENT_TREE_V2)) {
+               location.objectid = BTRFS_BLOCK_GROUP_TREE_OBJECTID;
+               root = btrfs_read_tree_root(tree_root, &location);
+               if (IS_ERR(root)) {
+                       if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
+                               ret = PTR_ERR(root);
+                               goto out;
+                       }
+               } else {
+                       set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+                       fs_info->block_group_root = root;
+               }
+       }
+
+       location.objectid = BTRFS_DEV_TREE_OBJECTID;
        root = btrfs_read_tree_root(tree_root, &location);
        if (IS_ERR(root)) {
                if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
@@ -2858,17 +2868,7 @@ static int load_important_roots(struct btrfs_fs_info *fs_info)
                btrfs_warn(fs_info, "couldn't read tree root");
                return ret;
        }
-
-       if (!btrfs_fs_incompat(fs_info, EXTENT_TREE_V2))
-               return 0;
-
-       bytenr = btrfs_super_block_group_root(sb);
-       gen = btrfs_super_block_group_root_generation(sb);
-       level = btrfs_super_block_group_root_level(sb);
-       ret = load_super_root(fs_info->block_group_root, bytenr, gen, level);
-       if (ret)
-               btrfs_warn(fs_info, "couldn't read block group root");
-       return ret;
+       return 0;
 }
 
 static int __cold init_tree_roots(struct btrfs_fs_info *fs_info)
index 4c87bf2abc1424cec569278daaffec964a7d031a..d9e608935e6497bd4d99a3276947a71e03ba4360 100644 (file)
@@ -1894,14 +1894,6 @@ static void update_super_roots(struct btrfs_fs_info *fs_info)
                super->cache_generation = 0;
        if (test_bit(BTRFS_FS_UPDATE_UUID_TREE_GEN, &fs_info->flags))
                super->uuid_tree_generation = root_item->generation;
-
-       if (btrfs_fs_incompat(fs_info, EXTENT_TREE_V2)) {
-               root_item = &fs_info->block_group_root->root_item;
-
-               super->block_group_root = root_item->bytenr;
-               super->block_group_root_generation = root_item->generation;
-               super->block_group_root_level = root_item->level;
-       }
 }
 
 int btrfs_transaction_in_commit(struct btrfs_fs_info *info)