On 10.01.2018 06:56, Qu Wenruo wrote:
> When creating btrfs, mkfs.btrfs will firstly create a temporary system
> chunk as basis, and then created needed trees or new devices.
>
> However the layout temporary system chunk is hard-coded and uses
> reserved [0, 1M) range of devid 1.
>
> Change the temporary chunk layout from old:
>
> 0 1M 4M 5M
> |<----------- temp chunk -------------->|
> And it's 1:1 mapped, which means it's a SINGLE chunk,
> and stripe offset is also 0.
>
> to new layout:
>
> 0 1M 4M 5M
> |<----------- temp chunk -------------->|
> And still keeps the 1:1 mapping.
>
> The problem can only be exposed by "-m single" or "-M" where we reuse the
> temporary chunk.
>
> With other meta profiles, system and meta chunks are allocated by later
> btrfs_alloc_chunk() call, and old SINGLE chunks are removed, so it will
> be no such problem for other meta profiles.
>
> Reported-by: Nikolay Borisov <nborisov@xxxxxxxx>
> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
Tested-by: Nikolay Borisov <nborisov@xxxxxxxx>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
After creating in -M or in -m single I can see:
item 0 key (1 DEV_EXTENT 1048576) itemoff 3947 itemsize 48
and
item 1 key (1048576 BLOCK_GROUP_ITEM 4194304) itemoff 3938 itemsize 24
block group used 4096 chunk_objectid 256 flags SYSTEM
> ---
> mkfs/common.c | 29 +++++++++++++++++++++++------
> mkfs/main.c | 7 ++++++-
> 2 files changed, 29 insertions(+), 7 deletions(-)
>
> diff --git a/mkfs/common.c b/mkfs/common.c
> index dd5e7ecff479..5c5e9c3b9e01 100644
> --- a/mkfs/common.c
> +++ b/mkfs/common.c
> @@ -100,6 +100,21 @@ static int btrfs_create_tree_root(int fd, struct btrfs_mkfs_config *cfg,
> *
> * The superblock signature is not valid, denotes a partially created
> * filesystem, needs to be finalized.
> + *
> + * The temporary fs will have the following chunk layout:
> + * Device extent:
> + * 0 1M 5M ......
> + * | Reserved | dev extent for SYS chunk |
> + *
> + * And chunk mapping will be:
> + * Chunk mapping:
> + * 0 1M 5M
> + * | | System chunk, 1:1 mapped |
> + *
> + * That's to say, there will only be *ONE* system chunk, mapped to
> + * [1M, 5M) physical offset.
> + * And the only chunk is also in logical address [1M, 5M), containing
> + * all essential tree blocks.
> */
> int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
> {
> @@ -154,8 +169,8 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>
> cfg->blocks[MKFS_SUPER_BLOCK] = BTRFS_SUPER_INFO_OFFSET;
> for (i = 1; i < MKFS_BLOCK_COUNT; i++) {
> - cfg->blocks[i] = BTRFS_SUPER_INFO_OFFSET + SZ_1M +
> - cfg->nodesize * i;
> + cfg->blocks[i] = BTRFS_BLOCK_RESERVED_1M_FOR_SUPER +
> + cfg->nodesize * (i - 1);
> }
>
> btrfs_set_super_bytenr(&super, cfg->blocks[MKFS_SUPER_BLOCK]);
> @@ -309,7 +324,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
>
> /* then we have chunk 0 */
> btrfs_set_disk_key_objectid(&disk_key, BTRFS_FIRST_CHUNK_TREE_OBJECTID);
> - btrfs_set_disk_key_offset(&disk_key, 0);
> + btrfs_set_disk_key_offset(&disk_key, BTRFS_BLOCK_RESERVED_1M_FOR_SUPER);
> btrfs_set_disk_key_type(&disk_key, BTRFS_CHUNK_ITEM_KEY);
> btrfs_set_item_key(buf, &disk_key, nritems);
> btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
> @@ -325,7 +340,8 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
> btrfs_set_chunk_sector_size(buf, chunk, cfg->sectorsize);
> btrfs_set_chunk_num_stripes(buf, chunk, 1);
> btrfs_set_stripe_devid_nr(buf, chunk, 0, 1);
> - btrfs_set_stripe_offset_nr(buf, chunk, 0, 0);
> + btrfs_set_stripe_offset_nr(buf, chunk, 0,
> + BTRFS_BLOCK_RESERVED_1M_FOR_SUPER);
> nritems++;
>
> write_extent_buffer(buf, super.dev_item.uuid,
> @@ -363,7 +379,7 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
> sizeof(struct btrfs_dev_extent);
>
> btrfs_set_disk_key_objectid(&disk_key, 1);
> - btrfs_set_disk_key_offset(&disk_key, 0);
> + btrfs_set_disk_key_offset(&disk_key, BTRFS_BLOCK_RESERVED_1M_FOR_SUPER);
> btrfs_set_disk_key_type(&disk_key, BTRFS_DEV_EXTENT_KEY);
> btrfs_set_item_key(buf, &disk_key, nritems);
> btrfs_set_item_offset(buf, btrfs_item_nr(nritems), itemoff);
> @@ -374,7 +390,8 @@ int make_btrfs(int fd, struct btrfs_mkfs_config *cfg)
> BTRFS_CHUNK_TREE_OBJECTID);
> btrfs_set_dev_extent_chunk_objectid(buf, dev_extent,
> BTRFS_FIRST_CHUNK_TREE_OBJECTID);
> - btrfs_set_dev_extent_chunk_offset(buf, dev_extent, 0);
> + btrfs_set_dev_extent_chunk_offset(buf, dev_extent,
> + BTRFS_BLOCK_RESERVED_1M_FOR_SUPER);
>
> write_extent_buffer(buf, chunk_tree_uuid,
> (unsigned long)btrfs_dev_extent_chunk_tree_uuid(dev_extent),
> diff --git a/mkfs/main.c b/mkfs/main.c
> index d817ad8dfd1a..8e3d19acb6f2 100644
> --- a/mkfs/main.c
> +++ b/mkfs/main.c
> @@ -81,10 +81,15 @@ static int create_metadata_block_groups(struct btrfs_root *root, int mixed,
> bytes_used = btrfs_super_bytes_used(fs_info->super_copy);
>
> root->fs_info->system_allocs = 1;
> + /*
> + * First temporary system chunk must match the chunk layout
> + * created in make_btrfs().
> + */
> ret = btrfs_make_block_group(trans, fs_info, bytes_used,
> BTRFS_BLOCK_GROUP_SYSTEM,
> BTRFS_FIRST_CHUNK_TREE_OBJECTID,
> - 0, BTRFS_MKFS_SYSTEM_GROUP_SIZE);
> + BTRFS_BLOCK_RESERVED_1M_FOR_SUPER,
> + BTRFS_MKFS_SYSTEM_GROUP_SIZE);
> allocation->system += BTRFS_MKFS_SYSTEM_GROUP_SIZE;
> if (ret)
> return ret;
>
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