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>
---
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;
--
2.15.1
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