On Tue, Oct 22, 2013 at 04:39:38PM +0900, Akira Fujita wrote:
> If we create ext4 filesystem without resize_inode feature,
> mke2fs command does not initialize block groups
> which have backup superblock and/or group descriptor block
> (With meta_bg feature, backup superblock and group descriptor block
> are located separately).
> So we have to fix block bitmaps when we run "e2fsck -b superblock device".
> This patch fixes the issue by initializing block bitmaps correctly.
>
> Steps to reproduce:
> 1. mke2fs -t ext4 -b 4096 -O ^resize_inode device
> 2. e2fsck -b 32768 DEV
> <snip>
> Pass 1: Checking inodes, blocks, and sizes
> Pass 2: Checking directory structure
> Pass 3: Checking directory connectivity
> Pass 4: Checking reference counts
> Pass 5: Checking group summary information
> Block bitmap differences: +(32768--32769) +(98304--98305) +(163840--163841)
> Fix<y>?
>
> Signed-off-by: Akira Fujita <a-fujita@xxxxxxxxxxxxx>
> ---
> lib/ext2fs/alloc_sb.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
> diff --git a/lib/ext2fs/alloc_sb.c b/lib/ext2fs/alloc_sb.c
> index 223ec51..5419d0d 100644
> --- a/lib/ext2fs/alloc_sb.c
> +++ b/lib/ext2fs/alloc_sb.c
> @@ -58,23 +58,25 @@ int ext2fs_reserve_super_and_bgd(ext2_filsys fs,
> old_desc_blocks =
> fs->desc_blocks + fs->super->s_reserved_gdt_blocks;
>
> - if (super_blk || (group == 0))
> + if (super_blk || (group == 0)) {
> + ext2fs_bg_flags_clear(fs, group, EXT2_BG_BLOCK_UNINIT);
I'm not sure I agree with clearing the uninit flag unconditionally. Consider
the case where bmap != fs->block_map, which happens in mark_table_blocks()
(e2fsck pass1) and ext2fs_check_desc (libext2fs). In these two cases, the
function will mark superblock and group descriptor blocks in a separate bitmap,
leaving everything under fs alone. IOW: It doesn't make sense to mess with the
fs' uninit flags if we're not marking the fs' bitmap.
As you point out, however, if we /are/ being called with fs->block_bitmap ==
bmap, then we're probably initializing the fs and it makes sense to clear the
uninit flags.
Maybe something like this, just after the call to ext2fs_super_and_bgd_loc2?
if (fs->block_map == bmap && (new_desc_block || old_desc_block || super_blk))
ext2fs_bg_flags_clear(fs, group, EXT2_BG_BLOCK_UNINIT);
<shrug>
I've been wondering for a while -- if we have a FS with meta_bg and
s_first_meta_bg > 0, does that mean we have "old" style group descriptor
layouts up to whatever block group s_first_meta_bg points to? And why do we
set old_desc_blocks to s_first_meta_bg, since the former is used as a block
length offset for old_desc_blk for block groups beneath s_first_meta_bg?
Group descriptors aren't the same size as a block.
This all seems kinda moot since the only initialization I can find for
s_first_meta_bg sets it to zero.
<confused>
> ext2fs_mark_block_bitmap2(bmap, super_blk);
> + }
> if ((group == 0) && (fs->blocksize == 1024) &&
> EXT2FS_CLUSTER_RATIO(fs) > 1)
> ext2fs_mark_block_bitmap2(bmap, 0);
>
> if (old_desc_blk) {
> - if (fs->super->s_reserved_gdt_blocks && fs->block_map == bmap)
> - ext2fs_bg_flags_clear(fs, group, EXT2_BG_BLOCK_UNINIT);
Why remove this?
> num_blocks = old_desc_blocks;
> if (old_desc_blk + num_blocks >= ext2fs_blocks_count(fs->super))
> num_blocks = ext2fs_blocks_count(fs->super) -
> old_desc_blk;
> ext2fs_mark_block_bitmap_range2(bmap, old_desc_blk, num_blocks);
> }
> - if (new_desc_blk)
> + if (new_desc_blk) {
> + ext2fs_bg_flags_clear(fs, group, EXT2_BG_BLOCK_UNINIT);
Same comment here as that first chunk of reply.
--D
> ext2fs_mark_block_bitmap2(bmap, new_desc_blk);
> + }
>
> num_blocks = ext2fs_group_blocks_count(fs, group);
> num_blocks -= 2 + fs->inode_blocks_per_group + used_blks;
>
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