linux-ext4 - Re: [PATCH 2/2] resize2fs: fix overhead calculation for meta

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Date:	Tue, 4 Sep 2012 09:59:55 +0800
From:	Yongqiang Yang <xiaoqiangnk@...il.com>
To:	Kevin Liao <kevinlia@...il.com>
Cc:	Ext4 Developers List <linux-ext4@...r.kernel.org>,
	"Theodore Ts'o" <tytso@....edu>
Subject: Re: [PATCH 2/2] resize2fs: fix overhead calculation for meta_bg file systems

Hi Kevin,

  Ted has sent out the patches on online resizing for meta_bg and
64bits, so you can have a try again. It seems that the bug in
e2fsprogs has been fixed.

Yongqiang.

On Tue, Sep 4, 2012 at 12:45 AM, Theodore Ts'o <tytso@....edu> wrote:
> The file system overhead calculation in calculate_minimum_resize_size
> was incorrect meta_bg file systems.  This caused the minimum size to
> underflow for very large file systems, which threw resize2fs into a
> loop generally lasted longer than the user's patience.
>
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> ---
>  resize/resize2fs.c | 25 ++++++++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)
>
> diff --git a/resize/resize2fs.c b/resize/resize2fs.c
> index dc2805d..1dce498 100644
> --- a/resize/resize2fs.c
> +++ b/resize/resize2fs.c
> @@ -1890,6 +1890,8 @@ blk64_t calculate_minimum_resize_size(ext2_filsys fs)
>         blk64_t grp, data_needed, last_start;
>         blk64_t overhead = 0;
>         int num_of_superblocks = 0;
> +       blk64_t super_overhead = 0;
> +       int old_desc_blocks;
>         int extra_groups = 0;
>         int flexbg_size = 1 << fs->super->s_log_groups_per_flex;
>
> @@ -1909,15 +1911,36 @@ blk64_t calculate_minimum_resize_size(ext2_filsys fs)
>          * we need to figure out how many backup superblocks we have so we can
>          * account for that in the metadata
>          */
> +       if (fs->super->s_feature_incompat & EXT2_FEATURE_INCOMPAT_META_BG)
> +               old_desc_blocks = fs->super->s_first_meta_bg;
> +       else
> +               old_desc_blocks = fs->desc_blocks +
> +                       fs->super->s_reserved_gdt_blocks;
> +
>         for (grp = 0; grp < fs->group_desc_count; grp++) {
> +               blk64_t super_blk, old_desc_blk, new_desc_blk;
> +               int has_super;
> +
> +               ext2fs_super_and_bgd_loc2(fs, grp, &super_blk,
> +                                         &old_desc_blk, &new_desc_blk, 0);
> +               has_super = ((grp == 0) || super_blk);
> +               if (has_super)
> +                       super_overhead++;
> +               if (old_desc_blk)
> +                       super_overhead += old_desc_blocks;
> +               else if (new_desc_blk)
> +                       super_overhead++;
>                 if (ext2fs_bg_has_super(fs, grp))
>                         num_of_superblocks++;
> +
>         }
> +       printf("super overhead is %llu, old algorithm was %llu\n",
> +              super_overhead, SUPER_OVERHEAD(fs) * num_of_superblocks);
>
>         /* calculate how many blocks are needed for data */
>         data_needed = ext2fs_blocks_count(fs->super) -
>                 ext2fs_free_blocks_count(fs->super);
> -       data_needed -= SUPER_OVERHEAD(fs) * num_of_superblocks;
> +       data_needed -= super_overhead;
>         data_needed -= META_OVERHEAD(fs) * fs->group_desc_count;
>
>         if (fs->super->s_feature_incompat & EXT4_FEATURE_INCOMPAT_FLEX_BG) {
> --
> 1.7.12.rc0.22.gcdd159b
>
> --
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-- 
Best Wishes
Yongqiang Yang
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