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From:   Andreas Dilger <adilger@dilger.ca>
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Subject: Re: [PATCH] tune2fs: Update overhead when toggling journal feature
Date:   Mon, 14 Jun 2021 15:38:57 -0600
In-Reply-To: <20210614212830.20207-1-jack@suse.cz>
Cc:     Ted Tso <tytso@mit.edu>,
        Ext4 Developers List <linux-ext4@vger.kernel.org>
To:     Jan Kara <jack@suse.cz>
References: <20210614212830.20207-1-jack@suse.cz>
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> On Jun 14, 2021, at 3:28 PM, Jan Kara <jack@suse.cz> wrote:
> 
> When adding or removing journal from a filesystem, we also need to add /
> remove journal blocks from overhead stored in the superblock.  Otherwise
> total number of blocks in the filesystem as reported by statfs(2) need
> not match reality and could lead to odd results like negative number of
> used blocks reported by df(1).
> 
> Signed-off-by: Jan Kara <jack@suse.cz>

You could add:

Fixes: 9046b4dfd0ce ("mke2fs: set overhead in super block")

and

Reviewed-by: Andreas Dilger <adilger@dilger.ca>

That also makes me wonder if resize2fs also needs to recalculate or
invalidate the s_overhead_clusters field when adding new block groups.
It *looks* like that is done correctly in adjust_fs_info() already?

Cheers, Andreas

> ---
> misc/tune2fs.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/misc/tune2fs.c b/misc/tune2fs.c
> index 4d4cf5a13384..2f6858abda32 100644
> --- a/misc/tune2fs.c
> +++ b/misc/tune2fs.c
> @@ -396,6 +396,8 @@ static errcode_t remove_journal_inode(ext2_filsys fs)
> 				_("while clearing journal inode"));
> 			return retval;
> 		}
> +		fs->super->s_overhead_clusters -=
> +			EXT2FS_NUM_B2C(fs, EXT2_I_SIZE(&inode) / fs->blocksize);
> 		memset(&inode, 0, sizeof(inode));
> 		ext2fs_mark_bb_dirty(fs);
> 		fs->flags &= ~EXT2_FLAG_SUPER_ONLY;
> @@ -1663,8 +1665,12 @@ static int add_journal(ext2_filsys fs)
> 			com_err(program_name, retval, "%s",
> 				_("\n\twhile trying to create journal file"));
> 			return retval;
> -		} else
> -			fputs(_("done\n"), stdout);
> +		}
> +		fs->super->s_overhead_clusters += EXT2FS_NUM_B2C(fs,
> +			jparams.num_journal_blocks + jparams.num_fc_blocks);
> +		ext2fs_mark_super_dirty(fs);
> +		fputs(_("done\n"), stdout);
> +
> 		/*
> 		 * If the filesystem wasn't mounted, we need to force
> 		 * the block group descriptors out.
> --
> 2.26.2
> 


Cheers, Andreas


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