Re: [PATCH 1/2] ext4: update s_overhead_clusters in the superblock during an on-line resize

From: Andreas Dilger <adilger@dilger.ca>
To: Theodore Ts'o <tytso@mit.edu>
Cc: Ext4 Developers List <linux-ext4@vger.kernel.org>, stable@kernel.org
Subject: Re: [PATCH 1/2] ext4: update s_overhead_clusters in the superblock during an on-line resize
Date: Mon, 4 Jul 2022 14:47:43 -0600	[thread overview]
Message-ID: <2F240021-C24A-4F86-ACDA-2FF944F9FE6F@dilger.ca> (raw)
In-Reply-To: <20220629040026.112371-1-tytso@mit.edu>

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On Jun 28, 2022, at 10:00 PM, Theodore Ts'o <tytso@mit.edu> wrote:
> 
> When doing an online resize, the on-disk superblock on-disk wasn't
> updated.  This means that when the file system is unmounted and
> remounted, and the on-disk overhead value is non-zero, this would
> result in the results of statfs(2) to be incorrect.
> 
> This was partially fixed by Commits 10b01ee92df5 ("ext4: fix overhead
> calculation to account for the reserved gdt blocks"), 85d825dbf489
> ("ext4: force overhead calculation if the s_overhead_cluster makes no
> sense"), and eb7054212eac ("ext4: update the cached overhead value in
> the superblock").

Would these be better referenced by Fixes: labels?

> However, since it was too expensive to forcibly recalculate the
> overhead for bigalloc file systems at every mount, this didn't fix the
> problem for bigalloc file systems.  This commit should address the
> problem when resizing file systems with the bigalloc feature enabled.
> 
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> Cc: stable@kernel.org

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

> ---
> fs/ext4/resize.c | 1 +
> 1 file changed, 1 insertion(+)
> 
> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index 8b70a4701293..e5c2713aa11a 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -1484,6 +1484,7 @@ static void ext4_update_super(struct super_block *sb,
> 	 * Update the fs overhead information
> 	 */
> 	ext4_calculate_overhead(sb);
> +	es->s_overhead_clusters = cpu_to_le32(sbi->s_overhead);
> 
> 	if (test_opt(sb, DEBUG))
> 		printk(KERN_DEBUG "EXT4-fs: added group %u:"
> --
> 2.31.0
> 

Cheers, Andreas

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