linux-kernel - Re: [PATCH v2 1/2] ext4: Check stripe size compatibility on remount as well

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Message-ID: <87v7zlq9e4.fsf@gmail.com>
Date: Wed, 28 Aug 2024 15:03:39 +0530
From: Ritesh Harjani (IBM) <ritesh.list@...il.com>
To: Ojaswin Mujoo <ojaswin@...ux.ibm.com>, linux-ext4@...r.kernel.org, Theodore Ts'o <tytso@....edu>
Cc: linux-kernel@...r.kernel.org, Kemeng Shi <shikemeng@...weicloud.com>, syzbot+1ad8bac5af24d01e2cbd@...kaller.appspotmail.com
Subject: Re: [PATCH v2 1/2] ext4: Check stripe size compatibility on remount as well

Ojaswin Mujoo <ojaswin@...ux.ibm.com> writes:

> We disable stripe size in __ext4_fill_super if it is not a multiple of
> the cluster ratio however this check is missed when trying to remount.
> This can leave us with cases where stripe < cluster_ratio after
> remount:set making EXT4_B2C(sbi->s_stripe) become 0 that can cause some
> unforeseen bugs like divide by 0.
>
> Fix that by adding the check in remount path as well.
>
> Reported-by: syzbot+1ad8bac5af24d01e2cbd@...kaller.appspotmail.com
> Tested-by: syzbot+1ad8bac5af24d01e2cbd@...kaller.appspotmail.com
> Reviewed-by: Kemeng Shi <shikemeng@...weicloud.com>
> Fixes: c3defd99d58c ("ext4: treat stripe in block unit")
> Signed-off-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
> ---
>  fs/ext4/super.c | 29 ++++++++++++++++++++++-------
>  1 file changed, 22 insertions(+), 7 deletions(-)

Minor nits below, but otherwise looks good to me.

Please feel free to add - 
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>

>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index e72145c4ae5a..9d495d78d262 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -5165,6 +5165,18 @@ static int ext4_block_group_meta_init(struct super_block *sb, int silent)
>  	return 0;
>  }
>  
> +/*
> + * It's hard to get stripe aligned blocks if stripe is not aligned with
> + * cluster, just disable stripe and alert user to simpfy code and avoid

s/simpfy/simplify

> + * stripe aligned allocation which will rarely successes.

s/successes/succeed

-ritesh