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

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Message-ID: <ZtFShfK/bj9WOShI@li-bb2b2a4c-3307-11b2-a85c-8fa5c3a69313.ibm.com>
Date: Fri, 30 Aug 2024 10:33:01 +0530
From: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
To: Ritesh Harjani <ritesh.list@...il.com>
Cc: linux-ext4@...r.kernel.org, "Theodore Ts'o" <tytso@....edu>,
        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

On Wed, Aug 28, 2024 at 03:03:39PM +0530, Ritesh Harjani wrote:
> 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>

Thanks for the review Ritesh, I'll fix these in next revision

> 
> >
> > 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