linux-kernel - Re: [PATCH] quota: don't let mark_dquot

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Message-ID: <20240408143043.65yowy2yvf46weab@quack3>
Date: Mon, 8 Apr 2024 16:30:43 +0200
From: Jan Kara <jack@...e.cz>
To: Chao Yu <chao@...nel.org>
Cc: jack@...e.com, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] quota: don't let mark_dquot_dirty() fail silently

On Sun 07-04-24 15:31:28, Chao Yu wrote:
> mark_dquot_dirty() will callback to specified filesystem function,
> it may fail due to any reasons, however, no caller will check return
> value of mark_dquot_dirty(), so, it may fail silently, let's print
> one line message for such case.
> 
> Signed-off-by: Chao Yu <chao@...nel.org>
> ---
>  fs/quota/dquot.c | 23 +++++++++++++----------
>  1 file changed, 13 insertions(+), 10 deletions(-)
> 
> diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
> index dacbee455c03..c5df7863942a 100644
> --- a/fs/quota/dquot.c
> +++ b/fs/quota/dquot.c
> @@ -399,21 +399,20 @@ int dquot_mark_dquot_dirty(struct dquot *dquot)
>  EXPORT_SYMBOL(dquot_mark_dquot_dirty);
>  
>  /* Dirtify all the dquots - this can block when journalling */
> -static inline int mark_all_dquot_dirty(struct dquot __rcu * const *dquots)
> +static inline void mark_all_dquot_dirty(struct dquot __rcu * const *dquots)
>  {
> -	int ret, err, cnt;
> +	int ret, cnt;
>  	struct dquot *dquot;
>  
> -	ret = err = 0;
>  	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
>  		dquot = srcu_dereference(dquots[cnt], &dquot_srcu);
> -		if (dquot)
> -			/* Even in case of error we have to continue */
> -			ret = mark_dquot_dirty(dquot);
> -		if (!err)
> -			err = ret;
> +		if (!dquot)
> +			continue;
> +		ret = mark_dquot_dirty(dquot);
> +		if (ret < 0)
> +			quota_error(dquot->dq_sb,
> +				"mark_all_dquot_dirty fails, ret: %d", ret);

Do you have any practical case you care about? Because in practice the
filesystem will usually report if there's some catastrophic error (and the
errors from ->mark_dirty() all mean the filesystem is in unhealthy state).
So this message just adds to the noise in the error log - and e.g. if the
disk goes bad so we cannot write, we could spew a lot of messages like
this.

>  	}
> -	return err;
>  }
>  
>  static inline void dqput_all(struct dquot **dquot)
> @@ -2725,6 +2724,7 @@ static int do_set_dqblk(struct dquot *dquot, struct qc_dqblk *di)
>  {
>  	struct mem_dqblk *dm = &dquot->dq_dqb;
>  	int check_blim = 0, check_ilim = 0;
> +	int ret;
>  	struct mem_dqinfo *dqi = &sb_dqopt(dquot->dq_sb)->info[dquot->dq_id.type];
>  
>  	if (di->d_fieldmask & ~VFS_QC_MASK)
> @@ -2807,7 +2807,10 @@ static int do_set_dqblk(struct dquot *dquot, struct qc_dqblk *di)
>  	else
>  		set_bit(DQ_FAKE_B, &dquot->dq_flags);
>  	spin_unlock(&dquot->dq_dqb_lock);
> -	mark_dquot_dirty(dquot);
> +	ret = mark_dquot_dirty(dquot);
> +	if (ret < 0)
> +		quota_error(dquot->dq_sb,
> +			"mark_dquot_dirty fails, ret: %d", ret);

Here, we can propagate the error back to userspace, which is probably
better than spamming the logs.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR