[Cluster-devel] [GFS2 PATCH 2/2] gfs2: limit quota log messages

[Bob Peterson <rpeterso@redhat.com>]

Hi,

Comment embedded below:

----- Original Message -----
> This patch makes the quota subsystem only report once that a
> particular user/group has exceeded their allotted quota.
> 
> Previously, it was possible for a program to continuously try
> exceeding quota (despite receiving EDQUOT) and in turn trigger
> gfs2 to issue a kernel log message about quota exceed. In theory,
> this could get out of hand and flood the log and the filesystem
> hosting the log files.
> 
> Resolves: rhbz#1174295
> Signed-off-by: Abhi Das <adas@redhat.com>
> ---
>  fs/gfs2/incore.h |  1 +
>  fs/gfs2/quota.c  | 13 +++++++++----
>  2 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/gfs2/incore.h b/fs/gfs2/incore.h
> index 58b75ab..304a223 100644
> --- a/fs/gfs2/incore.h
> +++ b/fs/gfs2/incore.h
> @@ -432,6 +432,7 @@ enum {
>  	QDF_CHANGE		= 1,
>  	QDF_LOCKED		= 2,
>  	QDF_REFRESH		= 3,
> +	QDF_QMSG_QUIET          = 4,
>  };
>  
>  struct gfs2_quota_data {
> diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
> index 01f4d40..3dc13b53 100644
> --- a/fs/gfs2/quota.c
> +++ b/fs/gfs2/quota.c
> @@ -649,6 +649,8 @@ static void do_qc(struct gfs2_quota_data *qd, s64 change)
>  		slot_hold(qd);
>  	}
>  
> +	if (change < 0) /* Reset quiet flag if we freed some blocks */
> +		clear_bit(QDF_QMSG_QUIET, &qd->qd_flags);
>  	mutex_unlock(&sdp->sd_quota_mutex);
>  }
>  
> @@ -1187,10 +1189,13 @@ int gfs2_quota_check(struct gfs2_inode *ip, kuid_t
> uid, kgid_t gid,
>  			/* If no min_target specified or we don't meet
>  			 * min_target, return -EDQUOT */
>  			if (!ap->min_target || ap->min_target > ap->allowed) {
> -				print_message(qd, "exceeded");
> -				quota_send_warning(qd->qd_id,
> -						   sdp->sd_vfs->s_dev,
> -						   QUOTA_NL_BHARDWARN);
> +				if (!test_bit(QDF_QMSG_QUIET, &qd->qd_flags)) {
> +					print_message(qd, "exceeded");
> +					quota_send_warning(qd->qd_id,
> +							   sdp->sd_vfs->s_dev,
> +							   QUOTA_NL_BHARDWARN);
> +					set_bit(QDF_QMSG_QUIET, &qd->qd_flags);
> +				}

Looks good, except that this is a perfect place to use test_and_set_bit().

I don't know the gfs2 quota code like you do, but does the bit also need to
be cleared if the user's quotas are increased?

Regards,

Bob Peterson
Red Hat File Systems