Re: [PATCH 01/01] quota: atomic dq_flags operations in do_set_dqblk

[Jan Kara <jack@suse.cz>]

On Mon 12-04-10 22:16:50, Andrew Perepechko wrote:
> From: Andrew Perepechko <andrew.perepechko@sun.com>
> 
> Non-atomic __set_bit calls are replaced with atomic set_bit calls in do_set_dqblk
> so that individual bits should not be lost in a possible race condition.
  I took a liberty of modifying the changelog to be more descriptive:

quota: Fix possible dq_flags corruption
    
dq_flags are modified non-atomically in do_set_dqblk via __set_bit calls
and atomically for example in mark_dquot_dirty or clear_dquot_dirty.  Hence
a change done by an atomic operation can be overwritten by a change done by
a non-atomic one. Fix the problem by using atomic bitops even in
do_set_dqblk.

  Otherwise I've merged the patch.

								Honza

> Signed-off-by: Andrew Perepechko <andrew.perepechko@sun.com>
> ---
> diff -puN fs/dquot.c fs/dquot.c
> --- a/fs/dquot.c
> +++ b/fs/dquot.c
> @@ -2065,32 +2065,32 @@ static int do_set_dqblk(struct dquot *dq
>  	if (di->dqb_valid & QIF_SPACE) {
>  		dm->dqb_curspace = di->dqb_curspace;
>  		check_blim = 1;
> -		__set_bit(DQ_LASTSET_B + QIF_SPACE_B, &dquot->dq_flags);
> +		set_bit(DQ_LASTSET_B + QIF_SPACE_B, &dquot->dq_flags);
>  	}
>  	if (di->dqb_valid & QIF_BLIMITS) {
>  		dm->dqb_bsoftlimit = qbtos(di->dqb_bsoftlimit);
>  		dm->dqb_bhardlimit = qbtos(di->dqb_bhardlimit);
>  		check_blim = 1;
> -		__set_bit(DQ_LASTSET_B + QIF_BLIMITS_B, &dquot->dq_flags);
> +		set_bit(DQ_LASTSET_B + QIF_BLIMITS_B, &dquot->dq_flags);
>  	}
>  	if (di->dqb_valid & QIF_INODES) {
>  		dm->dqb_curinodes = di->dqb_curinodes;
>  		check_ilim = 1;
> -		__set_bit(DQ_LASTSET_B + QIF_INODES_B, &dquot->dq_flags);
> +		set_bit(DQ_LASTSET_B + QIF_INODES_B, &dquot->dq_flags);
>  	}
>  	if (di->dqb_valid & QIF_ILIMITS) {
>  		dm->dqb_isoftlimit = di->dqb_isoftlimit;
>  		dm->dqb_ihardlimit = di->dqb_ihardlimit;
>  		check_ilim = 1;
> -		__set_bit(DQ_LASTSET_B + QIF_ILIMITS_B, &dquot->dq_flags);
> +		set_bit(DQ_LASTSET_B + QIF_ILIMITS_B, &dquot->dq_flags);
>  	}
>  	if (di->dqb_valid & QIF_BTIME) {
>  		dm->dqb_btime = di->dqb_btime;
> -		__set_bit(DQ_LASTSET_B + QIF_BTIME_B, &dquot->dq_flags);
> +		set_bit(DQ_LASTSET_B + QIF_BTIME_B, &dquot->dq_flags);
>  	}
>  	if (di->dqb_valid & QIF_ITIME) {
>  		dm->dqb_itime = di->dqb_itime;
> -		__set_bit(DQ_LASTSET_B + QIF_ITIME_B, &dquot->dq_flags);
> +		set_bit(DQ_LASTSET_B + QIF_ITIME_B, &dquot->dq_flags);
>  	}
>  
>  	if (check_blim) {
-- 
Jan Kara <jack@suse.cz>
SUSE Labs, CR