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

[Andrew Perepechko <Andrew.Perepechko@Sun.COM>]

Thanks a lot, Jan!

Andrew.

On Monday 12 April 2010 11:09:17 pm Jan Kara wrote:
> 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) {