Re: [PATCHv5 04/16] VFS: add memory barrier to sb_mark_clean and sb_mark_dirty

[Artem Bityutskiy <dedekind1@gmail.com>]

On Sun, 2010-06-06 at 20:16 +0300, Artem Bityutskiy wrote:
> On Sun, 2010-06-06 at 17:50 +0300, Artem Bityutskiy wrote:
> >  void sb_mark_dirty(struct super_block *sb);
> >  static inline void sb_mark_clean(struct super_block *sb)
> >  {
> >  	sb->s_dirty = 0;
> > +	/*
> > +	 * Normally FSes first unset the sb->s_dirty flag, and then start
> > +	 * synchronizing the SB. The memory barrier ensures this order.
> > +	 */
> > +	smp_mb();
> ...
> >  void sb_mark_dirty(struct super_block *sb)
> >  {
> > +	/*
> > +	 * Normally FSes modify the SB, and then mark it as dirty. The memory
> > +	 * barrier ensures this order.
> > +	 */
> > +	smp_mb();
> ...
> 
> Hmm, these ones should be 'mb()', not 'smp_mb()'.

Actually no, sorry, I completely missed that all memory barriers are a
compiler barriers. I thought smp_mb() is nought, which is not true -
smp_mb() is a barrier() on UP.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)

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