Re: [PATCH 2/6] lightnvm: pblk: protect line bitmap while submitting meta io

[Matias BjÃrling]

On 09/22/2017 10:49 AM, Javier GonzÃlez wrote:
> > On 21 Sep 2017, at 13.26, Rakesh Pandit <rakesh@xxxxxxxxxx> wrote:
> >
> > It seems pblk_dealloc_page would race against pblk_alloc_pages for
> > line bitmap for sector allocation.  The chances are very low but might
> > as well protect the bitmap properly.  It's not even in fast path.
> >
> > Signed-off-by: Rakesh Pandit <rakesh@xxxxxxxxxx>
> > ---
> > drivers/lightnvm/pblk-core.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
> > index a230125..b92eabc 100644
> > --- a/drivers/lightnvm/pblk-core.c
> > +++ b/drivers/lightnvm/pblk-core.c
> > @@ -502,12 +502,14 @@ void pblk_dealloc_page(struct pblk *pblk, struct pblk_line *line, int nr_secs)
> > 	u64 addr;
> > 	int i;
> >
> > +	spin_lock(&line->lock);
> > 	addr = find_next_zero_bit(line->map_bitmap,
> > 					pblk->lm.sec_per_line, line->cur_sec);
> > 	line->cur_sec = addr - nr_secs;
> >
> > 	for (i = 0; i < nr_secs; i++, line->cur_sec--)
> > 		WARN_ON(!test_and_clear_bit(line->cur_sec, line->map_bitmap));
> > +	spin_lock(&line->lock);
> > }
> >
> > u64 __pblk_alloc_page(struct pblk *pblk, struct pblk_line *line, int nr_secs)
> > --
> > 2.5.0
>
> Looks good. The reason not to have locks here was that the caller is
> always on the write thread - who did the allocation -, since it is error
> handling. So there is no protection needed. In any case, it is better to
> have it since it is implemented as a helper function.
>
>
> Reviewed-by: Javier GonzÃlez <javier@xxxxxxxxxxxx>

Thanks, I picked it up.