Re: [PATCH] lightnvm: pblk: adjust the position of the lock

[Matias BjÃrling]

On 11/27/2018 03:24 PM, Javier Gonzalez wrote:
> > On 27 Nov 2018, at 15.22, Matias BjÃrling <mb@xxxxxxxxxxx> wrote:
> >
> > On 11/27/2018 01:57 PM, Javier Gonzalez wrote:
> > > > On 27 Nov 2018, at 02.53, Hua Su <suhua.tanke@xxxxxxxxx> wrote:
> > > >
> > > > Add lock protection for list operations.
> > > > Signed-off-by: Hua Su <suhua.tanke@xxxxxxxxx>
> > > > ---
> > > > drivers/lightnvm/pblk-core.c | 17 ++++++++++-------
> > > > 1 file changed, 10 insertions(+), 7 deletions(-)
> > > >
> > > > diff --git a/drivers/lightnvm/pblk-core.c b/drivers/lightnvm/pblk-core.c
> > > > index 6944aac43b01..e490df217dac 100644
> > > > --- a/drivers/lightnvm/pblk-core.c
> > > > +++ b/drivers/lightnvm/pblk-core.c
> > > > @@ -1286,24 +1286,27 @@ int pblk_line_recov_alloc(struct pblk *pblk, struct pblk_line *line)
> > > >     list_del(&line->list);
> > > >
> > > >     ret = pblk_line_prepare(pblk, line);
> > > > -    if (ret) {
> > > > -        list_add(&line->list, &l_mg->free_list);
> > > > -        spin_unlock(&l_mg->free_lock);
> > > > -        return ret;
> > > > -    }
> > > > -    spin_unlock(&l_mg->free_lock);
> > > > +    if (ret)
> > > > +        goto out;
> > > >
> > > >     ret = pblk_line_alloc_bitmaps(pblk, line);
> > > >     if (ret)
> > > > -        return ret;
> > > > +        goto out;
> > > >
> > > >     if (!pblk_line_init_bb(pblk, line, 0)) {
> > > >         list_add(&line->list, &l_mg->free_list);
> > > > +        spin_unlock(&l_mg->free_lock);
> > > >         return -EINTR;
> > > >     }
> > > > +    spin_unlock(&l_mg->free_lock);
> > > >
> > > >     pblk_rl_free_lines_dec(&pblk->rl, line, true);
> > > >     return 0;
> > > > +
> > > > +out:
> > > > +    list_add(&line->list, &l_mg->free_list);
> > > > +    spin_unlock(&l_mg->free_lock);
> > > > +    return ret;
> > > > }
> > > >
> > > > void pblk_line_recov_close(struct pblk *pblk, struct pblk_line *line)
> > > > --
> > > > 2.19.1
> > > This path is only touched by the recovery path, which is single
> > > threaded, so there is no race condition as is. Also, if recovery fails,
> > > pblk will not create the instance at all. This said, it would be
> > > good to protect the list_add on the pblk_line_init_bb() error path in
> > > case this code is used for some other purpose in the future.
> >
> > I like your explanation here. Another option is that we could add a comment to notify the developer that it safe in this context?
>
> Sure. Do you want to add it? Or should I send it?
>
> Javier

Please send it. Thanks!