linux-kernel - Re: [PATCH] mm/sparse.c: fix error path in sparse_add_one

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Date:   Fri, 6 Jul 2018 15:54:37 -0600
From:   Ross Zwisler <ross.zwisler@...ux.intel.com>
To:     Oscar Salvador <osalvador@...hadventures.net>
Cc:     Ross Zwisler <ross.zwisler@...ux.intel.com>,
        pasha.tatashin@...cle.com, linux-nvdimm@...ts.01.org,
        bhe@...hat.com, Dave Hansen <dave.hansen@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>, Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        osalvador@...e.de
Subject: Re: [PATCH] mm/sparse.c: fix error path in sparse_add_one_section

On Fri, Jul 06, 2018 at 11:23:27PM +0200, Oscar Salvador wrote:
> On Fri, Jul 06, 2018 at 01:06:58PM -0600, Ross Zwisler wrote:
> > The following commit in -next:
> > 
> > commit 054620849110 ("mm/sparse.c: make sparse_init_one_section void and
> > remove check")
> > 
> > changed how the error handling in sparse_add_one_section() works.
> > 
> > Previously sparse_index_init() could return -EEXIST, and the function would
> > continue on happily.  'ret' would get unconditionally overwritten by the
> > result from sparse_init_one_section() and the error code after the 'out:'
> > label wouldn't be triggered.
> 
> My bad, I missed that.
> 
> > diff --git a/mm/sparse.c b/mm/sparse.c
> > index 9574113fc745..d254bd2d3289 100644
> > --- a/mm/sparse.c
> > +++ b/mm/sparse.c
> > @@ -753,8 +753,12 @@ int __meminit sparse_add_one_section(struct pglist_data *pgdat,
> >  	 * plus, it does a kmalloc
> >  	 */
> >  	ret = sparse_index_init(section_nr, pgdat->node_id);
> > -	if (ret < 0 && ret != -EEXIST)
> > -		return ret;
> > +	if (ret < 0) {
> > +		if (ret == -EEXIST)
> > +			ret = 0;
> > +		else
> > +			return ret;
> > +	}
> 
> sparse_index_init() can return:
> 
> -ENOMEM, -EEXIST or 0.
> 
> So what about this?:
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index f55e79fda03e..eb188eb6b82d 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -770,6 +770,7 @@ int __meminit sparse_add_one_section(struct pglist_data *pgdat,
>         ret = sparse_index_init(section_nr, pgdat->node_id);
>         if (ret < 0 && ret != -EEXIST)
>                 return ret;
> +       ret = 0;
> 
> Does this look more clean?

Sure, that's probably better.

Andrew, what's the easiest way forward?  I can send out a v2, you can fold
this into his previous patch, or something else?