linux-kernel - Re: [PATCH 2/5] mm/sparse: free section usage memory in case populate_section

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Date:   Tue, 18 May 2021 14:43:15 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Dong Aisheng <dongas86@...il.com>
Cc:     Dong Aisheng <aisheng.dong@....com>, linux-mm@...ck.org,
        open list <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/5] mm/sparse: free section usage memory in case
 populate_section_memmap failed

On Tue, May 18, 2021 at 06:25:28PM +0800, Dong Aisheng wrote:
> On Tue, May 18, 2021 at 6:09 PM Mike Rapoport <rppt@...nel.org> wrote:
> >
> > On Mon, May 17, 2021 at 07:20:41PM +0800, Dong Aisheng wrote:
> > > Free section usage memory in case populate_section_memmap failed.
> > > We use map_count to track the remain unused memory to be freed.
> > >
> > > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > > Signed-off-by: Dong Aisheng <aisheng.dong@....com>
> > > ---
> > >  mm/sparse.c | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/mm/sparse.c b/mm/sparse.c
> > > index 7ac481353b6b..98bfacc763da 100644
> > > --- a/mm/sparse.c
> > > +++ b/mm/sparse.c
> > > @@ -549,12 +549,14 @@ static void __init sparse_init_nid(int nid, unsigned long pnum_begin,
> > >                              __func__, nid);
> > >                       pnum_begin = pnum;
> > >                       sparse_buffer_fini();
> > > +                     memblock_free_early(__pa(usage), map_count * mem_section_usage_size());
> >
> > I'd move both sparse_buffer_fini() and freeing of 'usage' memory after the
> > failed label.
> >
> 
> Doing that needs to introduce another 'failed' label.
> Do you think if it's necessary?

In general, it's preferred way of error handling:

https://www.kernel.org/doc/html/latest/process/coding-style.html#centralized-exiting-of-functions
 
> e.g.
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 7ac481353b6b..408b737e168e 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -533,7 +533,7 @@ static void __init sparse_init_nid(int nid,
> unsigned long pnum_begin,
>                         mem_section_usage_size() * map_count);
>         if (!usage) {
>                 pr_err("%s: node[%d] usemap allocation failed", __func__, nid);
> -               goto failed;
> +               goto failed1;
>         }
>         sparse_buffer_init(map_count * section_map_size(), nid);
>         for_each_present_section_nr(pnum_begin, pnum) {
> @@ -548,17 +548,20 @@ static void __init sparse_init_nid(int nid,
> unsigned long pnum_begin,
>                         pr_err("%s: node[%d] memory map backing
> failed. Some memory will not be available.",
>                                __func__, nid);
>                         pnum_begin = pnum;
> -                       sparse_buffer_fini();
> -                       goto failed;
> +                       goto failed2;
>                 }
>                 check_usemap_section_nr(nid, usage);
>                 sparse_init_one_section(__nr_to_section(pnum), pnum, map, usage,
>                                 SECTION_IS_EARLY);
>                 usage = (void *) usage + mem_section_usage_size();
> +               map_count--;
>         }
>         sparse_buffer_fini();
>         return;
> -failed:
> +failed2:
> +       sparse_buffer_fini();
> +       memblock_free_early(__pa(usage), map_count * mem_section_usage_size());
> +failed1:
>         /* We failed to allocate, mark all the following pnums as not present */
>         for_each_present_section_nr(pnum_begin, pnum) {
>                 struct mem_section *ms;
> 
> Regards
> Aisheng
> > >                       goto failed;
> > >               }
> > >               check_usemap_section_nr(nid, usage);
> > >               sparse_init_one_section(__nr_to_section(pnum), pnum, map, usage,
> > >                               SECTION_IS_EARLY);
> > >               usage = (void *) usage + mem_section_usage_size();
> > > +             map_count--;
> > >       }
> > >       sparse_buffer_fini();
> > >       return;
> > > --
> > > 2.25.1
> > >
> > >
> >
> > --
> > Sincerely yours,
> > Mike.

-- 
Sincerely yours,
Mike.