linux-kernel - Re: [PATCH] mm/vmalloc: move 'area->pages' after if statement

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Date:   Tue, 3 Sep 2019 06:28:08 +0900
From:   Austin Kim <austindh.kim@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     urezki@...il.com, guro@...com, rpenyaev@...e.de, mhocko@...e.com,
        rick.p.edgecombe@...el.com, rppt@...ux.ibm.com,
        aryabinin@...tuozzo.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/vmalloc: move 'area->pages' after if statement

2019년 8월 31일 (토) 오전 5:50, Andrew Morton <akpm@...ux-foundation.org>님이 작성:
>
> On Fri, 30 Aug 2019 12:57:16 +0900 Austin Kim <austindh.kim@...il.com> wrote:
>
> > If !area->pages statement is true where memory allocation fails,
> > area is freed.
> >
> > In this case 'area->pages = pages' should not executed.
> > So move 'area->pages = pages' after if statement.
> >
> > ...
> >
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2416,13 +2416,15 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> >       } else {
> >               pages = kmalloc_node(array_size, nested_gfp, node);
> >       }
> > -     area->pages = pages;
> > -     if (!area->pages) {
> > +
> > +     if (!pages) {
> >               remove_vm_area(area->addr);
> >               kfree(area);
> >               return NULL;
> >       }
> >
> > +     area->pages = pages;
> > +
> >       for (i = 0; i < area->nr_pages; i++) {
> >               struct page *page;
> >
>
> Fair enough.  But we can/should also do this?

I agreed since it is the same treatment.
Thanks for feedback.

>
> --- a/mm/vmalloc.c~mm-vmalloc-move-area-pages-after-if-statement-fix
> +++ a/mm/vmalloc.c
> @@ -2409,7 +2409,6 @@ static void *__vmalloc_area_node(struct
>         nr_pages = get_vm_area_size(area) >> PAGE_SHIFT;
>         array_size = (nr_pages * sizeof(struct page *));
>
> -       area->nr_pages = nr_pages;
>         /* Please note that the recursion is strictly bounded. */
>         if (array_size > PAGE_SIZE) {
>                 pages = __vmalloc_node(array_size, 1, nested_gfp|highmem_mask,
> @@ -2425,6 +2424,7 @@ static void *__vmalloc_area_node(struct
>         }
>
>         area->pages = pages;
> +       area->nr_pages = nr_pages;
>
>         for (i = 0; i < area->nr_pages; i++) {
>                 struct page *page;
> _
>