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Date: Mon, 5 Mar 2018 12:31:14 -0800
From: J Freyensee <why2jjj.linux@...il.com>
To: Igor Stoppa <igor.stoppa@...wei.com>, david@...morbit.com,
willy@...radead.org, keescook@...omium.org, mhocko@...nel.org
Cc: labbott@...hat.com, linux-security-module@...r.kernel.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH 3/7] struct page: add field for vm_struct
Reviewed-by: Jay Freyensee <why2jjj.linux@...il.com>
On 2/28/18 12:06 PM, Igor Stoppa wrote:
> When a page is used for virtual memory, it is often necessary to obtain
> a handler to the corresponding vm_struct, which refers to the virtually
> continuous area generated when invoking vmalloc.
>
> The struct page has a "mapping" field, which can be re-used, to store a
> pointer to the parent area.
>
> This will avoid more expensive searches, later on.
>
> Signed-off-by: Igor Stoppa <igor.stoppa@...wei.com>
> ---
> include/linux/mm_types.h | 1 +
> mm/vmalloc.c | 2 ++
> 2 files changed, 3 insertions(+)
>
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> index fd1af6b9591d..c3a4825e10c0 100644
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -84,6 +84,7 @@ struct page {
> void *s_mem; /* slab first object */
> atomic_t compound_mapcount; /* first tail page */
> /* page_deferred_list().next -- second tail page */
> + struct vm_struct *area;
> };
>
> /* Second double word */
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index ebff729cc956..61a1ca22b0f6 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -1536,6 +1536,7 @@ static void __vunmap(const void *addr, int deallocate_pages)
> struct page *page = area->pages[i];
>
> BUG_ON(!page);
> + page->area = NULL;
> __free_pages(page, 0);
> }
>
> @@ -1705,6 +1706,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
> area->nr_pages = i;
> goto fail;
> }
> + page->area = area;
> area->pages[i] = page;
> if (gfpflags_allow_blocking(gfp_mask|highmem_mask))
> cond_resched();
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