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mm: maintain randomization of page free lists

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When freeing a page with an order >= shuffle_page_order randomly select
the front or back of the list for insertion.

While the mm tries to defragment physical pages into huge pages this can
tend to make the page allocator more predictable over time.  Inject the
front-back randomness to preserve the initial randomness established by
shuffle_free_memory() when the kernel was booted.

The overhead of this manipulation is constrained by only being applied
for MAX_ORDER sized pages by default.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/154899812788.3165233.9066631950746578517.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Robert Elliott <elliott@hpe.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dan Williams 2019-05-14 15:41:35 -07:00 • committed by Linus Torvalds
parent b03641af68
commit 97500a4a54
4 changed files with 56 additions and 2 deletions
Download patch file Download diff file Expand all files Collapse all files

12
include/linux/mmzone.h
View file

@ -116,6 +116,18 @@ static inline void add_to_free_area_tail(struct page *page, struct free_area *ar
area->nr_free++;
}
#ifdef CONFIG_SHUFFLE_PAGE_ALLOCATOR
/* Used to preserve page allocation order entropy */
void add_to_free_area_random(struct page *page, struct free_area *area,
int migratetype);
#else
static inline void add_to_free_area_random(struct page *page,
struct free_area *area, int migratetype)
{
add_to_free_area(page, area, migratetype);
}
#endif
/* Used for pages which are on another list */
static inline void move_to_free_area(struct page *page, struct free_area *area,
int migratetype)