This is a note to let you know that I've just added the patch titled

cma: fix calculation of aligned offset

to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: cma-fix-calculation-of-aligned-offset.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From e048cb32f69038aa1c8f11e5c1b331be4181659d Mon Sep 17 00:00:00 2001

From: Doug Berger opendmb@gmail.com Date: Mon, 10 Jul 2017 15:49:44 -0700 Subject: cma: fix calculation of aligned offset

From: Doug Berger opendmb@gmail.com

commit e048cb32f69038aa1c8f11e5c1b331be4181659d upstream.

The align_offset parameter is used by bitmap_find_next_zero_area_off() to represent the offset of map's base from the previous alignment boundary; the function ensures that the returned index, plus the align_offset, honors the specified align_mask.

The logic introduced by commit b5be83e308f7 ("mm: cma: align to physical address, not CMA region position") has the cma driver calculate the offset to the *next* alignment boundary. In most cases, the base alignment is greater than that specified when making allocations, resulting in a zero offset whether we align up or down. In the example given with the commit, the base alignment (8MB) was half the requested alignment (16MB) so the math also happened to work since the offset is 8MB in both directions. However, when requesting allocations with an alignment greater than twice that of the base, the returned index would not be correctly aligned.

Also, the align_order arguments of cma_bitmap_aligned_mask() and cma_bitmap_aligned_offset() should not be negative so the argument type was made unsigned.

Fixes: b5be83e308f7 ("mm: cma: align to physical address, not CMA region position") Link: http://lkml.kernel.org/r/20170628170742.2895-1-opendmb@gmail.com Signed-off-by: Angus Clark angus@angusclark.org Signed-off-by: Doug Berger opendmb@gmail.com Acked-by: Gregory Fong gregory.0xf0@gmail.com Cc: Doug Berger opendmb@gmail.com Cc: Angus Clark angus@angusclark.org Cc: Laura Abbott labbott@redhat.com Cc: Vlastimil Babka vbabka@suse.cz Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Lucas Stach l.stach@pengutronix.de Cc: Catalin Marinas catalin.marinas@arm.com Cc: Shiraz Hashim shashim@codeaurora.org Cc: Jaewon Kim jaewon31.kim@samsung.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Vlastimil Babka vbabka@suse.cz Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- mm/cma.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-)

--- a/mm/cma.c +++ b/mm/cma.c @@ -54,7 +54,7 @@ unsigned long cma_get_size(const struct }

static unsigned long cma_bitmap_aligned_mask(const struct cma *cma, - int align_order) + unsigned int align_order) { if (align_order <= cma->order_per_bit) return 0; @@ -62,17 +62,14 @@ static unsigned long cma_bitmap_aligned_ }

/* - * Find a PFN aligned to the specified order and return an offset represented in - * order_per_bits. + * Find the offset of the base PFN from the specified align_order. + * The value returned is represented in order_per_bits. */ static unsigned long cma_bitmap_aligned_offset(const struct cma *cma, - int align_order) + unsigned int align_order) { - if (align_order <= cma->order_per_bit) - return 0; - - return (ALIGN(cma->base_pfn, (1UL << align_order)) - - cma->base_pfn) >> cma->order_per_bit; + return (cma->base_pfn & ((1UL << align_order) - 1)) + >> cma->order_per_bit; }

static unsigned long cma_bitmap_pages_to_bits(const struct cma *cma,

Patches currently in stable-queue which might be from opendmb@gmail.com are

queue-4.9/cma-fix-calculation-of-aligned-offset.patch