This is a note to let you know that I've just added the patch titled mm: cma: align to physical address, not CMA region position to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: mm-cma-align-to-physical-address-not-cma-region-position.patch and it can be found in the queue-3.18 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From b5be83e308f70e16c63c4e520ea7bb03ef57c46f Mon Sep 17 00:00:00 2001 From: Gregory Fong <gregory.0xf0@xxxxxxxxx> Date: Fri, 12 Dec 2014 16:54:48 -0800 Subject: mm: cma: align to physical address, not CMA region position From: Gregory Fong <gregory.0xf0@xxxxxxxxx> commit b5be83e308f70e16c63c4e520ea7bb03ef57c46f upstream. The alignment in cma_alloc() was done w.r.t. the bitmap. This is a problem when, for example: - a device requires 16M (order 12) alignment - the CMA region is not 16 M aligned In such a case, can result with the CMA region starting at, say, 0x2f800000 but any allocation you make from there will be aligned from there. Requesting an allocation of 32 M with 16 M alignment will result in an allocation from 0x2f800000 to 0x31800000, which doesn't work very well if your strange device requires 16M alignment. Change to use bitmap_find_next_zero_area_off() to account for the difference in alignment at reserve-time and alloc-time. Signed-off-by: Gregory Fong <gregory.0xf0@xxxxxxxxx> Acked-by: Michal Nazarewicz <mina86@xxxxxxxxxx> Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: Kukjin Kim <kgene.kim@xxxxxxxxxxx> Cc: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx> Cc: Laura Abbott <lauraa@xxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- mm/cma.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) --- a/mm/cma.c +++ b/mm/cma.c @@ -63,6 +63,17 @@ static unsigned long cma_bitmap_aligned_ return (1UL << (align_order - cma->order_per_bit)) - 1; } +static unsigned long cma_bitmap_aligned_offset(struct cma *cma, int align_order) +{ + unsigned int alignment; + + if (align_order <= cma->order_per_bit) + return 0; + alignment = 1UL << (align_order - cma->order_per_bit); + return ALIGN(cma->base_pfn, alignment) - + (cma->base_pfn >> cma->order_per_bit); +} + static unsigned long cma_bitmap_maxno(struct cma *cma) { return cma->count >> cma->order_per_bit; @@ -341,7 +352,7 @@ err: */ struct page *cma_alloc(struct cma *cma, int count, unsigned int align) { - unsigned long mask, pfn, start = 0; + unsigned long mask, offset, pfn, start = 0; unsigned long bitmap_maxno, bitmap_no, bitmap_count; struct page *page = NULL; int ret; @@ -356,13 +367,15 @@ struct page *cma_alloc(struct cma *cma, return NULL; mask = cma_bitmap_aligned_mask(cma, align); + offset = cma_bitmap_aligned_offset(cma, align); bitmap_maxno = cma_bitmap_maxno(cma); bitmap_count = cma_bitmap_pages_to_bits(cma, count); for (;;) { mutex_lock(&cma->lock); - bitmap_no = bitmap_find_next_zero_area(cma->bitmap, - bitmap_maxno, start, bitmap_count, mask); + bitmap_no = bitmap_find_next_zero_area_off(cma->bitmap, + bitmap_maxno, start, bitmap_count, mask, + offset); if (bitmap_no >= bitmap_maxno) { mutex_unlock(&cma->lock); break; Patches currently in stable-queue which might be from gregory.0xf0@xxxxxxxxx are queue-3.18/lib-bitmap-add-alignment-offset-for-bitmap_find_next_zero_area.patch queue-3.18/mm-cma-fix-cma-aligned-offset-calculation.patch queue-3.18/mm-cma-align-to-physical-address-not-cma-region-position.patch queue-3.18/mm-cma-constify-and-use-correct-signness-in-mm-cma.c.patch