linux-kernel - [PATCH 3.18 09/24] mm: cma: align to physical address, not CMA region position

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Date:   Thu, 31 Aug 2017 17:43:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Gregory Fong <gregory.0xf0@...il.com>,
        Michal Nazarewicz <mina86@...a86.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Kukjin Kim <kgene.kim@...sung.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Laura Abbott <lauraa@...eaurora.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3.18 09/24] mm: cma: align to physical address, not CMA region position

3.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gregory Fong <gregory.0xf0@...il.com>

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@...il.com>
Acked-by: Michal Nazarewicz <mina86@...a86.com>
Cc: Marek Szyprowski <m.szyprowski@...sung.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
Cc: Kukjin Kim <kgene.kim@...sung.com>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Laura Abbott <lauraa@...eaurora.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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;