| Message ID | 1415218078-10078-2-git-send-email-gregory.0xf0@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Nov 05 2014, Gregory Fong wrote: > 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. > > Cc: Michal Nazarewicz <mina86@mina86.com> Acked-by: Michal Nazarewicz <mina86@mina86.com> > Signed-off-by: Gregory Fong <gregory.0xf0@gmail.com> > --- > mm/cma.c | 19 ++++++++++++++++--- > 1 file changed, 16 insertions(+), 3 deletions(-) > > diff --git a/mm/cma.c b/mm/cma.c > index fde706e..0813599 100644 > --- a/mm/cma.c > +++ b/mm/cma.c > @@ -63,6 +63,17 @@ static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order) > 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; > @@ -328,7 +339,7 @@ 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; > @@ -343,13 +354,15 @@ struct page *cma_alloc(struct cma *cma, int count, unsigned int align) > 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; > -- > 1.9.1 >
diff --git a/mm/cma.c b/mm/cma.c index fde706e..0813599 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -63,6 +63,17 @@ static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order) 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; @@ -328,7 +339,7 @@ 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; @@ -343,13 +354,15 @@ struct page *cma_alloc(struct cma *cma, int count, unsigned int align) 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;
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. Cc: Michal Nazarewicz <mina86@mina86.com> Signed-off-by: Gregory Fong <gregory.0xf0@gmail.com> --- mm/cma.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-)