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    SubjectRe: [PATCH v3 -next 5/9] CMA: generalize CMA reserved area management functionality
    Hello,

    On 2014-06-16 07:40, Joonsoo Kim wrote:
    > Currently, there are two users on CMA functionality, one is the DMA
    > subsystem and the other is the KVM on powerpc. They have their own code
    > to manage CMA reserved area even if they looks really similar.
    > >From my guess, it is caused by some needs on bitmap management. KVM side
    > wants to maintain bitmap not for 1 page, but for more size. Eventually it
    > use bitmap where one bit represents 64 pages.
    >
    > When I implement CMA related patches, I should change those two places
    > to apply my change and it seem to be painful to me. I want to change
    > this situation and reduce future code management overhead through
    > this patch.
    >
    > This change could also help developer who want to use CMA in their
    > new feature development, since they can use CMA easily without
    > copying & pasting this reserved area management code.
    >
    > In previous patches, we have prepared some features to generalize
    > CMA reserved area management and now it's time to do it. This patch
    > moves core functions to mm/cma.c and change DMA APIs to use
    > these functions.
    >
    > There is no functional change in DMA APIs.
    >
    > v2: There is no big change from v1 in mm/cma.c. Mostly renaming.
    > v3: remove log2.h in dma-contiguous.c (Minchan)
    > add some accessor functions to pass aligned base and size to
    > dma_contiguous_early_fixup() function
    > move MAX_CMA_AREAS to cma.h

    I've just noticed that MAX_CMA_AREAS is used also by
    arch/arm/mm/dma-mapping.c,
    so we need to provide correct definition if CMA is disabled in kconfig.
    I will
    send a fixup patch in a few minutes.

    > Acked-by: Michal Nazarewicz <mina86@mina86.com>
    > Acked-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
    > Acked-by: Minchan Kim <minchan@kernel.org>
    > Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
    >
    > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
    > index 4c88935..3116880 100644
    > --- a/arch/arm/mm/dma-mapping.c
    > +++ b/arch/arm/mm/dma-mapping.c
    > @@ -26,6 +26,7 @@
    > #include <linux/io.h>
    > #include <linux/vmalloc.h>
    > #include <linux/sizes.h>
    > +#include <linux/cma.h>
    >
    > #include <asm/memory.h>
    > #include <asm/highmem.h>
    > diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
    > index 00e13ce..4eac559 100644
    > --- a/drivers/base/Kconfig
    > +++ b/drivers/base/Kconfig
    > @@ -283,16 +283,6 @@ config CMA_ALIGNMENT
    >
    > If unsure, leave the default value "8".
    >
    > -config CMA_AREAS
    > - int "Maximum count of the CMA device-private areas"
    > - default 7
    > - help
    > - CMA allows to create CMA areas for particular devices. This parameter
    > - sets the maximum number of such device private CMA areas in the
    > - system.
    > -
    > - If unsure, leave the default value "7".
    > -
    > endif
    >
    > endmenu
    > diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
    > index c6eeb2c..0411c1c 100644
    > --- a/drivers/base/dma-contiguous.c
    > +++ b/drivers/base/dma-contiguous.c
    > @@ -24,25 +24,9 @@
    >
    > #include <linux/memblock.h>
    > #include <linux/err.h>
    > -#include <linux/mm.h>
    > -#include <linux/mutex.h>
    > -#include <linux/page-isolation.h>
    > #include <linux/sizes.h>
    > -#include <linux/slab.h>
    > -#include <linux/swap.h>
    > -#include <linux/mm_types.h>
    > #include <linux/dma-contiguous.h>
    > -#include <linux/log2.h>
    > -
    > -struct cma {
    > - unsigned long base_pfn;
    > - unsigned long count;
    > - unsigned long *bitmap;
    > - unsigned int order_per_bit; /* Order of pages represented by one bit */
    > - struct mutex lock;
    > -};
    > -
    > -struct cma *dma_contiguous_default_area;
    > +#include <linux/cma.h>
    >
    > #ifdef CONFIG_CMA_SIZE_MBYTES
    > #define CMA_SIZE_MBYTES CONFIG_CMA_SIZE_MBYTES
    > @@ -50,6 +34,8 @@ struct cma *dma_contiguous_default_area;
    > #define CMA_SIZE_MBYTES 0
    > #endif
    >
    > +struct cma *dma_contiguous_default_area;
    > +
    > /*
    > * Default global CMA area size can be defined in kernel's .config.
    > * This is useful mainly for distro maintainers to create a kernel
    > @@ -156,169 +142,6 @@ void __init dma_contiguous_reserve(phys_addr_t limit)
    > }
    > }
    >
    > -static DEFINE_MUTEX(cma_mutex);
    > -
    > -static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
    > -{
    > - return (1 << (align_order >> cma->order_per_bit)) - 1;
    > -}
    > -
    > -static unsigned long cma_bitmap_maxno(struct cma *cma)
    > -{
    > - return cma->count >> cma->order_per_bit;
    > -}
    > -
    > -static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
    > - unsigned long pages)
    > -{
    > - return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
    > -}
    > -
    > -static void cma_clear_bitmap(struct cma *cma, unsigned long pfn, int count)
    > -{
    > - unsigned long bitmap_no, bitmap_count;
    > -
    > - bitmap_no = (pfn - cma->base_pfn) >> cma->order_per_bit;
    > - bitmap_count = cma_bitmap_pages_to_bits(cma, count);
    > -
    > - mutex_lock(&cma->lock);
    > - bitmap_clear(cma->bitmap, bitmap_no, bitmap_count);
    > - mutex_unlock(&cma->lock);
    > -}
    > -
    > -static int __init cma_activate_area(struct cma *cma)
    > -{
    > - int bitmap_size = BITS_TO_LONGS(cma_bitmap_maxno(cma)) * sizeof(long);
    > - unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
    > - unsigned i = cma->count >> pageblock_order;
    > - struct zone *zone;
    > -
    > - cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
    > -
    > - if (!cma->bitmap)
    > - return -ENOMEM;
    > -
    > - WARN_ON_ONCE(!pfn_valid(pfn));
    > - zone = page_zone(pfn_to_page(pfn));
    > -
    > - do {
    > - unsigned j;
    > - base_pfn = pfn;
    > - for (j = pageblock_nr_pages; j; --j, pfn++) {
    > - WARN_ON_ONCE(!pfn_valid(pfn));
    > - /*
    > - * alloc_contig_range requires the pfn range
    > - * specified to be in the same zone. Make this
    > - * simple by forcing the entire CMA resv range
    > - * to be in the same zone.
    > - */
    > - if (page_zone(pfn_to_page(pfn)) != zone)
    > - goto err;
    > - }
    > - init_cma_reserved_pageblock(pfn_to_page(base_pfn));
    > - } while (--i);
    > -
    > - mutex_init(&cma->lock);
    > - return 0;
    > -
    > -err:
    > - kfree(cma->bitmap);
    > - return -EINVAL;
    > -}
    > -
    > -static struct cma cma_areas[MAX_CMA_AREAS];
    > -static unsigned cma_area_count;
    > -
    > -static int __init cma_init_reserved_areas(void)
    > -{
    > - int i;
    > -
    > - for (i = 0; i < cma_area_count; i++) {
    > - int ret = cma_activate_area(&cma_areas[i]);
    > - if (ret)
    > - return ret;
    > - }
    > -
    > - return 0;
    > -}
    > -core_initcall(cma_init_reserved_areas);
    > -
    > -static int __init __dma_contiguous_reserve_area(phys_addr_t size,
    > - phys_addr_t base, phys_addr_t limit,
    > - phys_addr_t alignment, unsigned int order_per_bit,
    > - struct cma **res_cma, bool fixed)
    > -{
    > - struct cma *cma = &cma_areas[cma_area_count];
    > - int ret = 0;
    > -
    > - pr_debug("%s(size %lx, base %08lx, limit %08lx alignment %08lx)\n",
    > - __func__, (unsigned long)size, (unsigned long)base,
    > - (unsigned long)limit, (unsigned long)alignment);
    > -
    > - if (cma_area_count == ARRAY_SIZE(cma_areas)) {
    > - pr_err("Not enough slots for CMA reserved regions!\n");
    > - return -ENOSPC;
    > - }
    > -
    > - if (!size)
    > - return -EINVAL;
    > -
    > - if (alignment && !is_power_of_2(alignment))
    > - return -EINVAL;
    > -
    > - /*
    > - * Sanitise input arguments.
    > - * Pages both ends in CMA area could be merged into adjacent unmovable
    > - * migratetype page by page allocator's buddy algorithm. In the case,
    > - * you couldn't get a contiguous memory, which is not what we want.
    > - */
    > - alignment = max(alignment,
    > - (phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
    > - base = ALIGN(base, alignment);
    > - size = ALIGN(size, alignment);
    > - limit &= ~(alignment - 1);
    > -
    > - /* size should be aligned with order_per_bit */
    > - if (!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit))
    > - return -EINVAL;
    > -
    > - /* Reserve memory */
    > - if (base && fixed) {
    > - if (memblock_is_region_reserved(base, size) ||
    > - memblock_reserve(base, size) < 0) {
    > - ret = -EBUSY;
    > - goto err;
    > - }
    > - } else {
    > - phys_addr_t addr = memblock_alloc_range(size, alignment, base,
    > - limit);
    > - if (!addr) {
    > - ret = -ENOMEM;
    > - goto err;
    > - } else {
    > - base = addr;
    > - }
    > - }
    > -
    > - /*
    > - * Each reserved area must be initialised later, when more kernel
    > - * subsystems (like slab allocator) are available.
    > - */
    > - cma->base_pfn = PFN_DOWN(base);
    > - cma->count = size >> PAGE_SHIFT;
    > - cma->order_per_bit = order_per_bit;
    > - *res_cma = cma;
    > - cma_area_count++;
    > -
    > - pr_info("CMA: reserved %ld MiB at %08lx\n", (unsigned long)size / SZ_1M,
    > - (unsigned long)base);
    > - return 0;
    > -
    > -err:
    > - pr_err("CMA: failed to reserve %ld MiB\n", (unsigned long)size / SZ_1M);
    > - return ret;
    > -}
    > -
    > /**
    > * dma_contiguous_reserve_area() - reserve custom contiguous area
    > * @size: Size of the reserved area (in bytes),
    > @@ -342,77 +165,17 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
    > {
    > int ret;
    >
    > - ret = __dma_contiguous_reserve_area(size, base, limit, 0, 0,
    > - res_cma, fixed);
    > + ret = cma_declare_contiguous(size, base, limit, 0, 0, res_cma, fixed);
    > if (ret)
    > return ret;
    >
    > /* Architecture specific contiguous memory fixup. */
    > - dma_contiguous_early_fixup(PFN_PHYS((*res_cma)->base_pfn),
    > - (*res_cma)->count << PAGE_SHIFT);
    > + dma_contiguous_early_fixup(cma_get_base(*res_cma),
    > + cma_get_size(*res_cma));
    >
    > return 0;
    > }
    >
    > -static struct page *__dma_alloc_from_contiguous(struct cma *cma, int count,
    > - unsigned int align)
    > -{
    > - unsigned long mask, pfn, start = 0;
    > - unsigned long bitmap_maxno, bitmap_no, bitmap_count;
    > - struct page *page = NULL;
    > - int ret;
    > -
    > - if (!cma || !cma->count)
    > - return NULL;
    > -
    > - pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
    > - count, align);
    > -
    > - if (!count)
    > - return NULL;
    > -
    > - mask = cma_bitmap_aligned_mask(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);
    > - if (bitmap_no >= bitmap_maxno) {
    > - mutex_unlock(&cma->lock);
    > - break;
    > - }
    > - bitmap_set(cma->bitmap, bitmap_no, bitmap_count);
    > - /*
    > - * It's safe to drop the lock here. We've marked this region for
    > - * our exclusive use. If the migration fails we will take the
    > - * lock again and unmark it.
    > - */
    > - mutex_unlock(&cma->lock);
    > -
    > - pfn = cma->base_pfn + (bitmap_no << cma->order_per_bit);
    > - mutex_lock(&cma_mutex);
    > - ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
    > - mutex_unlock(&cma_mutex);
    > - if (ret == 0) {
    > - page = pfn_to_page(pfn);
    > - break;
    > - } else if (ret != -EBUSY) {
    > - cma_clear_bitmap(cma, pfn, count);
    > - break;
    > - }
    > - cma_clear_bitmap(cma, pfn, count);
    > - pr_debug("%s(): memory range at %p is busy, retrying\n",
    > - __func__, pfn_to_page(pfn));
    > - /* try again with a bit different memory target */
    > - start = bitmap_no + mask + 1;
    > - }
    > -
    > - pr_debug("%s(): returned %p\n", __func__, page);
    > - return page;
    > -}
    > -
    > /**
    > * dma_alloc_from_contiguous() - allocate pages from contiguous area
    > * @dev: Pointer to device for which the allocation is performed.
    > @@ -427,35 +190,10 @@ static struct page *__dma_alloc_from_contiguous(struct cma *cma, int count,
    > struct page *dma_alloc_from_contiguous(struct device *dev, int count,
    > unsigned int align)
    > {
    > - struct cma *cma = dev_get_cma_area(dev);
    > -
    > if (align > CONFIG_CMA_ALIGNMENT)
    > align = CONFIG_CMA_ALIGNMENT;
    >
    > - return __dma_alloc_from_contiguous(cma, count, align);
    > -}
    > -
    > -static bool __dma_release_from_contiguous(struct cma *cma, struct page *pages,
    > - int count)
    > -{
    > - unsigned long pfn;
    > -
    > - if (!cma || !pages)
    > - return false;
    > -
    > - pr_debug("%s(page %p)\n", __func__, (void *)pages);
    > -
    > - pfn = page_to_pfn(pages);
    > -
    > - if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
    > - return false;
    > -
    > - VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
    > -
    > - free_contig_range(pfn, count);
    > - cma_clear_bitmap(cma, pfn, count);
    > -
    > - return true;
    > + return cma_alloc(dev_get_cma_area(dev), count, align);
    > }
    >
    > /**
    > @@ -471,7 +209,5 @@ static bool __dma_release_from_contiguous(struct cma *cma, struct page *pages,
    > bool dma_release_from_contiguous(struct device *dev, struct page *pages,
    > int count)
    > {
    > - struct cma *cma = dev_get_cma_area(dev);
    > -
    > - return __dma_release_from_contiguous(cma, pages, count);
    > + return cma_release(dev_get_cma_area(dev), pages, count);
    > }
    > diff --git a/include/linux/cma.h b/include/linux/cma.h
    > new file mode 100644
    > index 0000000..69d3726
    > --- /dev/null
    > +++ b/include/linux/cma.h
    > @@ -0,0 +1,21 @@
    > +#ifndef __CMA_H__
    > +#define __CMA_H__
    > +
    > +/*
    > + * There is always at least global CMA area and a few optional
    > + * areas configured in kernel .config.
    > + */
    > +#define MAX_CMA_AREAS (1 + CONFIG_CMA_AREAS)
    > +
    > +struct cma;
    > +
    > +extern phys_addr_t cma_get_base(struct cma *cma);
    > +extern unsigned long cma_get_size(struct cma *cma);
    > +
    > +extern int __init cma_declare_contiguous(phys_addr_t size,
    > + phys_addr_t base, phys_addr_t limit,
    > + phys_addr_t alignment, unsigned int order_per_bit,
    > + struct cma **res_cma, bool fixed);
    > +extern struct page *cma_alloc(struct cma *cma, int count, unsigned int align);
    > +extern bool cma_release(struct cma *cma, struct page *pages, int count);
    > +#endif
    > diff --git a/include/linux/dma-contiguous.h b/include/linux/dma-contiguous.h
    > index 772eab5..569bbd0 100644
    > --- a/include/linux/dma-contiguous.h
    > +++ b/include/linux/dma-contiguous.h
    > @@ -53,18 +53,13 @@
    >
    > #ifdef __KERNEL__
    >
    > +#include <linux/device.h>
    > +
    > struct cma;
    > struct page;
    > -struct device;
    >
    > #ifdef CONFIG_DMA_CMA
    >
    > -/*
    > - * There is always at least global CMA area and a few optional device
    > - * private areas configured in kernel .config.
    > - */
    > -#define MAX_CMA_AREAS (1 + CONFIG_CMA_AREAS)
    > -
    > extern struct cma *dma_contiguous_default_area;
    >
    > static inline struct cma *dev_get_cma_area(struct device *dev)
    > @@ -123,8 +118,6 @@ bool dma_release_from_contiguous(struct device *dev, struct page *pages,
    >
    > #else
    >
    > -#define MAX_CMA_AREAS (0)
    > -
    > static inline struct cma *dev_get_cma_area(struct device *dev)
    > {
    > return NULL;
    > diff --git a/mm/Kconfig b/mm/Kconfig
    > index 3e9977a..f4899ec 100644
    > --- a/mm/Kconfig
    > +++ b/mm/Kconfig
    > @@ -508,6 +508,17 @@ config CMA_DEBUG
    > processing calls such as dma_alloc_from_contiguous().
    > This option does not affect warning and error messages.
    >
    > +config CMA_AREAS
    > + int "Maximum count of the CMA areas"
    > + depends on CMA
    > + default 7
    > + help
    > + CMA allows to create CMA areas for particular purpose, mainly,
    > + used as device private area. This parameter sets the maximum
    > + number of CMA area in the system.
    > +
    > + If unsure, leave the default value "7".
    > +
    > config ZBUD
    > tristate
    > default n
    > diff --git a/mm/Makefile b/mm/Makefile
    > index 1eaa70b..bc0422b 100644
    > --- a/mm/Makefile
    > +++ b/mm/Makefile
    > @@ -62,3 +62,4 @@ obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
    > obj-$(CONFIG_ZBUD) += zbud.o
    > obj-$(CONFIG_ZSMALLOC) += zsmalloc.o
    > obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
    > +obj-$(CONFIG_CMA) += cma.o
    > diff --git a/mm/cma.c b/mm/cma.c
    > new file mode 100644
    > index 0000000..0cf50da
    > --- /dev/null
    > +++ b/mm/cma.c
    > @@ -0,0 +1,333 @@
    > +/*
    > + * Contiguous Memory Allocator
    > + *
    > + * Copyright (c) 2010-2011 by Samsung Electronics.
    > + * Copyright IBM Corporation, 2013
    > + * Copyright LG Electronics Inc., 2014
    > + * Written by:
    > + * Marek Szyprowski <m.szyprowski@samsung.com>
    > + * Michal Nazarewicz <mina86@mina86.com>
    > + * Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    > + * Joonsoo Kim <iamjoonsoo.kim@lge.com>
    > + *
    > + * This program is free software; you can redistribute it and/or
    > + * modify it under the terms of the GNU General Public License as
    > + * published by the Free Software Foundation; either version 2 of the
    > + * License or (at your optional) any later version of the license.
    > + */
    > +
    > +#define pr_fmt(fmt) "cma: " fmt
    > +
    > +#ifdef CONFIG_CMA_DEBUG
    > +#ifndef DEBUG
    > +# define DEBUG
    > +#endif
    > +#endif
    > +
    > +#include <linux/memblock.h>
    > +#include <linux/err.h>
    > +#include <linux/mm.h>
    > +#include <linux/mutex.h>
    > +#include <linux/sizes.h>
    > +#include <linux/slab.h>
    > +#include <linux/log2.h>
    > +#include <linux/cma.h>
    > +
    > +struct cma {
    > + unsigned long base_pfn;
    > + unsigned long count;
    > + unsigned long *bitmap;
    > + unsigned int order_per_bit; /* Order of pages represented by one bit */
    > + struct mutex lock;
    > +};
    > +
    > +static struct cma cma_areas[MAX_CMA_AREAS];
    > +static unsigned cma_area_count;
    > +static DEFINE_MUTEX(cma_mutex);
    > +
    > +phys_addr_t cma_get_base(struct cma *cma)
    > +{
    > + return PFN_PHYS(cma->base_pfn);
    > +}
    > +
    > +unsigned long cma_get_size(struct cma *cma)
    > +{
    > + return cma->count << PAGE_SHIFT;
    > +}
    > +
    > +static unsigned long cma_bitmap_aligned_mask(struct cma *cma, int align_order)
    > +{
    > + return (1 << (align_order >> cma->order_per_bit)) - 1;
    > +}
    > +
    > +static unsigned long cma_bitmap_maxno(struct cma *cma)
    > +{
    > + return cma->count >> cma->order_per_bit;
    > +}
    > +
    > +static unsigned long cma_bitmap_pages_to_bits(struct cma *cma,
    > + unsigned long pages)
    > +{
    > + return ALIGN(pages, 1 << cma->order_per_bit) >> cma->order_per_bit;
    > +}
    > +
    > +static void cma_clear_bitmap(struct cma *cma, unsigned long pfn, int count)
    > +{
    > + unsigned long bitmap_no, bitmap_count;
    > +
    > + bitmap_no = (pfn - cma->base_pfn) >> cma->order_per_bit;
    > + bitmap_count = cma_bitmap_pages_to_bits(cma, count);
    > +
    > + mutex_lock(&cma->lock);
    > + bitmap_clear(cma->bitmap, bitmap_no, bitmap_count);
    > + mutex_unlock(&cma->lock);
    > +}
    > +
    > +static int __init cma_activate_area(struct cma *cma)
    > +{
    > + int bitmap_size = BITS_TO_LONGS(cma_bitmap_maxno(cma)) * sizeof(long);
    > + unsigned long base_pfn = cma->base_pfn, pfn = base_pfn;
    > + unsigned i = cma->count >> pageblock_order;
    > + struct zone *zone;
    > +
    > + cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
    > +
    > + if (!cma->bitmap)
    > + return -ENOMEM;
    > +
    > + WARN_ON_ONCE(!pfn_valid(pfn));
    > + zone = page_zone(pfn_to_page(pfn));
    > +
    > + do {
    > + unsigned j;
    > +
    > + base_pfn = pfn;
    > + for (j = pageblock_nr_pages; j; --j, pfn++) {
    > + WARN_ON_ONCE(!pfn_valid(pfn));
    > + /*
    > + * alloc_contig_range requires the pfn range
    > + * specified to be in the same zone. Make this
    > + * simple by forcing the entire CMA resv range
    > + * to be in the same zone.
    > + */
    > + if (page_zone(pfn_to_page(pfn)) != zone)
    > + goto err;
    > + }
    > + init_cma_reserved_pageblock(pfn_to_page(base_pfn));
    > + } while (--i);
    > +
    > + mutex_init(&cma->lock);
    > + return 0;
    > +
    > +err:
    > + kfree(cma->bitmap);
    > + return -EINVAL;
    > +}
    > +
    > +static int __init cma_init_reserved_areas(void)
    > +{
    > + int i;
    > +
    > + for (i = 0; i < cma_area_count; i++) {
    > + int ret = cma_activate_area(&cma_areas[i]);
    > +
    > + if (ret)
    > + return ret;
    > + }
    > +
    > + return 0;
    > +}
    > +core_initcall(cma_init_reserved_areas);
    > +
    > +/**
    > + * cma_declare_contiguous() - reserve custom contiguous area
    > + * @size: Size of the reserved area (in bytes),
    > + * @base: Base address of the reserved area optional, use 0 for any
    > + * @limit: End address of the reserved memory (optional, 0 for any).
    > + * @alignment: Alignment for the CMA area, should be power of 2 or zero
    > + * @order_per_bit: Order of pages represented by one bit on bitmap.
    > + * @res_cma: Pointer to store the created cma region.
    > + * @fixed: hint about where to place the reserved area
    > + *
    > + * This function reserves memory from early allocator. It should be
    > + * called by arch specific code once the early allocator (memblock or bootmem)
    > + * has been activated and all other subsystems have already allocated/reserved
    > + * memory. This function allows to create custom reserved areas.
    > + *
    > + * If @fixed is true, reserve contiguous area at exactly @base. If false,
    > + * reserve in range from @base to @limit.
    > + */
    > +int __init cma_declare_contiguous(phys_addr_t size,
    > + phys_addr_t base, phys_addr_t limit,
    > + phys_addr_t alignment, unsigned int order_per_bit,
    > + struct cma **res_cma, bool fixed)
    > +{
    > + struct cma *cma = &cma_areas[cma_area_count];
    > + int ret = 0;
    > +
    > + pr_debug("%s(size %lx, base %08lx, limit %08lx alignment %08lx)\n",
    > + __func__, (unsigned long)size, (unsigned long)base,
    > + (unsigned long)limit, (unsigned long)alignment);
    > +
    > + if (cma_area_count == ARRAY_SIZE(cma_areas)) {
    > + pr_err("Not enough slots for CMA reserved regions!\n");
    > + return -ENOSPC;
    > + }
    > +
    > + if (!size)
    > + return -EINVAL;
    > +
    > + if (alignment && !is_power_of_2(alignment))
    > + return -EINVAL;
    > +
    > + /*
    > + * Sanitise input arguments.
    > + * Pages both ends in CMA area could be merged into adjacent unmovable
    > + * migratetype page by page allocator's buddy algorithm. In the case,
    > + * you couldn't get a contiguous memory, which is not what we want.
    > + */
    > + alignment = max(alignment,
    > + (phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
    > + base = ALIGN(base, alignment);
    > + size = ALIGN(size, alignment);
    > + limit &= ~(alignment - 1);
    > +
    > + /* size should be aligned with order_per_bit */
    > + if (!IS_ALIGNED(size >> PAGE_SHIFT, 1 << order_per_bit))
    > + return -EINVAL;
    > +
    > + /* Reserve memory */
    > + if (base && fixed) {
    > + if (memblock_is_region_reserved(base, size) ||
    > + memblock_reserve(base, size) < 0) {
    > + ret = -EBUSY;
    > + goto err;
    > + }
    > + } else {
    > + phys_addr_t addr = memblock_alloc_range(size, alignment, base,
    > + limit);
    > + if (!addr) {
    > + ret = -ENOMEM;
    > + goto err;
    > + } else {
    > + base = addr;
    > + }
    > + }
    > +
    > + /*
    > + * Each reserved area must be initialised later, when more kernel
    > + * subsystems (like slab allocator) are available.
    > + */
    > + cma->base_pfn = PFN_DOWN(base);
    > + cma->count = size >> PAGE_SHIFT;
    > + cma->order_per_bit = order_per_bit;
    > + *res_cma = cma;
    > + cma_area_count++;
    > +
    > + pr_info("CMA: reserved %ld MiB at %08lx\n", (unsigned long)size / SZ_1M,
    > + (unsigned long)base);
    > + return 0;
    > +
    > +err:
    > + pr_err("CMA: failed to reserve %ld MiB\n", (unsigned long)size / SZ_1M);
    > + return ret;
    > +}
    > +
    > +/**
    > + * cma_alloc() - allocate pages from contiguous area
    > + * @cma: Contiguous memory region for which the allocation is performed.
    > + * @count: Requested number of pages.
    > + * @align: Requested alignment of pages (in PAGE_SIZE order).
    > + *
    > + * This function allocates part of contiguous memory on specific
    > + * contiguous memory area.
    > + */
    > +struct page *cma_alloc(struct cma *cma, int count, unsigned int align)
    > +{
    > + unsigned long mask, pfn, start = 0;
    > + unsigned long bitmap_maxno, bitmap_no, bitmap_count;
    > + struct page *page = NULL;
    > + int ret;
    > +
    > + if (!cma || !cma->count)
    > + return NULL;
    > +
    > + pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,
    > + count, align);
    > +
    > + if (!count)
    > + return NULL;
    > +
    > + mask = cma_bitmap_aligned_mask(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);
    > + if (bitmap_no >= bitmap_maxno) {
    > + mutex_unlock(&cma->lock);
    > + break;
    > + }
    > + bitmap_set(cma->bitmap, bitmap_no, bitmap_count);
    > + /*
    > + * It's safe to drop the lock here. We've marked this region for
    > + * our exclusive use. If the migration fails we will take the
    > + * lock again and unmark it.
    > + */
    > + mutex_unlock(&cma->lock);
    > +
    > + pfn = cma->base_pfn + (bitmap_no << cma->order_per_bit);
    > + mutex_lock(&cma_mutex);
    > + ret = alloc_contig_range(pfn, pfn + count, MIGRATE_CMA);
    > + mutex_unlock(&cma_mutex);
    > + if (ret == 0) {
    > + page = pfn_to_page(pfn);
    > + break;
    > + } else if (ret != -EBUSY) {
    > + cma_clear_bitmap(cma, pfn, count);
    > + break;
    > + }
    > + cma_clear_bitmap(cma, pfn, count);
    > + pr_debug("%s(): memory range at %p is busy, retrying\n",
    > + __func__, pfn_to_page(pfn));
    > + /* try again with a bit different memory target */
    > + start = bitmap_no + mask + 1;
    > + }
    > +
    > + pr_debug("%s(): returned %p\n", __func__, page);
    > + return page;
    > +}
    > +
    > +/**
    > + * cma_release() - release allocated pages
    > + * @cma: Contiguous memory region for which the allocation is performed.
    > + * @pages: Allocated pages.
    > + * @count: Number of allocated pages.
    > + *
    > + * This function releases memory allocated by alloc_cma().
    > + * It returns false when provided pages do not belong to contiguous area and
    > + * true otherwise.
    > + */
    > +bool cma_release(struct cma *cma, struct page *pages, int count)
    > +{
    > + unsigned long pfn;
    > +
    > + if (!cma || !pages)
    > + return false;
    > +
    > + pr_debug("%s(page %p)\n", __func__, (void *)pages);
    > +
    > + pfn = page_to_pfn(pages);
    > +
    > + if (pfn < cma->base_pfn || pfn >= cma->base_pfn + cma->count)
    > + return false;
    > +
    > + VM_BUG_ON(pfn + count > cma->base_pfn + cma->count);
    > +
    > + free_contig_range(pfn, count);
    > + cma_clear_bitmap(cma, pfn, count);
    > +
    > + return true;
    > +}

    Best regards
    --
    Marek Szyprowski, PhD
    Samsung R&D Institute Poland



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