[mirror_ubuntu-kernels.git] / kernel / memremap.c

/*
 * Copyright(c) 2015 Intel Corporation. All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 */
#include <linux/radix-tree.h>
#include <linux/memremap.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/pfn_t.h>
#include <linux/io.h>
#include <linux/mm.h>
#include <linux/memory_hotplug.h>

#ifndef ioremap_cache
/* temporary while we convert existing ioremap_cache users to memremap */
__weak void __iomem *ioremap_cache(resource_size_t offset, unsigned long size)
{
	return ioremap(offset, size);
}
#endif

static void *try_ram_remap(resource_size_t offset, size_t size)
{
	struct page *page = pfn_to_page(offset >> PAGE_SHIFT);

	/* In the simple case just return the existing linear address */
	if (!PageHighMem(page))
		return __va(offset);
	return NULL; /* fallback to ioremap_cache */
}

/**
 * memremap() - remap an iomem_resource as cacheable memory
 * @offset: iomem resource start address
 * @size: size of remap
 * @flags: either MEMREMAP_WB or MEMREMAP_WT
 *
 * memremap() is "ioremap" for cases where it is known that the resource
 * being mapped does not have i/o side effects and the __iomem
 * annotation is not applicable.
 *
 * MEMREMAP_WB - matches the default mapping for "System RAM" on
 * the architecture.  This is usually a read-allocate write-back cache.
 * Morever, if MEMREMAP_WB is specified and the requested remap region is RAM
 * memremap() will bypass establishing a new mapping and instead return
 * a pointer into the direct map.
 *
 * MEMREMAP_WT - establish a mapping whereby writes either bypass the
 * cache or are written through to memory and never exist in a
 * cache-dirty state with respect to program visibility.  Attempts to
 * map "System RAM" with this mapping type will fail.
 */
void *memremap(resource_size_t offset, size_t size, unsigned long flags)
{
	int is_ram = region_intersects(offset, size, "System RAM");
	void *addr = NULL;

	if (is_ram == REGION_MIXED) {
		WARN_ONCE(1, "memremap attempted on mixed range %pa size: %#lx\n",
				&offset, (unsigned long) size);
		return NULL;
	}

	/* Try all mapping types requested until one returns non-NULL */
	if (flags & MEMREMAP_WB) {
		flags &= ~MEMREMAP_WB;
		/*
		 * MEMREMAP_WB is special in that it can be satisifed
		 * from the direct map.  Some archs depend on the
		 * capability of memremap() to autodetect cases where
		 * the requested range is potentially in "System RAM"
		 */
		if (is_ram == REGION_INTERSECTS)
			addr = try_ram_remap(offset, size);
		if (!addr)
			addr = ioremap_cache(offset, size);
	}

	/*
	 * If we don't have a mapping yet and more request flags are
	 * pending then we will be attempting to establish a new virtual
	 * address mapping.  Enforce that this mapping is not aliasing
	 * "System RAM"
	 */
	if (!addr && is_ram == REGION_INTERSECTS && flags) {
		WARN_ONCE(1, "memremap attempted on ram %pa size: %#lx\n",
				&offset, (unsigned long) size);
		return NULL;
	}

	if (!addr && (flags & MEMREMAP_WT)) {
		flags &= ~MEMREMAP_WT;
		addr = ioremap_wt(offset, size);
	}

	return addr;
}
EXPORT_SYMBOL(memremap);

void memunmap(void *addr)
{
	if (is_vmalloc_addr(addr))
		iounmap((void __iomem *) addr);
}
EXPORT_SYMBOL(memunmap);

static void devm_memremap_release(struct device *dev, void *res)
{
	memunmap(res);
}

static int devm_memremap_match(struct device *dev, void *res, void *match_data)
{
	return *(void **)res == match_data;
}

void *devm_memremap(struct device *dev, resource_size_t offset,
		size_t size, unsigned long flags)
{
	void **ptr, *addr;

	ptr = devres_alloc_node(devm_memremap_release, sizeof(*ptr), GFP_KERNEL,
			dev_to_node(dev));
	if (!ptr)
		return ERR_PTR(-ENOMEM);

	addr = memremap(offset, size, flags);
	if (addr) {
		*ptr = addr;
		devres_add(dev, ptr);
	} else
		devres_free(ptr);

	return addr;
}
EXPORT_SYMBOL(devm_memremap);

void devm_memunmap(struct device *dev, void *addr)
{
	WARN_ON(devres_release(dev, devm_memremap_release,
				devm_memremap_match, addr));
}
EXPORT_SYMBOL(devm_memunmap);

pfn_t phys_to_pfn_t(dma_addr_t addr, unsigned long flags)
{
	return __pfn_to_pfn_t(addr >> PAGE_SHIFT, flags);
}
EXPORT_SYMBOL(phys_to_pfn_t);

#ifdef CONFIG_ZONE_DEVICE
static DEFINE_MUTEX(pgmap_lock);
static RADIX_TREE(pgmap_radix, GFP_KERNEL);
#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
#define SECTION_SIZE (1UL << PA_SECTION_SHIFT)

struct page_map {
	struct resource res;
	struct percpu_ref *ref;
	struct dev_pagemap pgmap;
	struct vmem_altmap altmap;
};

static void pgmap_radix_release(struct resource *res)
{
	resource_size_t key;

	mutex_lock(&pgmap_lock);
	for (key = res->start; key <= res->end; key += SECTION_SIZE)
		radix_tree_delete(&pgmap_radix, key >> PA_SECTION_SHIFT);
	mutex_unlock(&pgmap_lock);
}

static void devm_memremap_pages_release(struct device *dev, void *data)
{
	struct page_map *page_map = data;
	struct resource *res = &page_map->res;
	resource_size_t align_start, align_size;
	struct dev_pagemap *pgmap = &page_map->pgmap;

	pgmap_radix_release(res);

	/* pages are dead and unused, undo the arch mapping */
	align_start = res->start & ~(SECTION_SIZE - 1);
	align_size = ALIGN(resource_size(res), SECTION_SIZE);
	arch_remove_memory(align_start, align_size);
	dev_WARN_ONCE(dev, pgmap->altmap && pgmap->altmap->alloc,
			"%s: failed to free all reserved pages\n", __func__);
}

/* assumes rcu_read_lock() held at entry */
struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
{
	struct page_map *page_map;

	WARN_ON_ONCE(!rcu_read_lock_held());

	page_map = radix_tree_lookup(&pgmap_radix, phys >> PA_SECTION_SHIFT);
	return page_map ? &page_map->pgmap : NULL;
}

/**
 * devm_memremap_pages - remap and provide memmap backing for the given resource
 * @dev: hosting device for @res
 * @res: "host memory" address range
 * @altmap: optional descriptor for allocating the memmap from @res
 *
 * Note, the expectation is that @res is a host memory range that could
 * feasibly be treated as a "System RAM" range, i.e. not a device mmio
 * range, but this is not enforced.
 */
void *devm_memremap_pages(struct device *dev, struct resource *res,
		struct vmem_altmap *altmap)
{
	int is_ram = region_intersects(res->start, resource_size(res),
			"System RAM");
	resource_size_t key, align_start, align_size;
	struct dev_pagemap *pgmap;
	struct page_map *page_map;
	int error, nid;

	if (is_ram == REGION_MIXED) {
		WARN_ONCE(1, "%s attempted on mixed region %pr\n",
				__func__, res);
		return ERR_PTR(-ENXIO);
	}

	if (is_ram == REGION_INTERSECTS)
		return __va(res->start);

	if (altmap && !IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)) {
		dev_err(dev, "%s: altmap requires CONFIG_SPARSEMEM_VMEMMAP=y\n",
				__func__);
		return ERR_PTR(-ENXIO);
	}

	page_map = devres_alloc_node(devm_memremap_pages_release,
			sizeof(*page_map), GFP_KERNEL, dev_to_node(dev));
	if (!page_map)
		return ERR_PTR(-ENOMEM);
	pgmap = &page_map->pgmap;

	memcpy(&page_map->res, res, sizeof(*res));

	pgmap->dev = dev;
	if (altmap) {
		memcpy(&page_map->altmap, altmap, sizeof(*altmap));
		pgmap->altmap = &page_map->altmap;
	}
	pgmap->res = &page_map->res;

	mutex_lock(&pgmap_lock);
	error = 0;
	for (key = res->start; key <= res->end; key += SECTION_SIZE) {
		struct dev_pagemap *dup;

		rcu_read_lock();
		dup = find_dev_pagemap(key);
		rcu_read_unlock();
		if (dup) {
			dev_err(dev, "%s: %pr collides with mapping for %s\n",
					__func__, res, dev_name(dup->dev));
			error = -EBUSY;
			break;
		}
		error = radix_tree_insert(&pgmap_radix, key >> PA_SECTION_SHIFT,
				page_map);
		if (error) {
			dev_err(dev, "%s: failed: %d\n", __func__, error);
			break;
		}
	}
	mutex_unlock(&pgmap_lock);
	if (error)
		goto err_radix;

	nid = dev_to_node(dev);
	if (nid < 0)
		nid = numa_mem_id();

	align_start = res->start & ~(SECTION_SIZE - 1);
	align_size = ALIGN(resource_size(res), SECTION_SIZE);
	error = arch_add_memory(nid, align_start, align_size, true);
	if (error)
		goto err_add_memory;

	devres_add(dev, page_map);
	return __va(res->start);

 err_add_memory:
 err_radix:
	pgmap_radix_release(res);
	devres_free(page_map);
	return ERR_PTR(error);
}
EXPORT_SYMBOL(devm_memremap_pages);

unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
{
	/* number of pfns from base where pfn_to_page() is valid */
	return altmap->reserve + altmap->free;
}

void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
{
	altmap->alloc -= nr_pfns;
}

#ifdef CONFIG_SPARSEMEM_VMEMMAP
struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
{
	/*
	 * 'memmap_start' is the virtual address for the first "struct
	 * page" in this range of the vmemmap array.  In the case of
	 * CONFIG_SPARSE_VMEMMAP a page_to_pfn conversion is simple
	 * pointer arithmetic, so we can perform this to_vmem_altmap()
	 * conversion without concern for the initialization state of
	 * the struct page fields.
	 */
	struct page *page = (struct page *) memmap_start;
	struct dev_pagemap *pgmap;

	/*
	 * Uncoditionally retrieve a dev_pagemap associated with the
	 * given physical address, this is only for use in the
	 * arch_{add|remove}_memory() for setting up and tearing down
	 * the memmap.
	 */
	rcu_read_lock();
	pgmap = find_dev_pagemap(__pfn_to_phys(page_to_pfn(page)));
	rcu_read_unlock();

	return pgmap ? pgmap->altmap : NULL;
}
#endif /* CONFIG_SPARSEMEM_VMEMMAP */
#endif /* CONFIG_ZONE_DEVICE */
Commit	Line	Data
92281dee DW	1	/*
	2	* Copyright(c) 2015 Intel Corporation. All rights reserved.
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of version 2 of the GNU General Public License as
	6	* published by the Free Software Foundation.
	7	*
	8	* This program is distributed in the hope that it will be useful, but
	9	* WITHOUT ANY WARRANTY; without even the implied warranty of
	10	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	11	* General Public License for more details.
	12	*/
9476df7d DW	13	#include <linux/radix-tree.h>
9476df7d DW	14	#include <linux/memremap.h>
7d3dcf26	15	#include <linux/device.h>
92281dee	16	#include <linux/types.h>
34c0fd54	17	#include <linux/pfn_t.h>
92281dee DW	18	#include <linux/io.h>
92281dee DW	19	#include <linux/mm.h>
41e94a85	20	#include <linux/memory_hotplug.h>
92281dee DW	21
	22	#ifndef ioremap_cache
	23	/* temporary while we convert existing ioremap_cache users to memremap */
	24	__weak void __iomem *ioremap_cache(resource_size_t offset, unsigned long size)
	25	{
	26	return ioremap(offset, size);
	27	}
	28	#endif
	29
182475b7 DW	30	static void *try_ram_remap(resource_size_t offset, size_t size)
	31	{
	32	struct page *page = pfn_to_page(offset >> PAGE_SHIFT);
	33
	34	/* In the simple case just return the existing linear address */
	35	if (!PageHighMem(page))
	36	return __va(offset);
	37	return NULL; /* fallback to ioremap_cache */
	38	}
	39
92281dee DW	40	/**
	41	* memremap() - remap an iomem_resource as cacheable memory
	42	* @offset: iomem resource start address
	43	* @size: size of remap
	44	* @flags: either MEMREMAP_WB or MEMREMAP_WT
	45	*
	46	* memremap() is "ioremap" for cases where it is known that the resource
	47	* being mapped does not have i/o side effects and the __iomem
	48	* annotation is not applicable.
	49	*
	50	* MEMREMAP_WB - matches the default mapping for "System RAM" on
	51	* the architecture. This is usually a read-allocate write-back cache.
	52	* Morever, if MEMREMAP_WB is specified and the requested remap region is RAM
	53	* memremap() will bypass establishing a new mapping and instead return
	54	* a pointer into the direct map.
	55	*
	56	* MEMREMAP_WT - establish a mapping whereby writes either bypass the
	57	* cache or are written through to memory and never exist in a
	58	* cache-dirty state with respect to program visibility. Attempts to
	59	* map "System RAM" with this mapping type will fail.
	60	*/
	61	void *memremap(resource_size_t offset, size_t size, unsigned long flags)
	62	{
	63	int is_ram = region_intersects(offset, size, "System RAM");
	64	void *addr = NULL;
	65
	66	if (is_ram == REGION_MIXED) {
	67	WARN_ONCE(1, "memremap attempted on mixed range %pa size: %#lx\n",
	68	&offset, (unsigned long) size);
	69	return NULL;
	70	}
	71
	72	/* Try all mapping types requested until one returns non-NULL */
	73	if (flags & MEMREMAP_WB) {
	74	flags &= ~MEMREMAP_WB;
	75	/*
	76	* MEMREMAP_WB is special in that it can be satisifed
	77	* from the direct map. Some archs depend on the
	78	* capability of memremap() to autodetect cases where
	79	* the requested range is potentially in "System RAM"
	80	*/
	81	if (is_ram == REGION_INTERSECTS)
182475b7 DW	82	addr = try_ram_remap(offset, size);
182475b7 DW	83	if (!addr)
92281dee DW	84	addr = ioremap_cache(offset, size);
	85	}
	86
	87	/*
	88	* If we don't have a mapping yet and more request flags are
	89	* pending then we will be attempting to establish a new virtual
	90	* address mapping. Enforce that this mapping is not aliasing
	91	* "System RAM"
	92	*/
	93	if (!addr && is_ram == REGION_INTERSECTS && flags) {
	94	WARN_ONCE(1, "memremap attempted on ram %pa size: %#lx\n",
	95	&offset, (unsigned long) size);
	96	return NULL;
	97	}
	98
	99	if (!addr && (flags & MEMREMAP_WT)) {
	100	flags &= ~MEMREMAP_WT;
	101	addr = ioremap_wt(offset, size);
	102	}
	103
	104	return addr;
	105	}
	106	EXPORT_SYMBOL(memremap);
	107
	108	void memunmap(void *addr)
	109	{
	110	if (is_vmalloc_addr(addr))
	111	iounmap((void __iomem *) addr);
	112	}
	113	EXPORT_SYMBOL(memunmap);
7d3dcf26 CH	114
	115	static void devm_memremap_release(struct device dev, void res)
	116	{
	117	memunmap(res);
	118	}
	119
	120	static int devm_memremap_match(struct device dev, void res, void *match_data)
	121	{
	122	return (void *)res == match_data;
	123	}
	124
	125	void devm_memremap(struct device dev, resource_size_t offset,
	126	size_t size, unsigned long flags)
	127	{
	128	void *ptr, addr;
	129
538ea4aa DW	130	ptr = devres_alloc_node(devm_memremap_release, sizeof(*ptr), GFP_KERNEL,
538ea4aa DW	131	dev_to_node(dev));
7d3dcf26	132	if (!ptr)
b36f4761	133	return ERR_PTR(-ENOMEM);
7d3dcf26 CH	134
	135	addr = memremap(offset, size, flags);
	136	if (addr) {
	137	*ptr = addr;
	138	devres_add(dev, ptr);
	139	} else
	140	devres_free(ptr);
	141
	142	return addr;
	143	}
	144	EXPORT_SYMBOL(devm_memremap);
	145
	146	void devm_memunmap(struct device dev, void addr)
	147	{
d741314f DW	148	WARN_ON(devres_release(dev, devm_memremap_release,
d741314f DW	149	devm_memremap_match, addr));
7d3dcf26 CH	150	}
7d3dcf26 CH	151	EXPORT_SYMBOL(devm_memunmap);
41e94a85	152
34c0fd54 DW	153	pfn_t phys_to_pfn_t(dma_addr_t addr, unsigned long flags)
	154	{
	155	return __pfn_to_pfn_t(addr >> PAGE_SHIFT, flags);
	156	}
	157	EXPORT_SYMBOL(phys_to_pfn_t);
	158
41e94a85	159	#ifdef CONFIG_ZONE_DEVICE
9476df7d DW	160	static DEFINE_MUTEX(pgmap_lock);
	161	static RADIX_TREE(pgmap_radix, GFP_KERNEL);
	162	#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
	163	#define SECTION_SIZE (1UL << PA_SECTION_SHIFT)
	164
41e94a85 CH	165	struct page_map {
41e94a85 CH	166	struct resource res;
9476df7d DW	167	struct percpu_ref *ref;
9476df7d DW	168	struct dev_pagemap pgmap;
4b94ffdc	169	struct vmem_altmap altmap;
41e94a85 CH	170	};
41e94a85 CH	171
9476df7d DW	172	static void pgmap_radix_release(struct resource *res)
	173	{
	174	resource_size_t key;
	175
	176	mutex_lock(&pgmap_lock);
	177	for (key = res->start; key <= res->end; key += SECTION_SIZE)
	178	radix_tree_delete(&pgmap_radix, key >> PA_SECTION_SHIFT);
	179	mutex_unlock(&pgmap_lock);
	180	}
	181
	182	static void devm_memremap_pages_release(struct device dev, void data)
41e94a85	183	{
9476df7d DW	184	struct page_map *page_map = data;
	185	struct resource *res = &page_map->res;
	186	resource_size_t align_start, align_size;
4b94ffdc	187	struct dev_pagemap *pgmap = &page_map->pgmap;
9476df7d DW	188
9476df7d DW	189	pgmap_radix_release(res);
41e94a85 CH	190
41e94a85 CH	191	/* pages are dead and unused, undo the arch mapping */
9476df7d DW	192	align_start = res->start & ~(SECTION_SIZE - 1);
	193	align_size = ALIGN(resource_size(res), SECTION_SIZE);
	194	arch_remove_memory(align_start, align_size);
4b94ffdc DW	195	dev_WARN_ONCE(dev, pgmap->altmap && pgmap->altmap->alloc,
4b94ffdc DW	196	"%s: failed to free all reserved pages\n", __func__);
9476df7d DW	197	}
	198
	199	/* assumes rcu_read_lock() held at entry */
	200	struct dev_pagemap *find_dev_pagemap(resource_size_t phys)
	201	{
	202	struct page_map *page_map;
	203
	204	WARN_ON_ONCE(!rcu_read_lock_held());
	205
	206	page_map = radix_tree_lookup(&pgmap_radix, phys >> PA_SECTION_SHIFT);
	207	return page_map ? &page_map->pgmap : NULL;
41e94a85 CH	208	}
41e94a85 CH	209
4b94ffdc DW	210	/**
	211	* devm_memremap_pages - remap and provide memmap backing for the given resource
	212	* @dev: hosting device for @res
	213	* @res: "host memory" address range
	214	* @altmap: optional descriptor for allocating the memmap from @res
	215	*
	216	* Note, the expectation is that @res is a host memory range that could
	217	* feasibly be treated as a "System RAM" range, i.e. not a device mmio
	218	* range, but this is not enforced.
	219	*/
	220	void devm_memremap_pages(struct device dev, struct resource *res,
	221	struct vmem_altmap *altmap)
41e94a85 CH	222	{
	223	int is_ram = region_intersects(res->start, resource_size(res),
	224	"System RAM");
9476df7d	225	resource_size_t key, align_start, align_size;
4b94ffdc	226	struct dev_pagemap *pgmap;
41e94a85 CH	227	struct page_map *page_map;
	228	int error, nid;
	229
	230	if (is_ram == REGION_MIXED) {
	231	WARN_ONCE(1, "%s attempted on mixed region %pr\n",
	232	__func__, res);
	233	return ERR_PTR(-ENXIO);
	234	}
	235
	236	if (is_ram == REGION_INTERSECTS)
	237	return __va(res->start);
	238
4b94ffdc DW	239	if (altmap && !IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)) {
	240	dev_err(dev, "%s: altmap requires CONFIG_SPARSEMEM_VMEMMAP=y\n",
	241	__func__);
	242	return ERR_PTR(-ENXIO);
	243	}
	244
538ea4aa DW	245	page_map = devres_alloc_node(devm_memremap_pages_release,
538ea4aa DW	246	sizeof(*page_map), GFP_KERNEL, dev_to_node(dev));
41e94a85 CH	247	if (!page_map)
41e94a85 CH	248	return ERR_PTR(-ENOMEM);
4b94ffdc	249	pgmap = &page_map->pgmap;
41e94a85 CH	250
	251	memcpy(&page_map->res, res, sizeof(*res));
	252
4b94ffdc DW	253	pgmap->dev = dev;
	254	if (altmap) {
	255	memcpy(&page_map->altmap, altmap, sizeof(*altmap));
	256	pgmap->altmap = &page_map->altmap;
	257	}
	258	pgmap->res = &page_map->res;
	259
9476df7d DW	260	mutex_lock(&pgmap_lock);
	261	error = 0;
	262	for (key = res->start; key <= res->end; key += SECTION_SIZE) {
	263	struct dev_pagemap *dup;
	264
	265	rcu_read_lock();
	266	dup = find_dev_pagemap(key);
	267	rcu_read_unlock();
	268	if (dup) {
	269	dev_err(dev, "%s: %pr collides with mapping for %s\n",
	270	__func__, res, dev_name(dup->dev));
	271	error = -EBUSY;
	272	break;
	273	}
	274	error = radix_tree_insert(&pgmap_radix, key >> PA_SECTION_SHIFT,
	275	page_map);
	276	if (error) {
	277	dev_err(dev, "%s: failed: %d\n", __func__, error);
	278	break;
	279	}
	280	}
	281	mutex_unlock(&pgmap_lock);
	282	if (error)
	283	goto err_radix;
	284
41e94a85 CH	285	nid = dev_to_node(dev);
41e94a85 CH	286	if (nid < 0)
7eff93b7	287	nid = numa_mem_id();
41e94a85	288
9476df7d DW	289	align_start = res->start & ~(SECTION_SIZE - 1);
	290	align_size = ALIGN(resource_size(res), SECTION_SIZE);
	291	error = arch_add_memory(nid, align_start, align_size, true);
	292	if (error)
	293	goto err_add_memory;
41e94a85 CH	294
	295	devres_add(dev, page_map);
	296	return __va(res->start);
9476df7d DW	297
	298	err_add_memory:
	299	err_radix:
	300	pgmap_radix_release(res);
	301	devres_free(page_map);
	302	return ERR_PTR(error);
41e94a85 CH	303	}
41e94a85 CH	304	EXPORT_SYMBOL(devm_memremap_pages);
4b94ffdc DW	305
	306	unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
	307	{
	308	/* number of pfns from base where pfn_to_page() is valid */
	309	return altmap->reserve + altmap->free;
	310	}
	311
	312	void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
	313	{
	314	altmap->alloc -= nr_pfns;
	315	}
	316
	317	#ifdef CONFIG_SPARSEMEM_VMEMMAP
	318	struct vmem_altmap *to_vmem_altmap(unsigned long memmap_start)
	319	{
	320	/*
	321	* 'memmap_start' is the virtual address for the first "struct
	322	* page" in this range of the vmemmap array. In the case of
	323	* CONFIG_SPARSE_VMEMMAP a page_to_pfn conversion is simple
	324	* pointer arithmetic, so we can perform this to_vmem_altmap()
	325	* conversion without concern for the initialization state of
	326	* the struct page fields.
	327	*/
	328	struct page page = (struct page ) memmap_start;
	329	struct dev_pagemap *pgmap;
	330
	331	/*
	332	* Uncoditionally retrieve a dev_pagemap associated with the
	333	* given physical address, this is only for use in the
	334	* arch_{add\|remove}_memory() for setting up and tearing down
	335	* the memmap.
	336	*/
	337	rcu_read_lock();
	338	pgmap = find_dev_pagemap(__pfn_to_phys(page_to_pfn(page)));
	339	rcu_read_unlock();
	340
	341	return pgmap ? pgmap->altmap : NULL;
	342	}
	343	#endif /* CONFIG_SPARSEMEM_VMEMMAP */
41e94a85	344	#endif /* CONFIG_ZONE_DEVICE */