[linux-2.6-block.git] / kernel / memremap.c

/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright(c) 2015 Intel Corporation. All rights reserved. */
#include <linux/device.h>
#include <linux/io.h>
#include <linux/kasan.h>
#include <linux/memory_hotplug.h>
#include <linux/mm.h>
#include <linux/pfn_t.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/types.h>
#include <linux/wait_bit.h>
#include <linux/xarray.h>

static DEFINE_XARRAY(pgmap_array);
#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
#define SECTION_SIZE (1UL << PA_SECTION_SHIFT)

#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
		       unsigned long addr,
		       swp_entry_t entry,
		       unsigned int flags,
		       pmd_t *pmdp)
{
	struct page *page = device_private_entry_to_page(entry);

	/*
	 * The page_fault() callback must migrate page back to system memory
	 * so that CPU can access it. This might fail for various reasons
	 * (device issue, device was unsafely unplugged, ...). When such
	 * error conditions happen, the callback must return VM_FAULT_SIGBUS.
	 *
	 * Note that because memory cgroup charges are accounted to the device
	 * memory, this should never fail because of memory restrictions (but
	 * allocation of regular system page might still fail because we are
	 * out of memory).
	 *
	 * There is a more in-depth description of what that callback can and
	 * cannot do, in include/linux/memremap.h
	 */
	return page->pgmap->page_fault(vma, addr, page, flags, pmdp);
}
EXPORT_SYMBOL(device_private_entry_fault);
#endif /* CONFIG_DEVICE_PRIVATE */

static void pgmap_array_delete(struct resource *res)
{
	xa_store_range(&pgmap_array, PHYS_PFN(res->start), PHYS_PFN(res->end),
			NULL, GFP_KERNEL);
	synchronize_rcu();
}

static unsigned long pfn_first(struct dev_pagemap *pgmap)
{
	const struct resource *res = &pgmap->res;
	struct vmem_altmap *altmap = &pgmap->altmap;
	unsigned long pfn;

	pfn = res->start >> PAGE_SHIFT;
	if (pgmap->altmap_valid)
		pfn += vmem_altmap_offset(altmap);
	return pfn;
}

static unsigned long pfn_end(struct dev_pagemap *pgmap)
{
	const struct resource *res = &pgmap->res;

	return (res->start + resource_size(res)) >> PAGE_SHIFT;
}

static unsigned long pfn_next(unsigned long pfn)
{
	if (pfn % 1024 == 0)
		cond_resched();
	return pfn + 1;
}

#define for_each_device_pfn(pfn, map) \
	for (pfn = pfn_first(map); pfn < pfn_end(map); pfn = pfn_next(pfn))

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

	pgmap->kill(pgmap->ref);
	for_each_device_pfn(pfn, pgmap)
		put_page(pfn_to_page(pfn));

	/* pages are dead and unused, undo the arch mapping */
	align_start = res->start & ~(SECTION_SIZE - 1);
	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
		- align_start;

	mem_hotplug_begin();
	arch_remove_memory(align_start, align_size, pgmap->altmap_valid ?
			&pgmap->altmap : NULL);
	kasan_remove_zero_shadow(__va(align_start), align_size);
	mem_hotplug_done();

	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
	pgmap_array_delete(res);
	dev_WARN_ONCE(dev, pgmap->altmap.alloc,
		      "%s: failed to free all reserved pages\n", __func__);
}

/**
 * devm_memremap_pages - remap and provide memmap backing for the given resource
 * @dev: hosting device for @res
 * @pgmap: pointer to a struct dev_pagemap
 *
 * Notes:
 * 1/ At a minimum the res, ref and type members of @pgmap must be initialized
 *    by the caller before passing it to this function
 *
 * 2/ The altmap field may optionally be initialized, in which case altmap_valid
 *    must be set to true
 *
 * 3/ pgmap->ref must be 'live' on entry and will be killed at
 *    devm_memremap_pages_release() time, or if this routine fails.
 *
 * 4/ res is expected to be 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 dev_pagemap *pgmap)
{
	resource_size_t align_start, align_size, align_end;
	struct vmem_altmap *altmap = pgmap->altmap_valid ?
			&pgmap->altmap : NULL;
	struct resource *res = &pgmap->res;
	struct dev_pagemap *conflict_pgmap;
	pgprot_t pgprot = PAGE_KERNEL;
	int error, nid, is_ram;

	if (!pgmap->ref || !pgmap->kill)
		return ERR_PTR(-EINVAL);

	align_start = res->start & ~(SECTION_SIZE - 1);
	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
		- align_start;
	align_end = align_start + align_size - 1;

	conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_start), NULL);
	if (conflict_pgmap) {
		dev_WARN(dev, "Conflicting mapping in same section\n");
		put_dev_pagemap(conflict_pgmap);
		return ERR_PTR(-ENOMEM);
	}

	conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_end), NULL);
	if (conflict_pgmap) {
		dev_WARN(dev, "Conflicting mapping in same section\n");
		put_dev_pagemap(conflict_pgmap);
		return ERR_PTR(-ENOMEM);
	}

	is_ram = region_intersects(align_start, align_size,
		IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);

	if (is_ram != REGION_DISJOINT) {
		WARN_ONCE(1, "%s attempted on %s region %pr\n", __func__,
				is_ram == REGION_MIXED ? "mixed" : "ram", res);
		error = -ENXIO;
		goto err_array;
	}

	pgmap->dev = dev;

	error = xa_err(xa_store_range(&pgmap_array, PHYS_PFN(res->start),
				PHYS_PFN(res->end), pgmap, GFP_KERNEL));
	if (error)
		goto err_array;

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

	error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(align_start), 0,
			align_size);
	if (error)
		goto err_pfn_remap;

	mem_hotplug_begin();
	error = kasan_add_zero_shadow(__va(align_start), align_size);
	if (error) {
		mem_hotplug_done();
		goto err_kasan;
	}

	error = arch_add_memory(nid, align_start, align_size, altmap, false);
	if (!error)
		move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
					align_start >> PAGE_SHIFT,
					align_size >> PAGE_SHIFT, altmap);
	mem_hotplug_done();
	if (error)
		goto err_add_memory;

	/*
	 * Initialization of the pages has been deferred until now in order
	 * to allow us to do the work while not holding the hotplug lock.
	 */
	memmap_init_zone_device(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
				align_start >> PAGE_SHIFT,
				align_size >> PAGE_SHIFT, pgmap);
	percpu_ref_get_many(pgmap->ref, pfn_end(pgmap) - pfn_first(pgmap));

	error = devm_add_action_or_reset(dev, devm_memremap_pages_release,
			pgmap);
	if (error)
		return ERR_PTR(error);

	return __va(res->start);

 err_add_memory:
	kasan_remove_zero_shadow(__va(align_start), align_size);
 err_kasan:
	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
 err_pfn_remap:
	pgmap_array_delete(res);
 err_array:
	pgmap->kill(pgmap->ref);
	return ERR_PTR(error);
}
EXPORT_SYMBOL_GPL(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;
}

/**
 * get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
 * @pfn: page frame number to lookup page_map
 * @pgmap: optional known pgmap that already has a reference
 *
 * If @pgmap is non-NULL and covers @pfn it will be returned as-is.  If @pgmap
 * is non-NULL but does not cover @pfn the reference to it will be released.
 */
struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
		struct dev_pagemap *pgmap)
{
	resource_size_t phys = PFN_PHYS(pfn);

	/*
	 * In the cached case we're already holding a live reference.
	 */
	if (pgmap) {
		if (phys >= pgmap->res.start && phys <= pgmap->res.end)
			return pgmap;
		put_dev_pagemap(pgmap);
	}

	/* fall back to slow path lookup */
	rcu_read_lock();
	pgmap = xa_load(&pgmap_array, PHYS_PFN(phys));
	if (pgmap && !percpu_ref_tryget_live(pgmap->ref))
		pgmap = NULL;
	rcu_read_unlock();

	return pgmap;
}
EXPORT_SYMBOL_GPL(get_dev_pagemap);

#ifdef CONFIG_DEV_PAGEMAP_OPS
DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
EXPORT_SYMBOL(devmap_managed_key);
static atomic_t devmap_enable;

/*
 * Toggle the static key for ->page_free() callbacks when dev_pagemap
 * pages go idle.
 */
void dev_pagemap_get_ops(void)
{
	if (atomic_inc_return(&devmap_enable) == 1)
		static_branch_enable(&devmap_managed_key);
}
EXPORT_SYMBOL_GPL(dev_pagemap_get_ops);

void dev_pagemap_put_ops(void)
{
	if (atomic_dec_and_test(&devmap_enable))
		static_branch_disable(&devmap_managed_key);
}
EXPORT_SYMBOL_GPL(dev_pagemap_put_ops);

void __put_devmap_managed_page(struct page *page)
{
	int count = page_ref_dec_return(page);

	/*
	 * If refcount is 1 then page is freed and refcount is stable as nobody
	 * holds a reference on the page.
	 */
	if (count == 1) {
		/* Clear Active bit in case of parallel mark_page_accessed */
		__ClearPageActive(page);
		__ClearPageWaiters(page);

		mem_cgroup_uncharge(page);

		page->pgmap->page_free(page, page->pgmap->data);
	} else if (!count)
		__put_page(page);
}
EXPORT_SYMBOL(__put_devmap_managed_page);
#endif /* CONFIG_DEV_PAGEMAP_OPS */
Commit	Line	Data
5981690d DW	1	/* SPDX-License-Identifier: GPL-2.0 */
5981690d DW	2	/* Copyright(c) 2015 Intel Corporation. All rights reserved. */
7d3dcf26	3	#include <linux/device.h>
92281dee	4	#include <linux/io.h>
0207df4f	5	#include <linux/kasan.h>
41e94a85	6	#include <linux/memory_hotplug.h>
bcfa4b72 MW	7	#include <linux/mm.h>
bcfa4b72 MW	8	#include <linux/pfn_t.h>
5042db43 JG	9	#include <linux/swap.h>
5042db43 JG	10	#include <linux/swapops.h>
bcfa4b72	11	#include <linux/types.h>
e7638488	12	#include <linux/wait_bit.h>
bcfa4b72	13	#include <linux/xarray.h>
92281dee	14
bcfa4b72	15	static DEFINE_XARRAY(pgmap_array);
9476df7d DW	16	#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
	17	#define SECTION_SIZE (1UL << PA_SECTION_SHIFT)
	18
5042db43	19	#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
2b740303	20	vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
5042db43 JG	21	unsigned long addr,
	22	swp_entry_t entry,
	23	unsigned int flags,
	24	pmd_t *pmdp)
	25	{
	26	struct page *page = device_private_entry_to_page(entry);
	27
	28	/*
	29	* The page_fault() callback must migrate page back to system memory
	30	* so that CPU can access it. This might fail for various reasons
	31	* (device issue, device was unsafely unplugged, ...). When such
	32	* error conditions happen, the callback must return VM_FAULT_SIGBUS.
	33	*
	34	* Note that because memory cgroup charges are accounted to the device
	35	* memory, this should never fail because of memory restrictions (but
	36	* allocation of regular system page might still fail because we are
	37	* out of memory).
	38	*
	39	* There is a more in-depth description of what that callback can and
	40	* cannot do, in include/linux/memremap.h
	41	*/
	42	return page->pgmap->page_fault(vma, addr, page, flags, pmdp);
	43	}
	44	EXPORT_SYMBOL(device_private_entry_fault);
	45	#endif /* CONFIG_DEVICE_PRIVATE */
	46
bcfa4b72	47	static void pgmap_array_delete(struct resource *res)
ab1b597e	48	{
bcfa4b72 MW	49	xa_store_range(&pgmap_array, PHYS_PFN(res->start), PHYS_PFN(res->end),
bcfa4b72 MW	50	NULL, GFP_KERNEL);
ab1b597e	51	synchronize_rcu();
9476df7d DW	52	}
9476df7d DW	53
e7744aa2	54	static unsigned long pfn_first(struct dev_pagemap *pgmap)
5c2c2587	55	{
e7744aa2 LG	56	const struct resource *res = &pgmap->res;
e7744aa2 LG	57	struct vmem_altmap *altmap = &pgmap->altmap;
5c2c2587 DW	58	unsigned long pfn;
	59
	60	pfn = res->start >> PAGE_SHIFT;
e7744aa2	61	if (pgmap->altmap_valid)
5c2c2587 DW	62	pfn += vmem_altmap_offset(altmap);
	63	return pfn;
	64	}
	65
e7744aa2	66	static unsigned long pfn_end(struct dev_pagemap *pgmap)
5c2c2587	67	{
e7744aa2	68	const struct resource *res = &pgmap->res;
5c2c2587 DW	69
	70	return (res->start + resource_size(res)) >> PAGE_SHIFT;
	71	}
	72
949b9325 DW	73	static unsigned long pfn_next(unsigned long pfn)
	74	{
	75	if (pfn % 1024 == 0)
	76	cond_resched();
	77	return pfn + 1;
	78	}
	79
5c2c2587	80	#define for_each_device_pfn(pfn, map) \
949b9325	81	for (pfn = pfn_first(map); pfn < pfn_end(map); pfn = pfn_next(pfn))
5c2c2587	82
e8d51348	83	static void devm_memremap_pages_release(void *data)
41e94a85	84	{
e7744aa2	85	struct dev_pagemap *pgmap = data;
e8d51348	86	struct device *dev = pgmap->dev;
e7744aa2	87	struct resource *res = &pgmap->res;
9476df7d	88	resource_size_t align_start, align_size;
71389703 DW	89	unsigned long pfn;
71389703 DW	90
a95c90f1	91	pgmap->kill(pgmap->ref);
e7744aa2	92	for_each_device_pfn(pfn, pgmap)
71389703	93	put_page(pfn_to_page(pfn));
9476df7d	94
41e94a85	95	/* pages are dead and unused, undo the arch mapping */
9476df7d	96	align_start = res->start & ~(SECTION_SIZE - 1);
10a0cd6e JS	97	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
10a0cd6e JS	98	- align_start;
b5d24fda	99
f931ab47	100	mem_hotplug_begin();
e7744aa2 LG	101	arch_remove_memory(align_start, align_size, pgmap->altmap_valid ?
e7744aa2 LG	102	&pgmap->altmap : NULL);
0207df4f	103	kasan_remove_zero_shadow(__va(align_start), align_size);
f931ab47	104	mem_hotplug_done();
b5d24fda	105
9049771f	106	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
bcfa4b72	107	pgmap_array_delete(res);
e7744aa2 LG	108	dev_WARN_ONCE(dev, pgmap->altmap.alloc,
e7744aa2 LG	109	"%s: failed to free all reserved pages\n", __func__);
9476df7d DW	110	}
9476df7d DW	111
4b94ffdc DW	112	/**
	113	* devm_memremap_pages - remap and provide memmap backing for the given resource
	114	* @dev: hosting device for @res
a95c90f1	115	* @pgmap: pointer to a struct dev_pagemap
4b94ffdc	116	*
5c2c2587	117	* Notes:
e8d51348 CH	118	* 1/ At a minimum the res, ref and type members of @pgmap must be initialized
	119	* by the caller before passing it to this function
	120	*
	121	* 2/ The altmap field may optionally be initialized, in which case altmap_valid
	122	* must be set to true
	123	*
a95c90f1 DW	124	* 3/ pgmap->ref must be 'live' on entry and will be killed at
a95c90f1 DW	125	* devm_memremap_pages_release() time, or if this routine fails.
5c2c2587	126	*
e8d51348	127	* 4/ res is expected to be a host memory range that could feasibly be
5c2c2587 DW	128	* treated as a "System RAM" range, i.e. not a device mmio range, but
5c2c2587 DW	129	* this is not enforced.
4b94ffdc	130	*/
e8d51348	131	void devm_memremap_pages(struct device dev, struct dev_pagemap *pgmap)
41e94a85	132	{
ab1b597e	133	resource_size_t align_start, align_size, align_end;
e8d51348 CH	134	struct vmem_altmap *altmap = pgmap->altmap_valid ?
e8d51348 CH	135	&pgmap->altmap : NULL;
949b9325	136	struct resource *res = &pgmap->res;
966cf44f	137	struct dev_pagemap *conflict_pgmap;
9049771f	138	pgprot_t pgprot = PAGE_KERNEL;
949b9325	139	int error, nid, is_ram;
5f29a77c	140
a95c90f1 DW	141	if (!pgmap->ref \|\| !pgmap->kill)
	142	return ERR_PTR(-EINVAL);
	143
5f29a77c DW	144	align_start = res->start & ~(SECTION_SIZE - 1);
	145	align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
	146	- align_start;
15d36fec DJ	147	align_end = align_start + align_size - 1;
	148
	149	conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_start), NULL);
	150	if (conflict_pgmap) {
	151	dev_WARN(dev, "Conflicting mapping in same section\n");
	152	put_dev_pagemap(conflict_pgmap);
	153	return ERR_PTR(-ENOMEM);
	154	}
	155
	156	conflict_pgmap = get_dev_pagemap(PHYS_PFN(align_end), NULL);
	157	if (conflict_pgmap) {
	158	dev_WARN(dev, "Conflicting mapping in same section\n");
	159	put_dev_pagemap(conflict_pgmap);
	160	return ERR_PTR(-ENOMEM);
	161	}
	162
d37a14bb LT	163	is_ram = region_intersects(align_start, align_size,
d37a14bb LT	164	IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
41e94a85	165
06489cfb DW	166	if (is_ram != REGION_DISJOINT) {
	167	WARN_ONCE(1, "%s attempted on %s region %pr\n", __func__,
	168	is_ram == REGION_MIXED ? "mixed" : "ram", res);
a95c90f1 DW	169	error = -ENXIO;
a95c90f1 DW	170	goto err_array;
41e94a85 CH	171	}
41e94a85 CH	172
4b94ffdc	173	pgmap->dev = dev;
4b94ffdc	174
bcfa4b72 MW	175	error = xa_err(xa_store_range(&pgmap_array, PHYS_PFN(res->start),
bcfa4b72 MW	176	PHYS_PFN(res->end), pgmap, GFP_KERNEL));
9476df7d	177	if (error)
bcfa4b72	178	goto err_array;
9476df7d	179
41e94a85 CH	180	nid = dev_to_node(dev);
41e94a85 CH	181	if (nid < 0)
7eff93b7	182	nid = numa_mem_id();
41e94a85	183
9049771f DW	184	error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(align_start), 0,
	185	align_size);
	186	if (error)
	187	goto err_pfn_remap;
	188
f931ab47	189	mem_hotplug_begin();
0207df4f AR	190	error = kasan_add_zero_shadow(__va(align_start), align_size);
	191	if (error) {
	192	mem_hotplug_done();
	193	goto err_kasan;
	194	}
	195
24e6d5a5	196	error = arch_add_memory(nid, align_start, align_size, altmap, false);
f1dd2cd1 MH	197	if (!error)
	198	move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
	199	align_start >> PAGE_SHIFT,
a99583e7	200	align_size >> PAGE_SHIFT, altmap);
f931ab47	201	mem_hotplug_done();
9476df7d DW	202	if (error)
9476df7d DW	203	goto err_add_memory;
41e94a85	204
966cf44f AD	205	/*
	206	* Initialization of the pages has been deferred until now in order
	207	* to allow us to do the work while not holding the hotplug lock.
	208	*/
	209	memmap_init_zone_device(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
	210	align_start >> PAGE_SHIFT,
	211	align_size >> PAGE_SHIFT, pgmap);
	212	percpu_ref_get_many(pgmap->ref, pfn_end(pgmap) - pfn_first(pgmap));
e8d51348	213
a95c90f1 DW	214	error = devm_add_action_or_reset(dev, devm_memremap_pages_release,
	215	pgmap);
	216	if (error)
	217	return ERR_PTR(error);
e8d51348	218
41e94a85	219	return __va(res->start);
9476df7d DW	220
9476df7d DW	221	err_add_memory:
0207df4f AR	222	kasan_remove_zero_shadow(__va(align_start), align_size);
0207df4f AR	223	err_kasan:
9049771f DW	224	untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
9049771f DW	225	err_pfn_remap:
bcfa4b72 MW	226	pgmap_array_delete(res);
bcfa4b72 MW	227	err_array:
a95c90f1	228	pgmap->kill(pgmap->ref);
9476df7d	229	return ERR_PTR(error);
41e94a85	230	}
808153e1	231	EXPORT_SYMBOL_GPL(devm_memremap_pages);
4b94ffdc DW	232
	233	unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
	234	{
	235	/* number of pfns from base where pfn_to_page() is valid */
	236	return altmap->reserve + altmap->free;
	237	}
	238
	239	void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
	240	{
	241	altmap->alloc -= nr_pfns;
	242	}
	243
0822acb8 CH	244	/**
	245	* get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
	246	* @pfn: page frame number to lookup page_map
	247	* @pgmap: optional known pgmap that already has a reference
	248	*
832d7aa0 CH	249	* If @pgmap is non-NULL and covers @pfn it will be returned as-is. If @pgmap
832d7aa0 CH	250	* is non-NULL but does not cover @pfn the reference to it will be released.
0822acb8 CH	251	*/
	252	struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
	253	struct dev_pagemap *pgmap)
	254	{
0822acb8 CH	255	resource_size_t phys = PFN_PHYS(pfn);
	256
	257	/*
832d7aa0	258	* In the cached case we're already holding a live reference.
0822acb8	259	*/
832d7aa0	260	if (pgmap) {
e7744aa2	261	if (phys >= pgmap->res.start && phys <= pgmap->res.end)
832d7aa0 CH	262	return pgmap;
832d7aa0 CH	263	put_dev_pagemap(pgmap);
0822acb8 CH	264	}
	265
	266	/* fall back to slow path lookup */
	267	rcu_read_lock();
bcfa4b72	268	pgmap = xa_load(&pgmap_array, PHYS_PFN(phys));
0822acb8 CH	269	if (pgmap && !percpu_ref_tryget_live(pgmap->ref))
	270	pgmap = NULL;
	271	rcu_read_unlock();
	272
	273	return pgmap;
	274	}
e7638488	275	EXPORT_SYMBOL_GPL(get_dev_pagemap);
7b2d55d2	276
e7638488 DW	277	#ifdef CONFIG_DEV_PAGEMAP_OPS
e7638488 DW	278	DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
31c5bda3	279	EXPORT_SYMBOL(devmap_managed_key);
e7638488 DW	280	static atomic_t devmap_enable;
	281
	282	/*
	283	* Toggle the static key for ->page_free() callbacks when dev_pagemap
	284	* pages go idle.
	285	*/
	286	void dev_pagemap_get_ops(void)
	287	{
	288	if (atomic_inc_return(&devmap_enable) == 1)
	289	static_branch_enable(&devmap_managed_key);
	290	}
	291	EXPORT_SYMBOL_GPL(dev_pagemap_get_ops);
	292
	293	void dev_pagemap_put_ops(void)
	294	{
	295	if (atomic_dec_and_test(&devmap_enable))
	296	static_branch_disable(&devmap_managed_key);
	297	}
	298	EXPORT_SYMBOL_GPL(dev_pagemap_put_ops);
	299
	300	void __put_devmap_managed_page(struct page *page)
7b2d55d2 JG	301	{
	302	int count = page_ref_dec_return(page);
	303
	304	/*
	305	* If refcount is 1 then page is freed and refcount is stable as nobody
	306	* holds a reference on the page.
	307	*/
	308	if (count == 1) {
	309	/* Clear Active bit in case of parallel mark_page_accessed */
	310	__ClearPageActive(page);
	311	__ClearPageWaiters(page);
	312
c733a828	313	mem_cgroup_uncharge(page);
7b2d55d2 JG	314
	315	page->pgmap->page_free(page, page->pgmap->data);
	316	} else if (!count)
	317	__put_page(page);
	318	}
31c5bda3	319	EXPORT_SYMBOL(__put_devmap_managed_page);
e7638488	320	#endif /* CONFIG_DEV_PAGEMAP_OPS */