[people/ms/linux.git] / mm / mapping_dirty_helpers.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/pagewalk.h>
#include <linux/hugetlb.h>
#include <linux/bitops.h>
#include <linux/mmu_notifier.h>
#include <linux/mm_inline.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>

/**
 * struct wp_walk - Private struct for pagetable walk callbacks
 * @range: Range for mmu notifiers
 * @tlbflush_start: Address of first modified pte
 * @tlbflush_end: Address of last modified pte + 1
 * @total: Total number of modified ptes
 */
struct wp_walk {
	struct mmu_notifier_range range;
	unsigned long tlbflush_start;
	unsigned long tlbflush_end;
	unsigned long total;
};

/**
 * wp_pte - Write-protect a pte
 * @pte: Pointer to the pte
 * @addr: The start of protecting virtual address
 * @end: The end of protecting virtual address
 * @walk: pagetable walk callback argument
 *
 * The function write-protects a pte and records the range in
 * virtual address space of touched ptes for efficient range TLB flushes.
 */
static int wp_pte(pte_t *pte, unsigned long addr, unsigned long end,
		  struct mm_walk *walk)
{
	struct wp_walk *wpwalk = walk->private;
	pte_t ptent = *pte;

	if (pte_write(ptent)) {
		pte_t old_pte = ptep_modify_prot_start(walk->vma, addr, pte);

		ptent = pte_wrprotect(old_pte);
		ptep_modify_prot_commit(walk->vma, addr, pte, old_pte, ptent);
		wpwalk->total++;
		wpwalk->tlbflush_start = min(wpwalk->tlbflush_start, addr);
		wpwalk->tlbflush_end = max(wpwalk->tlbflush_end,
					   addr + PAGE_SIZE);
	}

	return 0;
}

/**
 * struct clean_walk - Private struct for the clean_record_pte function.
 * @base: struct wp_walk we derive from
 * @bitmap_pgoff: Address_space Page offset of the first bit in @bitmap
 * @bitmap: Bitmap with one bit for each page offset in the address_space range
 * covered.
 * @start: Address_space page offset of first modified pte relative
 * to @bitmap_pgoff
 * @end: Address_space page offset of last modified pte relative
 * to @bitmap_pgoff
 */
struct clean_walk {
	struct wp_walk base;
	pgoff_t bitmap_pgoff;
	unsigned long *bitmap;
	pgoff_t start;
	pgoff_t end;
};

#define to_clean_walk(_wpwalk) container_of(_wpwalk, struct clean_walk, base)

/**
 * clean_record_pte - Clean a pte and record its address space offset in a
 * bitmap
 * @pte: Pointer to the pte
 * @addr: The start of virtual address to be clean
 * @end: The end of virtual address to be clean
 * @walk: pagetable walk callback argument
 *
 * The function cleans a pte and records the range in
 * virtual address space of touched ptes for efficient TLB flushes.
 * It also records dirty ptes in a bitmap representing page offsets
 * in the address_space, as well as the first and last of the bits
 * touched.
 */
static int clean_record_pte(pte_t *pte, unsigned long addr,
			    unsigned long end, struct mm_walk *walk)
{
	struct wp_walk *wpwalk = walk->private;
	struct clean_walk *cwalk = to_clean_walk(wpwalk);
	pte_t ptent = *pte;

	if (pte_dirty(ptent)) {
		pgoff_t pgoff = ((addr - walk->vma->vm_start) >> PAGE_SHIFT) +
			walk->vma->vm_pgoff - cwalk->bitmap_pgoff;
		pte_t old_pte = ptep_modify_prot_start(walk->vma, addr, pte);

		ptent = pte_mkclean(old_pte);
		ptep_modify_prot_commit(walk->vma, addr, pte, old_pte, ptent);

		wpwalk->total++;
		wpwalk->tlbflush_start = min(wpwalk->tlbflush_start, addr);
		wpwalk->tlbflush_end = max(wpwalk->tlbflush_end,
					   addr + PAGE_SIZE);

		__set_bit(pgoff, cwalk->bitmap);
		cwalk->start = min(cwalk->start, pgoff);
		cwalk->end = max(cwalk->end, pgoff + 1);
	}

	return 0;
}

/*
 * wp_clean_pmd_entry - The pagewalk pmd callback.
 *
 * Dirty-tracking should take place on the PTE level, so
 * WARN() if encountering a dirty huge pmd.
 * Furthermore, never split huge pmds, since that currently
 * causes dirty info loss. The pagefault handler should do
 * that if needed.
 */
static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end,
			      struct mm_walk *walk)
{
	pmd_t pmdval = pmd_read_atomic(pmd);

	if (!pmd_trans_unstable(&pmdval))
		return 0;

	if (pmd_none(pmdval)) {
		walk->action = ACTION_AGAIN;
		return 0;
	}

	/* Huge pmd, present or migrated */
	walk->action = ACTION_CONTINUE;
	if (pmd_trans_huge(pmdval) || pmd_devmap(pmdval))
		WARN_ON(pmd_write(pmdval) || pmd_dirty(pmdval));

	return 0;
}

/*
 * wp_clean_pud_entry - The pagewalk pud callback.
 *
 * Dirty-tracking should take place on the PTE level, so
 * WARN() if encountering a dirty huge puds.
 * Furthermore, never split huge puds, since that currently
 * causes dirty info loss. The pagefault handler should do
 * that if needed.
 */
static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end,
			      struct mm_walk *walk)
{
	pud_t pudval = READ_ONCE(*pud);

	if (!pud_trans_unstable(&pudval))
		return 0;

	if (pud_none(pudval)) {
		walk->action = ACTION_AGAIN;
		return 0;
	}

#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
	/* Huge pud */
	walk->action = ACTION_CONTINUE;
	if (pud_trans_huge(pudval) || pud_devmap(pudval))
		WARN_ON(pud_write(pudval) || pud_dirty(pudval));
#endif

	return 0;
}

/*
 * wp_clean_pre_vma - The pagewalk pre_vma callback.
 *
 * The pre_vma callback performs the cache flush, stages the tlb flush
 * and calls the necessary mmu notifiers.
 */
static int wp_clean_pre_vma(unsigned long start, unsigned long end,
			    struct mm_walk *walk)
{
	struct wp_walk *wpwalk = walk->private;

	wpwalk->tlbflush_start = end;
	wpwalk->tlbflush_end = start;

	mmu_notifier_range_init(&wpwalk->range, MMU_NOTIFY_PROTECTION_PAGE, 0,
				walk->vma, walk->mm, start, end);
	mmu_notifier_invalidate_range_start(&wpwalk->range);
	flush_cache_range(walk->vma, start, end);

	/*
	 * We're not using tlb_gather_mmu() since typically
	 * only a small subrange of PTEs are affected, whereas
	 * tlb_gather_mmu() records the full range.
	 */
	inc_tlb_flush_pending(walk->mm);

	return 0;
}

/*
 * wp_clean_post_vma - The pagewalk post_vma callback.
 *
 * The post_vma callback performs the tlb flush and calls necessary mmu
 * notifiers.
 */
static void wp_clean_post_vma(struct mm_walk *walk)
{
	struct wp_walk *wpwalk = walk->private;

	if (mm_tlb_flush_nested(walk->mm))
		flush_tlb_range(walk->vma, wpwalk->range.start,
				wpwalk->range.end);
	else if (wpwalk->tlbflush_end > wpwalk->tlbflush_start)
		flush_tlb_range(walk->vma, wpwalk->tlbflush_start,
				wpwalk->tlbflush_end);

	mmu_notifier_invalidate_range_end(&wpwalk->range);
	dec_tlb_flush_pending(walk->mm);
}

/*
 * wp_clean_test_walk - The pagewalk test_walk callback.
 *
 * Won't perform dirty-tracking on COW, read-only or HUGETLB vmas.
 */
static int wp_clean_test_walk(unsigned long start, unsigned long end,
			      struct mm_walk *walk)
{
	unsigned long vm_flags = READ_ONCE(walk->vma->vm_flags);

	/* Skip non-applicable VMAs */
	if ((vm_flags & (VM_SHARED | VM_MAYWRITE | VM_HUGETLB)) !=
	    (VM_SHARED | VM_MAYWRITE))
		return 1;

	return 0;
}

static const struct mm_walk_ops clean_walk_ops = {
	.pte_entry = clean_record_pte,
	.pmd_entry = wp_clean_pmd_entry,
	.pud_entry = wp_clean_pud_entry,
	.test_walk = wp_clean_test_walk,
	.pre_vma = wp_clean_pre_vma,
	.post_vma = wp_clean_post_vma
};

static const struct mm_walk_ops wp_walk_ops = {
	.pte_entry = wp_pte,
	.pmd_entry = wp_clean_pmd_entry,
	.pud_entry = wp_clean_pud_entry,
	.test_walk = wp_clean_test_walk,
	.pre_vma = wp_clean_pre_vma,
	.post_vma = wp_clean_post_vma
};

/**
 * wp_shared_mapping_range - Write-protect all ptes in an address space range
 * @mapping: The address_space we want to write protect
 * @first_index: The first page offset in the range
 * @nr: Number of incremental page offsets to cover
 *
 * Note: This function currently skips transhuge page-table entries, since
 * it's intended for dirty-tracking on the PTE level. It will warn on
 * encountering transhuge write-enabled entries, though, and can easily be
 * extended to handle them as well.
 *
 * Return: The number of ptes actually write-protected. Note that
 * already write-protected ptes are not counted.
 */
unsigned long wp_shared_mapping_range(struct address_space *mapping,
				      pgoff_t first_index, pgoff_t nr)
{
	struct wp_walk wpwalk = { .total = 0 };

	i_mmap_lock_read(mapping);
	WARN_ON(walk_page_mapping(mapping, first_index, nr, &wp_walk_ops,
				  &wpwalk));
	i_mmap_unlock_read(mapping);

	return wpwalk.total;
}
EXPORT_SYMBOL_GPL(wp_shared_mapping_range);

/**
 * clean_record_shared_mapping_range - Clean and record all ptes in an
 * address space range
 * @mapping: The address_space we want to clean
 * @first_index: The first page offset in the range
 * @nr: Number of incremental page offsets to cover
 * @bitmap_pgoff: The page offset of the first bit in @bitmap
 * @bitmap: Pointer to a bitmap of at least @nr bits. The bitmap needs to
 * cover the whole range @first_index..@first_index + @nr.
 * @start: Pointer to number of the first set bit in @bitmap.
 * is modified as new bits are set by the function.
 * @end: Pointer to the number of the last set bit in @bitmap.
 * none set. The value is modified as new bits are set by the function.
 *
 * Note: When this function returns there is no guarantee that a CPU has
 * not already dirtied new ptes. However it will not clean any ptes not
 * reported in the bitmap. The guarantees are as follows:
 * a) All ptes dirty when the function starts executing will end up recorded
 *    in the bitmap.
 * b) All ptes dirtied after that will either remain dirty, be recorded in the
 *    bitmap or both.
 *
 * If a caller needs to make sure all dirty ptes are picked up and none
 * additional are added, it first needs to write-protect the address-space
 * range and make sure new writers are blocked in page_mkwrite() or
 * pfn_mkwrite(). And then after a TLB flush following the write-protection
 * pick up all dirty bits.
 *
 * This function currently skips transhuge page-table entries, since
 * it's intended for dirty-tracking on the PTE level. It will warn on
 * encountering transhuge dirty entries, though, and can easily be extended
 * to handle them as well.
 *
 * Return: The number of dirty ptes actually cleaned.
 */
unsigned long clean_record_shared_mapping_range(struct address_space *mapping,
						pgoff_t first_index, pgoff_t nr,
						pgoff_t bitmap_pgoff,
						unsigned long *bitmap,
						pgoff_t *start,
						pgoff_t *end)
{
	bool none_set = (*start >= *end);
	struct clean_walk cwalk = {
		.base = { .total = 0 },
		.bitmap_pgoff = bitmap_pgoff,
		.bitmap = bitmap,
		.start = none_set ? nr : *start,
		.end = none_set ? 0 : *end,
	};

	i_mmap_lock_read(mapping);
	WARN_ON(walk_page_mapping(mapping, first_index, nr, &clean_walk_ops,
				  &cwalk.base));
	i_mmap_unlock_read(mapping);

	*start = cwalk.start;
	*end = cwalk.end;

	return cwalk.base.total;
}
EXPORT_SYMBOL_GPL(clean_record_shared_mapping_range);
Commit	Line	Data
c5acad84 TH	1	// SPDX-License-Identifier: GPL-2.0
	2	#include <linux/pagewalk.h>
	3	#include <linux/hugetlb.h>
	4	#include <linux/bitops.h>
	5	#include <linux/mmu_notifier.h>
36090def	6	#include <linux/mm_inline.h>
c5acad84 TH	7	#include <asm/cacheflush.h>
	8	#include <asm/tlbflush.h>
	9
	10	/**
	11	* struct wp_walk - Private struct for pagetable walk callbacks
	12	* @range: Range for mmu notifiers
	13	* @tlbflush_start: Address of first modified pte
	14	* @tlbflush_end: Address of last modified pte + 1
	15	* @total: Total number of modified ptes
	16	*/
	17	struct wp_walk {
	18	struct mmu_notifier_range range;
	19	unsigned long tlbflush_start;
	20	unsigned long tlbflush_end;
	21	unsigned long total;
	22	};
	23
	24	/**
	25	* wp_pte - Write-protect a pte
	26	* @pte: Pointer to the pte
f5b7e739 AS	27	* @addr: The start of protecting virtual address
f5b7e739 AS	28	* @end: The end of protecting virtual address
c5acad84 TH	29	* @walk: pagetable walk callback argument
	30	*
	31	* The function write-protects a pte and records the range in
	32	* virtual address space of touched ptes for efficient range TLB flushes.
	33	*/
	34	static int wp_pte(pte_t *pte, unsigned long addr, unsigned long end,
	35	struct mm_walk *walk)
	36	{
	37	struct wp_walk *wpwalk = walk->private;
	38	pte_t ptent = *pte;
	39
	40	if (pte_write(ptent)) {
	41	pte_t old_pte = ptep_modify_prot_start(walk->vma, addr, pte);
	42
	43	ptent = pte_wrprotect(old_pte);
	44	ptep_modify_prot_commit(walk->vma, addr, pte, old_pte, ptent);
	45	wpwalk->total++;
	46	wpwalk->tlbflush_start = min(wpwalk->tlbflush_start, addr);
	47	wpwalk->tlbflush_end = max(wpwalk->tlbflush_end,
	48	addr + PAGE_SIZE);
	49	}
	50
	51	return 0;
	52	}
	53
	54	/**
	55	* struct clean_walk - Private struct for the clean_record_pte function.
	56	* @base: struct wp_walk we derive from
	57	* @bitmap_pgoff: Address_space Page offset of the first bit in @bitmap
	58	* @bitmap: Bitmap with one bit for each page offset in the address_space range
	59	* covered.
	60	* @start: Address_space page offset of first modified pte relative
	61	* to @bitmap_pgoff
	62	* @end: Address_space page offset of last modified pte relative
	63	* to @bitmap_pgoff
	64	*/
	65	struct clean_walk {
	66	struct wp_walk base;
	67	pgoff_t bitmap_pgoff;
	68	unsigned long *bitmap;
	69	pgoff_t start;
	70	pgoff_t end;
	71	};
	72
	73	#define to_clean_walk(_wpwalk) container_of(_wpwalk, struct clean_walk, base)
	74
	75	/**
	76	* clean_record_pte - Clean a pte and record its address space offset in a
	77	* bitmap
	78	* @pte: Pointer to the pte
f5b7e739 AS	79	* @addr: The start of virtual address to be clean
f5b7e739 AS	80	* @end: The end of virtual address to be clean
c5acad84 TH	81	* @walk: pagetable walk callback argument
	82	*
	83	* The function cleans a pte and records the range in
	84	* virtual address space of touched ptes for efficient TLB flushes.
	85	* It also records dirty ptes in a bitmap representing page offsets
	86	* in the address_space, as well as the first and last of the bits
	87	* touched.
	88	*/
	89	static int clean_record_pte(pte_t *pte, unsigned long addr,
	90	unsigned long end, struct mm_walk *walk)
	91	{
	92	struct wp_walk *wpwalk = walk->private;
	93	struct clean_walk *cwalk = to_clean_walk(wpwalk);
	94	pte_t ptent = *pte;
	95
	96	if (pte_dirty(ptent)) {
	97	pgoff_t pgoff = ((addr - walk->vma->vm_start) >> PAGE_SHIFT) +
	98	walk->vma->vm_pgoff - cwalk->bitmap_pgoff;
	99	pte_t old_pte = ptep_modify_prot_start(walk->vma, addr, pte);
	100
	101	ptent = pte_mkclean(old_pte);
	102	ptep_modify_prot_commit(walk->vma, addr, pte, old_pte, ptent);
	103
	104	wpwalk->total++;
	105	wpwalk->tlbflush_start = min(wpwalk->tlbflush_start, addr);
	106	wpwalk->tlbflush_end = max(wpwalk->tlbflush_end,
	107	addr + PAGE_SIZE);
	108
	109	__set_bit(pgoff, cwalk->bitmap);
	110	cwalk->start = min(cwalk->start, pgoff);
	111	cwalk->end = max(cwalk->end, pgoff + 1);
	112	}
	113
	114	return 0;
	115	}
	116
b2a403fd TH	117	/*
	118	* wp_clean_pmd_entry - The pagewalk pmd callback.
	119	*
	120	* Dirty-tracking should take place on the PTE level, so
	121	* WARN() if encountering a dirty huge pmd.
	122	* Furthermore, never split huge pmds, since that currently
	123	* causes dirty info loss. The pagefault handler should do
	124	* that if needed.
	125	*/
c5acad84 TH	126	static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end,
	127	struct mm_walk *walk)
	128	{
c5acad84 TH	129	pmd_t pmdval = pmd_read_atomic(pmd);
c5acad84 TH	130
b2a403fd TH	131	if (!pmd_trans_unstable(&pmdval))
	132	return 0;
	133
	134	if (pmd_none(pmdval)) {
	135	walk->action = ACTION_AGAIN;
	136	return 0;
	137	}
	138
	139	/* Huge pmd, present or migrated */
	140	walk->action = ACTION_CONTINUE;
c5acad84 TH	141	if (pmd_trans_huge(pmdval) \|\| pmd_devmap(pmdval))
	142	WARN_ON(pmd_write(pmdval) \|\| pmd_dirty(pmdval));
	143
	144	return 0;
	145	}
	146
b2a403fd TH	147	/*
	148	* wp_clean_pud_entry - The pagewalk pud callback.
	149	*
	150	* Dirty-tracking should take place on the PTE level, so
	151	* WARN() if encountering a dirty huge puds.
	152	* Furthermore, never split huge puds, since that currently
	153	* causes dirty info loss. The pagefault handler should do
	154	* that if needed.
	155	*/
c5acad84 TH	156	static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end,
	157	struct mm_walk *walk)
	158	{
c5acad84 TH	159	pud_t pudval = READ_ONCE(*pud);
c5acad84 TH	160
b2a403fd TH	161	if (!pud_trans_unstable(&pudval))
	162	return 0;
	163
	164	if (pud_none(pudval)) {
	165	walk->action = ACTION_AGAIN;
	166	return 0;
	167	}
	168
94036f4c	169	#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
b2a403fd TH	170	/* Huge pud */
b2a403fd TH	171	walk->action = ACTION_CONTINUE;
c5acad84 TH	172	if (pud_trans_huge(pudval) \|\| pud_devmap(pudval))
c5acad84 TH	173	WARN_ON(pud_write(pudval) \|\| pud_dirty(pudval));
94036f4c	174	#endif
c5acad84 TH	175
	176	return 0;
	177	}
	178
	179	/*
	180	* wp_clean_pre_vma - The pagewalk pre_vma callback.
	181	*
	182	* The pre_vma callback performs the cache flush, stages the tlb flush
	183	* and calls the necessary mmu notifiers.
	184	*/
	185	static int wp_clean_pre_vma(unsigned long start, unsigned long end,
	186	struct mm_walk *walk)
	187	{
	188	struct wp_walk *wpwalk = walk->private;
	189
	190	wpwalk->tlbflush_start = end;
	191	wpwalk->tlbflush_end = start;
	192
	193	mmu_notifier_range_init(&wpwalk->range, MMU_NOTIFY_PROTECTION_PAGE, 0,
	194	walk->vma, walk->mm, start, end);
	195	mmu_notifier_invalidate_range_start(&wpwalk->range);
	196	flush_cache_range(walk->vma, start, end);
	197
	198	/*
	199	* We're not using tlb_gather_mmu() since typically
	200	* only a small subrange of PTEs are affected, whereas
	201	* tlb_gather_mmu() records the full range.
	202	*/
	203	inc_tlb_flush_pending(walk->mm);
	204
	205	return 0;
	206	}
	207
	208	/*
	209	* wp_clean_post_vma - The pagewalk post_vma callback.
	210	*
	211	* The post_vma callback performs the tlb flush and calls necessary mmu
	212	* notifiers.
	213	*/
	214	static void wp_clean_post_vma(struct mm_walk *walk)
	215	{
	216	struct wp_walk *wpwalk = walk->private;
	217
	218	if (mm_tlb_flush_nested(walk->mm))
	219	flush_tlb_range(walk->vma, wpwalk->range.start,
	220	wpwalk->range.end);
	221	else if (wpwalk->tlbflush_end > wpwalk->tlbflush_start)
	222	flush_tlb_range(walk->vma, wpwalk->tlbflush_start,
	223	wpwalk->tlbflush_end);
	224
	225	mmu_notifier_invalidate_range_end(&wpwalk->range);
	226	dec_tlb_flush_pending(walk->mm);
	227	}
	228
	229	/*
	230	* wp_clean_test_walk - The pagewalk test_walk callback.
	231	*
	232	* Won't perform dirty-tracking on COW, read-only or HUGETLB vmas.
	233	*/
	234	static int wp_clean_test_walk(unsigned long start, unsigned long end,
	235	struct mm_walk *walk)
	236	{
	237	unsigned long vm_flags = READ_ONCE(walk->vma->vm_flags);
	238
239	/* Skip non-applicable VMAs */
240	if ((vm_flags & (VM_SHARED \| VM_MAYWRITE \| VM_HUGETLB)) !=
241	(VM_SHARED \| VM_MAYWRITE))
242	return 1;
243
244	return 0;
245	}
246
247	static const struct mm_walk_ops clean_walk_ops = {
248	.pte_entry = clean_record_pte,
249	.pmd_entry = wp_clean_pmd_entry,
250	.pud_entry = wp_clean_pud_entry,
251	.test_walk = wp_clean_test_walk,
252	.pre_vma = wp_clean_pre_vma,
253	.post_vma = wp_clean_post_vma
254	};
255
256	static const struct mm_walk_ops wp_walk_ops = {
257	.pte_entry = wp_pte,
258	.pmd_entry = wp_clean_pmd_entry,
259	.pud_entry = wp_clean_pud_entry,
260	.test_walk = wp_clean_test_walk,
261	.pre_vma = wp_clean_pre_vma,
262	.post_vma = wp_clean_post_vma
263	};
264
265	/**
266	* wp_shared_mapping_range - Write-protect all ptes in an address space range
267	* @mapping: The address_space we want to write protect
268	* @first_index: The first page offset in the range
269	* @nr: Number of incremental page offsets to cover
270	*
271	* Note: This function currently skips transhuge page-table entries, since
272	* it's intended for dirty-tracking on the PTE level. It will warn on
273	* encountering transhuge write-enabled entries, though, and can easily be
274	* extended to handle them as well.
275	*
276	* Return: The number of ptes actually write-protected. Note that
277	* already write-protected ptes are not counted.
278	*/
279	unsigned long wp_shared_mapping_range(struct address_space *mapping,
280	pgoff_t first_index, pgoff_t nr)
281	{
282	struct wp_walk wpwalk = { .total = 0 };
283
284	i_mmap_lock_read(mapping);
285	WARN_ON(walk_page_mapping(mapping, first_index, nr, &wp_walk_ops,
286	&wpwalk));
287	i_mmap_unlock_read(mapping);
288
289	return wpwalk.total;
290	}
291	EXPORT_SYMBOL_GPL(wp_shared_mapping_range);
292
293	/**
294	* clean_record_shared_mapping_range - Clean and record all ptes in an
295	* address space range
296	* @mapping: The address_space we want to clean
297	* @first_index: The first page offset in the range
298	* @nr: Number of incremental page offsets to cover
299	* @bitmap_pgoff: The page offset of the first bit in @bitmap
300	* @bitmap: Pointer to a bitmap of at least @nr bits. The bitmap needs to
301	* cover the whole range @first_index..@first_index + @nr.
302	* @start: Pointer to number of the first set bit in @bitmap.
303	* is modified as new bits are set by the function.
304	* @end: Pointer to the number of the last set bit in @bitmap.
305	* none set. The value is modified as new bits are set by the function.
306	*
307	* Note: When this function returns there is no guarantee that a CPU has
308	* not already dirtied new ptes. However it will not clean any ptes not
309	* reported in the bitmap. The guarantees are as follows:
310	* a) All ptes dirty when the function starts executing will end up recorded
311	* in the bitmap.
312	* b) All ptes dirtied after that will either remain dirty, be recorded in the
313	* bitmap or both.
314	*
315	* If a caller needs to make sure all dirty ptes are picked up and none
316	* additional are added, it first needs to write-protect the address-space
317	* range and make sure new writers are blocked in page_mkwrite() or
318	* pfn_mkwrite(). And then after a TLB flush following the write-protection
319	* pick up all dirty bits.
320	*
b417941f	321	* This function currently skips transhuge page-table entries, since
c5acad84 TH	322	* it's intended for dirty-tracking on the PTE level. It will warn on
	323	* encountering transhuge dirty entries, though, and can easily be extended
	324	* to handle them as well.
	325	*
	326	* Return: The number of dirty ptes actually cleaned.
	327	*/
	328	unsigned long clean_record_shared_mapping_range(struct address_space *mapping,
	329	pgoff_t first_index, pgoff_t nr,
	330	pgoff_t bitmap_pgoff,
	331	unsigned long *bitmap,
	332	pgoff_t *start,
	333	pgoff_t *end)
	334	{
	335	bool none_set = (start >= end);
	336	struct clean_walk cwalk = {
	337	.base = { .total = 0 },
	338	.bitmap_pgoff = bitmap_pgoff,
	339	.bitmap = bitmap,
	340	.start = none_set ? nr : *start,
	341	.end = none_set ? 0 : *end,
	342	};
	343
	344	i_mmap_lock_read(mapping);
	345	WARN_ON(walk_page_mapping(mapping, first_index, nr, &clean_walk_ops,
	346	&cwalk.base));
	347	i_mmap_unlock_read(mapping);
	348
	349	*start = cwalk.start;
	350	*end = cwalk.end;
	351
	352	return cwalk.base.total;
	353	}
	354	EXPORT_SYMBOL_GPL(clean_record_shared_mapping_range);