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