| 1 | /* |
| 2 | * mm/rmap.c - physical to virtual reverse mappings |
| 3 | * |
| 4 | * Copyright 2001, Rik van Riel <riel@conectiva.com.br> |
| 5 | * Released under the General Public License (GPL). |
| 6 | * |
| 7 | * Simple, low overhead reverse mapping scheme. |
| 8 | * Please try to keep this thing as modular as possible. |
| 9 | * |
| 10 | * Provides methods for unmapping each kind of mapped page: |
| 11 | * the anon methods track anonymous pages, and |
| 12 | * the file methods track pages belonging to an inode. |
| 13 | * |
| 14 | * Original design by Rik van Riel <riel@conectiva.com.br> 2001 |
| 15 | * File methods by Dave McCracken <dmccr@us.ibm.com> 2003, 2004 |
| 16 | * Anonymous methods by Andrea Arcangeli <andrea@suse.de> 2004 |
| 17 | * Contributions by Hugh Dickins 2003, 2004 |
| 18 | */ |
| 19 | |
| 20 | /* |
| 21 | * Lock ordering in mm: |
| 22 | * |
| 23 | * inode->i_rwsem (while writing or truncating, not reading or faulting) |
| 24 | * mm->mmap_lock |
| 25 | * mapping->invalidate_lock (in filemap_fault) |
| 26 | * folio_lock |
| 27 | * hugetlbfs_i_mmap_rwsem_key (in huge_pmd_share, see hugetlbfs below) |
| 28 | * vma_start_write |
| 29 | * mapping->i_mmap_rwsem |
| 30 | * anon_vma->rwsem |
| 31 | * mm->page_table_lock or pte_lock |
| 32 | * swap_lock (in swap_duplicate, swap_info_get) |
| 33 | * mmlist_lock (in mmput, drain_mmlist and others) |
| 34 | * mapping->private_lock (in block_dirty_folio) |
| 35 | * folio_lock_memcg move_lock (in block_dirty_folio) |
| 36 | * i_pages lock (widely used) |
| 37 | * lruvec->lru_lock (in folio_lruvec_lock_irq) |
| 38 | * inode->i_lock (in set_page_dirty's __mark_inode_dirty) |
| 39 | * bdi.wb->list_lock (in set_page_dirty's __mark_inode_dirty) |
| 40 | * sb_lock (within inode_lock in fs/fs-writeback.c) |
| 41 | * i_pages lock (widely used, in set_page_dirty, |
| 42 | * in arch-dependent flush_dcache_mmap_lock, |
| 43 | * within bdi.wb->list_lock in __sync_single_inode) |
| 44 | * |
| 45 | * anon_vma->rwsem,mapping->i_mmap_rwsem (memory_failure, collect_procs_anon) |
| 46 | * ->tasklist_lock |
| 47 | * pte map lock |
| 48 | * |
| 49 | * hugetlbfs PageHuge() take locks in this order: |
| 50 | * hugetlb_fault_mutex (hugetlbfs specific page fault mutex) |
| 51 | * vma_lock (hugetlb specific lock for pmd_sharing) |
| 52 | * mapping->i_mmap_rwsem (also used for hugetlb pmd sharing) |
| 53 | * folio_lock |
| 54 | */ |
| 55 | |
| 56 | #include <linux/mm.h> |
| 57 | #include <linux/sched/mm.h> |
| 58 | #include <linux/sched/task.h> |
| 59 | #include <linux/pagemap.h> |
| 60 | #include <linux/swap.h> |
| 61 | #include <linux/swapops.h> |
| 62 | #include <linux/slab.h> |
| 63 | #include <linux/init.h> |
| 64 | #include <linux/ksm.h> |
| 65 | #include <linux/rmap.h> |
| 66 | #include <linux/rcupdate.h> |
| 67 | #include <linux/export.h> |
| 68 | #include <linux/memcontrol.h> |
| 69 | #include <linux/mmu_notifier.h> |
| 70 | #include <linux/migrate.h> |
| 71 | #include <linux/hugetlb.h> |
| 72 | #include <linux/huge_mm.h> |
| 73 | #include <linux/backing-dev.h> |
| 74 | #include <linux/page_idle.h> |
| 75 | #include <linux/memremap.h> |
| 76 | #include <linux/userfaultfd_k.h> |
| 77 | #include <linux/mm_inline.h> |
| 78 | |
| 79 | #include <asm/tlbflush.h> |
| 80 | |
| 81 | #define CREATE_TRACE_POINTS |
| 82 | #include <trace/events/tlb.h> |
| 83 | #include <trace/events/migrate.h> |
| 84 | |
| 85 | #include "internal.h" |
| 86 | |
| 87 | static struct kmem_cache *anon_vma_cachep; |
| 88 | static struct kmem_cache *anon_vma_chain_cachep; |
| 89 | |
| 90 | static inline struct anon_vma *anon_vma_alloc(void) |
| 91 | { |
| 92 | struct anon_vma *anon_vma; |
| 93 | |
| 94 | anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL); |
| 95 | if (anon_vma) { |
| 96 | atomic_set(&anon_vma->refcount, 1); |
| 97 | anon_vma->num_children = 0; |
| 98 | anon_vma->num_active_vmas = 0; |
| 99 | anon_vma->parent = anon_vma; |
| 100 | /* |
| 101 | * Initialise the anon_vma root to point to itself. If called |
| 102 | * from fork, the root will be reset to the parents anon_vma. |
| 103 | */ |
| 104 | anon_vma->root = anon_vma; |
| 105 | } |
| 106 | |
| 107 | return anon_vma; |
| 108 | } |
| 109 | |
| 110 | static inline void anon_vma_free(struct anon_vma *anon_vma) |
| 111 | { |
| 112 | VM_BUG_ON(atomic_read(&anon_vma->refcount)); |
| 113 | |
| 114 | /* |
| 115 | * Synchronize against folio_lock_anon_vma_read() such that |
| 116 | * we can safely hold the lock without the anon_vma getting |
| 117 | * freed. |
| 118 | * |
| 119 | * Relies on the full mb implied by the atomic_dec_and_test() from |
| 120 | * put_anon_vma() against the acquire barrier implied by |
| 121 | * down_read_trylock() from folio_lock_anon_vma_read(). This orders: |
| 122 | * |
| 123 | * folio_lock_anon_vma_read() VS put_anon_vma() |
| 124 | * down_read_trylock() atomic_dec_and_test() |
| 125 | * LOCK MB |
| 126 | * atomic_read() rwsem_is_locked() |
| 127 | * |
| 128 | * LOCK should suffice since the actual taking of the lock must |
| 129 | * happen _before_ what follows. |
| 130 | */ |
| 131 | might_sleep(); |
| 132 | if (rwsem_is_locked(&anon_vma->root->rwsem)) { |
| 133 | anon_vma_lock_write(anon_vma); |
| 134 | anon_vma_unlock_write(anon_vma); |
| 135 | } |
| 136 | |
| 137 | kmem_cache_free(anon_vma_cachep, anon_vma); |
| 138 | } |
| 139 | |
| 140 | static inline struct anon_vma_chain *anon_vma_chain_alloc(gfp_t gfp) |
| 141 | { |
| 142 | return kmem_cache_alloc(anon_vma_chain_cachep, gfp); |
| 143 | } |
| 144 | |
| 145 | static void anon_vma_chain_free(struct anon_vma_chain *anon_vma_chain) |
| 146 | { |
| 147 | kmem_cache_free(anon_vma_chain_cachep, anon_vma_chain); |
| 148 | } |
| 149 | |
| 150 | static void anon_vma_chain_link(struct vm_area_struct *vma, |
| 151 | struct anon_vma_chain *avc, |
| 152 | struct anon_vma *anon_vma) |
| 153 | { |
| 154 | avc->vma = vma; |
| 155 | avc->anon_vma = anon_vma; |
| 156 | list_add(&avc->same_vma, &vma->anon_vma_chain); |
| 157 | anon_vma_interval_tree_insert(avc, &anon_vma->rb_root); |
| 158 | } |
| 159 | |
| 160 | /** |
| 161 | * __anon_vma_prepare - attach an anon_vma to a memory region |
| 162 | * @vma: the memory region in question |
| 163 | * |
| 164 | * This makes sure the memory mapping described by 'vma' has |
| 165 | * an 'anon_vma' attached to it, so that we can associate the |
| 166 | * anonymous pages mapped into it with that anon_vma. |
| 167 | * |
| 168 | * The common case will be that we already have one, which |
| 169 | * is handled inline by anon_vma_prepare(). But if |
| 170 | * not we either need to find an adjacent mapping that we |
| 171 | * can re-use the anon_vma from (very common when the only |
| 172 | * reason for splitting a vma has been mprotect()), or we |
| 173 | * allocate a new one. |
| 174 | * |
| 175 | * Anon-vma allocations are very subtle, because we may have |
| 176 | * optimistically looked up an anon_vma in folio_lock_anon_vma_read() |
| 177 | * and that may actually touch the rwsem even in the newly |
| 178 | * allocated vma (it depends on RCU to make sure that the |
| 179 | * anon_vma isn't actually destroyed). |
| 180 | * |
| 181 | * As a result, we need to do proper anon_vma locking even |
| 182 | * for the new allocation. At the same time, we do not want |
| 183 | * to do any locking for the common case of already having |
| 184 | * an anon_vma. |
| 185 | */ |
| 186 | int __anon_vma_prepare(struct vm_area_struct *vma) |
| 187 | { |
| 188 | struct mm_struct *mm = vma->vm_mm; |
| 189 | struct anon_vma *anon_vma, *allocated; |
| 190 | struct anon_vma_chain *avc; |
| 191 | |
| 192 | mmap_assert_locked(mm); |
| 193 | might_sleep(); |
| 194 | |
| 195 | avc = anon_vma_chain_alloc(GFP_KERNEL); |
| 196 | if (!avc) |
| 197 | goto out_enomem; |
| 198 | |
| 199 | anon_vma = find_mergeable_anon_vma(vma); |
| 200 | allocated = NULL; |
| 201 | if (!anon_vma) { |
| 202 | anon_vma = anon_vma_alloc(); |
| 203 | if (unlikely(!anon_vma)) |
| 204 | goto out_enomem_free_avc; |
| 205 | anon_vma->num_children++; /* self-parent link for new root */ |
| 206 | allocated = anon_vma; |
| 207 | } |
| 208 | |
| 209 | anon_vma_lock_write(anon_vma); |
| 210 | /* page_table_lock to protect against threads */ |
| 211 | spin_lock(&mm->page_table_lock); |
| 212 | if (likely(!vma->anon_vma)) { |
| 213 | vma->anon_vma = anon_vma; |
| 214 | anon_vma_chain_link(vma, avc, anon_vma); |
| 215 | anon_vma->num_active_vmas++; |
| 216 | allocated = NULL; |
| 217 | avc = NULL; |
| 218 | } |
| 219 | spin_unlock(&mm->page_table_lock); |
| 220 | anon_vma_unlock_write(anon_vma); |
| 221 | |
| 222 | if (unlikely(allocated)) |
| 223 | put_anon_vma(allocated); |
| 224 | if (unlikely(avc)) |
| 225 | anon_vma_chain_free(avc); |
| 226 | |
| 227 | return 0; |
| 228 | |
| 229 | out_enomem_free_avc: |
| 230 | anon_vma_chain_free(avc); |
| 231 | out_enomem: |
| 232 | return -ENOMEM; |
| 233 | } |
| 234 | |
| 235 | /* |
| 236 | * This is a useful helper function for locking the anon_vma root as |
| 237 | * we traverse the vma->anon_vma_chain, looping over anon_vma's that |
| 238 | * have the same vma. |
| 239 | * |
| 240 | * Such anon_vma's should have the same root, so you'd expect to see |
| 241 | * just a single mutex_lock for the whole traversal. |
| 242 | */ |
| 243 | static inline struct anon_vma *lock_anon_vma_root(struct anon_vma *root, struct anon_vma *anon_vma) |
| 244 | { |
| 245 | struct anon_vma *new_root = anon_vma->root; |
| 246 | if (new_root != root) { |
| 247 | if (WARN_ON_ONCE(root)) |
| 248 | up_write(&root->rwsem); |
| 249 | root = new_root; |
| 250 | down_write(&root->rwsem); |
| 251 | } |
| 252 | return root; |
| 253 | } |
| 254 | |
| 255 | static inline void unlock_anon_vma_root(struct anon_vma *root) |
| 256 | { |
| 257 | if (root) |
| 258 | up_write(&root->rwsem); |
| 259 | } |
| 260 | |
| 261 | /* |
| 262 | * Attach the anon_vmas from src to dst. |
| 263 | * Returns 0 on success, -ENOMEM on failure. |
| 264 | * |
| 265 | * anon_vma_clone() is called by vma_expand(), vma_merge(), __split_vma(), |
| 266 | * copy_vma() and anon_vma_fork(). The first four want an exact copy of src, |
| 267 | * while the last one, anon_vma_fork(), may try to reuse an existing anon_vma to |
| 268 | * prevent endless growth of anon_vma. Since dst->anon_vma is set to NULL before |
| 269 | * call, we can identify this case by checking (!dst->anon_vma && |
| 270 | * src->anon_vma). |
| 271 | * |
| 272 | * If (!dst->anon_vma && src->anon_vma) is true, this function tries to find |
| 273 | * and reuse existing anon_vma which has no vmas and only one child anon_vma. |
| 274 | * This prevents degradation of anon_vma hierarchy to endless linear chain in |
| 275 | * case of constantly forking task. On the other hand, an anon_vma with more |
| 276 | * than one child isn't reused even if there was no alive vma, thus rmap |
| 277 | * walker has a good chance of avoiding scanning the whole hierarchy when it |
| 278 | * searches where page is mapped. |
| 279 | */ |
| 280 | int anon_vma_clone(struct vm_area_struct *dst, struct vm_area_struct *src) |
| 281 | { |
| 282 | struct anon_vma_chain *avc, *pavc; |
| 283 | struct anon_vma *root = NULL; |
| 284 | |
| 285 | list_for_each_entry_reverse(pavc, &src->anon_vma_chain, same_vma) { |
| 286 | struct anon_vma *anon_vma; |
| 287 | |
| 288 | avc = anon_vma_chain_alloc(GFP_NOWAIT | __GFP_NOWARN); |
| 289 | if (unlikely(!avc)) { |
| 290 | unlock_anon_vma_root(root); |
| 291 | root = NULL; |
| 292 | avc = anon_vma_chain_alloc(GFP_KERNEL); |
| 293 | if (!avc) |
| 294 | goto enomem_failure; |
| 295 | } |
| 296 | anon_vma = pavc->anon_vma; |
| 297 | root = lock_anon_vma_root(root, anon_vma); |
| 298 | anon_vma_chain_link(dst, avc, anon_vma); |
| 299 | |
| 300 | /* |
| 301 | * Reuse existing anon_vma if it has no vma and only one |
| 302 | * anon_vma child. |
| 303 | * |
| 304 | * Root anon_vma is never reused: |
| 305 | * it has self-parent reference and at least one child. |
| 306 | */ |
| 307 | if (!dst->anon_vma && src->anon_vma && |
| 308 | anon_vma->num_children < 2 && |
| 309 | anon_vma->num_active_vmas == 0) |
| 310 | dst->anon_vma = anon_vma; |
| 311 | } |
| 312 | if (dst->anon_vma) |
| 313 | dst->anon_vma->num_active_vmas++; |
| 314 | unlock_anon_vma_root(root); |
| 315 | return 0; |
| 316 | |
| 317 | enomem_failure: |
| 318 | /* |
| 319 | * dst->anon_vma is dropped here otherwise its num_active_vmas can |
| 320 | * be incorrectly decremented in unlink_anon_vmas(). |
| 321 | * We can safely do this because callers of anon_vma_clone() don't care |
| 322 | * about dst->anon_vma if anon_vma_clone() failed. |
| 323 | */ |
| 324 | dst->anon_vma = NULL; |
| 325 | unlink_anon_vmas(dst); |
| 326 | return -ENOMEM; |
| 327 | } |
| 328 | |
| 329 | /* |
| 330 | * Attach vma to its own anon_vma, as well as to the anon_vmas that |
| 331 | * the corresponding VMA in the parent process is attached to. |
| 332 | * Returns 0 on success, non-zero on failure. |
| 333 | */ |
| 334 | int anon_vma_fork(struct vm_area_struct *vma, struct vm_area_struct *pvma) |
| 335 | { |
| 336 | struct anon_vma_chain *avc; |
| 337 | struct anon_vma *anon_vma; |
| 338 | int error; |
| 339 | |
| 340 | /* Don't bother if the parent process has no anon_vma here. */ |
| 341 | if (!pvma->anon_vma) |
| 342 | return 0; |
| 343 | |
| 344 | /* Drop inherited anon_vma, we'll reuse existing or allocate new. */ |
| 345 | vma->anon_vma = NULL; |
| 346 | |
| 347 | /* |
| 348 | * First, attach the new VMA to the parent VMA's anon_vmas, |
| 349 | * so rmap can find non-COWed pages in child processes. |
| 350 | */ |
| 351 | error = anon_vma_clone(vma, pvma); |
| 352 | if (error) |
| 353 | return error; |
| 354 | |
| 355 | /* An existing anon_vma has been reused, all done then. */ |
| 356 | if (vma->anon_vma) |
| 357 | return 0; |
| 358 | |
| 359 | /* Then add our own anon_vma. */ |
| 360 | anon_vma = anon_vma_alloc(); |
| 361 | if (!anon_vma) |
| 362 | goto out_error; |
| 363 | anon_vma->num_active_vmas++; |
| 364 | avc = anon_vma_chain_alloc(GFP_KERNEL); |
| 365 | if (!avc) |
| 366 | goto out_error_free_anon_vma; |
| 367 | |
| 368 | /* |
| 369 | * The root anon_vma's rwsem is the lock actually used when we |
| 370 | * lock any of the anon_vmas in this anon_vma tree. |
| 371 | */ |
| 372 | anon_vma->root = pvma->anon_vma->root; |
| 373 | anon_vma->parent = pvma->anon_vma; |
| 374 | /* |
| 375 | * With refcounts, an anon_vma can stay around longer than the |
| 376 | * process it belongs to. The root anon_vma needs to be pinned until |
| 377 | * this anon_vma is freed, because the lock lives in the root. |
| 378 | */ |
| 379 | get_anon_vma(anon_vma->root); |
| 380 | /* Mark this anon_vma as the one where our new (COWed) pages go. */ |
| 381 | vma->anon_vma = anon_vma; |
| 382 | anon_vma_lock_write(anon_vma); |
| 383 | anon_vma_chain_link(vma, avc, anon_vma); |
| 384 | anon_vma->parent->num_children++; |
| 385 | anon_vma_unlock_write(anon_vma); |
| 386 | |
| 387 | return 0; |
| 388 | |
| 389 | out_error_free_anon_vma: |
| 390 | put_anon_vma(anon_vma); |
| 391 | out_error: |
| 392 | unlink_anon_vmas(vma); |
| 393 | return -ENOMEM; |
| 394 | } |
| 395 | |
| 396 | void unlink_anon_vmas(struct vm_area_struct *vma) |
| 397 | { |
| 398 | struct anon_vma_chain *avc, *next; |
| 399 | struct anon_vma *root = NULL; |
| 400 | |
| 401 | /* |
| 402 | * Unlink each anon_vma chained to the VMA. This list is ordered |
| 403 | * from newest to oldest, ensuring the root anon_vma gets freed last. |
| 404 | */ |
| 405 | list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { |
| 406 | struct anon_vma *anon_vma = avc->anon_vma; |
| 407 | |
| 408 | root = lock_anon_vma_root(root, anon_vma); |
| 409 | anon_vma_interval_tree_remove(avc, &anon_vma->rb_root); |
| 410 | |
| 411 | /* |
| 412 | * Leave empty anon_vmas on the list - we'll need |
| 413 | * to free them outside the lock. |
| 414 | */ |
| 415 | if (RB_EMPTY_ROOT(&anon_vma->rb_root.rb_root)) { |
| 416 | anon_vma->parent->num_children--; |
| 417 | continue; |
| 418 | } |
| 419 | |
| 420 | list_del(&avc->same_vma); |
| 421 | anon_vma_chain_free(avc); |
| 422 | } |
| 423 | if (vma->anon_vma) { |
| 424 | vma->anon_vma->num_active_vmas--; |
| 425 | |
| 426 | /* |
| 427 | * vma would still be needed after unlink, and anon_vma will be prepared |
| 428 | * when handle fault. |
| 429 | */ |
| 430 | vma->anon_vma = NULL; |
| 431 | } |
| 432 | unlock_anon_vma_root(root); |
| 433 | |
| 434 | /* |
| 435 | * Iterate the list once more, it now only contains empty and unlinked |
| 436 | * anon_vmas, destroy them. Could not do before due to __put_anon_vma() |
| 437 | * needing to write-acquire the anon_vma->root->rwsem. |
| 438 | */ |
| 439 | list_for_each_entry_safe(avc, next, &vma->anon_vma_chain, same_vma) { |
| 440 | struct anon_vma *anon_vma = avc->anon_vma; |
| 441 | |
| 442 | VM_WARN_ON(anon_vma->num_children); |
| 443 | VM_WARN_ON(anon_vma->num_active_vmas); |
| 444 | put_anon_vma(anon_vma); |
| 445 | |
| 446 | list_del(&avc->same_vma); |
| 447 | anon_vma_chain_free(avc); |
| 448 | } |
| 449 | } |
| 450 | |
| 451 | static void anon_vma_ctor(void *data) |
| 452 | { |
| 453 | struct anon_vma *anon_vma = data; |
| 454 | |
| 455 | init_rwsem(&anon_vma->rwsem); |
| 456 | atomic_set(&anon_vma->refcount, 0); |
| 457 | anon_vma->rb_root = RB_ROOT_CACHED; |
| 458 | } |
| 459 | |
| 460 | void __init anon_vma_init(void) |
| 461 | { |
| 462 | anon_vma_cachep = kmem_cache_create("anon_vma", sizeof(struct anon_vma), |
| 463 | 0, SLAB_TYPESAFE_BY_RCU|SLAB_PANIC|SLAB_ACCOUNT, |
| 464 | anon_vma_ctor); |
| 465 | anon_vma_chain_cachep = KMEM_CACHE(anon_vma_chain, |
| 466 | SLAB_PANIC|SLAB_ACCOUNT); |
| 467 | } |
| 468 | |
| 469 | /* |
| 470 | * Getting a lock on a stable anon_vma from a page off the LRU is tricky! |
| 471 | * |
| 472 | * Since there is no serialization what so ever against folio_remove_rmap_*() |
| 473 | * the best this function can do is return a refcount increased anon_vma |
| 474 | * that might have been relevant to this page. |
| 475 | * |
| 476 | * The page might have been remapped to a different anon_vma or the anon_vma |
| 477 | * returned may already be freed (and even reused). |
| 478 | * |
| 479 | * In case it was remapped to a different anon_vma, the new anon_vma will be a |
| 480 | * child of the old anon_vma, and the anon_vma lifetime rules will therefore |
| 481 | * ensure that any anon_vma obtained from the page will still be valid for as |
| 482 | * long as we observe page_mapped() [ hence all those page_mapped() tests ]. |
| 483 | * |
| 484 | * All users of this function must be very careful when walking the anon_vma |
| 485 | * chain and verify that the page in question is indeed mapped in it |
| 486 | * [ something equivalent to page_mapped_in_vma() ]. |
| 487 | * |
| 488 | * Since anon_vma's slab is SLAB_TYPESAFE_BY_RCU and we know from |
| 489 | * folio_remove_rmap_*() that the anon_vma pointer from page->mapping is valid |
| 490 | * if there is a mapcount, we can dereference the anon_vma after observing |
| 491 | * those. |
| 492 | * |
| 493 | * NOTE: the caller should normally hold folio lock when calling this. If |
| 494 | * not, the caller needs to double check the anon_vma didn't change after |
| 495 | * taking the anon_vma lock for either read or write (UFFDIO_MOVE can modify it |
| 496 | * concurrently without folio lock protection). See folio_lock_anon_vma_read() |
| 497 | * which has already covered that, and comment above remap_pages(). |
| 498 | */ |
| 499 | struct anon_vma *folio_get_anon_vma(struct folio *folio) |
| 500 | { |
| 501 | struct anon_vma *anon_vma = NULL; |
| 502 | unsigned long anon_mapping; |
| 503 | |
| 504 | rcu_read_lock(); |
| 505 | anon_mapping = (unsigned long)READ_ONCE(folio->mapping); |
| 506 | if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) |
| 507 | goto out; |
| 508 | if (!folio_mapped(folio)) |
| 509 | goto out; |
| 510 | |
| 511 | anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); |
| 512 | if (!atomic_inc_not_zero(&anon_vma->refcount)) { |
| 513 | anon_vma = NULL; |
| 514 | goto out; |
| 515 | } |
| 516 | |
| 517 | /* |
| 518 | * If this folio is still mapped, then its anon_vma cannot have been |
| 519 | * freed. But if it has been unmapped, we have no security against the |
| 520 | * anon_vma structure being freed and reused (for another anon_vma: |
| 521 | * SLAB_TYPESAFE_BY_RCU guarantees that - so the atomic_inc_not_zero() |
| 522 | * above cannot corrupt). |
| 523 | */ |
| 524 | if (!folio_mapped(folio)) { |
| 525 | rcu_read_unlock(); |
| 526 | put_anon_vma(anon_vma); |
| 527 | return NULL; |
| 528 | } |
| 529 | out: |
| 530 | rcu_read_unlock(); |
| 531 | |
| 532 | return anon_vma; |
| 533 | } |
| 534 | |
| 535 | /* |
| 536 | * Similar to folio_get_anon_vma() except it locks the anon_vma. |
| 537 | * |
| 538 | * Its a little more complex as it tries to keep the fast path to a single |
| 539 | * atomic op -- the trylock. If we fail the trylock, we fall back to getting a |
| 540 | * reference like with folio_get_anon_vma() and then block on the mutex |
| 541 | * on !rwc->try_lock case. |
| 542 | */ |
| 543 | struct anon_vma *folio_lock_anon_vma_read(struct folio *folio, |
| 544 | struct rmap_walk_control *rwc) |
| 545 | { |
| 546 | struct anon_vma *anon_vma = NULL; |
| 547 | struct anon_vma *root_anon_vma; |
| 548 | unsigned long anon_mapping; |
| 549 | |
| 550 | retry: |
| 551 | rcu_read_lock(); |
| 552 | anon_mapping = (unsigned long)READ_ONCE(folio->mapping); |
| 553 | if ((anon_mapping & PAGE_MAPPING_FLAGS) != PAGE_MAPPING_ANON) |
| 554 | goto out; |
| 555 | if (!folio_mapped(folio)) |
| 556 | goto out; |
| 557 | |
| 558 | anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON); |
| 559 | root_anon_vma = READ_ONCE(anon_vma->root); |
| 560 | if (down_read_trylock(&root_anon_vma->rwsem)) { |
| 561 | /* |
| 562 | * folio_move_anon_rmap() might have changed the anon_vma as we |
| 563 | * might not hold the folio lock here. |
| 564 | */ |
| 565 | if (unlikely((unsigned long)READ_ONCE(folio->mapping) != |
| 566 | anon_mapping)) { |
| 567 | up_read(&root_anon_vma->rwsem); |
| 568 | rcu_read_unlock(); |
| 569 | goto retry; |
| 570 | } |
| 571 | |
| 572 | /* |
| 573 | * If the folio is still mapped, then this anon_vma is still |
| 574 | * its anon_vma, and holding the mutex ensures that it will |
| 575 | * not go away, see anon_vma_free(). |
| 576 | */ |
| 577 | if (!folio_mapped(folio)) { |
| 578 | up_read(&root_anon_vma->rwsem); |
| 579 | anon_vma = NULL; |
| 580 | } |
| 581 | goto out; |
| 582 | } |
| 583 | |
| 584 | if (rwc && rwc->try_lock) { |
| 585 | anon_vma = NULL; |
| 586 | rwc->contended = true; |
| 587 | goto out; |
| 588 | } |
| 589 | |
| 590 | /* trylock failed, we got to sleep */ |
| 591 | if (!atomic_inc_not_zero(&anon_vma->refcount)) { |
| 592 | anon_vma = NULL; |
| 593 | goto out; |
| 594 | } |
| 595 | |
| 596 | if (!folio_mapped(folio)) { |
| 597 | rcu_read_unlock(); |
| 598 | put_anon_vma(anon_vma); |
| 599 | return NULL; |
| 600 | } |
| 601 | |
| 602 | /* we pinned the anon_vma, its safe to sleep */ |
| 603 | rcu_read_unlock(); |
| 604 | anon_vma_lock_read(anon_vma); |
| 605 | |
| 606 | /* |
| 607 | * folio_move_anon_rmap() might have changed the anon_vma as we might |
| 608 | * not hold the folio lock here. |
| 609 | */ |
| 610 | if (unlikely((unsigned long)READ_ONCE(folio->mapping) != |
| 611 | anon_mapping)) { |
| 612 | anon_vma_unlock_read(anon_vma); |
| 613 | put_anon_vma(anon_vma); |
| 614 | anon_vma = NULL; |
| 615 | goto retry; |
| 616 | } |
| 617 | |
| 618 | if (atomic_dec_and_test(&anon_vma->refcount)) { |
| 619 | /* |
| 620 | * Oops, we held the last refcount, release the lock |
| 621 | * and bail -- can't simply use put_anon_vma() because |
| 622 | * we'll deadlock on the anon_vma_lock_write() recursion. |
| 623 | */ |
| 624 | anon_vma_unlock_read(anon_vma); |
| 625 | __put_anon_vma(anon_vma); |
| 626 | anon_vma = NULL; |
| 627 | } |
| 628 | |
| 629 | return anon_vma; |
| 630 | |
| 631 | out: |
| 632 | rcu_read_unlock(); |
| 633 | return anon_vma; |
| 634 | } |
| 635 | |
| 636 | #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH |
| 637 | /* |
| 638 | * Flush TLB entries for recently unmapped pages from remote CPUs. It is |
| 639 | * important if a PTE was dirty when it was unmapped that it's flushed |
| 640 | * before any IO is initiated on the page to prevent lost writes. Similarly, |
| 641 | * it must be flushed before freeing to prevent data leakage. |
| 642 | */ |
| 643 | void try_to_unmap_flush(void) |
| 644 | { |
| 645 | struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; |
| 646 | |
| 647 | if (!tlb_ubc->flush_required) |
| 648 | return; |
| 649 | |
| 650 | arch_tlbbatch_flush(&tlb_ubc->arch); |
| 651 | tlb_ubc->flush_required = false; |
| 652 | tlb_ubc->writable = false; |
| 653 | } |
| 654 | |
| 655 | /* Flush iff there are potentially writable TLB entries that can race with IO */ |
| 656 | void try_to_unmap_flush_dirty(void) |
| 657 | { |
| 658 | struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; |
| 659 | |
| 660 | if (tlb_ubc->writable) |
| 661 | try_to_unmap_flush(); |
| 662 | } |
| 663 | |
| 664 | /* |
| 665 | * Bits 0-14 of mm->tlb_flush_batched record pending generations. |
| 666 | * Bits 16-30 of mm->tlb_flush_batched bit record flushed generations. |
| 667 | */ |
| 668 | #define TLB_FLUSH_BATCH_FLUSHED_SHIFT 16 |
| 669 | #define TLB_FLUSH_BATCH_PENDING_MASK \ |
| 670 | ((1 << (TLB_FLUSH_BATCH_FLUSHED_SHIFT - 1)) - 1) |
| 671 | #define TLB_FLUSH_BATCH_PENDING_LARGE \ |
| 672 | (TLB_FLUSH_BATCH_PENDING_MASK / 2) |
| 673 | |
| 674 | static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval, |
| 675 | unsigned long uaddr) |
| 676 | { |
| 677 | struct tlbflush_unmap_batch *tlb_ubc = ¤t->tlb_ubc; |
| 678 | int batch; |
| 679 | bool writable = pte_dirty(pteval); |
| 680 | |
| 681 | if (!pte_accessible(mm, pteval)) |
| 682 | return; |
| 683 | |
| 684 | arch_tlbbatch_add_pending(&tlb_ubc->arch, mm, uaddr); |
| 685 | tlb_ubc->flush_required = true; |
| 686 | |
| 687 | /* |
| 688 | * Ensure compiler does not re-order the setting of tlb_flush_batched |
| 689 | * before the PTE is cleared. |
| 690 | */ |
| 691 | barrier(); |
| 692 | batch = atomic_read(&mm->tlb_flush_batched); |
| 693 | retry: |
| 694 | if ((batch & TLB_FLUSH_BATCH_PENDING_MASK) > TLB_FLUSH_BATCH_PENDING_LARGE) { |
| 695 | /* |
| 696 | * Prevent `pending' from catching up with `flushed' because of |
| 697 | * overflow. Reset `pending' and `flushed' to be 1 and 0 if |
| 698 | * `pending' becomes large. |
| 699 | */ |
| 700 | if (!atomic_try_cmpxchg(&mm->tlb_flush_batched, &batch, 1)) |
| 701 | goto retry; |
| 702 | } else { |
| 703 | atomic_inc(&mm->tlb_flush_batched); |
| 704 | } |
| 705 | |
| 706 | /* |
| 707 | * If the PTE was dirty then it's best to assume it's writable. The |
| 708 | * caller must use try_to_unmap_flush_dirty() or try_to_unmap_flush() |
| 709 | * before the page is queued for IO. |
| 710 | */ |
| 711 | if (writable) |
| 712 | tlb_ubc->writable = true; |
| 713 | } |
| 714 | |
| 715 | /* |
| 716 | * Returns true if the TLB flush should be deferred to the end of a batch of |
| 717 | * unmap operations to reduce IPIs. |
| 718 | */ |
| 719 | static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags) |
| 720 | { |
| 721 | if (!(flags & TTU_BATCH_FLUSH)) |
| 722 | return false; |
| 723 | |
| 724 | return arch_tlbbatch_should_defer(mm); |
| 725 | } |
| 726 | |
| 727 | /* |
| 728 | * Reclaim unmaps pages under the PTL but do not flush the TLB prior to |
| 729 | * releasing the PTL if TLB flushes are batched. It's possible for a parallel |
| 730 | * operation such as mprotect or munmap to race between reclaim unmapping |
| 731 | * the page and flushing the page. If this race occurs, it potentially allows |
| 732 | * access to data via a stale TLB entry. Tracking all mm's that have TLB |
| 733 | * batching in flight would be expensive during reclaim so instead track |
| 734 | * whether TLB batching occurred in the past and if so then do a flush here |
| 735 | * if required. This will cost one additional flush per reclaim cycle paid |
| 736 | * by the first operation at risk such as mprotect and mumap. |
| 737 | * |
| 738 | * This must be called under the PTL so that an access to tlb_flush_batched |
| 739 | * that is potentially a "reclaim vs mprotect/munmap/etc" race will synchronise |
| 740 | * via the PTL. |
| 741 | */ |
| 742 | void flush_tlb_batched_pending(struct mm_struct *mm) |
| 743 | { |
| 744 | int batch = atomic_read(&mm->tlb_flush_batched); |
| 745 | int pending = batch & TLB_FLUSH_BATCH_PENDING_MASK; |
| 746 | int flushed = batch >> TLB_FLUSH_BATCH_FLUSHED_SHIFT; |
| 747 | |
| 748 | if (pending != flushed) { |
| 749 | arch_flush_tlb_batched_pending(mm); |
| 750 | /* |
| 751 | * If the new TLB flushing is pending during flushing, leave |
| 752 | * mm->tlb_flush_batched as is, to avoid losing flushing. |
| 753 | */ |
| 754 | atomic_cmpxchg(&mm->tlb_flush_batched, batch, |
| 755 | pending | (pending << TLB_FLUSH_BATCH_FLUSHED_SHIFT)); |
| 756 | } |
| 757 | } |
| 758 | #else |
| 759 | static void set_tlb_ubc_flush_pending(struct mm_struct *mm, pte_t pteval, |
| 760 | unsigned long uaddr) |
| 761 | { |
| 762 | } |
| 763 | |
| 764 | static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags) |
| 765 | { |
| 766 | return false; |
| 767 | } |
| 768 | #endif /* CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH */ |
| 769 | |
| 770 | /* |
| 771 | * At what user virtual address is page expected in vma? |
| 772 | * Caller should check the page is actually part of the vma. |
| 773 | */ |
| 774 | unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma) |
| 775 | { |
| 776 | struct folio *folio = page_folio(page); |
| 777 | pgoff_t pgoff; |
| 778 | |
| 779 | if (folio_test_anon(folio)) { |
| 780 | struct anon_vma *page__anon_vma = folio_anon_vma(folio); |
| 781 | /* |
| 782 | * Note: swapoff's unuse_vma() is more efficient with this |
| 783 | * check, and needs it to match anon_vma when KSM is active. |
| 784 | */ |
| 785 | if (!vma->anon_vma || !page__anon_vma || |
| 786 | vma->anon_vma->root != page__anon_vma->root) |
| 787 | return -EFAULT; |
| 788 | } else if (!vma->vm_file) { |
| 789 | return -EFAULT; |
| 790 | } else if (vma->vm_file->f_mapping != folio->mapping) { |
| 791 | return -EFAULT; |
| 792 | } |
| 793 | |
| 794 | /* The !page__anon_vma above handles KSM folios */ |
| 795 | pgoff = folio->index + folio_page_idx(folio, page); |
| 796 | return vma_address(vma, pgoff, 1); |
| 797 | } |
| 798 | |
| 799 | /* |
| 800 | * Returns the actual pmd_t* where we expect 'address' to be mapped from, or |
| 801 | * NULL if it doesn't exist. No guarantees / checks on what the pmd_t* |
| 802 | * represents. |
| 803 | */ |
| 804 | pmd_t *mm_find_pmd(struct mm_struct *mm, unsigned long address) |
| 805 | { |
| 806 | pgd_t *pgd; |
| 807 | p4d_t *p4d; |
| 808 | pud_t *pud; |
| 809 | pmd_t *pmd = NULL; |
| 810 | |
| 811 | pgd = pgd_offset(mm, address); |
| 812 | if (!pgd_present(*pgd)) |
| 813 | goto out; |
| 814 | |
| 815 | p4d = p4d_offset(pgd, address); |
| 816 | if (!p4d_present(*p4d)) |
| 817 | goto out; |
| 818 | |
| 819 | pud = pud_offset(p4d, address); |
| 820 | if (!pud_present(*pud)) |
| 821 | goto out; |
| 822 | |
| 823 | pmd = pmd_offset(pud, address); |
| 824 | out: |
| 825 | return pmd; |
| 826 | } |
| 827 | |
| 828 | struct folio_referenced_arg { |
| 829 | int mapcount; |
| 830 | int referenced; |
| 831 | unsigned long vm_flags; |
| 832 | struct mem_cgroup *memcg; |
| 833 | }; |
| 834 | |
| 835 | /* |
| 836 | * arg: folio_referenced_arg will be passed |
| 837 | */ |
| 838 | static bool folio_referenced_one(struct folio *folio, |
| 839 | struct vm_area_struct *vma, unsigned long address, void *arg) |
| 840 | { |
| 841 | struct folio_referenced_arg *pra = arg; |
| 842 | DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); |
| 843 | int referenced = 0; |
| 844 | unsigned long start = address, ptes = 0; |
| 845 | |
| 846 | while (page_vma_mapped_walk(&pvmw)) { |
| 847 | address = pvmw.address; |
| 848 | |
| 849 | if (vma->vm_flags & VM_LOCKED) { |
| 850 | if (!folio_test_large(folio) || !pvmw.pte) { |
| 851 | /* Restore the mlock which got missed */ |
| 852 | mlock_vma_folio(folio, vma); |
| 853 | page_vma_mapped_walk_done(&pvmw); |
| 854 | pra->vm_flags |= VM_LOCKED; |
| 855 | return false; /* To break the loop */ |
| 856 | } |
| 857 | /* |
| 858 | * For large folio fully mapped to VMA, will |
| 859 | * be handled after the pvmw loop. |
| 860 | * |
| 861 | * For large folio cross VMA boundaries, it's |
| 862 | * expected to be picked by page reclaim. But |
| 863 | * should skip reference of pages which are in |
| 864 | * the range of VM_LOCKED vma. As page reclaim |
| 865 | * should just count the reference of pages out |
| 866 | * the range of VM_LOCKED vma. |
| 867 | */ |
| 868 | ptes++; |
| 869 | pra->mapcount--; |
| 870 | continue; |
| 871 | } |
| 872 | |
| 873 | if (pvmw.pte) { |
| 874 | if (lru_gen_enabled() && |
| 875 | pte_young(ptep_get(pvmw.pte))) { |
| 876 | lru_gen_look_around(&pvmw); |
| 877 | referenced++; |
| 878 | } |
| 879 | |
| 880 | if (ptep_clear_flush_young_notify(vma, address, |
| 881 | pvmw.pte)) |
| 882 | referenced++; |
| 883 | } else if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE)) { |
| 884 | if (pmdp_clear_flush_young_notify(vma, address, |
| 885 | pvmw.pmd)) |
| 886 | referenced++; |
| 887 | } else { |
| 888 | /* unexpected pmd-mapped folio? */ |
| 889 | WARN_ON_ONCE(1); |
| 890 | } |
| 891 | |
| 892 | pra->mapcount--; |
| 893 | } |
| 894 | |
| 895 | if ((vma->vm_flags & VM_LOCKED) && |
| 896 | folio_test_large(folio) && |
| 897 | folio_within_vma(folio, vma)) { |
| 898 | unsigned long s_align, e_align; |
| 899 | |
| 900 | s_align = ALIGN_DOWN(start, PMD_SIZE); |
| 901 | e_align = ALIGN_DOWN(start + folio_size(folio) - 1, PMD_SIZE); |
| 902 | |
| 903 | /* folio doesn't cross page table boundary and fully mapped */ |
| 904 | if ((s_align == e_align) && (ptes == folio_nr_pages(folio))) { |
| 905 | /* Restore the mlock which got missed */ |
| 906 | mlock_vma_folio(folio, vma); |
| 907 | pra->vm_flags |= VM_LOCKED; |
| 908 | return false; /* To break the loop */ |
| 909 | } |
| 910 | } |
| 911 | |
| 912 | if (referenced) |
| 913 | folio_clear_idle(folio); |
| 914 | if (folio_test_clear_young(folio)) |
| 915 | referenced++; |
| 916 | |
| 917 | if (referenced) { |
| 918 | pra->referenced++; |
| 919 | pra->vm_flags |= vma->vm_flags & ~VM_LOCKED; |
| 920 | } |
| 921 | |
| 922 | if (!pra->mapcount) |
| 923 | return false; /* To break the loop */ |
| 924 | |
| 925 | return true; |
| 926 | } |
| 927 | |
| 928 | static bool invalid_folio_referenced_vma(struct vm_area_struct *vma, void *arg) |
| 929 | { |
| 930 | struct folio_referenced_arg *pra = arg; |
| 931 | struct mem_cgroup *memcg = pra->memcg; |
| 932 | |
| 933 | /* |
| 934 | * Ignore references from this mapping if it has no recency. If the |
| 935 | * folio has been used in another mapping, we will catch it; if this |
| 936 | * other mapping is already gone, the unmap path will have set the |
| 937 | * referenced flag or activated the folio in zap_pte_range(). |
| 938 | */ |
| 939 | if (!vma_has_recency(vma)) |
| 940 | return true; |
| 941 | |
| 942 | /* |
| 943 | * If we are reclaiming on behalf of a cgroup, skip counting on behalf |
| 944 | * of references from different cgroups. |
| 945 | */ |
| 946 | if (memcg && !mm_match_cgroup(vma->vm_mm, memcg)) |
| 947 | return true; |
| 948 | |
| 949 | return false; |
| 950 | } |
| 951 | |
| 952 | /** |
| 953 | * folio_referenced() - Test if the folio was referenced. |
| 954 | * @folio: The folio to test. |
| 955 | * @is_locked: Caller holds lock on the folio. |
| 956 | * @memcg: target memory cgroup |
| 957 | * @vm_flags: A combination of all the vma->vm_flags which referenced the folio. |
| 958 | * |
| 959 | * Quick test_and_clear_referenced for all mappings of a folio, |
| 960 | * |
| 961 | * Return: The number of mappings which referenced the folio. Return -1 if |
| 962 | * the function bailed out due to rmap lock contention. |
| 963 | */ |
| 964 | int folio_referenced(struct folio *folio, int is_locked, |
| 965 | struct mem_cgroup *memcg, unsigned long *vm_flags) |
| 966 | { |
| 967 | bool we_locked = false; |
| 968 | struct folio_referenced_arg pra = { |
| 969 | .mapcount = folio_mapcount(folio), |
| 970 | .memcg = memcg, |
| 971 | }; |
| 972 | struct rmap_walk_control rwc = { |
| 973 | .rmap_one = folio_referenced_one, |
| 974 | .arg = (void *)&pra, |
| 975 | .anon_lock = folio_lock_anon_vma_read, |
| 976 | .try_lock = true, |
| 977 | .invalid_vma = invalid_folio_referenced_vma, |
| 978 | }; |
| 979 | |
| 980 | *vm_flags = 0; |
| 981 | if (!pra.mapcount) |
| 982 | return 0; |
| 983 | |
| 984 | if (!folio_raw_mapping(folio)) |
| 985 | return 0; |
| 986 | |
| 987 | if (!is_locked && (!folio_test_anon(folio) || folio_test_ksm(folio))) { |
| 988 | we_locked = folio_trylock(folio); |
| 989 | if (!we_locked) |
| 990 | return 1; |
| 991 | } |
| 992 | |
| 993 | rmap_walk(folio, &rwc); |
| 994 | *vm_flags = pra.vm_flags; |
| 995 | |
| 996 | if (we_locked) |
| 997 | folio_unlock(folio); |
| 998 | |
| 999 | return rwc.contended ? -1 : pra.referenced; |
| 1000 | } |
| 1001 | |
| 1002 | static int page_vma_mkclean_one(struct page_vma_mapped_walk *pvmw) |
| 1003 | { |
| 1004 | int cleaned = 0; |
| 1005 | struct vm_area_struct *vma = pvmw->vma; |
| 1006 | struct mmu_notifier_range range; |
| 1007 | unsigned long address = pvmw->address; |
| 1008 | |
| 1009 | /* |
| 1010 | * We have to assume the worse case ie pmd for invalidation. Note that |
| 1011 | * the folio can not be freed from this function. |
| 1012 | */ |
| 1013 | mmu_notifier_range_init(&range, MMU_NOTIFY_PROTECTION_PAGE, 0, |
| 1014 | vma->vm_mm, address, vma_address_end(pvmw)); |
| 1015 | mmu_notifier_invalidate_range_start(&range); |
| 1016 | |
| 1017 | while (page_vma_mapped_walk(pvmw)) { |
| 1018 | int ret = 0; |
| 1019 | |
| 1020 | address = pvmw->address; |
| 1021 | if (pvmw->pte) { |
| 1022 | pte_t *pte = pvmw->pte; |
| 1023 | pte_t entry = ptep_get(pte); |
| 1024 | |
| 1025 | if (!pte_dirty(entry) && !pte_write(entry)) |
| 1026 | continue; |
| 1027 | |
| 1028 | flush_cache_page(vma, address, pte_pfn(entry)); |
| 1029 | entry = ptep_clear_flush(vma, address, pte); |
| 1030 | entry = pte_wrprotect(entry); |
| 1031 | entry = pte_mkclean(entry); |
| 1032 | set_pte_at(vma->vm_mm, address, pte, entry); |
| 1033 | ret = 1; |
| 1034 | } else { |
| 1035 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| 1036 | pmd_t *pmd = pvmw->pmd; |
| 1037 | pmd_t entry; |
| 1038 | |
| 1039 | if (!pmd_dirty(*pmd) && !pmd_write(*pmd)) |
| 1040 | continue; |
| 1041 | |
| 1042 | flush_cache_range(vma, address, |
| 1043 | address + HPAGE_PMD_SIZE); |
| 1044 | entry = pmdp_invalidate(vma, address, pmd); |
| 1045 | entry = pmd_wrprotect(entry); |
| 1046 | entry = pmd_mkclean(entry); |
| 1047 | set_pmd_at(vma->vm_mm, address, pmd, entry); |
| 1048 | ret = 1; |
| 1049 | #else |
| 1050 | /* unexpected pmd-mapped folio? */ |
| 1051 | WARN_ON_ONCE(1); |
| 1052 | #endif |
| 1053 | } |
| 1054 | |
| 1055 | if (ret) |
| 1056 | cleaned++; |
| 1057 | } |
| 1058 | |
| 1059 | mmu_notifier_invalidate_range_end(&range); |
| 1060 | |
| 1061 | return cleaned; |
| 1062 | } |
| 1063 | |
| 1064 | static bool page_mkclean_one(struct folio *folio, struct vm_area_struct *vma, |
| 1065 | unsigned long address, void *arg) |
| 1066 | { |
| 1067 | DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, PVMW_SYNC); |
| 1068 | int *cleaned = arg; |
| 1069 | |
| 1070 | *cleaned += page_vma_mkclean_one(&pvmw); |
| 1071 | |
| 1072 | return true; |
| 1073 | } |
| 1074 | |
| 1075 | static bool invalid_mkclean_vma(struct vm_area_struct *vma, void *arg) |
| 1076 | { |
| 1077 | if (vma->vm_flags & VM_SHARED) |
| 1078 | return false; |
| 1079 | |
| 1080 | return true; |
| 1081 | } |
| 1082 | |
| 1083 | int folio_mkclean(struct folio *folio) |
| 1084 | { |
| 1085 | int cleaned = 0; |
| 1086 | struct address_space *mapping; |
| 1087 | struct rmap_walk_control rwc = { |
| 1088 | .arg = (void *)&cleaned, |
| 1089 | .rmap_one = page_mkclean_one, |
| 1090 | .invalid_vma = invalid_mkclean_vma, |
| 1091 | }; |
| 1092 | |
| 1093 | BUG_ON(!folio_test_locked(folio)); |
| 1094 | |
| 1095 | if (!folio_mapped(folio)) |
| 1096 | return 0; |
| 1097 | |
| 1098 | mapping = folio_mapping(folio); |
| 1099 | if (!mapping) |
| 1100 | return 0; |
| 1101 | |
| 1102 | rmap_walk(folio, &rwc); |
| 1103 | |
| 1104 | return cleaned; |
| 1105 | } |
| 1106 | EXPORT_SYMBOL_GPL(folio_mkclean); |
| 1107 | |
| 1108 | /** |
| 1109 | * pfn_mkclean_range - Cleans the PTEs (including PMDs) mapped with range of |
| 1110 | * [@pfn, @pfn + @nr_pages) at the specific offset (@pgoff) |
| 1111 | * within the @vma of shared mappings. And since clean PTEs |
| 1112 | * should also be readonly, write protects them too. |
| 1113 | * @pfn: start pfn. |
| 1114 | * @nr_pages: number of physically contiguous pages srarting with @pfn. |
| 1115 | * @pgoff: page offset that the @pfn mapped with. |
| 1116 | * @vma: vma that @pfn mapped within. |
| 1117 | * |
| 1118 | * Returns the number of cleaned PTEs (including PMDs). |
| 1119 | */ |
| 1120 | int pfn_mkclean_range(unsigned long pfn, unsigned long nr_pages, pgoff_t pgoff, |
| 1121 | struct vm_area_struct *vma) |
| 1122 | { |
| 1123 | struct page_vma_mapped_walk pvmw = { |
| 1124 | .pfn = pfn, |
| 1125 | .nr_pages = nr_pages, |
| 1126 | .pgoff = pgoff, |
| 1127 | .vma = vma, |
| 1128 | .flags = PVMW_SYNC, |
| 1129 | }; |
| 1130 | |
| 1131 | if (invalid_mkclean_vma(vma, NULL)) |
| 1132 | return 0; |
| 1133 | |
| 1134 | pvmw.address = vma_address(vma, pgoff, nr_pages); |
| 1135 | VM_BUG_ON_VMA(pvmw.address == -EFAULT, vma); |
| 1136 | |
| 1137 | return page_vma_mkclean_one(&pvmw); |
| 1138 | } |
| 1139 | |
| 1140 | static __always_inline unsigned int __folio_add_rmap(struct folio *folio, |
| 1141 | struct page *page, int nr_pages, enum rmap_level level, |
| 1142 | int *nr_pmdmapped) |
| 1143 | { |
| 1144 | atomic_t *mapped = &folio->_nr_pages_mapped; |
| 1145 | const int orig_nr_pages = nr_pages; |
| 1146 | int first, nr = 0; |
| 1147 | |
| 1148 | __folio_rmap_sanity_checks(folio, page, nr_pages, level); |
| 1149 | |
| 1150 | switch (level) { |
| 1151 | case RMAP_LEVEL_PTE: |
| 1152 | if (!folio_test_large(folio)) { |
| 1153 | nr = atomic_inc_and_test(&page->_mapcount); |
| 1154 | break; |
| 1155 | } |
| 1156 | |
| 1157 | do { |
| 1158 | first = atomic_inc_and_test(&page->_mapcount); |
| 1159 | if (first) { |
| 1160 | first = atomic_inc_return_relaxed(mapped); |
| 1161 | if (first < ENTIRELY_MAPPED) |
| 1162 | nr++; |
| 1163 | } |
| 1164 | } while (page++, --nr_pages > 0); |
| 1165 | atomic_add(orig_nr_pages, &folio->_large_mapcount); |
| 1166 | break; |
| 1167 | case RMAP_LEVEL_PMD: |
| 1168 | first = atomic_inc_and_test(&folio->_entire_mapcount); |
| 1169 | if (first) { |
| 1170 | nr = atomic_add_return_relaxed(ENTIRELY_MAPPED, mapped); |
| 1171 | if (likely(nr < ENTIRELY_MAPPED + ENTIRELY_MAPPED)) { |
| 1172 | *nr_pmdmapped = folio_nr_pages(folio); |
| 1173 | nr = *nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED); |
| 1174 | /* Raced ahead of a remove and another add? */ |
| 1175 | if (unlikely(nr < 0)) |
| 1176 | nr = 0; |
| 1177 | } else { |
| 1178 | /* Raced ahead of a remove of ENTIRELY_MAPPED */ |
| 1179 | nr = 0; |
| 1180 | } |
| 1181 | } |
| 1182 | atomic_inc(&folio->_large_mapcount); |
| 1183 | break; |
| 1184 | } |
| 1185 | return nr; |
| 1186 | } |
| 1187 | |
| 1188 | /** |
| 1189 | * folio_move_anon_rmap - move a folio to our anon_vma |
| 1190 | * @folio: The folio to move to our anon_vma |
| 1191 | * @vma: The vma the folio belongs to |
| 1192 | * |
| 1193 | * When a folio belongs exclusively to one process after a COW event, |
| 1194 | * that folio can be moved into the anon_vma that belongs to just that |
| 1195 | * process, so the rmap code will not search the parent or sibling processes. |
| 1196 | */ |
| 1197 | void folio_move_anon_rmap(struct folio *folio, struct vm_area_struct *vma) |
| 1198 | { |
| 1199 | void *anon_vma = vma->anon_vma; |
| 1200 | |
| 1201 | VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
| 1202 | VM_BUG_ON_VMA(!anon_vma, vma); |
| 1203 | |
| 1204 | anon_vma += PAGE_MAPPING_ANON; |
| 1205 | /* |
| 1206 | * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written |
| 1207 | * simultaneously, so a concurrent reader (eg folio_referenced()'s |
| 1208 | * folio_test_anon()) will not see one without the other. |
| 1209 | */ |
| 1210 | WRITE_ONCE(folio->mapping, anon_vma); |
| 1211 | } |
| 1212 | |
| 1213 | /** |
| 1214 | * __folio_set_anon - set up a new anonymous rmap for a folio |
| 1215 | * @folio: The folio to set up the new anonymous rmap for. |
| 1216 | * @vma: VM area to add the folio to. |
| 1217 | * @address: User virtual address of the mapping |
| 1218 | * @exclusive: Whether the folio is exclusive to the process. |
| 1219 | */ |
| 1220 | static void __folio_set_anon(struct folio *folio, struct vm_area_struct *vma, |
| 1221 | unsigned long address, bool exclusive) |
| 1222 | { |
| 1223 | struct anon_vma *anon_vma = vma->anon_vma; |
| 1224 | |
| 1225 | BUG_ON(!anon_vma); |
| 1226 | |
| 1227 | /* |
| 1228 | * If the folio isn't exclusive to this vma, we must use the _oldest_ |
| 1229 | * possible anon_vma for the folio mapping! |
| 1230 | */ |
| 1231 | if (!exclusive) |
| 1232 | anon_vma = anon_vma->root; |
| 1233 | |
| 1234 | /* |
| 1235 | * page_idle does a lockless/optimistic rmap scan on folio->mapping. |
| 1236 | * Make sure the compiler doesn't split the stores of anon_vma and |
| 1237 | * the PAGE_MAPPING_ANON type identifier, otherwise the rmap code |
| 1238 | * could mistake the mapping for a struct address_space and crash. |
| 1239 | */ |
| 1240 | anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON; |
| 1241 | WRITE_ONCE(folio->mapping, (struct address_space *) anon_vma); |
| 1242 | folio->index = linear_page_index(vma, address); |
| 1243 | } |
| 1244 | |
| 1245 | /** |
| 1246 | * __page_check_anon_rmap - sanity check anonymous rmap addition |
| 1247 | * @folio: The folio containing @page. |
| 1248 | * @page: the page to check the mapping of |
| 1249 | * @vma: the vm area in which the mapping is added |
| 1250 | * @address: the user virtual address mapped |
| 1251 | */ |
| 1252 | static void __page_check_anon_rmap(struct folio *folio, struct page *page, |
| 1253 | struct vm_area_struct *vma, unsigned long address) |
| 1254 | { |
| 1255 | /* |
| 1256 | * The page's anon-rmap details (mapping and index) are guaranteed to |
| 1257 | * be set up correctly at this point. |
| 1258 | * |
| 1259 | * We have exclusion against folio_add_anon_rmap_*() because the caller |
| 1260 | * always holds the page locked. |
| 1261 | * |
| 1262 | * We have exclusion against folio_add_new_anon_rmap because those pages |
| 1263 | * are initially only visible via the pagetables, and the pte is locked |
| 1264 | * over the call to folio_add_new_anon_rmap. |
| 1265 | */ |
| 1266 | VM_BUG_ON_FOLIO(folio_anon_vma(folio)->root != vma->anon_vma->root, |
| 1267 | folio); |
| 1268 | VM_BUG_ON_PAGE(page_to_pgoff(page) != linear_page_index(vma, address), |
| 1269 | page); |
| 1270 | } |
| 1271 | |
| 1272 | static __always_inline void __folio_add_anon_rmap(struct folio *folio, |
| 1273 | struct page *page, int nr_pages, struct vm_area_struct *vma, |
| 1274 | unsigned long address, rmap_t flags, enum rmap_level level) |
| 1275 | { |
| 1276 | int i, nr, nr_pmdmapped = 0; |
| 1277 | |
| 1278 | nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped); |
| 1279 | if (nr_pmdmapped) |
| 1280 | __lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr_pmdmapped); |
| 1281 | if (nr) |
| 1282 | __lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr); |
| 1283 | |
| 1284 | if (unlikely(!folio_test_anon(folio))) { |
| 1285 | VM_WARN_ON_FOLIO(!folio_test_locked(folio), folio); |
| 1286 | /* |
| 1287 | * For a PTE-mapped large folio, we only know that the single |
| 1288 | * PTE is exclusive. Further, __folio_set_anon() might not get |
| 1289 | * folio->index right when not given the address of the head |
| 1290 | * page. |
| 1291 | */ |
| 1292 | VM_WARN_ON_FOLIO(folio_test_large(folio) && |
| 1293 | level != RMAP_LEVEL_PMD, folio); |
| 1294 | __folio_set_anon(folio, vma, address, |
| 1295 | !!(flags & RMAP_EXCLUSIVE)); |
| 1296 | } else if (likely(!folio_test_ksm(folio))) { |
| 1297 | __page_check_anon_rmap(folio, page, vma, address); |
| 1298 | } |
| 1299 | |
| 1300 | if (flags & RMAP_EXCLUSIVE) { |
| 1301 | switch (level) { |
| 1302 | case RMAP_LEVEL_PTE: |
| 1303 | for (i = 0; i < nr_pages; i++) |
| 1304 | SetPageAnonExclusive(page + i); |
| 1305 | break; |
| 1306 | case RMAP_LEVEL_PMD: |
| 1307 | SetPageAnonExclusive(page); |
| 1308 | break; |
| 1309 | } |
| 1310 | } |
| 1311 | for (i = 0; i < nr_pages; i++) { |
| 1312 | struct page *cur_page = page + i; |
| 1313 | |
| 1314 | /* While PTE-mapping a THP we have a PMD and a PTE mapping. */ |
| 1315 | VM_WARN_ON_FOLIO((atomic_read(&cur_page->_mapcount) > 0 || |
| 1316 | (folio_test_large(folio) && |
| 1317 | folio_entire_mapcount(folio) > 1)) && |
| 1318 | PageAnonExclusive(cur_page), folio); |
| 1319 | } |
| 1320 | |
| 1321 | /* |
| 1322 | * For large folio, only mlock it if it's fully mapped to VMA. It's |
| 1323 | * not easy to check whether the large folio is fully mapped to VMA |
| 1324 | * here. Only mlock normal 4K folio and leave page reclaim to handle |
| 1325 | * large folio. |
| 1326 | */ |
| 1327 | if (!folio_test_large(folio)) |
| 1328 | mlock_vma_folio(folio, vma); |
| 1329 | } |
| 1330 | |
| 1331 | /** |
| 1332 | * folio_add_anon_rmap_ptes - add PTE mappings to a page range of an anon folio |
| 1333 | * @folio: The folio to add the mappings to |
| 1334 | * @page: The first page to add |
| 1335 | * @nr_pages: The number of pages which will be mapped |
| 1336 | * @vma: The vm area in which the mappings are added |
| 1337 | * @address: The user virtual address of the first page to map |
| 1338 | * @flags: The rmap flags |
| 1339 | * |
| 1340 | * The page range of folio is defined by [first_page, first_page + nr_pages) |
| 1341 | * |
| 1342 | * The caller needs to hold the page table lock, and the page must be locked in |
| 1343 | * the anon_vma case: to serialize mapping,index checking after setting, |
| 1344 | * and to ensure that an anon folio is not being upgraded racily to a KSM folio |
| 1345 | * (but KSM folios are never downgraded). |
| 1346 | */ |
| 1347 | void folio_add_anon_rmap_ptes(struct folio *folio, struct page *page, |
| 1348 | int nr_pages, struct vm_area_struct *vma, unsigned long address, |
| 1349 | rmap_t flags) |
| 1350 | { |
| 1351 | __folio_add_anon_rmap(folio, page, nr_pages, vma, address, flags, |
| 1352 | RMAP_LEVEL_PTE); |
| 1353 | } |
| 1354 | |
| 1355 | /** |
| 1356 | * folio_add_anon_rmap_pmd - add a PMD mapping to a page range of an anon folio |
| 1357 | * @folio: The folio to add the mapping to |
| 1358 | * @page: The first page to add |
| 1359 | * @vma: The vm area in which the mapping is added |
| 1360 | * @address: The user virtual address of the first page to map |
| 1361 | * @flags: The rmap flags |
| 1362 | * |
| 1363 | * The page range of folio is defined by [first_page, first_page + HPAGE_PMD_NR) |
| 1364 | * |
| 1365 | * The caller needs to hold the page table lock, and the page must be locked in |
| 1366 | * the anon_vma case: to serialize mapping,index checking after setting. |
| 1367 | */ |
| 1368 | void folio_add_anon_rmap_pmd(struct folio *folio, struct page *page, |
| 1369 | struct vm_area_struct *vma, unsigned long address, rmap_t flags) |
| 1370 | { |
| 1371 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| 1372 | __folio_add_anon_rmap(folio, page, HPAGE_PMD_NR, vma, address, flags, |
| 1373 | RMAP_LEVEL_PMD); |
| 1374 | #else |
| 1375 | WARN_ON_ONCE(true); |
| 1376 | #endif |
| 1377 | } |
| 1378 | |
| 1379 | /** |
| 1380 | * folio_add_new_anon_rmap - Add mapping to a new anonymous folio. |
| 1381 | * @folio: The folio to add the mapping to. |
| 1382 | * @vma: the vm area in which the mapping is added |
| 1383 | * @address: the user virtual address mapped |
| 1384 | * |
| 1385 | * Like folio_add_anon_rmap_*() but must only be called on *new* folios. |
| 1386 | * This means the inc-and-test can be bypassed. |
| 1387 | * The folio does not have to be locked. |
| 1388 | * |
| 1389 | * If the folio is pmd-mappable, it is accounted as a THP. As the folio |
| 1390 | * is new, it's assumed to be mapped exclusively by a single process. |
| 1391 | */ |
| 1392 | void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma, |
| 1393 | unsigned long address) |
| 1394 | { |
| 1395 | int nr = folio_nr_pages(folio); |
| 1396 | |
| 1397 | VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio); |
| 1398 | VM_BUG_ON_VMA(address < vma->vm_start || |
| 1399 | address + (nr << PAGE_SHIFT) > vma->vm_end, vma); |
| 1400 | __folio_set_swapbacked(folio); |
| 1401 | __folio_set_anon(folio, vma, address, true); |
| 1402 | |
| 1403 | if (likely(!folio_test_large(folio))) { |
| 1404 | /* increment count (starts at -1) */ |
| 1405 | atomic_set(&folio->_mapcount, 0); |
| 1406 | SetPageAnonExclusive(&folio->page); |
| 1407 | } else if (!folio_test_pmd_mappable(folio)) { |
| 1408 | int i; |
| 1409 | |
| 1410 | for (i = 0; i < nr; i++) { |
| 1411 | struct page *page = folio_page(folio, i); |
| 1412 | |
| 1413 | /* increment count (starts at -1) */ |
| 1414 | atomic_set(&page->_mapcount, 0); |
| 1415 | SetPageAnonExclusive(page); |
| 1416 | } |
| 1417 | |
| 1418 | /* increment count (starts at -1) */ |
| 1419 | atomic_set(&folio->_large_mapcount, nr - 1); |
| 1420 | atomic_set(&folio->_nr_pages_mapped, nr); |
| 1421 | } else { |
| 1422 | /* increment count (starts at -1) */ |
| 1423 | atomic_set(&folio->_entire_mapcount, 0); |
| 1424 | /* increment count (starts at -1) */ |
| 1425 | atomic_set(&folio->_large_mapcount, 0); |
| 1426 | atomic_set(&folio->_nr_pages_mapped, ENTIRELY_MAPPED); |
| 1427 | SetPageAnonExclusive(&folio->page); |
| 1428 | __lruvec_stat_mod_folio(folio, NR_ANON_THPS, nr); |
| 1429 | } |
| 1430 | |
| 1431 | __lruvec_stat_mod_folio(folio, NR_ANON_MAPPED, nr); |
| 1432 | } |
| 1433 | |
| 1434 | static __always_inline void __folio_add_file_rmap(struct folio *folio, |
| 1435 | struct page *page, int nr_pages, struct vm_area_struct *vma, |
| 1436 | enum rmap_level level) |
| 1437 | { |
| 1438 | pg_data_t *pgdat = folio_pgdat(folio); |
| 1439 | int nr, nr_pmdmapped = 0; |
| 1440 | |
| 1441 | VM_WARN_ON_FOLIO(folio_test_anon(folio), folio); |
| 1442 | |
| 1443 | nr = __folio_add_rmap(folio, page, nr_pages, level, &nr_pmdmapped); |
| 1444 | if (nr_pmdmapped) |
| 1445 | __mod_node_page_state(pgdat, folio_test_swapbacked(folio) ? |
| 1446 | NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED, nr_pmdmapped); |
| 1447 | if (nr) |
| 1448 | __lruvec_stat_mod_folio(folio, NR_FILE_MAPPED, nr); |
| 1449 | |
| 1450 | /* See comments in folio_add_anon_rmap_*() */ |
| 1451 | if (!folio_test_large(folio)) |
| 1452 | mlock_vma_folio(folio, vma); |
| 1453 | } |
| 1454 | |
| 1455 | /** |
| 1456 | * folio_add_file_rmap_ptes - add PTE mappings to a page range of a folio |
| 1457 | * @folio: The folio to add the mappings to |
| 1458 | * @page: The first page to add |
| 1459 | * @nr_pages: The number of pages that will be mapped using PTEs |
| 1460 | * @vma: The vm area in which the mappings are added |
| 1461 | * |
| 1462 | * The page range of the folio is defined by [page, page + nr_pages) |
| 1463 | * |
| 1464 | * The caller needs to hold the page table lock. |
| 1465 | */ |
| 1466 | void folio_add_file_rmap_ptes(struct folio *folio, struct page *page, |
| 1467 | int nr_pages, struct vm_area_struct *vma) |
| 1468 | { |
| 1469 | __folio_add_file_rmap(folio, page, nr_pages, vma, RMAP_LEVEL_PTE); |
| 1470 | } |
| 1471 | |
| 1472 | /** |
| 1473 | * folio_add_file_rmap_pmd - add a PMD mapping to a page range of a folio |
| 1474 | * @folio: The folio to add the mapping to |
| 1475 | * @page: The first page to add |
| 1476 | * @vma: The vm area in which the mapping is added |
| 1477 | * |
| 1478 | * The page range of the folio is defined by [page, page + HPAGE_PMD_NR) |
| 1479 | * |
| 1480 | * The caller needs to hold the page table lock. |
| 1481 | */ |
| 1482 | void folio_add_file_rmap_pmd(struct folio *folio, struct page *page, |
| 1483 | struct vm_area_struct *vma) |
| 1484 | { |
| 1485 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| 1486 | __folio_add_file_rmap(folio, page, HPAGE_PMD_NR, vma, RMAP_LEVEL_PMD); |
| 1487 | #else |
| 1488 | WARN_ON_ONCE(true); |
| 1489 | #endif |
| 1490 | } |
| 1491 | |
| 1492 | static __always_inline void __folio_remove_rmap(struct folio *folio, |
| 1493 | struct page *page, int nr_pages, struct vm_area_struct *vma, |
| 1494 | enum rmap_level level) |
| 1495 | { |
| 1496 | atomic_t *mapped = &folio->_nr_pages_mapped; |
| 1497 | pg_data_t *pgdat = folio_pgdat(folio); |
| 1498 | int last, nr = 0, nr_pmdmapped = 0; |
| 1499 | bool partially_mapped = false; |
| 1500 | enum node_stat_item idx; |
| 1501 | |
| 1502 | __folio_rmap_sanity_checks(folio, page, nr_pages, level); |
| 1503 | |
| 1504 | switch (level) { |
| 1505 | case RMAP_LEVEL_PTE: |
| 1506 | if (!folio_test_large(folio)) { |
| 1507 | nr = atomic_add_negative(-1, &page->_mapcount); |
| 1508 | break; |
| 1509 | } |
| 1510 | |
| 1511 | atomic_sub(nr_pages, &folio->_large_mapcount); |
| 1512 | do { |
| 1513 | last = atomic_add_negative(-1, &page->_mapcount); |
| 1514 | if (last) { |
| 1515 | last = atomic_dec_return_relaxed(mapped); |
| 1516 | if (last < ENTIRELY_MAPPED) |
| 1517 | nr++; |
| 1518 | } |
| 1519 | } while (page++, --nr_pages > 0); |
| 1520 | |
| 1521 | partially_mapped = nr && atomic_read(mapped); |
| 1522 | break; |
| 1523 | case RMAP_LEVEL_PMD: |
| 1524 | atomic_dec(&folio->_large_mapcount); |
| 1525 | last = atomic_add_negative(-1, &folio->_entire_mapcount); |
| 1526 | if (last) { |
| 1527 | nr = atomic_sub_return_relaxed(ENTIRELY_MAPPED, mapped); |
| 1528 | if (likely(nr < ENTIRELY_MAPPED)) { |
| 1529 | nr_pmdmapped = folio_nr_pages(folio); |
| 1530 | nr = nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED); |
| 1531 | /* Raced ahead of another remove and an add? */ |
| 1532 | if (unlikely(nr < 0)) |
| 1533 | nr = 0; |
| 1534 | } else { |
| 1535 | /* An add of ENTIRELY_MAPPED raced ahead */ |
| 1536 | nr = 0; |
| 1537 | } |
| 1538 | } |
| 1539 | |
| 1540 | partially_mapped = nr < nr_pmdmapped; |
| 1541 | break; |
| 1542 | } |
| 1543 | |
| 1544 | if (nr_pmdmapped) { |
| 1545 | /* NR_{FILE/SHMEM}_PMDMAPPED are not maintained per-memcg */ |
| 1546 | if (folio_test_anon(folio)) |
| 1547 | __lruvec_stat_mod_folio(folio, NR_ANON_THPS, -nr_pmdmapped); |
| 1548 | else |
| 1549 | __mod_node_page_state(pgdat, |
| 1550 | folio_test_swapbacked(folio) ? |
| 1551 | NR_SHMEM_PMDMAPPED : NR_FILE_PMDMAPPED, |
| 1552 | -nr_pmdmapped); |
| 1553 | } |
| 1554 | if (nr) { |
| 1555 | idx = folio_test_anon(folio) ? NR_ANON_MAPPED : NR_FILE_MAPPED; |
| 1556 | __lruvec_stat_mod_folio(folio, idx, -nr); |
| 1557 | |
| 1558 | /* |
| 1559 | * Queue anon large folio for deferred split if at least one |
| 1560 | * page of the folio is unmapped and at least one page |
| 1561 | * is still mapped. |
| 1562 | * |
| 1563 | * Check partially_mapped first to ensure it is a large folio. |
| 1564 | */ |
| 1565 | if (folio_test_anon(folio) && partially_mapped && |
| 1566 | list_empty(&folio->_deferred_list)) |
| 1567 | deferred_split_folio(folio); |
| 1568 | } |
| 1569 | |
| 1570 | /* |
| 1571 | * It would be tidy to reset folio_test_anon mapping when fully |
| 1572 | * unmapped, but that might overwrite a racing folio_add_anon_rmap_*() |
| 1573 | * which increments mapcount after us but sets mapping before us: |
| 1574 | * so leave the reset to free_pages_prepare, and remember that |
| 1575 | * it's only reliable while mapped. |
| 1576 | */ |
| 1577 | |
| 1578 | munlock_vma_folio(folio, vma); |
| 1579 | } |
| 1580 | |
| 1581 | /** |
| 1582 | * folio_remove_rmap_ptes - remove PTE mappings from a page range of a folio |
| 1583 | * @folio: The folio to remove the mappings from |
| 1584 | * @page: The first page to remove |
| 1585 | * @nr_pages: The number of pages that will be removed from the mapping |
| 1586 | * @vma: The vm area from which the mappings are removed |
| 1587 | * |
| 1588 | * The page range of the folio is defined by [page, page + nr_pages) |
| 1589 | * |
| 1590 | * The caller needs to hold the page table lock. |
| 1591 | */ |
| 1592 | void folio_remove_rmap_ptes(struct folio *folio, struct page *page, |
| 1593 | int nr_pages, struct vm_area_struct *vma) |
| 1594 | { |
| 1595 | __folio_remove_rmap(folio, page, nr_pages, vma, RMAP_LEVEL_PTE); |
| 1596 | } |
| 1597 | |
| 1598 | /** |
| 1599 | * folio_remove_rmap_pmd - remove a PMD mapping from a page range of a folio |
| 1600 | * @folio: The folio to remove the mapping from |
| 1601 | * @page: The first page to remove |
| 1602 | * @vma: The vm area from which the mapping is removed |
| 1603 | * |
| 1604 | * The page range of the folio is defined by [page, page + HPAGE_PMD_NR) |
| 1605 | * |
| 1606 | * The caller needs to hold the page table lock. |
| 1607 | */ |
| 1608 | void folio_remove_rmap_pmd(struct folio *folio, struct page *page, |
| 1609 | struct vm_area_struct *vma) |
| 1610 | { |
| 1611 | #ifdef CONFIG_TRANSPARENT_HUGEPAGE |
| 1612 | __folio_remove_rmap(folio, page, HPAGE_PMD_NR, vma, RMAP_LEVEL_PMD); |
| 1613 | #else |
| 1614 | WARN_ON_ONCE(true); |
| 1615 | #endif |
| 1616 | } |
| 1617 | |
| 1618 | /* |
| 1619 | * @arg: enum ttu_flags will be passed to this argument |
| 1620 | */ |
| 1621 | static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma, |
| 1622 | unsigned long address, void *arg) |
| 1623 | { |
| 1624 | struct mm_struct *mm = vma->vm_mm; |
| 1625 | DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); |
| 1626 | pte_t pteval; |
| 1627 | struct page *subpage; |
| 1628 | bool anon_exclusive, ret = true; |
| 1629 | struct mmu_notifier_range range; |
| 1630 | enum ttu_flags flags = (enum ttu_flags)(long)arg; |
| 1631 | unsigned long pfn; |
| 1632 | unsigned long hsz = 0; |
| 1633 | |
| 1634 | /* |
| 1635 | * When racing against e.g. zap_pte_range() on another cpu, |
| 1636 | * in between its ptep_get_and_clear_full() and folio_remove_rmap_*(), |
| 1637 | * try_to_unmap() may return before page_mapped() has become false, |
| 1638 | * if page table locking is skipped: use TTU_SYNC to wait for that. |
| 1639 | */ |
| 1640 | if (flags & TTU_SYNC) |
| 1641 | pvmw.flags = PVMW_SYNC; |
| 1642 | |
| 1643 | if (flags & TTU_SPLIT_HUGE_PMD) |
| 1644 | split_huge_pmd_address(vma, address, false, folio); |
| 1645 | |
| 1646 | /* |
| 1647 | * For THP, we have to assume the worse case ie pmd for invalidation. |
| 1648 | * For hugetlb, it could be much worse if we need to do pud |
| 1649 | * invalidation in the case of pmd sharing. |
| 1650 | * |
| 1651 | * Note that the folio can not be freed in this function as call of |
| 1652 | * try_to_unmap() must hold a reference on the folio. |
| 1653 | */ |
| 1654 | range.end = vma_address_end(&pvmw); |
| 1655 | mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm, |
| 1656 | address, range.end); |
| 1657 | if (folio_test_hugetlb(folio)) { |
| 1658 | /* |
| 1659 | * If sharing is possible, start and end will be adjusted |
| 1660 | * accordingly. |
| 1661 | */ |
| 1662 | adjust_range_if_pmd_sharing_possible(vma, &range.start, |
| 1663 | &range.end); |
| 1664 | |
| 1665 | /* We need the huge page size for set_huge_pte_at() */ |
| 1666 | hsz = huge_page_size(hstate_vma(vma)); |
| 1667 | } |
| 1668 | mmu_notifier_invalidate_range_start(&range); |
| 1669 | |
| 1670 | while (page_vma_mapped_walk(&pvmw)) { |
| 1671 | /* Unexpected PMD-mapped THP? */ |
| 1672 | VM_BUG_ON_FOLIO(!pvmw.pte, folio); |
| 1673 | |
| 1674 | /* |
| 1675 | * If the folio is in an mlock()d vma, we must not swap it out. |
| 1676 | */ |
| 1677 | if (!(flags & TTU_IGNORE_MLOCK) && |
| 1678 | (vma->vm_flags & VM_LOCKED)) { |
| 1679 | /* Restore the mlock which got missed */ |
| 1680 | if (!folio_test_large(folio)) |
| 1681 | mlock_vma_folio(folio, vma); |
| 1682 | page_vma_mapped_walk_done(&pvmw); |
| 1683 | ret = false; |
| 1684 | break; |
| 1685 | } |
| 1686 | |
| 1687 | pfn = pte_pfn(ptep_get(pvmw.pte)); |
| 1688 | subpage = folio_page(folio, pfn - folio_pfn(folio)); |
| 1689 | address = pvmw.address; |
| 1690 | anon_exclusive = folio_test_anon(folio) && |
| 1691 | PageAnonExclusive(subpage); |
| 1692 | |
| 1693 | if (folio_test_hugetlb(folio)) { |
| 1694 | bool anon = folio_test_anon(folio); |
| 1695 | |
| 1696 | /* |
| 1697 | * The try_to_unmap() is only passed a hugetlb page |
| 1698 | * in the case where the hugetlb page is poisoned. |
| 1699 | */ |
| 1700 | VM_BUG_ON_PAGE(!PageHWPoison(subpage), subpage); |
| 1701 | /* |
| 1702 | * huge_pmd_unshare may unmap an entire PMD page. |
| 1703 | * There is no way of knowing exactly which PMDs may |
| 1704 | * be cached for this mm, so we must flush them all. |
| 1705 | * start/end were already adjusted above to cover this |
| 1706 | * range. |
| 1707 | */ |
| 1708 | flush_cache_range(vma, range.start, range.end); |
| 1709 | |
| 1710 | /* |
| 1711 | * To call huge_pmd_unshare, i_mmap_rwsem must be |
| 1712 | * held in write mode. Caller needs to explicitly |
| 1713 | * do this outside rmap routines. |
| 1714 | * |
| 1715 | * We also must hold hugetlb vma_lock in write mode. |
| 1716 | * Lock order dictates acquiring vma_lock BEFORE |
| 1717 | * i_mmap_rwsem. We can only try lock here and fail |
| 1718 | * if unsuccessful. |
| 1719 | */ |
| 1720 | if (!anon) { |
| 1721 | VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); |
| 1722 | if (!hugetlb_vma_trylock_write(vma)) { |
| 1723 | page_vma_mapped_walk_done(&pvmw); |
| 1724 | ret = false; |
| 1725 | break; |
| 1726 | } |
| 1727 | if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) { |
| 1728 | hugetlb_vma_unlock_write(vma); |
| 1729 | flush_tlb_range(vma, |
| 1730 | range.start, range.end); |
| 1731 | /* |
| 1732 | * The ref count of the PMD page was |
| 1733 | * dropped which is part of the way map |
| 1734 | * counting is done for shared PMDs. |
| 1735 | * Return 'true' here. When there is |
| 1736 | * no other sharing, huge_pmd_unshare |
| 1737 | * returns false and we will unmap the |
| 1738 | * actual page and drop map count |
| 1739 | * to zero. |
| 1740 | */ |
| 1741 | page_vma_mapped_walk_done(&pvmw); |
| 1742 | break; |
| 1743 | } |
| 1744 | hugetlb_vma_unlock_write(vma); |
| 1745 | } |
| 1746 | pteval = huge_ptep_clear_flush(vma, address, pvmw.pte); |
| 1747 | } else { |
| 1748 | flush_cache_page(vma, address, pfn); |
| 1749 | /* Nuke the page table entry. */ |
| 1750 | if (should_defer_flush(mm, flags)) { |
| 1751 | /* |
| 1752 | * We clear the PTE but do not flush so potentially |
| 1753 | * a remote CPU could still be writing to the folio. |
| 1754 | * If the entry was previously clean then the |
| 1755 | * architecture must guarantee that a clear->dirty |
| 1756 | * transition on a cached TLB entry is written through |
| 1757 | * and traps if the PTE is unmapped. |
| 1758 | */ |
| 1759 | pteval = ptep_get_and_clear(mm, address, pvmw.pte); |
| 1760 | |
| 1761 | set_tlb_ubc_flush_pending(mm, pteval, address); |
| 1762 | } else { |
| 1763 | pteval = ptep_clear_flush(vma, address, pvmw.pte); |
| 1764 | } |
| 1765 | } |
| 1766 | |
| 1767 | /* |
| 1768 | * Now the pte is cleared. If this pte was uffd-wp armed, |
| 1769 | * we may want to replace a none pte with a marker pte if |
| 1770 | * it's file-backed, so we don't lose the tracking info. |
| 1771 | */ |
| 1772 | pte_install_uffd_wp_if_needed(vma, address, pvmw.pte, pteval); |
| 1773 | |
| 1774 | /* Set the dirty flag on the folio now the pte is gone. */ |
| 1775 | if (pte_dirty(pteval)) |
| 1776 | folio_mark_dirty(folio); |
| 1777 | |
| 1778 | /* Update high watermark before we lower rss */ |
| 1779 | update_hiwater_rss(mm); |
| 1780 | |
| 1781 | if (PageHWPoison(subpage) && (flags & TTU_HWPOISON)) { |
| 1782 | pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); |
| 1783 | if (folio_test_hugetlb(folio)) { |
| 1784 | hugetlb_count_sub(folio_nr_pages(folio), mm); |
| 1785 | set_huge_pte_at(mm, address, pvmw.pte, pteval, |
| 1786 | hsz); |
| 1787 | } else { |
| 1788 | dec_mm_counter(mm, mm_counter(folio)); |
| 1789 | set_pte_at(mm, address, pvmw.pte, pteval); |
| 1790 | } |
| 1791 | |
| 1792 | } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) { |
| 1793 | /* |
| 1794 | * The guest indicated that the page content is of no |
| 1795 | * interest anymore. Simply discard the pte, vmscan |
| 1796 | * will take care of the rest. |
| 1797 | * A future reference will then fault in a new zero |
| 1798 | * page. When userfaultfd is active, we must not drop |
| 1799 | * this page though, as its main user (postcopy |
| 1800 | * migration) will not expect userfaults on already |
| 1801 | * copied pages. |
| 1802 | */ |
| 1803 | dec_mm_counter(mm, mm_counter(folio)); |
| 1804 | } else if (folio_test_anon(folio)) { |
| 1805 | swp_entry_t entry = page_swap_entry(subpage); |
| 1806 | pte_t swp_pte; |
| 1807 | /* |
| 1808 | * Store the swap location in the pte. |
| 1809 | * See handle_pte_fault() ... |
| 1810 | */ |
| 1811 | if (unlikely(folio_test_swapbacked(folio) != |
| 1812 | folio_test_swapcache(folio))) { |
| 1813 | WARN_ON_ONCE(1); |
| 1814 | ret = false; |
| 1815 | page_vma_mapped_walk_done(&pvmw); |
| 1816 | break; |
| 1817 | } |
| 1818 | |
| 1819 | /* MADV_FREE page check */ |
| 1820 | if (!folio_test_swapbacked(folio)) { |
| 1821 | int ref_count, map_count; |
| 1822 | |
| 1823 | /* |
| 1824 | * Synchronize with gup_pte_range(): |
| 1825 | * - clear PTE; barrier; read refcount |
| 1826 | * - inc refcount; barrier; read PTE |
| 1827 | */ |
| 1828 | smp_mb(); |
| 1829 | |
| 1830 | ref_count = folio_ref_count(folio); |
| 1831 | map_count = folio_mapcount(folio); |
| 1832 | |
| 1833 | /* |
| 1834 | * Order reads for page refcount and dirty flag |
| 1835 | * (see comments in __remove_mapping()). |
| 1836 | */ |
| 1837 | smp_rmb(); |
| 1838 | |
| 1839 | /* |
| 1840 | * The only page refs must be one from isolation |
| 1841 | * plus the rmap(s) (dropped by discard:). |
| 1842 | */ |
| 1843 | if (ref_count == 1 + map_count && |
| 1844 | !folio_test_dirty(folio)) { |
| 1845 | dec_mm_counter(mm, MM_ANONPAGES); |
| 1846 | goto discard; |
| 1847 | } |
| 1848 | |
| 1849 | /* |
| 1850 | * If the folio was redirtied, it cannot be |
| 1851 | * discarded. Remap the page to page table. |
| 1852 | */ |
| 1853 | set_pte_at(mm, address, pvmw.pte, pteval); |
| 1854 | folio_set_swapbacked(folio); |
| 1855 | ret = false; |
| 1856 | page_vma_mapped_walk_done(&pvmw); |
| 1857 | break; |
| 1858 | } |
| 1859 | |
| 1860 | if (swap_duplicate(entry) < 0) { |
| 1861 | set_pte_at(mm, address, pvmw.pte, pteval); |
| 1862 | ret = false; |
| 1863 | page_vma_mapped_walk_done(&pvmw); |
| 1864 | break; |
| 1865 | } |
| 1866 | if (arch_unmap_one(mm, vma, address, pteval) < 0) { |
| 1867 | swap_free(entry); |
| 1868 | set_pte_at(mm, address, pvmw.pte, pteval); |
| 1869 | ret = false; |
| 1870 | page_vma_mapped_walk_done(&pvmw); |
| 1871 | break; |
| 1872 | } |
| 1873 | |
| 1874 | /* See folio_try_share_anon_rmap(): clear PTE first. */ |
| 1875 | if (anon_exclusive && |
| 1876 | folio_try_share_anon_rmap_pte(folio, subpage)) { |
| 1877 | swap_free(entry); |
| 1878 | set_pte_at(mm, address, pvmw.pte, pteval); |
| 1879 | ret = false; |
| 1880 | page_vma_mapped_walk_done(&pvmw); |
| 1881 | break; |
| 1882 | } |
| 1883 | if (list_empty(&mm->mmlist)) { |
| 1884 | spin_lock(&mmlist_lock); |
| 1885 | if (list_empty(&mm->mmlist)) |
| 1886 | list_add(&mm->mmlist, &init_mm.mmlist); |
| 1887 | spin_unlock(&mmlist_lock); |
| 1888 | } |
| 1889 | dec_mm_counter(mm, MM_ANONPAGES); |
| 1890 | inc_mm_counter(mm, MM_SWAPENTS); |
| 1891 | swp_pte = swp_entry_to_pte(entry); |
| 1892 | if (anon_exclusive) |
| 1893 | swp_pte = pte_swp_mkexclusive(swp_pte); |
| 1894 | if (pte_soft_dirty(pteval)) |
| 1895 | swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| 1896 | if (pte_uffd_wp(pteval)) |
| 1897 | swp_pte = pte_swp_mkuffd_wp(swp_pte); |
| 1898 | set_pte_at(mm, address, pvmw.pte, swp_pte); |
| 1899 | } else { |
| 1900 | /* |
| 1901 | * This is a locked file-backed folio, |
| 1902 | * so it cannot be removed from the page |
| 1903 | * cache and replaced by a new folio before |
| 1904 | * mmu_notifier_invalidate_range_end, so no |
| 1905 | * concurrent thread might update its page table |
| 1906 | * to point at a new folio while a device is |
| 1907 | * still using this folio. |
| 1908 | * |
| 1909 | * See Documentation/mm/mmu_notifier.rst |
| 1910 | */ |
| 1911 | dec_mm_counter(mm, mm_counter_file(folio)); |
| 1912 | } |
| 1913 | discard: |
| 1914 | if (unlikely(folio_test_hugetlb(folio))) |
| 1915 | hugetlb_remove_rmap(folio); |
| 1916 | else |
| 1917 | folio_remove_rmap_pte(folio, subpage, vma); |
| 1918 | if (vma->vm_flags & VM_LOCKED) |
| 1919 | mlock_drain_local(); |
| 1920 | folio_put(folio); |
| 1921 | } |
| 1922 | |
| 1923 | mmu_notifier_invalidate_range_end(&range); |
| 1924 | |
| 1925 | return ret; |
| 1926 | } |
| 1927 | |
| 1928 | static bool invalid_migration_vma(struct vm_area_struct *vma, void *arg) |
| 1929 | { |
| 1930 | return vma_is_temporary_stack(vma); |
| 1931 | } |
| 1932 | |
| 1933 | static int folio_not_mapped(struct folio *folio) |
| 1934 | { |
| 1935 | return !folio_mapped(folio); |
| 1936 | } |
| 1937 | |
| 1938 | /** |
| 1939 | * try_to_unmap - Try to remove all page table mappings to a folio. |
| 1940 | * @folio: The folio to unmap. |
| 1941 | * @flags: action and flags |
| 1942 | * |
| 1943 | * Tries to remove all the page table entries which are mapping this |
| 1944 | * folio. It is the caller's responsibility to check if the folio is |
| 1945 | * still mapped if needed (use TTU_SYNC to prevent accounting races). |
| 1946 | * |
| 1947 | * Context: Caller must hold the folio lock. |
| 1948 | */ |
| 1949 | void try_to_unmap(struct folio *folio, enum ttu_flags flags) |
| 1950 | { |
| 1951 | struct rmap_walk_control rwc = { |
| 1952 | .rmap_one = try_to_unmap_one, |
| 1953 | .arg = (void *)flags, |
| 1954 | .done = folio_not_mapped, |
| 1955 | .anon_lock = folio_lock_anon_vma_read, |
| 1956 | }; |
| 1957 | |
| 1958 | if (flags & TTU_RMAP_LOCKED) |
| 1959 | rmap_walk_locked(folio, &rwc); |
| 1960 | else |
| 1961 | rmap_walk(folio, &rwc); |
| 1962 | } |
| 1963 | |
| 1964 | /* |
| 1965 | * @arg: enum ttu_flags will be passed to this argument. |
| 1966 | * |
| 1967 | * If TTU_SPLIT_HUGE_PMD is specified any PMD mappings will be split into PTEs |
| 1968 | * containing migration entries. |
| 1969 | */ |
| 1970 | static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma, |
| 1971 | unsigned long address, void *arg) |
| 1972 | { |
| 1973 | struct mm_struct *mm = vma->vm_mm; |
| 1974 | DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); |
| 1975 | pte_t pteval; |
| 1976 | struct page *subpage; |
| 1977 | bool anon_exclusive, ret = true; |
| 1978 | struct mmu_notifier_range range; |
| 1979 | enum ttu_flags flags = (enum ttu_flags)(long)arg; |
| 1980 | unsigned long pfn; |
| 1981 | unsigned long hsz = 0; |
| 1982 | |
| 1983 | /* |
| 1984 | * When racing against e.g. zap_pte_range() on another cpu, |
| 1985 | * in between its ptep_get_and_clear_full() and folio_remove_rmap_*(), |
| 1986 | * try_to_migrate() may return before page_mapped() has become false, |
| 1987 | * if page table locking is skipped: use TTU_SYNC to wait for that. |
| 1988 | */ |
| 1989 | if (flags & TTU_SYNC) |
| 1990 | pvmw.flags = PVMW_SYNC; |
| 1991 | |
| 1992 | /* |
| 1993 | * unmap_page() in mm/huge_memory.c is the only user of migration with |
| 1994 | * TTU_SPLIT_HUGE_PMD and it wants to freeze. |
| 1995 | */ |
| 1996 | if (flags & TTU_SPLIT_HUGE_PMD) |
| 1997 | split_huge_pmd_address(vma, address, true, folio); |
| 1998 | |
| 1999 | /* |
| 2000 | * For THP, we have to assume the worse case ie pmd for invalidation. |
| 2001 | * For hugetlb, it could be much worse if we need to do pud |
| 2002 | * invalidation in the case of pmd sharing. |
| 2003 | * |
| 2004 | * Note that the page can not be free in this function as call of |
| 2005 | * try_to_unmap() must hold a reference on the page. |
| 2006 | */ |
| 2007 | range.end = vma_address_end(&pvmw); |
| 2008 | mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm, |
| 2009 | address, range.end); |
| 2010 | if (folio_test_hugetlb(folio)) { |
| 2011 | /* |
| 2012 | * If sharing is possible, start and end will be adjusted |
| 2013 | * accordingly. |
| 2014 | */ |
| 2015 | adjust_range_if_pmd_sharing_possible(vma, &range.start, |
| 2016 | &range.end); |
| 2017 | |
| 2018 | /* We need the huge page size for set_huge_pte_at() */ |
| 2019 | hsz = huge_page_size(hstate_vma(vma)); |
| 2020 | } |
| 2021 | mmu_notifier_invalidate_range_start(&range); |
| 2022 | |
| 2023 | while (page_vma_mapped_walk(&pvmw)) { |
| 2024 | #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION |
| 2025 | /* PMD-mapped THP migration entry */ |
| 2026 | if (!pvmw.pte) { |
| 2027 | subpage = folio_page(folio, |
| 2028 | pmd_pfn(*pvmw.pmd) - folio_pfn(folio)); |
| 2029 | VM_BUG_ON_FOLIO(folio_test_hugetlb(folio) || |
| 2030 | !folio_test_pmd_mappable(folio), folio); |
| 2031 | |
| 2032 | if (set_pmd_migration_entry(&pvmw, subpage)) { |
| 2033 | ret = false; |
| 2034 | page_vma_mapped_walk_done(&pvmw); |
| 2035 | break; |
| 2036 | } |
| 2037 | continue; |
| 2038 | } |
| 2039 | #endif |
| 2040 | |
| 2041 | /* Unexpected PMD-mapped THP? */ |
| 2042 | VM_BUG_ON_FOLIO(!pvmw.pte, folio); |
| 2043 | |
| 2044 | pfn = pte_pfn(ptep_get(pvmw.pte)); |
| 2045 | |
| 2046 | if (folio_is_zone_device(folio)) { |
| 2047 | /* |
| 2048 | * Our PTE is a non-present device exclusive entry and |
| 2049 | * calculating the subpage as for the common case would |
| 2050 | * result in an invalid pointer. |
| 2051 | * |
| 2052 | * Since only PAGE_SIZE pages can currently be |
| 2053 | * migrated, just set it to page. This will need to be |
| 2054 | * changed when hugepage migrations to device private |
| 2055 | * memory are supported. |
| 2056 | */ |
| 2057 | VM_BUG_ON_FOLIO(folio_nr_pages(folio) > 1, folio); |
| 2058 | subpage = &folio->page; |
| 2059 | } else { |
| 2060 | subpage = folio_page(folio, pfn - folio_pfn(folio)); |
| 2061 | } |
| 2062 | address = pvmw.address; |
| 2063 | anon_exclusive = folio_test_anon(folio) && |
| 2064 | PageAnonExclusive(subpage); |
| 2065 | |
| 2066 | if (folio_test_hugetlb(folio)) { |
| 2067 | bool anon = folio_test_anon(folio); |
| 2068 | |
| 2069 | /* |
| 2070 | * huge_pmd_unshare may unmap an entire PMD page. |
| 2071 | * There is no way of knowing exactly which PMDs may |
| 2072 | * be cached for this mm, so we must flush them all. |
| 2073 | * start/end were already adjusted above to cover this |
| 2074 | * range. |
| 2075 | */ |
| 2076 | flush_cache_range(vma, range.start, range.end); |
| 2077 | |
| 2078 | /* |
| 2079 | * To call huge_pmd_unshare, i_mmap_rwsem must be |
| 2080 | * held in write mode. Caller needs to explicitly |
| 2081 | * do this outside rmap routines. |
| 2082 | * |
| 2083 | * We also must hold hugetlb vma_lock in write mode. |
| 2084 | * Lock order dictates acquiring vma_lock BEFORE |
| 2085 | * i_mmap_rwsem. We can only try lock here and |
| 2086 | * fail if unsuccessful. |
| 2087 | */ |
| 2088 | if (!anon) { |
| 2089 | VM_BUG_ON(!(flags & TTU_RMAP_LOCKED)); |
| 2090 | if (!hugetlb_vma_trylock_write(vma)) { |
| 2091 | page_vma_mapped_walk_done(&pvmw); |
| 2092 | ret = false; |
| 2093 | break; |
| 2094 | } |
| 2095 | if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) { |
| 2096 | hugetlb_vma_unlock_write(vma); |
| 2097 | flush_tlb_range(vma, |
| 2098 | range.start, range.end); |
| 2099 | |
| 2100 | /* |
| 2101 | * The ref count of the PMD page was |
| 2102 | * dropped which is part of the way map |
| 2103 | * counting is done for shared PMDs. |
| 2104 | * Return 'true' here. When there is |
| 2105 | * no other sharing, huge_pmd_unshare |
| 2106 | * returns false and we will unmap the |
| 2107 | * actual page and drop map count |
| 2108 | * to zero. |
| 2109 | */ |
| 2110 | page_vma_mapped_walk_done(&pvmw); |
| 2111 | break; |
| 2112 | } |
| 2113 | hugetlb_vma_unlock_write(vma); |
| 2114 | } |
| 2115 | /* Nuke the hugetlb page table entry */ |
| 2116 | pteval = huge_ptep_clear_flush(vma, address, pvmw.pte); |
| 2117 | } else { |
| 2118 | flush_cache_page(vma, address, pfn); |
| 2119 | /* Nuke the page table entry. */ |
| 2120 | if (should_defer_flush(mm, flags)) { |
| 2121 | /* |
| 2122 | * We clear the PTE but do not flush so potentially |
| 2123 | * a remote CPU could still be writing to the folio. |
| 2124 | * If the entry was previously clean then the |
| 2125 | * architecture must guarantee that a clear->dirty |
| 2126 | * transition on a cached TLB entry is written through |
| 2127 | * and traps if the PTE is unmapped. |
| 2128 | */ |
| 2129 | pteval = ptep_get_and_clear(mm, address, pvmw.pte); |
| 2130 | |
| 2131 | set_tlb_ubc_flush_pending(mm, pteval, address); |
| 2132 | } else { |
| 2133 | pteval = ptep_clear_flush(vma, address, pvmw.pte); |
| 2134 | } |
| 2135 | } |
| 2136 | |
| 2137 | /* Set the dirty flag on the folio now the pte is gone. */ |
| 2138 | if (pte_dirty(pteval)) |
| 2139 | folio_mark_dirty(folio); |
| 2140 | |
| 2141 | /* Update high watermark before we lower rss */ |
| 2142 | update_hiwater_rss(mm); |
| 2143 | |
| 2144 | if (folio_is_device_private(folio)) { |
| 2145 | unsigned long pfn = folio_pfn(folio); |
| 2146 | swp_entry_t entry; |
| 2147 | pte_t swp_pte; |
| 2148 | |
| 2149 | if (anon_exclusive) |
| 2150 | WARN_ON_ONCE(folio_try_share_anon_rmap_pte(folio, |
| 2151 | subpage)); |
| 2152 | |
| 2153 | /* |
| 2154 | * Store the pfn of the page in a special migration |
| 2155 | * pte. do_swap_page() will wait until the migration |
| 2156 | * pte is removed and then restart fault handling. |
| 2157 | */ |
| 2158 | entry = pte_to_swp_entry(pteval); |
| 2159 | if (is_writable_device_private_entry(entry)) |
| 2160 | entry = make_writable_migration_entry(pfn); |
| 2161 | else if (anon_exclusive) |
| 2162 | entry = make_readable_exclusive_migration_entry(pfn); |
| 2163 | else |
| 2164 | entry = make_readable_migration_entry(pfn); |
| 2165 | swp_pte = swp_entry_to_pte(entry); |
| 2166 | |
| 2167 | /* |
| 2168 | * pteval maps a zone device page and is therefore |
| 2169 | * a swap pte. |
| 2170 | */ |
| 2171 | if (pte_swp_soft_dirty(pteval)) |
| 2172 | swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| 2173 | if (pte_swp_uffd_wp(pteval)) |
| 2174 | swp_pte = pte_swp_mkuffd_wp(swp_pte); |
| 2175 | set_pte_at(mm, pvmw.address, pvmw.pte, swp_pte); |
| 2176 | trace_set_migration_pte(pvmw.address, pte_val(swp_pte), |
| 2177 | folio_order(folio)); |
| 2178 | /* |
| 2179 | * No need to invalidate here it will synchronize on |
| 2180 | * against the special swap migration pte. |
| 2181 | */ |
| 2182 | } else if (PageHWPoison(subpage)) { |
| 2183 | pteval = swp_entry_to_pte(make_hwpoison_entry(subpage)); |
| 2184 | if (folio_test_hugetlb(folio)) { |
| 2185 | hugetlb_count_sub(folio_nr_pages(folio), mm); |
| 2186 | set_huge_pte_at(mm, address, pvmw.pte, pteval, |
| 2187 | hsz); |
| 2188 | } else { |
| 2189 | dec_mm_counter(mm, mm_counter(folio)); |
| 2190 | set_pte_at(mm, address, pvmw.pte, pteval); |
| 2191 | } |
| 2192 | |
| 2193 | } else if (pte_unused(pteval) && !userfaultfd_armed(vma)) { |
| 2194 | /* |
| 2195 | * The guest indicated that the page content is of no |
| 2196 | * interest anymore. Simply discard the pte, vmscan |
| 2197 | * will take care of the rest. |
| 2198 | * A future reference will then fault in a new zero |
| 2199 | * page. When userfaultfd is active, we must not drop |
| 2200 | * this page though, as its main user (postcopy |
| 2201 | * migration) will not expect userfaults on already |
| 2202 | * copied pages. |
| 2203 | */ |
| 2204 | dec_mm_counter(mm, mm_counter(folio)); |
| 2205 | } else { |
| 2206 | swp_entry_t entry; |
| 2207 | pte_t swp_pte; |
| 2208 | |
| 2209 | if (arch_unmap_one(mm, vma, address, pteval) < 0) { |
| 2210 | if (folio_test_hugetlb(folio)) |
| 2211 | set_huge_pte_at(mm, address, pvmw.pte, |
| 2212 | pteval, hsz); |
| 2213 | else |
| 2214 | set_pte_at(mm, address, pvmw.pte, pteval); |
| 2215 | ret = false; |
| 2216 | page_vma_mapped_walk_done(&pvmw); |
| 2217 | break; |
| 2218 | } |
| 2219 | VM_BUG_ON_PAGE(pte_write(pteval) && folio_test_anon(folio) && |
| 2220 | !anon_exclusive, subpage); |
| 2221 | |
| 2222 | /* See folio_try_share_anon_rmap_pte(): clear PTE first. */ |
| 2223 | if (folio_test_hugetlb(folio)) { |
| 2224 | if (anon_exclusive && |
| 2225 | hugetlb_try_share_anon_rmap(folio)) { |
| 2226 | set_huge_pte_at(mm, address, pvmw.pte, |
| 2227 | pteval, hsz); |
| 2228 | ret = false; |
| 2229 | page_vma_mapped_walk_done(&pvmw); |
| 2230 | break; |
| 2231 | } |
| 2232 | } else if (anon_exclusive && |
| 2233 | folio_try_share_anon_rmap_pte(folio, subpage)) { |
| 2234 | set_pte_at(mm, address, pvmw.pte, pteval); |
| 2235 | ret = false; |
| 2236 | page_vma_mapped_walk_done(&pvmw); |
| 2237 | break; |
| 2238 | } |
| 2239 | |
| 2240 | /* |
| 2241 | * Store the pfn of the page in a special migration |
| 2242 | * pte. do_swap_page() will wait until the migration |
| 2243 | * pte is removed and then restart fault handling. |
| 2244 | */ |
| 2245 | if (pte_write(pteval)) |
| 2246 | entry = make_writable_migration_entry( |
| 2247 | page_to_pfn(subpage)); |
| 2248 | else if (anon_exclusive) |
| 2249 | entry = make_readable_exclusive_migration_entry( |
| 2250 | page_to_pfn(subpage)); |
| 2251 | else |
| 2252 | entry = make_readable_migration_entry( |
| 2253 | page_to_pfn(subpage)); |
| 2254 | if (pte_young(pteval)) |
| 2255 | entry = make_migration_entry_young(entry); |
| 2256 | if (pte_dirty(pteval)) |
| 2257 | entry = make_migration_entry_dirty(entry); |
| 2258 | swp_pte = swp_entry_to_pte(entry); |
| 2259 | if (pte_soft_dirty(pteval)) |
| 2260 | swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| 2261 | if (pte_uffd_wp(pteval)) |
| 2262 | swp_pte = pte_swp_mkuffd_wp(swp_pte); |
| 2263 | if (folio_test_hugetlb(folio)) |
| 2264 | set_huge_pte_at(mm, address, pvmw.pte, swp_pte, |
| 2265 | hsz); |
| 2266 | else |
| 2267 | set_pte_at(mm, address, pvmw.pte, swp_pte); |
| 2268 | trace_set_migration_pte(address, pte_val(swp_pte), |
| 2269 | folio_order(folio)); |
| 2270 | /* |
| 2271 | * No need to invalidate here it will synchronize on |
| 2272 | * against the special swap migration pte. |
| 2273 | */ |
| 2274 | } |
| 2275 | |
| 2276 | if (unlikely(folio_test_hugetlb(folio))) |
| 2277 | hugetlb_remove_rmap(folio); |
| 2278 | else |
| 2279 | folio_remove_rmap_pte(folio, subpage, vma); |
| 2280 | if (vma->vm_flags & VM_LOCKED) |
| 2281 | mlock_drain_local(); |
| 2282 | folio_put(folio); |
| 2283 | } |
| 2284 | |
| 2285 | mmu_notifier_invalidate_range_end(&range); |
| 2286 | |
| 2287 | return ret; |
| 2288 | } |
| 2289 | |
| 2290 | /** |
| 2291 | * try_to_migrate - try to replace all page table mappings with swap entries |
| 2292 | * @folio: the folio to replace page table entries for |
| 2293 | * @flags: action and flags |
| 2294 | * |
| 2295 | * Tries to remove all the page table entries which are mapping this folio and |
| 2296 | * replace them with special swap entries. Caller must hold the folio lock. |
| 2297 | */ |
| 2298 | void try_to_migrate(struct folio *folio, enum ttu_flags flags) |
| 2299 | { |
| 2300 | struct rmap_walk_control rwc = { |
| 2301 | .rmap_one = try_to_migrate_one, |
| 2302 | .arg = (void *)flags, |
| 2303 | .done = folio_not_mapped, |
| 2304 | .anon_lock = folio_lock_anon_vma_read, |
| 2305 | }; |
| 2306 | |
| 2307 | /* |
| 2308 | * Migration always ignores mlock and only supports TTU_RMAP_LOCKED and |
| 2309 | * TTU_SPLIT_HUGE_PMD, TTU_SYNC, and TTU_BATCH_FLUSH flags. |
| 2310 | */ |
| 2311 | if (WARN_ON_ONCE(flags & ~(TTU_RMAP_LOCKED | TTU_SPLIT_HUGE_PMD | |
| 2312 | TTU_SYNC | TTU_BATCH_FLUSH))) |
| 2313 | return; |
| 2314 | |
| 2315 | if (folio_is_zone_device(folio) && |
| 2316 | (!folio_is_device_private(folio) && !folio_is_device_coherent(folio))) |
| 2317 | return; |
| 2318 | |
| 2319 | /* |
| 2320 | * During exec, a temporary VMA is setup and later moved. |
| 2321 | * The VMA is moved under the anon_vma lock but not the |
| 2322 | * page tables leading to a race where migration cannot |
| 2323 | * find the migration ptes. Rather than increasing the |
| 2324 | * locking requirements of exec(), migration skips |
| 2325 | * temporary VMAs until after exec() completes. |
| 2326 | */ |
| 2327 | if (!folio_test_ksm(folio) && folio_test_anon(folio)) |
| 2328 | rwc.invalid_vma = invalid_migration_vma; |
| 2329 | |
| 2330 | if (flags & TTU_RMAP_LOCKED) |
| 2331 | rmap_walk_locked(folio, &rwc); |
| 2332 | else |
| 2333 | rmap_walk(folio, &rwc); |
| 2334 | } |
| 2335 | |
| 2336 | #ifdef CONFIG_DEVICE_PRIVATE |
| 2337 | struct make_exclusive_args { |
| 2338 | struct mm_struct *mm; |
| 2339 | unsigned long address; |
| 2340 | void *owner; |
| 2341 | bool valid; |
| 2342 | }; |
| 2343 | |
| 2344 | static bool page_make_device_exclusive_one(struct folio *folio, |
| 2345 | struct vm_area_struct *vma, unsigned long address, void *priv) |
| 2346 | { |
| 2347 | struct mm_struct *mm = vma->vm_mm; |
| 2348 | DEFINE_FOLIO_VMA_WALK(pvmw, folio, vma, address, 0); |
| 2349 | struct make_exclusive_args *args = priv; |
| 2350 | pte_t pteval; |
| 2351 | struct page *subpage; |
| 2352 | bool ret = true; |
| 2353 | struct mmu_notifier_range range; |
| 2354 | swp_entry_t entry; |
| 2355 | pte_t swp_pte; |
| 2356 | pte_t ptent; |
| 2357 | |
| 2358 | mmu_notifier_range_init_owner(&range, MMU_NOTIFY_EXCLUSIVE, 0, |
| 2359 | vma->vm_mm, address, min(vma->vm_end, |
| 2360 | address + folio_size(folio)), |
| 2361 | args->owner); |
| 2362 | mmu_notifier_invalidate_range_start(&range); |
| 2363 | |
| 2364 | while (page_vma_mapped_walk(&pvmw)) { |
| 2365 | /* Unexpected PMD-mapped THP? */ |
| 2366 | VM_BUG_ON_FOLIO(!pvmw.pte, folio); |
| 2367 | |
| 2368 | ptent = ptep_get(pvmw.pte); |
| 2369 | if (!pte_present(ptent)) { |
| 2370 | ret = false; |
| 2371 | page_vma_mapped_walk_done(&pvmw); |
| 2372 | break; |
| 2373 | } |
| 2374 | |
| 2375 | subpage = folio_page(folio, |
| 2376 | pte_pfn(ptent) - folio_pfn(folio)); |
| 2377 | address = pvmw.address; |
| 2378 | |
| 2379 | /* Nuke the page table entry. */ |
| 2380 | flush_cache_page(vma, address, pte_pfn(ptent)); |
| 2381 | pteval = ptep_clear_flush(vma, address, pvmw.pte); |
| 2382 | |
| 2383 | /* Set the dirty flag on the folio now the pte is gone. */ |
| 2384 | if (pte_dirty(pteval)) |
| 2385 | folio_mark_dirty(folio); |
| 2386 | |
| 2387 | /* |
| 2388 | * Check that our target page is still mapped at the expected |
| 2389 | * address. |
| 2390 | */ |
| 2391 | if (args->mm == mm && args->address == address && |
| 2392 | pte_write(pteval)) |
| 2393 | args->valid = true; |
| 2394 | |
| 2395 | /* |
| 2396 | * Store the pfn of the page in a special migration |
| 2397 | * pte. do_swap_page() will wait until the migration |
| 2398 | * pte is removed and then restart fault handling. |
| 2399 | */ |
| 2400 | if (pte_write(pteval)) |
| 2401 | entry = make_writable_device_exclusive_entry( |
| 2402 | page_to_pfn(subpage)); |
| 2403 | else |
| 2404 | entry = make_readable_device_exclusive_entry( |
| 2405 | page_to_pfn(subpage)); |
| 2406 | swp_pte = swp_entry_to_pte(entry); |
| 2407 | if (pte_soft_dirty(pteval)) |
| 2408 | swp_pte = pte_swp_mksoft_dirty(swp_pte); |
| 2409 | if (pte_uffd_wp(pteval)) |
| 2410 | swp_pte = pte_swp_mkuffd_wp(swp_pte); |
| 2411 | |
| 2412 | set_pte_at(mm, address, pvmw.pte, swp_pte); |
| 2413 | |
| 2414 | /* |
| 2415 | * There is a reference on the page for the swap entry which has |
| 2416 | * been removed, so shouldn't take another. |
| 2417 | */ |
| 2418 | folio_remove_rmap_pte(folio, subpage, vma); |
| 2419 | } |
| 2420 | |
| 2421 | mmu_notifier_invalidate_range_end(&range); |
| 2422 | |
| 2423 | return ret; |
| 2424 | } |
| 2425 | |
| 2426 | /** |
| 2427 | * folio_make_device_exclusive - Mark the folio exclusively owned by a device. |
| 2428 | * @folio: The folio to replace page table entries for. |
| 2429 | * @mm: The mm_struct where the folio is expected to be mapped. |
| 2430 | * @address: Address where the folio is expected to be mapped. |
| 2431 | * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier callbacks |
| 2432 | * |
| 2433 | * Tries to remove all the page table entries which are mapping this |
| 2434 | * folio and replace them with special device exclusive swap entries to |
| 2435 | * grant a device exclusive access to the folio. |
| 2436 | * |
| 2437 | * Context: Caller must hold the folio lock. |
| 2438 | * Return: false if the page is still mapped, or if it could not be unmapped |
| 2439 | * from the expected address. Otherwise returns true (success). |
| 2440 | */ |
| 2441 | static bool folio_make_device_exclusive(struct folio *folio, |
| 2442 | struct mm_struct *mm, unsigned long address, void *owner) |
| 2443 | { |
| 2444 | struct make_exclusive_args args = { |
| 2445 | .mm = mm, |
| 2446 | .address = address, |
| 2447 | .owner = owner, |
| 2448 | .valid = false, |
| 2449 | }; |
| 2450 | struct rmap_walk_control rwc = { |
| 2451 | .rmap_one = page_make_device_exclusive_one, |
| 2452 | .done = folio_not_mapped, |
| 2453 | .anon_lock = folio_lock_anon_vma_read, |
| 2454 | .arg = &args, |
| 2455 | }; |
| 2456 | |
| 2457 | /* |
| 2458 | * Restrict to anonymous folios for now to avoid potential writeback |
| 2459 | * issues. |
| 2460 | */ |
| 2461 | if (!folio_test_anon(folio)) |
| 2462 | return false; |
| 2463 | |
| 2464 | rmap_walk(folio, &rwc); |
| 2465 | |
| 2466 | return args.valid && !folio_mapcount(folio); |
| 2467 | } |
| 2468 | |
| 2469 | /** |
| 2470 | * make_device_exclusive_range() - Mark a range for exclusive use by a device |
| 2471 | * @mm: mm_struct of associated target process |
| 2472 | * @start: start of the region to mark for exclusive device access |
| 2473 | * @end: end address of region |
| 2474 | * @pages: returns the pages which were successfully marked for exclusive access |
| 2475 | * @owner: passed to MMU_NOTIFY_EXCLUSIVE range notifier to allow filtering |
| 2476 | * |
| 2477 | * Returns: number of pages found in the range by GUP. A page is marked for |
| 2478 | * exclusive access only if the page pointer is non-NULL. |
| 2479 | * |
| 2480 | * This function finds ptes mapping page(s) to the given address range, locks |
| 2481 | * them and replaces mappings with special swap entries preventing userspace CPU |
| 2482 | * access. On fault these entries are replaced with the original mapping after |
| 2483 | * calling MMU notifiers. |
| 2484 | * |
| 2485 | * A driver using this to program access from a device must use a mmu notifier |
| 2486 | * critical section to hold a device specific lock during programming. Once |
| 2487 | * programming is complete it should drop the page lock and reference after |
| 2488 | * which point CPU access to the page will revoke the exclusive access. |
| 2489 | */ |
| 2490 | int make_device_exclusive_range(struct mm_struct *mm, unsigned long start, |
| 2491 | unsigned long end, struct page **pages, |
| 2492 | void *owner) |
| 2493 | { |
| 2494 | long npages = (end - start) >> PAGE_SHIFT; |
| 2495 | long i; |
| 2496 | |
| 2497 | npages = get_user_pages_remote(mm, start, npages, |
| 2498 | FOLL_GET | FOLL_WRITE | FOLL_SPLIT_PMD, |
| 2499 | pages, NULL); |
| 2500 | if (npages < 0) |
| 2501 | return npages; |
| 2502 | |
| 2503 | for (i = 0; i < npages; i++, start += PAGE_SIZE) { |
| 2504 | struct folio *folio = page_folio(pages[i]); |
| 2505 | if (PageTail(pages[i]) || !folio_trylock(folio)) { |
| 2506 | folio_put(folio); |
| 2507 | pages[i] = NULL; |
| 2508 | continue; |
| 2509 | } |
| 2510 | |
| 2511 | if (!folio_make_device_exclusive(folio, mm, start, owner)) { |
| 2512 | folio_unlock(folio); |
| 2513 | folio_put(folio); |
| 2514 | pages[i] = NULL; |
| 2515 | } |
| 2516 | } |
| 2517 | |
| 2518 | return npages; |
| 2519 | } |
| 2520 | EXPORT_SYMBOL_GPL(make_device_exclusive_range); |
| 2521 | #endif |
| 2522 | |
| 2523 | void __put_anon_vma(struct anon_vma *anon_vma) |
| 2524 | { |
| 2525 | struct anon_vma *root = anon_vma->root; |
| 2526 | |
| 2527 | anon_vma_free(anon_vma); |
| 2528 | if (root != anon_vma && atomic_dec_and_test(&root->refcount)) |
| 2529 | anon_vma_free(root); |
| 2530 | } |
| 2531 | |
| 2532 | static struct anon_vma *rmap_walk_anon_lock(struct folio *folio, |
| 2533 | struct rmap_walk_control *rwc) |
| 2534 | { |
| 2535 | struct anon_vma *anon_vma; |
| 2536 | |
| 2537 | if (rwc->anon_lock) |
| 2538 | return rwc->anon_lock(folio, rwc); |
| 2539 | |
| 2540 | /* |
| 2541 | * Note: remove_migration_ptes() cannot use folio_lock_anon_vma_read() |
| 2542 | * because that depends on page_mapped(); but not all its usages |
| 2543 | * are holding mmap_lock. Users without mmap_lock are required to |
| 2544 | * take a reference count to prevent the anon_vma disappearing |
| 2545 | */ |
| 2546 | anon_vma = folio_anon_vma(folio); |
| 2547 | if (!anon_vma) |
| 2548 | return NULL; |
| 2549 | |
| 2550 | if (anon_vma_trylock_read(anon_vma)) |
| 2551 | goto out; |
| 2552 | |
| 2553 | if (rwc->try_lock) { |
| 2554 | anon_vma = NULL; |
| 2555 | rwc->contended = true; |
| 2556 | goto out; |
| 2557 | } |
| 2558 | |
| 2559 | anon_vma_lock_read(anon_vma); |
| 2560 | out: |
| 2561 | return anon_vma; |
| 2562 | } |
| 2563 | |
| 2564 | /* |
| 2565 | * rmap_walk_anon - do something to anonymous page using the object-based |
| 2566 | * rmap method |
| 2567 | * @folio: the folio to be handled |
| 2568 | * @rwc: control variable according to each walk type |
| 2569 | * @locked: caller holds relevant rmap lock |
| 2570 | * |
| 2571 | * Find all the mappings of a folio using the mapping pointer and the vma |
| 2572 | * chains contained in the anon_vma struct it points to. |
| 2573 | */ |
| 2574 | static void rmap_walk_anon(struct folio *folio, |
| 2575 | struct rmap_walk_control *rwc, bool locked) |
| 2576 | { |
| 2577 | struct anon_vma *anon_vma; |
| 2578 | pgoff_t pgoff_start, pgoff_end; |
| 2579 | struct anon_vma_chain *avc; |
| 2580 | |
| 2581 | if (locked) { |
| 2582 | anon_vma = folio_anon_vma(folio); |
| 2583 | /* anon_vma disappear under us? */ |
| 2584 | VM_BUG_ON_FOLIO(!anon_vma, folio); |
| 2585 | } else { |
| 2586 | anon_vma = rmap_walk_anon_lock(folio, rwc); |
| 2587 | } |
| 2588 | if (!anon_vma) |
| 2589 | return; |
| 2590 | |
| 2591 | pgoff_start = folio_pgoff(folio); |
| 2592 | pgoff_end = pgoff_start + folio_nr_pages(folio) - 1; |
| 2593 | anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, |
| 2594 | pgoff_start, pgoff_end) { |
| 2595 | struct vm_area_struct *vma = avc->vma; |
| 2596 | unsigned long address = vma_address(vma, pgoff_start, |
| 2597 | folio_nr_pages(folio)); |
| 2598 | |
| 2599 | VM_BUG_ON_VMA(address == -EFAULT, vma); |
| 2600 | cond_resched(); |
| 2601 | |
| 2602 | if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
| 2603 | continue; |
| 2604 | |
| 2605 | if (!rwc->rmap_one(folio, vma, address, rwc->arg)) |
| 2606 | break; |
| 2607 | if (rwc->done && rwc->done(folio)) |
| 2608 | break; |
| 2609 | } |
| 2610 | |
| 2611 | if (!locked) |
| 2612 | anon_vma_unlock_read(anon_vma); |
| 2613 | } |
| 2614 | |
| 2615 | /* |
| 2616 | * rmap_walk_file - do something to file page using the object-based rmap method |
| 2617 | * @folio: the folio to be handled |
| 2618 | * @rwc: control variable according to each walk type |
| 2619 | * @locked: caller holds relevant rmap lock |
| 2620 | * |
| 2621 | * Find all the mappings of a folio using the mapping pointer and the vma chains |
| 2622 | * contained in the address_space struct it points to. |
| 2623 | */ |
| 2624 | static void rmap_walk_file(struct folio *folio, |
| 2625 | struct rmap_walk_control *rwc, bool locked) |
| 2626 | { |
| 2627 | struct address_space *mapping = folio_mapping(folio); |
| 2628 | pgoff_t pgoff_start, pgoff_end; |
| 2629 | struct vm_area_struct *vma; |
| 2630 | |
| 2631 | /* |
| 2632 | * The page lock not only makes sure that page->mapping cannot |
| 2633 | * suddenly be NULLified by truncation, it makes sure that the |
| 2634 | * structure at mapping cannot be freed and reused yet, |
| 2635 | * so we can safely take mapping->i_mmap_rwsem. |
| 2636 | */ |
| 2637 | VM_BUG_ON_FOLIO(!folio_test_locked(folio), folio); |
| 2638 | |
| 2639 | if (!mapping) |
| 2640 | return; |
| 2641 | |
| 2642 | pgoff_start = folio_pgoff(folio); |
| 2643 | pgoff_end = pgoff_start + folio_nr_pages(folio) - 1; |
| 2644 | if (!locked) { |
| 2645 | if (i_mmap_trylock_read(mapping)) |
| 2646 | goto lookup; |
| 2647 | |
| 2648 | if (rwc->try_lock) { |
| 2649 | rwc->contended = true; |
| 2650 | return; |
| 2651 | } |
| 2652 | |
| 2653 | i_mmap_lock_read(mapping); |
| 2654 | } |
| 2655 | lookup: |
| 2656 | vma_interval_tree_foreach(vma, &mapping->i_mmap, |
| 2657 | pgoff_start, pgoff_end) { |
| 2658 | unsigned long address = vma_address(vma, pgoff_start, |
| 2659 | folio_nr_pages(folio)); |
| 2660 | |
| 2661 | VM_BUG_ON_VMA(address == -EFAULT, vma); |
| 2662 | cond_resched(); |
| 2663 | |
| 2664 | if (rwc->invalid_vma && rwc->invalid_vma(vma, rwc->arg)) |
| 2665 | continue; |
| 2666 | |
| 2667 | if (!rwc->rmap_one(folio, vma, address, rwc->arg)) |
| 2668 | goto done; |
| 2669 | if (rwc->done && rwc->done(folio)) |
| 2670 | goto done; |
| 2671 | } |
| 2672 | |
| 2673 | done: |
| 2674 | if (!locked) |
| 2675 | i_mmap_unlock_read(mapping); |
| 2676 | } |
| 2677 | |
| 2678 | void rmap_walk(struct folio *folio, struct rmap_walk_control *rwc) |
| 2679 | { |
| 2680 | if (unlikely(folio_test_ksm(folio))) |
| 2681 | rmap_walk_ksm(folio, rwc); |
| 2682 | else if (folio_test_anon(folio)) |
| 2683 | rmap_walk_anon(folio, rwc, false); |
| 2684 | else |
| 2685 | rmap_walk_file(folio, rwc, false); |
| 2686 | } |
| 2687 | |
| 2688 | /* Like rmap_walk, but caller holds relevant rmap lock */ |
| 2689 | void rmap_walk_locked(struct folio *folio, struct rmap_walk_control *rwc) |
| 2690 | { |
| 2691 | /* no ksm support for now */ |
| 2692 | VM_BUG_ON_FOLIO(folio_test_ksm(folio), folio); |
| 2693 | if (folio_test_anon(folio)) |
| 2694 | rmap_walk_anon(folio, rwc, true); |
| 2695 | else |
| 2696 | rmap_walk_file(folio, rwc, true); |
| 2697 | } |
| 2698 | |
| 2699 | #ifdef CONFIG_HUGETLB_PAGE |
| 2700 | /* |
| 2701 | * The following two functions are for anonymous (private mapped) hugepages. |
| 2702 | * Unlike common anonymous pages, anonymous hugepages have no accounting code |
| 2703 | * and no lru code, because we handle hugepages differently from common pages. |
| 2704 | */ |
| 2705 | void hugetlb_add_anon_rmap(struct folio *folio, struct vm_area_struct *vma, |
| 2706 | unsigned long address, rmap_t flags) |
| 2707 | { |
| 2708 | VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio); |
| 2709 | VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio); |
| 2710 | |
| 2711 | atomic_inc(&folio->_entire_mapcount); |
| 2712 | atomic_inc(&folio->_large_mapcount); |
| 2713 | if (flags & RMAP_EXCLUSIVE) |
| 2714 | SetPageAnonExclusive(&folio->page); |
| 2715 | VM_WARN_ON_FOLIO(folio_entire_mapcount(folio) > 1 && |
| 2716 | PageAnonExclusive(&folio->page), folio); |
| 2717 | } |
| 2718 | |
| 2719 | void hugetlb_add_new_anon_rmap(struct folio *folio, |
| 2720 | struct vm_area_struct *vma, unsigned long address) |
| 2721 | { |
| 2722 | VM_WARN_ON_FOLIO(!folio_test_hugetlb(folio), folio); |
| 2723 | |
| 2724 | BUG_ON(address < vma->vm_start || address >= vma->vm_end); |
| 2725 | /* increment count (starts at -1) */ |
| 2726 | atomic_set(&folio->_entire_mapcount, 0); |
| 2727 | atomic_set(&folio->_large_mapcount, 0); |
| 2728 | folio_clear_hugetlb_restore_reserve(folio); |
| 2729 | __folio_set_anon(folio, vma, address, true); |
| 2730 | SetPageAnonExclusive(&folio->page); |
| 2731 | } |
| 2732 | #endif /* CONFIG_HUGETLB_PAGE */ |