1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2008, 2009 Intel Corporation 4 * Authors: Andi Kleen, Fengguang Wu 5 * 6 * High level machine check handler. Handles pages reported by the 7 * hardware as being corrupted usually due to a multi-bit ECC memory or cache 8 * failure. 9 * 10 * In addition there is a "soft offline" entry point that allows stop using 11 * not-yet-corrupted-by-suspicious pages without killing anything. 12 * 13 * Handles page cache pages in various states. The tricky part 14 * here is that we can access any page asynchronously in respect to 15 * other VM users, because memory failures could happen anytime and 16 * anywhere. This could violate some of their assumptions. This is why 17 * this code has to be extremely careful. Generally it tries to use 18 * normal locking rules, as in get the standard locks, even if that means 19 * the error handling takes potentially a long time. 20 * 21 * It can be very tempting to add handling for obscure cases here. 22 * In general any code for handling new cases should only be added iff: 23 * - You know how to test it. 24 * - You have a test that can be added to mce-test 25 * https://git.kernel.org/cgit/utils/cpu/mce/mce-test.git/ 26 * - The case actually shows up as a frequent (top 10) page state in 27 * tools/mm/page-types when running a real workload. 28 * 29 * There are several operations here with exponential complexity because 30 * of unsuitable VM data structures. For example the operation to map back 31 * from RMAP chains to processes has to walk the complete process list and 32 * has non linear complexity with the number. But since memory corruptions 33 * are rare we hope to get away with this. This avoids impacting the core 34 * VM. 35 */ 36 37 #define pr_fmt(fmt) "Memory failure: " fmt 38 39 #include <linux/kernel.h> 40 #include <linux/mm.h> 41 #include <linux/page-flags.h> 42 #include <linux/sched/signal.h> 43 #include <linux/sched/task.h> 44 #include <linux/dax.h> 45 #include <linux/ksm.h> 46 #include <linux/rmap.h> 47 #include <linux/export.h> 48 #include <linux/pagemap.h> 49 #include <linux/swap.h> 50 #include <linux/backing-dev.h> 51 #include <linux/migrate.h> 52 #include <linux/slab.h> 53 #include <linux/swapops.h> 54 #include <linux/hugetlb.h> 55 #include <linux/memory_hotplug.h> 56 #include <linux/mm_inline.h> 57 #include <linux/memremap.h> 58 #include <linux/kfifo.h> 59 #include <linux/ratelimit.h> 60 #include <linux/pagewalk.h> 61 #include <linux/shmem_fs.h> 62 #include <linux/sysctl.h> 63 #include "swap.h" 64 #include "internal.h" 65 #include "ras/ras_event.h" 66 67 static int sysctl_memory_failure_early_kill __read_mostly; 68 69 static int sysctl_memory_failure_recovery __read_mostly = 1; 70 71 atomic_long_t num_poisoned_pages __read_mostly = ATOMIC_LONG_INIT(0); 72 73 static bool hw_memory_failure __read_mostly = false; 74 75 static DEFINE_MUTEX(mf_mutex); 76 77 void num_poisoned_pages_inc(unsigned long pfn) 78 { 79 atomic_long_inc(&num_poisoned_pages); 80 memblk_nr_poison_inc(pfn); 81 } 82 83 void num_poisoned_pages_sub(unsigned long pfn, long i) 84 { 85 atomic_long_sub(i, &num_poisoned_pages); 86 if (pfn != -1UL) 87 memblk_nr_poison_sub(pfn, i); 88 } 89 90 /** 91 * MF_ATTR_RO - Create sysfs entry for each memory failure statistics. 92 * @_name: name of the file in the per NUMA sysfs directory. 93 */ 94 #define MF_ATTR_RO(_name) \ 95 static ssize_t _name##_show(struct device *dev, \ 96 struct device_attribute *attr, \ 97 char *buf) \ 98 { \ 99 struct memory_failure_stats *mf_stats = \ 100 &NODE_DATA(dev->id)->mf_stats; \ 101 return sprintf(buf, "%lu\n", mf_stats->_name); \ 102 } \ 103 static DEVICE_ATTR_RO(_name) 104 105 MF_ATTR_RO(total); 106 MF_ATTR_RO(ignored); 107 MF_ATTR_RO(failed); 108 MF_ATTR_RO(delayed); 109 MF_ATTR_RO(recovered); 110 111 static struct attribute *memory_failure_attr[] = { 112 &dev_attr_total.attr, 113 &dev_attr_ignored.attr, 114 &dev_attr_failed.attr, 115 &dev_attr_delayed.attr, 116 &dev_attr_recovered.attr, 117 NULL, 118 }; 119 120 const struct attribute_group memory_failure_attr_group = { 121 .name = "memory_failure", 122 .attrs = memory_failure_attr, 123 }; 124 125 static struct ctl_table memory_failure_table[] = { 126 { 127 .procname = "memory_failure_early_kill", 128 .data = &sysctl_memory_failure_early_kill, 129 .maxlen = sizeof(sysctl_memory_failure_early_kill), 130 .mode = 0644, 131 .proc_handler = proc_dointvec_minmax, 132 .extra1 = SYSCTL_ZERO, 133 .extra2 = SYSCTL_ONE, 134 }, 135 { 136 .procname = "memory_failure_recovery", 137 .data = &sysctl_memory_failure_recovery, 138 .maxlen = sizeof(sysctl_memory_failure_recovery), 139 .mode = 0644, 140 .proc_handler = proc_dointvec_minmax, 141 .extra1 = SYSCTL_ZERO, 142 .extra2 = SYSCTL_ONE, 143 }, 144 { } 145 }; 146 147 /* 148 * Return values: 149 * 1: the page is dissolved (if needed) and taken off from buddy, 150 * 0: the page is dissolved (if needed) and not taken off from buddy, 151 * < 0: failed to dissolve. 152 */ 153 static int __page_handle_poison(struct page *page) 154 { 155 int ret; 156 157 zone_pcp_disable(page_zone(page)); 158 ret = dissolve_free_huge_page(page); 159 if (!ret) 160 ret = take_page_off_buddy(page); 161 zone_pcp_enable(page_zone(page)); 162 163 return ret; 164 } 165 166 static bool page_handle_poison(struct page *page, bool hugepage_or_freepage, bool release) 167 { 168 if (hugepage_or_freepage) { 169 /* 170 * Doing this check for free pages is also fine since dissolve_free_huge_page 171 * returns 0 for non-hugetlb pages as well. 172 */ 173 if (__page_handle_poison(page) <= 0) 174 /* 175 * We could fail to take off the target page from buddy 176 * for example due to racy page allocation, but that's 177 * acceptable because soft-offlined page is not broken 178 * and if someone really want to use it, they should 179 * take it. 180 */ 181 return false; 182 } 183 184 SetPageHWPoison(page); 185 if (release) 186 put_page(page); 187 page_ref_inc(page); 188 num_poisoned_pages_inc(page_to_pfn(page)); 189 190 return true; 191 } 192 193 #if IS_ENABLED(CONFIG_HWPOISON_INJECT) 194 195 u32 hwpoison_filter_enable = 0; 196 u32 hwpoison_filter_dev_major = ~0U; 197 u32 hwpoison_filter_dev_minor = ~0U; 198 u64 hwpoison_filter_flags_mask; 199 u64 hwpoison_filter_flags_value; 200 EXPORT_SYMBOL_GPL(hwpoison_filter_enable); 201 EXPORT_SYMBOL_GPL(hwpoison_filter_dev_major); 202 EXPORT_SYMBOL_GPL(hwpoison_filter_dev_minor); 203 EXPORT_SYMBOL_GPL(hwpoison_filter_flags_mask); 204 EXPORT_SYMBOL_GPL(hwpoison_filter_flags_value); 205 206 static int hwpoison_filter_dev(struct page *p) 207 { 208 struct address_space *mapping; 209 dev_t dev; 210 211 if (hwpoison_filter_dev_major == ~0U && 212 hwpoison_filter_dev_minor == ~0U) 213 return 0; 214 215 mapping = page_mapping(p); 216 if (mapping == NULL || mapping->host == NULL) 217 return -EINVAL; 218 219 dev = mapping->host->i_sb->s_dev; 220 if (hwpoison_filter_dev_major != ~0U && 221 hwpoison_filter_dev_major != MAJOR(dev)) 222 return -EINVAL; 223 if (hwpoison_filter_dev_minor != ~0U && 224 hwpoison_filter_dev_minor != MINOR(dev)) 225 return -EINVAL; 226 227 return 0; 228 } 229 230 static int hwpoison_filter_flags(struct page *p) 231 { 232 if (!hwpoison_filter_flags_mask) 233 return 0; 234 235 if ((stable_page_flags(p) & hwpoison_filter_flags_mask) == 236 hwpoison_filter_flags_value) 237 return 0; 238 else 239 return -EINVAL; 240 } 241 242 /* 243 * This allows stress tests to limit test scope to a collection of tasks 244 * by putting them under some memcg. This prevents killing unrelated/important 245 * processes such as /sbin/init. Note that the target task may share clean 246 * pages with init (eg. libc text), which is harmless. If the target task 247 * share _dirty_ pages with another task B, the test scheme must make sure B 248 * is also included in the memcg. At last, due to race conditions this filter 249 * can only guarantee that the page either belongs to the memcg tasks, or is 250 * a freed page. 251 */ 252 #ifdef CONFIG_MEMCG 253 u64 hwpoison_filter_memcg; 254 EXPORT_SYMBOL_GPL(hwpoison_filter_memcg); 255 static int hwpoison_filter_task(struct page *p) 256 { 257 if (!hwpoison_filter_memcg) 258 return 0; 259 260 if (page_cgroup_ino(p) != hwpoison_filter_memcg) 261 return -EINVAL; 262 263 return 0; 264 } 265 #else 266 static int hwpoison_filter_task(struct page *p) { return 0; } 267 #endif 268 269 int hwpoison_filter(struct page *p) 270 { 271 if (!hwpoison_filter_enable) 272 return 0; 273 274 if (hwpoison_filter_dev(p)) 275 return -EINVAL; 276 277 if (hwpoison_filter_flags(p)) 278 return -EINVAL; 279 280 if (hwpoison_filter_task(p)) 281 return -EINVAL; 282 283 return 0; 284 } 285 #else 286 int hwpoison_filter(struct page *p) 287 { 288 return 0; 289 } 290 #endif 291 292 EXPORT_SYMBOL_GPL(hwpoison_filter); 293 294 /* 295 * Kill all processes that have a poisoned page mapped and then isolate 296 * the page. 297 * 298 * General strategy: 299 * Find all processes having the page mapped and kill them. 300 * But we keep a page reference around so that the page is not 301 * actually freed yet. 302 * Then stash the page away 303 * 304 * There's no convenient way to get back to mapped processes 305 * from the VMAs. So do a brute-force search over all 306 * running processes. 307 * 308 * Remember that machine checks are not common (or rather 309 * if they are common you have other problems), so this shouldn't 310 * be a performance issue. 311 * 312 * Also there are some races possible while we get from the 313 * error detection to actually handle it. 314 */ 315 316 struct to_kill { 317 struct list_head nd; 318 struct task_struct *tsk; 319 unsigned long addr; 320 short size_shift; 321 }; 322 323 /* 324 * Send all the processes who have the page mapped a signal. 325 * ``action optional'' if they are not immediately affected by the error 326 * ``action required'' if error happened in current execution context 327 */ 328 static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags) 329 { 330 struct task_struct *t = tk->tsk; 331 short addr_lsb = tk->size_shift; 332 int ret = 0; 333 334 pr_err("%#lx: Sending SIGBUS to %s:%d due to hardware memory corruption\n", 335 pfn, t->comm, t->pid); 336 337 if ((flags & MF_ACTION_REQUIRED) && (t == current)) 338 ret = force_sig_mceerr(BUS_MCEERR_AR, 339 (void __user *)tk->addr, addr_lsb); 340 else 341 /* 342 * Signal other processes sharing the page if they have 343 * PF_MCE_EARLY set. 344 * Don't use force here, it's convenient if the signal 345 * can be temporarily blocked. 346 * This could cause a loop when the user sets SIGBUS 347 * to SIG_IGN, but hopefully no one will do that? 348 */ 349 ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr, 350 addr_lsb, t); 351 if (ret < 0) 352 pr_info("Error sending signal to %s:%d: %d\n", 353 t->comm, t->pid, ret); 354 return ret; 355 } 356 357 /* 358 * Unknown page type encountered. Try to check whether it can turn PageLRU by 359 * lru_add_drain_all. 360 */ 361 void shake_page(struct page *p) 362 { 363 if (PageHuge(p)) 364 return; 365 /* 366 * TODO: Could shrink slab caches here if a lightweight range-based 367 * shrinker will be available. 368 */ 369 if (PageSlab(p)) 370 return; 371 372 lru_add_drain_all(); 373 } 374 EXPORT_SYMBOL_GPL(shake_page); 375 376 static unsigned long dev_pagemap_mapping_shift(struct vm_area_struct *vma, 377 unsigned long address) 378 { 379 unsigned long ret = 0; 380 pgd_t *pgd; 381 p4d_t *p4d; 382 pud_t *pud; 383 pmd_t *pmd; 384 pte_t *pte; 385 pte_t ptent; 386 387 VM_BUG_ON_VMA(address == -EFAULT, vma); 388 pgd = pgd_offset(vma->vm_mm, address); 389 if (!pgd_present(*pgd)) 390 return 0; 391 p4d = p4d_offset(pgd, address); 392 if (!p4d_present(*p4d)) 393 return 0; 394 pud = pud_offset(p4d, address); 395 if (!pud_present(*pud)) 396 return 0; 397 if (pud_devmap(*pud)) 398 return PUD_SHIFT; 399 pmd = pmd_offset(pud, address); 400 if (!pmd_present(*pmd)) 401 return 0; 402 if (pmd_devmap(*pmd)) 403 return PMD_SHIFT; 404 pte = pte_offset_map(pmd, address); 405 if (!pte) 406 return 0; 407 ptent = ptep_get(pte); 408 if (pte_present(ptent) && pte_devmap(ptent)) 409 ret = PAGE_SHIFT; 410 pte_unmap(pte); 411 return ret; 412 } 413 414 /* 415 * Failure handling: if we can't find or can't kill a process there's 416 * not much we can do. We just print a message and ignore otherwise. 417 */ 418 419 #define FSDAX_INVALID_PGOFF ULONG_MAX 420 421 /* 422 * Schedule a process for later kill. 423 * Uses GFP_ATOMIC allocations to avoid potential recursions in the VM. 424 * 425 * Note: @fsdax_pgoff is used only when @p is a fsdax page and a 426 * filesystem with a memory failure handler has claimed the 427 * memory_failure event. In all other cases, page->index and 428 * page->mapping are sufficient for mapping the page back to its 429 * corresponding user virtual address. 430 */ 431 static void __add_to_kill(struct task_struct *tsk, struct page *p, 432 struct vm_area_struct *vma, struct list_head *to_kill, 433 unsigned long ksm_addr, pgoff_t fsdax_pgoff) 434 { 435 struct to_kill *tk; 436 437 tk = kmalloc(sizeof(struct to_kill), GFP_ATOMIC); 438 if (!tk) { 439 pr_err("Out of memory while machine check handling\n"); 440 return; 441 } 442 443 tk->addr = ksm_addr ? ksm_addr : page_address_in_vma(p, vma); 444 if (is_zone_device_page(p)) { 445 if (fsdax_pgoff != FSDAX_INVALID_PGOFF) 446 tk->addr = vma_pgoff_address(fsdax_pgoff, 1, vma); 447 tk->size_shift = dev_pagemap_mapping_shift(vma, tk->addr); 448 } else 449 tk->size_shift = page_shift(compound_head(p)); 450 451 /* 452 * Send SIGKILL if "tk->addr == -EFAULT". Also, as 453 * "tk->size_shift" is always non-zero for !is_zone_device_page(), 454 * so "tk->size_shift == 0" effectively checks no mapping on 455 * ZONE_DEVICE. Indeed, when a devdax page is mmapped N times 456 * to a process' address space, it's possible not all N VMAs 457 * contain mappings for the page, but at least one VMA does. 458 * Only deliver SIGBUS with payload derived from the VMA that 459 * has a mapping for the page. 460 */ 461 if (tk->addr == -EFAULT) { 462 pr_info("Unable to find user space address %lx in %s\n", 463 page_to_pfn(p), tsk->comm); 464 } else if (tk->size_shift == 0) { 465 kfree(tk); 466 return; 467 } 468 469 get_task_struct(tsk); 470 tk->tsk = tsk; 471 list_add_tail(&tk->nd, to_kill); 472 } 473 474 static void add_to_kill_anon_file(struct task_struct *tsk, struct page *p, 475 struct vm_area_struct *vma, 476 struct list_head *to_kill) 477 { 478 __add_to_kill(tsk, p, vma, to_kill, 0, FSDAX_INVALID_PGOFF); 479 } 480 481 #ifdef CONFIG_KSM 482 static bool task_in_to_kill_list(struct list_head *to_kill, 483 struct task_struct *tsk) 484 { 485 struct to_kill *tk, *next; 486 487 list_for_each_entry_safe(tk, next, to_kill, nd) { 488 if (tk->tsk == tsk) 489 return true; 490 } 491 492 return false; 493 } 494 void add_to_kill_ksm(struct task_struct *tsk, struct page *p, 495 struct vm_area_struct *vma, struct list_head *to_kill, 496 unsigned long ksm_addr) 497 { 498 if (!task_in_to_kill_list(to_kill, tsk)) 499 __add_to_kill(tsk, p, vma, to_kill, ksm_addr, FSDAX_INVALID_PGOFF); 500 } 501 #endif 502 /* 503 * Kill the processes that have been collected earlier. 504 * 505 * Only do anything when FORCEKILL is set, otherwise just free the 506 * list (this is used for clean pages which do not need killing) 507 * Also when FAIL is set do a force kill because something went 508 * wrong earlier. 509 */ 510 static void kill_procs(struct list_head *to_kill, int forcekill, bool fail, 511 unsigned long pfn, int flags) 512 { 513 struct to_kill *tk, *next; 514 515 list_for_each_entry_safe(tk, next, to_kill, nd) { 516 if (forcekill) { 517 /* 518 * In case something went wrong with munmapping 519 * make sure the process doesn't catch the 520 * signal and then access the memory. Just kill it. 521 */ 522 if (fail || tk->addr == -EFAULT) { 523 pr_err("%#lx: forcibly killing %s:%d because of failure to unmap corrupted page\n", 524 pfn, tk->tsk->comm, tk->tsk->pid); 525 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, 526 tk->tsk, PIDTYPE_PID); 527 } 528 529 /* 530 * In theory the process could have mapped 531 * something else on the address in-between. We could 532 * check for that, but we need to tell the 533 * process anyways. 534 */ 535 else if (kill_proc(tk, pfn, flags) < 0) 536 pr_err("%#lx: Cannot send advisory machine check signal to %s:%d\n", 537 pfn, tk->tsk->comm, tk->tsk->pid); 538 } 539 list_del(&tk->nd); 540 put_task_struct(tk->tsk); 541 kfree(tk); 542 } 543 } 544 545 /* 546 * Find a dedicated thread which is supposed to handle SIGBUS(BUS_MCEERR_AO) 547 * on behalf of the thread group. Return task_struct of the (first found) 548 * dedicated thread if found, and return NULL otherwise. 549 * 550 * We already hold rcu lock in the caller, so we don't have to call 551 * rcu_read_lock/unlock() in this function. 552 */ 553 static struct task_struct *find_early_kill_thread(struct task_struct *tsk) 554 { 555 struct task_struct *t; 556 557 for_each_thread(tsk, t) { 558 if (t->flags & PF_MCE_PROCESS) { 559 if (t->flags & PF_MCE_EARLY) 560 return t; 561 } else { 562 if (sysctl_memory_failure_early_kill) 563 return t; 564 } 565 } 566 return NULL; 567 } 568 569 /* 570 * Determine whether a given process is "early kill" process which expects 571 * to be signaled when some page under the process is hwpoisoned. 572 * Return task_struct of the dedicated thread (main thread unless explicitly 573 * specified) if the process is "early kill" and otherwise returns NULL. 574 * 575 * Note that the above is true for Action Optional case. For Action Required 576 * case, it's only meaningful to the current thread which need to be signaled 577 * with SIGBUS, this error is Action Optional for other non current 578 * processes sharing the same error page,if the process is "early kill", the 579 * task_struct of the dedicated thread will also be returned. 580 */ 581 struct task_struct *task_early_kill(struct task_struct *tsk, int force_early) 582 { 583 if (!tsk->mm) 584 return NULL; 585 /* 586 * Comparing ->mm here because current task might represent 587 * a subthread, while tsk always points to the main thread. 588 */ 589 if (force_early && tsk->mm == current->mm) 590 return current; 591 592 return find_early_kill_thread(tsk); 593 } 594 595 /* 596 * Collect processes when the error hit an anonymous page. 597 */ 598 static void collect_procs_anon(struct page *page, struct list_head *to_kill, 599 int force_early) 600 { 601 struct folio *folio = page_folio(page); 602 struct vm_area_struct *vma; 603 struct task_struct *tsk; 604 struct anon_vma *av; 605 pgoff_t pgoff; 606 607 av = folio_lock_anon_vma_read(folio, NULL); 608 if (av == NULL) /* Not actually mapped anymore */ 609 return; 610 611 pgoff = page_to_pgoff(page); 612 rcu_read_lock(); 613 for_each_process(tsk) { 614 struct anon_vma_chain *vmac; 615 struct task_struct *t = task_early_kill(tsk, force_early); 616 617 if (!t) 618 continue; 619 anon_vma_interval_tree_foreach(vmac, &av->rb_root, 620 pgoff, pgoff) { 621 vma = vmac->vma; 622 if (vma->vm_mm != t->mm) 623 continue; 624 if (!page_mapped_in_vma(page, vma)) 625 continue; 626 add_to_kill_anon_file(t, page, vma, to_kill); 627 } 628 } 629 rcu_read_unlock(); 630 anon_vma_unlock_read(av); 631 } 632 633 /* 634 * Collect processes when the error hit a file mapped page. 635 */ 636 static void collect_procs_file(struct page *page, struct list_head *to_kill, 637 int force_early) 638 { 639 struct vm_area_struct *vma; 640 struct task_struct *tsk; 641 struct address_space *mapping = page->mapping; 642 pgoff_t pgoff; 643 644 i_mmap_lock_read(mapping); 645 rcu_read_lock(); 646 pgoff = page_to_pgoff(page); 647 for_each_process(tsk) { 648 struct task_struct *t = task_early_kill(tsk, force_early); 649 650 if (!t) 651 continue; 652 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, 653 pgoff) { 654 /* 655 * Send early kill signal to tasks where a vma covers 656 * the page but the corrupted page is not necessarily 657 * mapped in its pte. 658 * Assume applications who requested early kill want 659 * to be informed of all such data corruptions. 660 */ 661 if (vma->vm_mm == t->mm) 662 add_to_kill_anon_file(t, page, vma, to_kill); 663 } 664 } 665 rcu_read_unlock(); 666 i_mmap_unlock_read(mapping); 667 } 668 669 #ifdef CONFIG_FS_DAX 670 static void add_to_kill_fsdax(struct task_struct *tsk, struct page *p, 671 struct vm_area_struct *vma, 672 struct list_head *to_kill, pgoff_t pgoff) 673 { 674 __add_to_kill(tsk, p, vma, to_kill, 0, pgoff); 675 } 676 677 /* 678 * Collect processes when the error hit a fsdax page. 679 */ 680 static void collect_procs_fsdax(struct page *page, 681 struct address_space *mapping, pgoff_t pgoff, 682 struct list_head *to_kill) 683 { 684 struct vm_area_struct *vma; 685 struct task_struct *tsk; 686 687 i_mmap_lock_read(mapping); 688 rcu_read_lock(); 689 for_each_process(tsk) { 690 struct task_struct *t = task_early_kill(tsk, true); 691 692 if (!t) 693 continue; 694 vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) { 695 if (vma->vm_mm == t->mm) 696 add_to_kill_fsdax(t, page, vma, to_kill, pgoff); 697 } 698 } 699 rcu_read_unlock(); 700 i_mmap_unlock_read(mapping); 701 } 702 #endif /* CONFIG_FS_DAX */ 703 704 /* 705 * Collect the processes who have the corrupted page mapped to kill. 706 */ 707 static void collect_procs(struct page *page, struct list_head *tokill, 708 int force_early) 709 { 710 if (!page->mapping) 711 return; 712 if (unlikely(PageKsm(page))) 713 collect_procs_ksm(page, tokill, force_early); 714 else if (PageAnon(page)) 715 collect_procs_anon(page, tokill, force_early); 716 else 717 collect_procs_file(page, tokill, force_early); 718 } 719 720 struct hwpoison_walk { 721 struct to_kill tk; 722 unsigned long pfn; 723 int flags; 724 }; 725 726 static void set_to_kill(struct to_kill *tk, unsigned long addr, short shift) 727 { 728 tk->addr = addr; 729 tk->size_shift = shift; 730 } 731 732 static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift, 733 unsigned long poisoned_pfn, struct to_kill *tk) 734 { 735 unsigned long pfn = 0; 736 737 if (pte_present(pte)) { 738 pfn = pte_pfn(pte); 739 } else { 740 swp_entry_t swp = pte_to_swp_entry(pte); 741 742 if (is_hwpoison_entry(swp)) 743 pfn = swp_offset_pfn(swp); 744 } 745 746 if (!pfn || pfn != poisoned_pfn) 747 return 0; 748 749 set_to_kill(tk, addr, shift); 750 return 1; 751 } 752 753 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 754 static int check_hwpoisoned_pmd_entry(pmd_t *pmdp, unsigned long addr, 755 struct hwpoison_walk *hwp) 756 { 757 pmd_t pmd = *pmdp; 758 unsigned long pfn; 759 unsigned long hwpoison_vaddr; 760 761 if (!pmd_present(pmd)) 762 return 0; 763 pfn = pmd_pfn(pmd); 764 if (pfn <= hwp->pfn && hwp->pfn < pfn + HPAGE_PMD_NR) { 765 hwpoison_vaddr = addr + ((hwp->pfn - pfn) << PAGE_SHIFT); 766 set_to_kill(&hwp->tk, hwpoison_vaddr, PAGE_SHIFT); 767 return 1; 768 } 769 return 0; 770 } 771 #else 772 static int check_hwpoisoned_pmd_entry(pmd_t *pmdp, unsigned long addr, 773 struct hwpoison_walk *hwp) 774 { 775 return 0; 776 } 777 #endif 778 779 static int hwpoison_pte_range(pmd_t *pmdp, unsigned long addr, 780 unsigned long end, struct mm_walk *walk) 781 { 782 struct hwpoison_walk *hwp = walk->private; 783 int ret = 0; 784 pte_t *ptep, *mapped_pte; 785 spinlock_t *ptl; 786 787 ptl = pmd_trans_huge_lock(pmdp, walk->vma); 788 if (ptl) { 789 ret = check_hwpoisoned_pmd_entry(pmdp, addr, hwp); 790 spin_unlock(ptl); 791 goto out; 792 } 793 794 mapped_pte = ptep = pte_offset_map_lock(walk->vma->vm_mm, pmdp, 795 addr, &ptl); 796 if (!ptep) 797 goto out; 798 799 for (; addr != end; ptep++, addr += PAGE_SIZE) { 800 ret = check_hwpoisoned_entry(ptep_get(ptep), addr, PAGE_SHIFT, 801 hwp->pfn, &hwp->tk); 802 if (ret == 1) 803 break; 804 } 805 pte_unmap_unlock(mapped_pte, ptl); 806 out: 807 cond_resched(); 808 return ret; 809 } 810 811 #ifdef CONFIG_HUGETLB_PAGE 812 static int hwpoison_hugetlb_range(pte_t *ptep, unsigned long hmask, 813 unsigned long addr, unsigned long end, 814 struct mm_walk *walk) 815 { 816 struct hwpoison_walk *hwp = walk->private; 817 pte_t pte = huge_ptep_get(ptep); 818 struct hstate *h = hstate_vma(walk->vma); 819 820 return check_hwpoisoned_entry(pte, addr, huge_page_shift(h), 821 hwp->pfn, &hwp->tk); 822 } 823 #else 824 #define hwpoison_hugetlb_range NULL 825 #endif 826 827 static const struct mm_walk_ops hwpoison_walk_ops = { 828 .pmd_entry = hwpoison_pte_range, 829 .hugetlb_entry = hwpoison_hugetlb_range, 830 .walk_lock = PGWALK_RDLOCK, 831 }; 832 833 /* 834 * Sends SIGBUS to the current process with error info. 835 * 836 * This function is intended to handle "Action Required" MCEs on already 837 * hardware poisoned pages. They could happen, for example, when 838 * memory_failure() failed to unmap the error page at the first call, or 839 * when multiple local machine checks happened on different CPUs. 840 * 841 * MCE handler currently has no easy access to the error virtual address, 842 * so this function walks page table to find it. The returned virtual address 843 * is proper in most cases, but it could be wrong when the application 844 * process has multiple entries mapping the error page. 845 */ 846 static int kill_accessing_process(struct task_struct *p, unsigned long pfn, 847 int flags) 848 { 849 int ret; 850 struct hwpoison_walk priv = { 851 .pfn = pfn, 852 }; 853 priv.tk.tsk = p; 854 855 if (!p->mm) 856 return -EFAULT; 857 858 mmap_read_lock(p->mm); 859 ret = walk_page_range(p->mm, 0, TASK_SIZE, &hwpoison_walk_ops, 860 (void *)&priv); 861 if (ret == 1 && priv.tk.addr) 862 kill_proc(&priv.tk, pfn, flags); 863 else 864 ret = 0; 865 mmap_read_unlock(p->mm); 866 return ret > 0 ? -EHWPOISON : -EFAULT; 867 } 868 869 static const char *action_name[] = { 870 [MF_IGNORED] = "Ignored", 871 [MF_FAILED] = "Failed", 872 [MF_DELAYED] = "Delayed", 873 [MF_RECOVERED] = "Recovered", 874 }; 875 876 static const char * const action_page_types[] = { 877 [MF_MSG_KERNEL] = "reserved kernel page", 878 [MF_MSG_KERNEL_HIGH_ORDER] = "high-order kernel page", 879 [MF_MSG_SLAB] = "kernel slab page", 880 [MF_MSG_DIFFERENT_COMPOUND] = "different compound page after locking", 881 [MF_MSG_HUGE] = "huge page", 882 [MF_MSG_FREE_HUGE] = "free huge page", 883 [MF_MSG_UNMAP_FAILED] = "unmapping failed page", 884 [MF_MSG_DIRTY_SWAPCACHE] = "dirty swapcache page", 885 [MF_MSG_CLEAN_SWAPCACHE] = "clean swapcache page", 886 [MF_MSG_DIRTY_MLOCKED_LRU] = "dirty mlocked LRU page", 887 [MF_MSG_CLEAN_MLOCKED_LRU] = "clean mlocked LRU page", 888 [MF_MSG_DIRTY_UNEVICTABLE_LRU] = "dirty unevictable LRU page", 889 [MF_MSG_CLEAN_UNEVICTABLE_LRU] = "clean unevictable LRU page", 890 [MF_MSG_DIRTY_LRU] = "dirty LRU page", 891 [MF_MSG_CLEAN_LRU] = "clean LRU page", 892 [MF_MSG_TRUNCATED_LRU] = "already truncated LRU page", 893 [MF_MSG_BUDDY] = "free buddy page", 894 [MF_MSG_DAX] = "dax page", 895 [MF_MSG_UNSPLIT_THP] = "unsplit thp", 896 [MF_MSG_UNKNOWN] = "unknown page", 897 }; 898 899 /* 900 * XXX: It is possible that a page is isolated from LRU cache, 901 * and then kept in swap cache or failed to remove from page cache. 902 * The page count will stop it from being freed by unpoison. 903 * Stress tests should be aware of this memory leak problem. 904 */ 905 static int delete_from_lru_cache(struct page *p) 906 { 907 if (isolate_lru_page(p)) { 908 /* 909 * Clear sensible page flags, so that the buddy system won't 910 * complain when the page is unpoison-and-freed. 911 */ 912 ClearPageActive(p); 913 ClearPageUnevictable(p); 914 915 /* 916 * Poisoned page might never drop its ref count to 0 so we have 917 * to uncharge it manually from its memcg. 918 */ 919 mem_cgroup_uncharge(page_folio(p)); 920 921 /* 922 * drop the page count elevated by isolate_lru_page() 923 */ 924 put_page(p); 925 return 0; 926 } 927 return -EIO; 928 } 929 930 static int truncate_error_page(struct page *p, unsigned long pfn, 931 struct address_space *mapping) 932 { 933 int ret = MF_FAILED; 934 935 if (mapping->a_ops->error_remove_page) { 936 struct folio *folio = page_folio(p); 937 int err = mapping->a_ops->error_remove_page(mapping, p); 938 939 if (err != 0) 940 pr_info("%#lx: Failed to punch page: %d\n", pfn, err); 941 else if (!filemap_release_folio(folio, GFP_NOIO)) 942 pr_info("%#lx: failed to release buffers\n", pfn); 943 else 944 ret = MF_RECOVERED; 945 } else { 946 /* 947 * If the file system doesn't support it just invalidate 948 * This fails on dirty or anything with private pages 949 */ 950 if (invalidate_inode_page(p)) 951 ret = MF_RECOVERED; 952 else 953 pr_info("%#lx: Failed to invalidate\n", pfn); 954 } 955 956 return ret; 957 } 958 959 struct page_state { 960 unsigned long mask; 961 unsigned long res; 962 enum mf_action_page_type type; 963 964 /* Callback ->action() has to unlock the relevant page inside it. */ 965 int (*action)(struct page_state *ps, struct page *p); 966 }; 967 968 /* 969 * Return true if page is still referenced by others, otherwise return 970 * false. 971 * 972 * The extra_pins is true when one extra refcount is expected. 973 */ 974 static bool has_extra_refcount(struct page_state *ps, struct page *p, 975 bool extra_pins) 976 { 977 int count = page_count(p) - 1; 978 979 if (extra_pins) 980 count -= 1; 981 982 if (count > 0) { 983 pr_err("%#lx: %s still referenced by %d users\n", 984 page_to_pfn(p), action_page_types[ps->type], count); 985 return true; 986 } 987 988 return false; 989 } 990 991 /* 992 * Error hit kernel page. 993 * Do nothing, try to be lucky and not touch this instead. For a few cases we 994 * could be more sophisticated. 995 */ 996 static int me_kernel(struct page_state *ps, struct page *p) 997 { 998 unlock_page(p); 999 return MF_IGNORED; 1000 } 1001 1002 /* 1003 * Page in unknown state. Do nothing. 1004 */ 1005 static int me_unknown(struct page_state *ps, struct page *p) 1006 { 1007 pr_err("%#lx: Unknown page state\n", page_to_pfn(p)); 1008 unlock_page(p); 1009 return MF_FAILED; 1010 } 1011 1012 /* 1013 * Clean (or cleaned) page cache page. 1014 */ 1015 static int me_pagecache_clean(struct page_state *ps, struct page *p) 1016 { 1017 int ret; 1018 struct address_space *mapping; 1019 bool extra_pins; 1020 1021 delete_from_lru_cache(p); 1022 1023 /* 1024 * For anonymous pages we're done the only reference left 1025 * should be the one m_f() holds. 1026 */ 1027 if (PageAnon(p)) { 1028 ret = MF_RECOVERED; 1029 goto out; 1030 } 1031 1032 /* 1033 * Now truncate the page in the page cache. This is really 1034 * more like a "temporary hole punch" 1035 * Don't do this for block devices when someone else 1036 * has a reference, because it could be file system metadata 1037 * and that's not safe to truncate. 1038 */ 1039 mapping = page_mapping(p); 1040 if (!mapping) { 1041 /* 1042 * Page has been teared down in the meanwhile 1043 */ 1044 ret = MF_FAILED; 1045 goto out; 1046 } 1047 1048 /* 1049 * The shmem page is kept in page cache instead of truncating 1050 * so is expected to have an extra refcount after error-handling. 1051 */ 1052 extra_pins = shmem_mapping(mapping); 1053 1054 /* 1055 * Truncation is a bit tricky. Enable it per file system for now. 1056 * 1057 * Open: to take i_rwsem or not for this? Right now we don't. 1058 */ 1059 ret = truncate_error_page(p, page_to_pfn(p), mapping); 1060 if (has_extra_refcount(ps, p, extra_pins)) 1061 ret = MF_FAILED; 1062 1063 out: 1064 unlock_page(p); 1065 1066 return ret; 1067 } 1068 1069 /* 1070 * Dirty pagecache page 1071 * Issues: when the error hit a hole page the error is not properly 1072 * propagated. 1073 */ 1074 static int me_pagecache_dirty(struct page_state *ps, struct page *p) 1075 { 1076 struct address_space *mapping = page_mapping(p); 1077 1078 SetPageError(p); 1079 /* TBD: print more information about the file. */ 1080 if (mapping) { 1081 /* 1082 * IO error will be reported by write(), fsync(), etc. 1083 * who check the mapping. 1084 * This way the application knows that something went 1085 * wrong with its dirty file data. 1086 * 1087 * There's one open issue: 1088 * 1089 * The EIO will be only reported on the next IO 1090 * operation and then cleared through the IO map. 1091 * Normally Linux has two mechanisms to pass IO error 1092 * first through the AS_EIO flag in the address space 1093 * and then through the PageError flag in the page. 1094 * Since we drop pages on memory failure handling the 1095 * only mechanism open to use is through AS_AIO. 1096 * 1097 * This has the disadvantage that it gets cleared on 1098 * the first operation that returns an error, while 1099 * the PageError bit is more sticky and only cleared 1100 * when the page is reread or dropped. If an 1101 * application assumes it will always get error on 1102 * fsync, but does other operations on the fd before 1103 * and the page is dropped between then the error 1104 * will not be properly reported. 1105 * 1106 * This can already happen even without hwpoisoned 1107 * pages: first on metadata IO errors (which only 1108 * report through AS_EIO) or when the page is dropped 1109 * at the wrong time. 1110 * 1111 * So right now we assume that the application DTRT on 1112 * the first EIO, but we're not worse than other parts 1113 * of the kernel. 1114 */ 1115 mapping_set_error(mapping, -EIO); 1116 } 1117 1118 return me_pagecache_clean(ps, p); 1119 } 1120 1121 /* 1122 * Clean and dirty swap cache. 1123 * 1124 * Dirty swap cache page is tricky to handle. The page could live both in page 1125 * cache and swap cache(ie. page is freshly swapped in). So it could be 1126 * referenced concurrently by 2 types of PTEs: 1127 * normal PTEs and swap PTEs. We try to handle them consistently by calling 1128 * try_to_unmap(!TTU_HWPOISON) to convert the normal PTEs to swap PTEs, 1129 * and then 1130 * - clear dirty bit to prevent IO 1131 * - remove from LRU 1132 * - but keep in the swap cache, so that when we return to it on 1133 * a later page fault, we know the application is accessing 1134 * corrupted data and shall be killed (we installed simple 1135 * interception code in do_swap_page to catch it). 1136 * 1137 * Clean swap cache pages can be directly isolated. A later page fault will 1138 * bring in the known good data from disk. 1139 */ 1140 static int me_swapcache_dirty(struct page_state *ps, struct page *p) 1141 { 1142 int ret; 1143 bool extra_pins = false; 1144 1145 ClearPageDirty(p); 1146 /* Trigger EIO in shmem: */ 1147 ClearPageUptodate(p); 1148 1149 ret = delete_from_lru_cache(p) ? MF_FAILED : MF_DELAYED; 1150 unlock_page(p); 1151 1152 if (ret == MF_DELAYED) 1153 extra_pins = true; 1154 1155 if (has_extra_refcount(ps, p, extra_pins)) 1156 ret = MF_FAILED; 1157 1158 return ret; 1159 } 1160 1161 static int me_swapcache_clean(struct page_state *ps, struct page *p) 1162 { 1163 struct folio *folio = page_folio(p); 1164 int ret; 1165 1166 delete_from_swap_cache(folio); 1167 1168 ret = delete_from_lru_cache(p) ? MF_FAILED : MF_RECOVERED; 1169 folio_unlock(folio); 1170 1171 if (has_extra_refcount(ps, p, false)) 1172 ret = MF_FAILED; 1173 1174 return ret; 1175 } 1176 1177 /* 1178 * Huge pages. Needs work. 1179 * Issues: 1180 * - Error on hugepage is contained in hugepage unit (not in raw page unit.) 1181 * To narrow down kill region to one page, we need to break up pmd. 1182 */ 1183 static int me_huge_page(struct page_state *ps, struct page *p) 1184 { 1185 int res; 1186 struct page *hpage = compound_head(p); 1187 struct address_space *mapping; 1188 bool extra_pins = false; 1189 1190 mapping = page_mapping(hpage); 1191 if (mapping) { 1192 res = truncate_error_page(hpage, page_to_pfn(p), mapping); 1193 /* The page is kept in page cache. */ 1194 extra_pins = true; 1195 unlock_page(hpage); 1196 } else { 1197 unlock_page(hpage); 1198 /* 1199 * migration entry prevents later access on error hugepage, 1200 * so we can free and dissolve it into buddy to save healthy 1201 * subpages. 1202 */ 1203 put_page(hpage); 1204 if (__page_handle_poison(p) >= 0) { 1205 page_ref_inc(p); 1206 res = MF_RECOVERED; 1207 } else { 1208 res = MF_FAILED; 1209 } 1210 } 1211 1212 if (has_extra_refcount(ps, p, extra_pins)) 1213 res = MF_FAILED; 1214 1215 return res; 1216 } 1217 1218 /* 1219 * Various page states we can handle. 1220 * 1221 * A page state is defined by its current page->flags bits. 1222 * The table matches them in order and calls the right handler. 1223 * 1224 * This is quite tricky because we can access page at any time 1225 * in its live cycle, so all accesses have to be extremely careful. 1226 * 1227 * This is not complete. More states could be added. 1228 * For any missing state don't attempt recovery. 1229 */ 1230 1231 #define dirty (1UL << PG_dirty) 1232 #define sc ((1UL << PG_swapcache) | (1UL << PG_swapbacked)) 1233 #define unevict (1UL << PG_unevictable) 1234 #define mlock (1UL << PG_mlocked) 1235 #define lru (1UL << PG_lru) 1236 #define head (1UL << PG_head) 1237 #define slab (1UL << PG_slab) 1238 #define reserved (1UL << PG_reserved) 1239 1240 static struct page_state error_states[] = { 1241 { reserved, reserved, MF_MSG_KERNEL, me_kernel }, 1242 /* 1243 * free pages are specially detected outside this table: 1244 * PG_buddy pages only make a small fraction of all free pages. 1245 */ 1246 1247 /* 1248 * Could in theory check if slab page is free or if we can drop 1249 * currently unused objects without touching them. But just 1250 * treat it as standard kernel for now. 1251 */ 1252 { slab, slab, MF_MSG_SLAB, me_kernel }, 1253 1254 { head, head, MF_MSG_HUGE, me_huge_page }, 1255 1256 { sc|dirty, sc|dirty, MF_MSG_DIRTY_SWAPCACHE, me_swapcache_dirty }, 1257 { sc|dirty, sc, MF_MSG_CLEAN_SWAPCACHE, me_swapcache_clean }, 1258 1259 { mlock|dirty, mlock|dirty, MF_MSG_DIRTY_MLOCKED_LRU, me_pagecache_dirty }, 1260 { mlock|dirty, mlock, MF_MSG_CLEAN_MLOCKED_LRU, me_pagecache_clean }, 1261 1262 { unevict|dirty, unevict|dirty, MF_MSG_DIRTY_UNEVICTABLE_LRU, me_pagecache_dirty }, 1263 { unevict|dirty, unevict, MF_MSG_CLEAN_UNEVICTABLE_LRU, me_pagecache_clean }, 1264 1265 { lru|dirty, lru|dirty, MF_MSG_DIRTY_LRU, me_pagecache_dirty }, 1266 { lru|dirty, lru, MF_MSG_CLEAN_LRU, me_pagecache_clean }, 1267 1268 /* 1269 * Catchall entry: must be at end. 1270 */ 1271 { 0, 0, MF_MSG_UNKNOWN, me_unknown }, 1272 }; 1273 1274 #undef dirty 1275 #undef sc 1276 #undef unevict 1277 #undef mlock 1278 #undef lru 1279 #undef head 1280 #undef slab 1281 #undef reserved 1282 1283 static void update_per_node_mf_stats(unsigned long pfn, 1284 enum mf_result result) 1285 { 1286 int nid = MAX_NUMNODES; 1287 struct memory_failure_stats *mf_stats = NULL; 1288 1289 nid = pfn_to_nid(pfn); 1290 if (unlikely(nid < 0 || nid >= MAX_NUMNODES)) { 1291 WARN_ONCE(1, "Memory failure: pfn=%#lx, invalid nid=%d", pfn, nid); 1292 return; 1293 } 1294 1295 mf_stats = &NODE_DATA(nid)->mf_stats; 1296 switch (result) { 1297 case MF_IGNORED: 1298 ++mf_stats->ignored; 1299 break; 1300 case MF_FAILED: 1301 ++mf_stats->failed; 1302 break; 1303 case MF_DELAYED: 1304 ++mf_stats->delayed; 1305 break; 1306 case MF_RECOVERED: 1307 ++mf_stats->recovered; 1308 break; 1309 default: 1310 WARN_ONCE(1, "Memory failure: mf_result=%d is not properly handled", result); 1311 break; 1312 } 1313 ++mf_stats->total; 1314 } 1315 1316 /* 1317 * "Dirty/Clean" indication is not 100% accurate due to the possibility of 1318 * setting PG_dirty outside page lock. See also comment above set_page_dirty(). 1319 */ 1320 static int action_result(unsigned long pfn, enum mf_action_page_type type, 1321 enum mf_result result) 1322 { 1323 trace_memory_failure_event(pfn, type, result); 1324 1325 num_poisoned_pages_inc(pfn); 1326 1327 update_per_node_mf_stats(pfn, result); 1328 1329 pr_err("%#lx: recovery action for %s: %s\n", 1330 pfn, action_page_types[type], action_name[result]); 1331 1332 return (result == MF_RECOVERED || result == MF_DELAYED) ? 0 : -EBUSY; 1333 } 1334 1335 static int page_action(struct page_state *ps, struct page *p, 1336 unsigned long pfn) 1337 { 1338 int result; 1339 1340 /* page p should be unlocked after returning from ps->action(). */ 1341 result = ps->action(ps, p); 1342 1343 /* Could do more checks here if page looks ok */ 1344 /* 1345 * Could adjust zone counters here to correct for the missing page. 1346 */ 1347 1348 return action_result(pfn, ps->type, result); 1349 } 1350 1351 static inline bool PageHWPoisonTakenOff(struct page *page) 1352 { 1353 return PageHWPoison(page) && page_private(page) == MAGIC_HWPOISON; 1354 } 1355 1356 void SetPageHWPoisonTakenOff(struct page *page) 1357 { 1358 set_page_private(page, MAGIC_HWPOISON); 1359 } 1360 1361 void ClearPageHWPoisonTakenOff(struct page *page) 1362 { 1363 if (PageHWPoison(page)) 1364 set_page_private(page, 0); 1365 } 1366 1367 /* 1368 * Return true if a page type of a given page is supported by hwpoison 1369 * mechanism (while handling could fail), otherwise false. This function 1370 * does not return true for hugetlb or device memory pages, so it's assumed 1371 * to be called only in the context where we never have such pages. 1372 */ 1373 static inline bool HWPoisonHandlable(struct page *page, unsigned long flags) 1374 { 1375 /* Soft offline could migrate non-LRU movable pages */ 1376 if ((flags & MF_SOFT_OFFLINE) && __PageMovable(page)) 1377 return true; 1378 1379 return PageLRU(page) || is_free_buddy_page(page); 1380 } 1381 1382 static int __get_hwpoison_page(struct page *page, unsigned long flags) 1383 { 1384 struct folio *folio = page_folio(page); 1385 int ret = 0; 1386 bool hugetlb = false; 1387 1388 ret = get_hwpoison_hugetlb_folio(folio, &hugetlb, false); 1389 if (hugetlb) { 1390 /* Make sure hugetlb demotion did not happen from under us. */ 1391 if (folio == page_folio(page)) 1392 return ret; 1393 if (ret > 0) { 1394 folio_put(folio); 1395 folio = page_folio(page); 1396 } 1397 } 1398 1399 /* 1400 * This check prevents from calling folio_try_get() for any 1401 * unsupported type of folio in order to reduce the risk of unexpected 1402 * races caused by taking a folio refcount. 1403 */ 1404 if (!HWPoisonHandlable(&folio->page, flags)) 1405 return -EBUSY; 1406 1407 if (folio_try_get(folio)) { 1408 if (folio == page_folio(page)) 1409 return 1; 1410 1411 pr_info("%#lx cannot catch tail\n", page_to_pfn(page)); 1412 folio_put(folio); 1413 } 1414 1415 return 0; 1416 } 1417 1418 static int get_any_page(struct page *p, unsigned long flags) 1419 { 1420 int ret = 0, pass = 0; 1421 bool count_increased = false; 1422 1423 if (flags & MF_COUNT_INCREASED) 1424 count_increased = true; 1425 1426 try_again: 1427 if (!count_increased) { 1428 ret = __get_hwpoison_page(p, flags); 1429 if (!ret) { 1430 if (page_count(p)) { 1431 /* We raced with an allocation, retry. */ 1432 if (pass++ < 3) 1433 goto try_again; 1434 ret = -EBUSY; 1435 } else if (!PageHuge(p) && !is_free_buddy_page(p)) { 1436 /* We raced with put_page, retry. */ 1437 if (pass++ < 3) 1438 goto try_again; 1439 ret = -EIO; 1440 } 1441 goto out; 1442 } else if (ret == -EBUSY) { 1443 /* 1444 * We raced with (possibly temporary) unhandlable 1445 * page, retry. 1446 */ 1447 if (pass++ < 3) { 1448 shake_page(p); 1449 goto try_again; 1450 } 1451 ret = -EIO; 1452 goto out; 1453 } 1454 } 1455 1456 if (PageHuge(p) || HWPoisonHandlable(p, flags)) { 1457 ret = 1; 1458 } else { 1459 /* 1460 * A page we cannot handle. Check whether we can turn 1461 * it into something we can handle. 1462 */ 1463 if (pass++ < 3) { 1464 put_page(p); 1465 shake_page(p); 1466 count_increased = false; 1467 goto try_again; 1468 } 1469 put_page(p); 1470 ret = -EIO; 1471 } 1472 out: 1473 if (ret == -EIO) 1474 pr_err("%#lx: unhandlable page.\n", page_to_pfn(p)); 1475 1476 return ret; 1477 } 1478 1479 static int __get_unpoison_page(struct page *page) 1480 { 1481 struct folio *folio = page_folio(page); 1482 int ret = 0; 1483 bool hugetlb = false; 1484 1485 ret = get_hwpoison_hugetlb_folio(folio, &hugetlb, true); 1486 if (hugetlb) { 1487 /* Make sure hugetlb demotion did not happen from under us. */ 1488 if (folio == page_folio(page)) 1489 return ret; 1490 if (ret > 0) 1491 folio_put(folio); 1492 } 1493 1494 /* 1495 * PageHWPoisonTakenOff pages are not only marked as PG_hwpoison, 1496 * but also isolated from buddy freelist, so need to identify the 1497 * state and have to cancel both operations to unpoison. 1498 */ 1499 if (PageHWPoisonTakenOff(page)) 1500 return -EHWPOISON; 1501 1502 return get_page_unless_zero(page) ? 1 : 0; 1503 } 1504 1505 /** 1506 * get_hwpoison_page() - Get refcount for memory error handling 1507 * @p: Raw error page (hit by memory error) 1508 * @flags: Flags controlling behavior of error handling 1509 * 1510 * get_hwpoison_page() takes a page refcount of an error page to handle memory 1511 * error on it, after checking that the error page is in a well-defined state 1512 * (defined as a page-type we can successfully handle the memory error on it, 1513 * such as LRU page and hugetlb page). 1514 * 1515 * Memory error handling could be triggered at any time on any type of page, 1516 * so it's prone to race with typical memory management lifecycle (like 1517 * allocation and free). So to avoid such races, get_hwpoison_page() takes 1518 * extra care for the error page's state (as done in __get_hwpoison_page()), 1519 * and has some retry logic in get_any_page(). 1520 * 1521 * When called from unpoison_memory(), the caller should already ensure that 1522 * the given page has PG_hwpoison. So it's never reused for other page 1523 * allocations, and __get_unpoison_page() never races with them. 1524 * 1525 * Return: 0 on failure, 1526 * 1 on success for in-use pages in a well-defined state, 1527 * -EIO for pages on which we can not handle memory errors, 1528 * -EBUSY when get_hwpoison_page() has raced with page lifecycle 1529 * operations like allocation and free, 1530 * -EHWPOISON when the page is hwpoisoned and taken off from buddy. 1531 */ 1532 static int get_hwpoison_page(struct page *p, unsigned long flags) 1533 { 1534 int ret; 1535 1536 zone_pcp_disable(page_zone(p)); 1537 if (flags & MF_UNPOISON) 1538 ret = __get_unpoison_page(p); 1539 else 1540 ret = get_any_page(p, flags); 1541 zone_pcp_enable(page_zone(p)); 1542 1543 return ret; 1544 } 1545 1546 /* 1547 * Do all that is necessary to remove user space mappings. Unmap 1548 * the pages and send SIGBUS to the processes if the data was dirty. 1549 */ 1550 static bool hwpoison_user_mappings(struct page *p, unsigned long pfn, 1551 int flags, struct page *hpage) 1552 { 1553 struct folio *folio = page_folio(hpage); 1554 enum ttu_flags ttu = TTU_IGNORE_MLOCK | TTU_SYNC | TTU_HWPOISON; 1555 struct address_space *mapping; 1556 LIST_HEAD(tokill); 1557 bool unmap_success; 1558 int forcekill; 1559 bool mlocked = PageMlocked(hpage); 1560 1561 /* 1562 * Here we are interested only in user-mapped pages, so skip any 1563 * other types of pages. 1564 */ 1565 if (PageReserved(p) || PageSlab(p) || PageTable(p) || PageOffline(p)) 1566 return true; 1567 if (!(PageLRU(hpage) || PageHuge(p))) 1568 return true; 1569 1570 /* 1571 * This check implies we don't kill processes if their pages 1572 * are in the swap cache early. Those are always late kills. 1573 */ 1574 if (!page_mapped(hpage)) 1575 return true; 1576 1577 if (PageSwapCache(p)) { 1578 pr_err("%#lx: keeping poisoned page in swap cache\n", pfn); 1579 ttu &= ~TTU_HWPOISON; 1580 } 1581 1582 /* 1583 * Propagate the dirty bit from PTEs to struct page first, because we 1584 * need this to decide if we should kill or just drop the page. 1585 * XXX: the dirty test could be racy: set_page_dirty() may not always 1586 * be called inside page lock (it's recommended but not enforced). 1587 */ 1588 mapping = page_mapping(hpage); 1589 if (!(flags & MF_MUST_KILL) && !PageDirty(hpage) && mapping && 1590 mapping_can_writeback(mapping)) { 1591 if (page_mkclean(hpage)) { 1592 SetPageDirty(hpage); 1593 } else { 1594 ttu &= ~TTU_HWPOISON; 1595 pr_info("%#lx: corrupted page was clean: dropped without side effects\n", 1596 pfn); 1597 } 1598 } 1599 1600 /* 1601 * First collect all the processes that have the page 1602 * mapped in dirty form. This has to be done before try_to_unmap, 1603 * because ttu takes the rmap data structures down. 1604 */ 1605 collect_procs(hpage, &tokill, flags & MF_ACTION_REQUIRED); 1606 1607 if (PageHuge(hpage) && !PageAnon(hpage)) { 1608 /* 1609 * For hugetlb pages in shared mappings, try_to_unmap 1610 * could potentially call huge_pmd_unshare. Because of 1611 * this, take semaphore in write mode here and set 1612 * TTU_RMAP_LOCKED to indicate we have taken the lock 1613 * at this higher level. 1614 */ 1615 mapping = hugetlb_page_mapping_lock_write(hpage); 1616 if (mapping) { 1617 try_to_unmap(folio, ttu|TTU_RMAP_LOCKED); 1618 i_mmap_unlock_write(mapping); 1619 } else 1620 pr_info("%#lx: could not lock mapping for mapped huge page\n", pfn); 1621 } else { 1622 try_to_unmap(folio, ttu); 1623 } 1624 1625 unmap_success = !page_mapped(hpage); 1626 if (!unmap_success) 1627 pr_err("%#lx: failed to unmap page (mapcount=%d)\n", 1628 pfn, page_mapcount(hpage)); 1629 1630 /* 1631 * try_to_unmap() might put mlocked page in lru cache, so call 1632 * shake_page() again to ensure that it's flushed. 1633 */ 1634 if (mlocked) 1635 shake_page(hpage); 1636 1637 /* 1638 * Now that the dirty bit has been propagated to the 1639 * struct page and all unmaps done we can decide if 1640 * killing is needed or not. Only kill when the page 1641 * was dirty or the process is not restartable, 1642 * otherwise the tokill list is merely 1643 * freed. When there was a problem unmapping earlier 1644 * use a more force-full uncatchable kill to prevent 1645 * any accesses to the poisoned memory. 1646 */ 1647 forcekill = PageDirty(hpage) || (flags & MF_MUST_KILL) || 1648 !unmap_success; 1649 kill_procs(&tokill, forcekill, !unmap_success, pfn, flags); 1650 1651 return unmap_success; 1652 } 1653 1654 static int identify_page_state(unsigned long pfn, struct page *p, 1655 unsigned long page_flags) 1656 { 1657 struct page_state *ps; 1658 1659 /* 1660 * The first check uses the current page flags which may not have any 1661 * relevant information. The second check with the saved page flags is 1662 * carried out only if the first check can't determine the page status. 1663 */ 1664 for (ps = error_states;; ps++) 1665 if ((p->flags & ps->mask) == ps->res) 1666 break; 1667 1668 page_flags |= (p->flags & (1UL << PG_dirty)); 1669 1670 if (!ps->mask) 1671 for (ps = error_states;; ps++) 1672 if ((page_flags & ps->mask) == ps->res) 1673 break; 1674 return page_action(ps, p, pfn); 1675 } 1676 1677 static int try_to_split_thp_page(struct page *page) 1678 { 1679 int ret; 1680 1681 lock_page(page); 1682 ret = split_huge_page(page); 1683 unlock_page(page); 1684 1685 if (unlikely(ret)) 1686 put_page(page); 1687 1688 return ret; 1689 } 1690 1691 static void unmap_and_kill(struct list_head *to_kill, unsigned long pfn, 1692 struct address_space *mapping, pgoff_t index, int flags) 1693 { 1694 struct to_kill *tk; 1695 unsigned long size = 0; 1696 1697 list_for_each_entry(tk, to_kill, nd) 1698 if (tk->size_shift) 1699 size = max(size, 1UL << tk->size_shift); 1700 1701 if (size) { 1702 /* 1703 * Unmap the largest mapping to avoid breaking up device-dax 1704 * mappings which are constant size. The actual size of the 1705 * mapping being torn down is communicated in siginfo, see 1706 * kill_proc() 1707 */ 1708 loff_t start = (index << PAGE_SHIFT) & ~(size - 1); 1709 1710 unmap_mapping_range(mapping, start, size, 0); 1711 } 1712 1713 kill_procs(to_kill, flags & MF_MUST_KILL, false, pfn, flags); 1714 } 1715 1716 /* 1717 * Only dev_pagemap pages get here, such as fsdax when the filesystem 1718 * either do not claim or fails to claim a hwpoison event, or devdax. 1719 * The fsdax pages are initialized per base page, and the devdax pages 1720 * could be initialized either as base pages, or as compound pages with 1721 * vmemmap optimization enabled. Devdax is simplistic in its dealing with 1722 * hwpoison, such that, if a subpage of a compound page is poisoned, 1723 * simply mark the compound head page is by far sufficient. 1724 */ 1725 static int mf_generic_kill_procs(unsigned long long pfn, int flags, 1726 struct dev_pagemap *pgmap) 1727 { 1728 struct folio *folio = pfn_folio(pfn); 1729 LIST_HEAD(to_kill); 1730 dax_entry_t cookie; 1731 int rc = 0; 1732 1733 /* 1734 * Prevent the inode from being freed while we are interrogating 1735 * the address_space, typically this would be handled by 1736 * lock_page(), but dax pages do not use the page lock. This 1737 * also prevents changes to the mapping of this pfn until 1738 * poison signaling is complete. 1739 */ 1740 cookie = dax_lock_folio(folio); 1741 if (!cookie) 1742 return -EBUSY; 1743 1744 if (hwpoison_filter(&folio->page)) { 1745 rc = -EOPNOTSUPP; 1746 goto unlock; 1747 } 1748 1749 switch (pgmap->type) { 1750 case MEMORY_DEVICE_PRIVATE: 1751 case MEMORY_DEVICE_COHERENT: 1752 /* 1753 * TODO: Handle device pages which may need coordination 1754 * with device-side memory. 1755 */ 1756 rc = -ENXIO; 1757 goto unlock; 1758 default: 1759 break; 1760 } 1761 1762 /* 1763 * Use this flag as an indication that the dax page has been 1764 * remapped UC to prevent speculative consumption of poison. 1765 */ 1766 SetPageHWPoison(&folio->page); 1767 1768 /* 1769 * Unlike System-RAM there is no possibility to swap in a 1770 * different physical page at a given virtual address, so all 1771 * userspace consumption of ZONE_DEVICE memory necessitates 1772 * SIGBUS (i.e. MF_MUST_KILL) 1773 */ 1774 flags |= MF_ACTION_REQUIRED | MF_MUST_KILL; 1775 collect_procs(&folio->page, &to_kill, true); 1776 1777 unmap_and_kill(&to_kill, pfn, folio->mapping, folio->index, flags); 1778 unlock: 1779 dax_unlock_folio(folio, cookie); 1780 return rc; 1781 } 1782 1783 #ifdef CONFIG_FS_DAX 1784 /** 1785 * mf_dax_kill_procs - Collect and kill processes who are using this file range 1786 * @mapping: address_space of the file in use 1787 * @index: start pgoff of the range within the file 1788 * @count: length of the range, in unit of PAGE_SIZE 1789 * @mf_flags: memory failure flags 1790 */ 1791 int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index, 1792 unsigned long count, int mf_flags) 1793 { 1794 LIST_HEAD(to_kill); 1795 dax_entry_t cookie; 1796 struct page *page; 1797 size_t end = index + count; 1798 1799 mf_flags |= MF_ACTION_REQUIRED | MF_MUST_KILL; 1800 1801 for (; index < end; index++) { 1802 page = NULL; 1803 cookie = dax_lock_mapping_entry(mapping, index, &page); 1804 if (!cookie) 1805 return -EBUSY; 1806 if (!page) 1807 goto unlock; 1808 1809 SetPageHWPoison(page); 1810 1811 collect_procs_fsdax(page, mapping, index, &to_kill); 1812 unmap_and_kill(&to_kill, page_to_pfn(page), mapping, 1813 index, mf_flags); 1814 unlock: 1815 dax_unlock_mapping_entry(mapping, index, cookie); 1816 } 1817 return 0; 1818 } 1819 EXPORT_SYMBOL_GPL(mf_dax_kill_procs); 1820 #endif /* CONFIG_FS_DAX */ 1821 1822 #ifdef CONFIG_HUGETLB_PAGE 1823 1824 /* 1825 * Struct raw_hwp_page represents information about "raw error page", 1826 * constructing singly linked list from ->_hugetlb_hwpoison field of folio. 1827 */ 1828 struct raw_hwp_page { 1829 struct llist_node node; 1830 struct page *page; 1831 }; 1832 1833 static inline struct llist_head *raw_hwp_list_head(struct folio *folio) 1834 { 1835 return (struct llist_head *)&folio->_hugetlb_hwpoison; 1836 } 1837 1838 bool is_raw_hwpoison_page_in_hugepage(struct page *page) 1839 { 1840 struct llist_head *raw_hwp_head; 1841 struct raw_hwp_page *p; 1842 struct folio *folio = page_folio(page); 1843 bool ret = false; 1844 1845 if (!folio_test_hwpoison(folio)) 1846 return false; 1847 1848 if (!folio_test_hugetlb(folio)) 1849 return PageHWPoison(page); 1850 1851 /* 1852 * When RawHwpUnreliable is set, kernel lost track of which subpages 1853 * are HWPOISON. So return as if ALL subpages are HWPOISONed. 1854 */ 1855 if (folio_test_hugetlb_raw_hwp_unreliable(folio)) 1856 return true; 1857 1858 mutex_lock(&mf_mutex); 1859 1860 raw_hwp_head = raw_hwp_list_head(folio); 1861 llist_for_each_entry(p, raw_hwp_head->first, node) { 1862 if (page == p->page) { 1863 ret = true; 1864 break; 1865 } 1866 } 1867 1868 mutex_unlock(&mf_mutex); 1869 1870 return ret; 1871 } 1872 1873 static unsigned long __folio_free_raw_hwp(struct folio *folio, bool move_flag) 1874 { 1875 struct llist_node *head; 1876 struct raw_hwp_page *p, *next; 1877 unsigned long count = 0; 1878 1879 head = llist_del_all(raw_hwp_list_head(folio)); 1880 llist_for_each_entry_safe(p, next, head, node) { 1881 if (move_flag) 1882 SetPageHWPoison(p->page); 1883 else 1884 num_poisoned_pages_sub(page_to_pfn(p->page), 1); 1885 kfree(p); 1886 count++; 1887 } 1888 return count; 1889 } 1890 1891 static int folio_set_hugetlb_hwpoison(struct folio *folio, struct page *page) 1892 { 1893 struct llist_head *head; 1894 struct raw_hwp_page *raw_hwp; 1895 struct raw_hwp_page *p, *next; 1896 int ret = folio_test_set_hwpoison(folio) ? -EHWPOISON : 0; 1897 1898 /* 1899 * Once the hwpoison hugepage has lost reliable raw error info, 1900 * there is little meaning to keep additional error info precisely, 1901 * so skip to add additional raw error info. 1902 */ 1903 if (folio_test_hugetlb_raw_hwp_unreliable(folio)) 1904 return -EHWPOISON; 1905 head = raw_hwp_list_head(folio); 1906 llist_for_each_entry_safe(p, next, head->first, node) { 1907 if (p->page == page) 1908 return -EHWPOISON; 1909 } 1910 1911 raw_hwp = kmalloc(sizeof(struct raw_hwp_page), GFP_ATOMIC); 1912 if (raw_hwp) { 1913 raw_hwp->page = page; 1914 llist_add(&raw_hwp->node, head); 1915 /* the first error event will be counted in action_result(). */ 1916 if (ret) 1917 num_poisoned_pages_inc(page_to_pfn(page)); 1918 } else { 1919 /* 1920 * Failed to save raw error info. We no longer trace all 1921 * hwpoisoned subpages, and we need refuse to free/dissolve 1922 * this hwpoisoned hugepage. 1923 */ 1924 folio_set_hugetlb_raw_hwp_unreliable(folio); 1925 /* 1926 * Once hugetlb_raw_hwp_unreliable is set, raw_hwp_page is not 1927 * used any more, so free it. 1928 */ 1929 __folio_free_raw_hwp(folio, false); 1930 } 1931 return ret; 1932 } 1933 1934 static unsigned long folio_free_raw_hwp(struct folio *folio, bool move_flag) 1935 { 1936 /* 1937 * hugetlb_vmemmap_optimized hugepages can't be freed because struct 1938 * pages for tail pages are required but they don't exist. 1939 */ 1940 if (move_flag && folio_test_hugetlb_vmemmap_optimized(folio)) 1941 return 0; 1942 1943 /* 1944 * hugetlb_raw_hwp_unreliable hugepages shouldn't be unpoisoned by 1945 * definition. 1946 */ 1947 if (folio_test_hugetlb_raw_hwp_unreliable(folio)) 1948 return 0; 1949 1950 return __folio_free_raw_hwp(folio, move_flag); 1951 } 1952 1953 void folio_clear_hugetlb_hwpoison(struct folio *folio) 1954 { 1955 if (folio_test_hugetlb_raw_hwp_unreliable(folio)) 1956 return; 1957 if (folio_test_hugetlb_vmemmap_optimized(folio)) 1958 return; 1959 folio_clear_hwpoison(folio); 1960 folio_free_raw_hwp(folio, true); 1961 } 1962 1963 /* 1964 * Called from hugetlb code with hugetlb_lock held. 1965 * 1966 * Return values: 1967 * 0 - free hugepage 1968 * 1 - in-use hugepage 1969 * 2 - not a hugepage 1970 * -EBUSY - the hugepage is busy (try to retry) 1971 * -EHWPOISON - the hugepage is already hwpoisoned 1972 */ 1973 int __get_huge_page_for_hwpoison(unsigned long pfn, int flags, 1974 bool *migratable_cleared) 1975 { 1976 struct page *page = pfn_to_page(pfn); 1977 struct folio *folio = page_folio(page); 1978 int ret = 2; /* fallback to normal page handling */ 1979 bool count_increased = false; 1980 1981 if (!folio_test_hugetlb(folio)) 1982 goto out; 1983 1984 if (flags & MF_COUNT_INCREASED) { 1985 ret = 1; 1986 count_increased = true; 1987 } else if (folio_test_hugetlb_freed(folio)) { 1988 ret = 0; 1989 } else if (folio_test_hugetlb_migratable(folio)) { 1990 ret = folio_try_get(folio); 1991 if (ret) 1992 count_increased = true; 1993 } else { 1994 ret = -EBUSY; 1995 if (!(flags & MF_NO_RETRY)) 1996 goto out; 1997 } 1998 1999 if (folio_set_hugetlb_hwpoison(folio, page)) { 2000 ret = -EHWPOISON; 2001 goto out; 2002 } 2003 2004 /* 2005 * Clearing hugetlb_migratable for hwpoisoned hugepages to prevent them 2006 * from being migrated by memory hotremove. 2007 */ 2008 if (count_increased && folio_test_hugetlb_migratable(folio)) { 2009 folio_clear_hugetlb_migratable(folio); 2010 *migratable_cleared = true; 2011 } 2012 2013 return ret; 2014 out: 2015 if (count_increased) 2016 folio_put(folio); 2017 return ret; 2018 } 2019 2020 /* 2021 * Taking refcount of hugetlb pages needs extra care about race conditions 2022 * with basic operations like hugepage allocation/free/demotion. 2023 * So some of prechecks for hwpoison (pinning, and testing/setting 2024 * PageHWPoison) should be done in single hugetlb_lock range. 2025 */ 2026 static int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb) 2027 { 2028 int res; 2029 struct page *p = pfn_to_page(pfn); 2030 struct folio *folio; 2031 unsigned long page_flags; 2032 bool migratable_cleared = false; 2033 2034 *hugetlb = 1; 2035 retry: 2036 res = get_huge_page_for_hwpoison(pfn, flags, &migratable_cleared); 2037 if (res == 2) { /* fallback to normal page handling */ 2038 *hugetlb = 0; 2039 return 0; 2040 } else if (res == -EHWPOISON) { 2041 pr_err("%#lx: already hardware poisoned\n", pfn); 2042 if (flags & MF_ACTION_REQUIRED) { 2043 folio = page_folio(p); 2044 res = kill_accessing_process(current, folio_pfn(folio), flags); 2045 } 2046 return res; 2047 } else if (res == -EBUSY) { 2048 if (!(flags & MF_NO_RETRY)) { 2049 flags |= MF_NO_RETRY; 2050 goto retry; 2051 } 2052 return action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED); 2053 } 2054 2055 folio = page_folio(p); 2056 folio_lock(folio); 2057 2058 if (hwpoison_filter(p)) { 2059 folio_clear_hugetlb_hwpoison(folio); 2060 if (migratable_cleared) 2061 folio_set_hugetlb_migratable(folio); 2062 folio_unlock(folio); 2063 if (res == 1) 2064 folio_put(folio); 2065 return -EOPNOTSUPP; 2066 } 2067 2068 /* 2069 * Handling free hugepage. The possible race with hugepage allocation 2070 * or demotion can be prevented by PageHWPoison flag. 2071 */ 2072 if (res == 0) { 2073 folio_unlock(folio); 2074 if (__page_handle_poison(p) >= 0) { 2075 page_ref_inc(p); 2076 res = MF_RECOVERED; 2077 } else { 2078 res = MF_FAILED; 2079 } 2080 return action_result(pfn, MF_MSG_FREE_HUGE, res); 2081 } 2082 2083 page_flags = folio->flags; 2084 2085 if (!hwpoison_user_mappings(p, pfn, flags, &folio->page)) { 2086 folio_unlock(folio); 2087 return action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED); 2088 } 2089 2090 return identify_page_state(pfn, p, page_flags); 2091 } 2092 2093 #else 2094 static inline int try_memory_failure_hugetlb(unsigned long pfn, int flags, int *hugetlb) 2095 { 2096 return 0; 2097 } 2098 2099 static inline unsigned long folio_free_raw_hwp(struct folio *folio, bool flag) 2100 { 2101 return 0; 2102 } 2103 #endif /* CONFIG_HUGETLB_PAGE */ 2104 2105 /* Drop the extra refcount in case we come from madvise() */ 2106 static void put_ref_page(unsigned long pfn, int flags) 2107 { 2108 struct page *page; 2109 2110 if (!(flags & MF_COUNT_INCREASED)) 2111 return; 2112 2113 page = pfn_to_page(pfn); 2114 if (page) 2115 put_page(page); 2116 } 2117 2118 static int memory_failure_dev_pagemap(unsigned long pfn, int flags, 2119 struct dev_pagemap *pgmap) 2120 { 2121 int rc = -ENXIO; 2122 2123 /* device metadata space is not recoverable */ 2124 if (!pgmap_pfn_valid(pgmap, pfn)) 2125 goto out; 2126 2127 /* 2128 * Call driver's implementation to handle the memory failure, otherwise 2129 * fall back to generic handler. 2130 */ 2131 if (pgmap_has_memory_failure(pgmap)) { 2132 rc = pgmap->ops->memory_failure(pgmap, pfn, 1, flags); 2133 /* 2134 * Fall back to generic handler too if operation is not 2135 * supported inside the driver/device/filesystem. 2136 */ 2137 if (rc != -EOPNOTSUPP) 2138 goto out; 2139 } 2140 2141 rc = mf_generic_kill_procs(pfn, flags, pgmap); 2142 out: 2143 /* drop pgmap ref acquired in caller */ 2144 put_dev_pagemap(pgmap); 2145 if (rc != -EOPNOTSUPP) 2146 action_result(pfn, MF_MSG_DAX, rc ? MF_FAILED : MF_RECOVERED); 2147 return rc; 2148 } 2149 2150 /** 2151 * memory_failure - Handle memory failure of a page. 2152 * @pfn: Page Number of the corrupted page 2153 * @flags: fine tune action taken 2154 * 2155 * This function is called by the low level machine check code 2156 * of an architecture when it detects hardware memory corruption 2157 * of a page. It tries its best to recover, which includes 2158 * dropping pages, killing processes etc. 2159 * 2160 * The function is primarily of use for corruptions that 2161 * happen outside the current execution context (e.g. when 2162 * detected by a background scrubber) 2163 * 2164 * Must run in process context (e.g. a work queue) with interrupts 2165 * enabled and no spinlocks held. 2166 * 2167 * Return: 0 for successfully handled the memory error, 2168 * -EOPNOTSUPP for hwpoison_filter() filtered the error event, 2169 * < 0(except -EOPNOTSUPP) on failure. 2170 */ 2171 int memory_failure(unsigned long pfn, int flags) 2172 { 2173 struct page *p; 2174 struct page *hpage; 2175 struct dev_pagemap *pgmap; 2176 int res = 0; 2177 unsigned long page_flags; 2178 bool retry = true; 2179 int hugetlb = 0; 2180 2181 if (!sysctl_memory_failure_recovery) 2182 panic("Memory failure on page %lx", pfn); 2183 2184 mutex_lock(&mf_mutex); 2185 2186 if (!(flags & MF_SW_SIMULATED)) 2187 hw_memory_failure = true; 2188 2189 p = pfn_to_online_page(pfn); 2190 if (!p) { 2191 res = arch_memory_failure(pfn, flags); 2192 if (res == 0) 2193 goto unlock_mutex; 2194 2195 if (pfn_valid(pfn)) { 2196 pgmap = get_dev_pagemap(pfn, NULL); 2197 put_ref_page(pfn, flags); 2198 if (pgmap) { 2199 res = memory_failure_dev_pagemap(pfn, flags, 2200 pgmap); 2201 goto unlock_mutex; 2202 } 2203 } 2204 pr_err("%#lx: memory outside kernel control\n", pfn); 2205 res = -ENXIO; 2206 goto unlock_mutex; 2207 } 2208 2209 try_again: 2210 res = try_memory_failure_hugetlb(pfn, flags, &hugetlb); 2211 if (hugetlb) 2212 goto unlock_mutex; 2213 2214 if (TestSetPageHWPoison(p)) { 2215 pr_err("%#lx: already hardware poisoned\n", pfn); 2216 res = -EHWPOISON; 2217 if (flags & MF_ACTION_REQUIRED) 2218 res = kill_accessing_process(current, pfn, flags); 2219 if (flags & MF_COUNT_INCREASED) 2220 put_page(p); 2221 goto unlock_mutex; 2222 } 2223 2224 /* 2225 * We need/can do nothing about count=0 pages. 2226 * 1) it's a free page, and therefore in safe hand: 2227 * check_new_page() will be the gate keeper. 2228 * 2) it's part of a non-compound high order page. 2229 * Implies some kernel user: cannot stop them from 2230 * R/W the page; let's pray that the page has been 2231 * used and will be freed some time later. 2232 * In fact it's dangerous to directly bump up page count from 0, 2233 * that may make page_ref_freeze()/page_ref_unfreeze() mismatch. 2234 */ 2235 if (!(flags & MF_COUNT_INCREASED)) { 2236 res = get_hwpoison_page(p, flags); 2237 if (!res) { 2238 if (is_free_buddy_page(p)) { 2239 if (take_page_off_buddy(p)) { 2240 page_ref_inc(p); 2241 res = MF_RECOVERED; 2242 } else { 2243 /* We lost the race, try again */ 2244 if (retry) { 2245 ClearPageHWPoison(p); 2246 retry = false; 2247 goto try_again; 2248 } 2249 res = MF_FAILED; 2250 } 2251 res = action_result(pfn, MF_MSG_BUDDY, res); 2252 } else { 2253 res = action_result(pfn, MF_MSG_KERNEL_HIGH_ORDER, MF_IGNORED); 2254 } 2255 goto unlock_mutex; 2256 } else if (res < 0) { 2257 res = action_result(pfn, MF_MSG_UNKNOWN, MF_IGNORED); 2258 goto unlock_mutex; 2259 } 2260 } 2261 2262 hpage = compound_head(p); 2263 if (PageTransHuge(hpage)) { 2264 /* 2265 * The flag must be set after the refcount is bumped 2266 * otherwise it may race with THP split. 2267 * And the flag can't be set in get_hwpoison_page() since 2268 * it is called by soft offline too and it is just called 2269 * for !MF_COUNT_INCREASED. So here seems to be the best 2270 * place. 2271 * 2272 * Don't need care about the above error handling paths for 2273 * get_hwpoison_page() since they handle either free page 2274 * or unhandlable page. The refcount is bumped iff the 2275 * page is a valid handlable page. 2276 */ 2277 SetPageHasHWPoisoned(hpage); 2278 if (try_to_split_thp_page(p) < 0) { 2279 res = action_result(pfn, MF_MSG_UNSPLIT_THP, MF_IGNORED); 2280 goto unlock_mutex; 2281 } 2282 VM_BUG_ON_PAGE(!page_count(p), p); 2283 } 2284 2285 /* 2286 * We ignore non-LRU pages for good reasons. 2287 * - PG_locked is only well defined for LRU pages and a few others 2288 * - to avoid races with __SetPageLocked() 2289 * - to avoid races with __SetPageSlab*() (and more non-atomic ops) 2290 * The check (unnecessarily) ignores LRU pages being isolated and 2291 * walked by the page reclaim code, however that's not a big loss. 2292 */ 2293 shake_page(p); 2294 2295 lock_page(p); 2296 2297 /* 2298 * We're only intended to deal with the non-Compound page here. 2299 * However, the page could have changed compound pages due to 2300 * race window. If this happens, we could try again to hopefully 2301 * handle the page next round. 2302 */ 2303 if (PageCompound(p)) { 2304 if (retry) { 2305 ClearPageHWPoison(p); 2306 unlock_page(p); 2307 put_page(p); 2308 flags &= ~MF_COUNT_INCREASED; 2309 retry = false; 2310 goto try_again; 2311 } 2312 res = action_result(pfn, MF_MSG_DIFFERENT_COMPOUND, MF_IGNORED); 2313 goto unlock_page; 2314 } 2315 2316 /* 2317 * We use page flags to determine what action should be taken, but 2318 * the flags can be modified by the error containment action. One 2319 * example is an mlocked page, where PG_mlocked is cleared by 2320 * page_remove_rmap() in try_to_unmap_one(). So to determine page status 2321 * correctly, we save a copy of the page flags at this time. 2322 */ 2323 page_flags = p->flags; 2324 2325 if (hwpoison_filter(p)) { 2326 ClearPageHWPoison(p); 2327 unlock_page(p); 2328 put_page(p); 2329 res = -EOPNOTSUPP; 2330 goto unlock_mutex; 2331 } 2332 2333 /* 2334 * __munlock_folio() may clear a writeback page's LRU flag without 2335 * page_lock. We need wait writeback completion for this page or it 2336 * may trigger vfs BUG while evict inode. 2337 */ 2338 if (!PageLRU(p) && !PageWriteback(p)) 2339 goto identify_page_state; 2340 2341 /* 2342 * It's very difficult to mess with pages currently under IO 2343 * and in many cases impossible, so we just avoid it here. 2344 */ 2345 wait_on_page_writeback(p); 2346 2347 /* 2348 * Now take care of user space mappings. 2349 * Abort on fail: __filemap_remove_folio() assumes unmapped page. 2350 */ 2351 if (!hwpoison_user_mappings(p, pfn, flags, p)) { 2352 res = action_result(pfn, MF_MSG_UNMAP_FAILED, MF_IGNORED); 2353 goto unlock_page; 2354 } 2355 2356 /* 2357 * Torn down by someone else? 2358 */ 2359 if (PageLRU(p) && !PageSwapCache(p) && p->mapping == NULL) { 2360 res = action_result(pfn, MF_MSG_TRUNCATED_LRU, MF_IGNORED); 2361 goto unlock_page; 2362 } 2363 2364 identify_page_state: 2365 res = identify_page_state(pfn, p, page_flags); 2366 mutex_unlock(&mf_mutex); 2367 return res; 2368 unlock_page: 2369 unlock_page(p); 2370 unlock_mutex: 2371 mutex_unlock(&mf_mutex); 2372 return res; 2373 } 2374 EXPORT_SYMBOL_GPL(memory_failure); 2375 2376 #define MEMORY_FAILURE_FIFO_ORDER 4 2377 #define MEMORY_FAILURE_FIFO_SIZE (1 << MEMORY_FAILURE_FIFO_ORDER) 2378 2379 struct memory_failure_entry { 2380 unsigned long pfn; 2381 int flags; 2382 }; 2383 2384 struct memory_failure_cpu { 2385 DECLARE_KFIFO(fifo, struct memory_failure_entry, 2386 MEMORY_FAILURE_FIFO_SIZE); 2387 spinlock_t lock; 2388 struct work_struct work; 2389 }; 2390 2391 static DEFINE_PER_CPU(struct memory_failure_cpu, memory_failure_cpu); 2392 2393 /** 2394 * memory_failure_queue - Schedule handling memory failure of a page. 2395 * @pfn: Page Number of the corrupted page 2396 * @flags: Flags for memory failure handling 2397 * 2398 * This function is called by the low level hardware error handler 2399 * when it detects hardware memory corruption of a page. It schedules 2400 * the recovering of error page, including dropping pages, killing 2401 * processes etc. 2402 * 2403 * The function is primarily of use for corruptions that 2404 * happen outside the current execution context (e.g. when 2405 * detected by a background scrubber) 2406 * 2407 * Can run in IRQ context. 2408 */ 2409 void memory_failure_queue(unsigned long pfn, int flags) 2410 { 2411 struct memory_failure_cpu *mf_cpu; 2412 unsigned long proc_flags; 2413 struct memory_failure_entry entry = { 2414 .pfn = pfn, 2415 .flags = flags, 2416 }; 2417 2418 mf_cpu = &get_cpu_var(memory_failure_cpu); 2419 spin_lock_irqsave(&mf_cpu->lock, proc_flags); 2420 if (kfifo_put(&mf_cpu->fifo, entry)) 2421 schedule_work_on(smp_processor_id(), &mf_cpu->work); 2422 else 2423 pr_err("buffer overflow when queuing memory failure at %#lx\n", 2424 pfn); 2425 spin_unlock_irqrestore(&mf_cpu->lock, proc_flags); 2426 put_cpu_var(memory_failure_cpu); 2427 } 2428 EXPORT_SYMBOL_GPL(memory_failure_queue); 2429 2430 static void memory_failure_work_func(struct work_struct *work) 2431 { 2432 struct memory_failure_cpu *mf_cpu; 2433 struct memory_failure_entry entry = { 0, }; 2434 unsigned long proc_flags; 2435 int gotten; 2436 2437 mf_cpu = container_of(work, struct memory_failure_cpu, work); 2438 for (;;) { 2439 spin_lock_irqsave(&mf_cpu->lock, proc_flags); 2440 gotten = kfifo_get(&mf_cpu->fifo, &entry); 2441 spin_unlock_irqrestore(&mf_cpu->lock, proc_flags); 2442 if (!gotten) 2443 break; 2444 if (entry.flags & MF_SOFT_OFFLINE) 2445 soft_offline_page(entry.pfn, entry.flags); 2446 else 2447 memory_failure(entry.pfn, entry.flags); 2448 } 2449 } 2450 2451 /* 2452 * Process memory_failure work queued on the specified CPU. 2453 * Used to avoid return-to-userspace racing with the memory_failure workqueue. 2454 */ 2455 void memory_failure_queue_kick(int cpu) 2456 { 2457 struct memory_failure_cpu *mf_cpu; 2458 2459 mf_cpu = &per_cpu(memory_failure_cpu, cpu); 2460 cancel_work_sync(&mf_cpu->work); 2461 memory_failure_work_func(&mf_cpu->work); 2462 } 2463 2464 static int __init memory_failure_init(void) 2465 { 2466 struct memory_failure_cpu *mf_cpu; 2467 int cpu; 2468 2469 for_each_possible_cpu(cpu) { 2470 mf_cpu = &per_cpu(memory_failure_cpu, cpu); 2471 spin_lock_init(&mf_cpu->lock); 2472 INIT_KFIFO(mf_cpu->fifo); 2473 INIT_WORK(&mf_cpu->work, memory_failure_work_func); 2474 } 2475 2476 register_sysctl_init("vm", memory_failure_table); 2477 2478 return 0; 2479 } 2480 core_initcall(memory_failure_init); 2481 2482 #undef pr_fmt 2483 #define pr_fmt(fmt) "" fmt 2484 #define unpoison_pr_info(fmt, pfn, rs) \ 2485 ({ \ 2486 if (__ratelimit(rs)) \ 2487 pr_info(fmt, pfn); \ 2488 }) 2489 2490 /** 2491 * unpoison_memory - Unpoison a previously poisoned page 2492 * @pfn: Page number of the to be unpoisoned page 2493 * 2494 * Software-unpoison a page that has been poisoned by 2495 * memory_failure() earlier. 2496 * 2497 * This is only done on the software-level, so it only works 2498 * for linux injected failures, not real hardware failures 2499 * 2500 * Returns 0 for success, otherwise -errno. 2501 */ 2502 int unpoison_memory(unsigned long pfn) 2503 { 2504 struct folio *folio; 2505 struct page *p; 2506 int ret = -EBUSY, ghp; 2507 unsigned long count = 1; 2508 bool huge = false; 2509 static DEFINE_RATELIMIT_STATE(unpoison_rs, DEFAULT_RATELIMIT_INTERVAL, 2510 DEFAULT_RATELIMIT_BURST); 2511 2512 if (!pfn_valid(pfn)) 2513 return -ENXIO; 2514 2515 p = pfn_to_page(pfn); 2516 folio = page_folio(p); 2517 2518 mutex_lock(&mf_mutex); 2519 2520 if (hw_memory_failure) { 2521 unpoison_pr_info("Unpoison: Disabled after HW memory failure %#lx\n", 2522 pfn, &unpoison_rs); 2523 ret = -EOPNOTSUPP; 2524 goto unlock_mutex; 2525 } 2526 2527 if (!PageHWPoison(p)) { 2528 unpoison_pr_info("Unpoison: Page was already unpoisoned %#lx\n", 2529 pfn, &unpoison_rs); 2530 goto unlock_mutex; 2531 } 2532 2533 if (folio_ref_count(folio) > 1) { 2534 unpoison_pr_info("Unpoison: Someone grabs the hwpoison page %#lx\n", 2535 pfn, &unpoison_rs); 2536 goto unlock_mutex; 2537 } 2538 2539 if (folio_test_slab(folio) || PageTable(&folio->page) || 2540 folio_test_reserved(folio) || PageOffline(&folio->page)) 2541 goto unlock_mutex; 2542 2543 /* 2544 * Note that folio->_mapcount is overloaded in SLAB, so the simple test 2545 * in folio_mapped() has to be done after folio_test_slab() is checked. 2546 */ 2547 if (folio_mapped(folio)) { 2548 unpoison_pr_info("Unpoison: Someone maps the hwpoison page %#lx\n", 2549 pfn, &unpoison_rs); 2550 goto unlock_mutex; 2551 } 2552 2553 if (folio_mapping(folio)) { 2554 unpoison_pr_info("Unpoison: the hwpoison page has non-NULL mapping %#lx\n", 2555 pfn, &unpoison_rs); 2556 goto unlock_mutex; 2557 } 2558 2559 ghp = get_hwpoison_page(p, MF_UNPOISON); 2560 if (!ghp) { 2561 if (PageHuge(p)) { 2562 huge = true; 2563 count = folio_free_raw_hwp(folio, false); 2564 if (count == 0) 2565 goto unlock_mutex; 2566 } 2567 ret = folio_test_clear_hwpoison(folio) ? 0 : -EBUSY; 2568 } else if (ghp < 0) { 2569 if (ghp == -EHWPOISON) { 2570 ret = put_page_back_buddy(p) ? 0 : -EBUSY; 2571 } else { 2572 ret = ghp; 2573 unpoison_pr_info("Unpoison: failed to grab page %#lx\n", 2574 pfn, &unpoison_rs); 2575 } 2576 } else { 2577 if (PageHuge(p)) { 2578 huge = true; 2579 count = folio_free_raw_hwp(folio, false); 2580 if (count == 0) { 2581 folio_put(folio); 2582 goto unlock_mutex; 2583 } 2584 } 2585 2586 folio_put(folio); 2587 if (TestClearPageHWPoison(p)) { 2588 folio_put(folio); 2589 ret = 0; 2590 } 2591 } 2592 2593 unlock_mutex: 2594 mutex_unlock(&mf_mutex); 2595 if (!ret) { 2596 if (!huge) 2597 num_poisoned_pages_sub(pfn, 1); 2598 unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n", 2599 page_to_pfn(p), &unpoison_rs); 2600 } 2601 return ret; 2602 } 2603 EXPORT_SYMBOL(unpoison_memory); 2604 2605 static bool isolate_page(struct page *page, struct list_head *pagelist) 2606 { 2607 bool isolated = false; 2608 2609 if (PageHuge(page)) { 2610 isolated = isolate_hugetlb(page_folio(page), pagelist); 2611 } else { 2612 bool lru = !__PageMovable(page); 2613 2614 if (lru) 2615 isolated = isolate_lru_page(page); 2616 else 2617 isolated = isolate_movable_page(page, 2618 ISOLATE_UNEVICTABLE); 2619 2620 if (isolated) { 2621 list_add(&page->lru, pagelist); 2622 if (lru) 2623 inc_node_page_state(page, NR_ISOLATED_ANON + 2624 page_is_file_lru(page)); 2625 } 2626 } 2627 2628 /* 2629 * If we succeed to isolate the page, we grabbed another refcount on 2630 * the page, so we can safely drop the one we got from get_any_page(). 2631 * If we failed to isolate the page, it means that we cannot go further 2632 * and we will return an error, so drop the reference we got from 2633 * get_any_page() as well. 2634 */ 2635 put_page(page); 2636 return isolated; 2637 } 2638 2639 /* 2640 * soft_offline_in_use_page handles hugetlb-pages and non-hugetlb pages. 2641 * If the page is a non-dirty unmapped page-cache page, it simply invalidates. 2642 * If the page is mapped, it migrates the contents over. 2643 */ 2644 static int soft_offline_in_use_page(struct page *page) 2645 { 2646 long ret = 0; 2647 unsigned long pfn = page_to_pfn(page); 2648 struct page *hpage = compound_head(page); 2649 char const *msg_page[] = {"page", "hugepage"}; 2650 bool huge = PageHuge(page); 2651 LIST_HEAD(pagelist); 2652 struct migration_target_control mtc = { 2653 .nid = NUMA_NO_NODE, 2654 .gfp_mask = GFP_USER | __GFP_MOVABLE | __GFP_RETRY_MAYFAIL, 2655 }; 2656 2657 if (!huge && PageTransHuge(hpage)) { 2658 if (try_to_split_thp_page(page)) { 2659 pr_info("soft offline: %#lx: thp split failed\n", pfn); 2660 return -EBUSY; 2661 } 2662 hpage = page; 2663 } 2664 2665 lock_page(page); 2666 if (!huge) 2667 wait_on_page_writeback(page); 2668 if (PageHWPoison(page)) { 2669 unlock_page(page); 2670 put_page(page); 2671 pr_info("soft offline: %#lx page already poisoned\n", pfn); 2672 return 0; 2673 } 2674 2675 if (!huge && PageLRU(page) && !PageSwapCache(page)) 2676 /* 2677 * Try to invalidate first. This should work for 2678 * non dirty unmapped page cache pages. 2679 */ 2680 ret = invalidate_inode_page(page); 2681 unlock_page(page); 2682 2683 if (ret) { 2684 pr_info("soft_offline: %#lx: invalidated\n", pfn); 2685 page_handle_poison(page, false, true); 2686 return 0; 2687 } 2688 2689 if (isolate_page(hpage, &pagelist)) { 2690 ret = migrate_pages(&pagelist, alloc_migration_target, NULL, 2691 (unsigned long)&mtc, MIGRATE_SYNC, MR_MEMORY_FAILURE, NULL); 2692 if (!ret) { 2693 bool release = !huge; 2694 2695 if (!page_handle_poison(page, huge, release)) 2696 ret = -EBUSY; 2697 } else { 2698 if (!list_empty(&pagelist)) 2699 putback_movable_pages(&pagelist); 2700 2701 pr_info("soft offline: %#lx: %s migration failed %ld, type %pGp\n", 2702 pfn, msg_page[huge], ret, &page->flags); 2703 if (ret > 0) 2704 ret = -EBUSY; 2705 } 2706 } else { 2707 pr_info("soft offline: %#lx: %s isolation failed, page count %d, type %pGp\n", 2708 pfn, msg_page[huge], page_count(page), &page->flags); 2709 ret = -EBUSY; 2710 } 2711 return ret; 2712 } 2713 2714 /** 2715 * soft_offline_page - Soft offline a page. 2716 * @pfn: pfn to soft-offline 2717 * @flags: flags. Same as memory_failure(). 2718 * 2719 * Returns 0 on success 2720 * -EOPNOTSUPP for hwpoison_filter() filtered the error event 2721 * < 0 otherwise negated errno. 2722 * 2723 * Soft offline a page, by migration or invalidation, 2724 * without killing anything. This is for the case when 2725 * a page is not corrupted yet (so it's still valid to access), 2726 * but has had a number of corrected errors and is better taken 2727 * out. 2728 * 2729 * The actual policy on when to do that is maintained by 2730 * user space. 2731 * 2732 * This should never impact any application or cause data loss, 2733 * however it might take some time. 2734 * 2735 * This is not a 100% solution for all memory, but tries to be 2736 * ``good enough'' for the majority of memory. 2737 */ 2738 int soft_offline_page(unsigned long pfn, int flags) 2739 { 2740 int ret; 2741 bool try_again = true; 2742 struct page *page; 2743 2744 if (!pfn_valid(pfn)) { 2745 WARN_ON_ONCE(flags & MF_COUNT_INCREASED); 2746 return -ENXIO; 2747 } 2748 2749 /* Only online pages can be soft-offlined (esp., not ZONE_DEVICE). */ 2750 page = pfn_to_online_page(pfn); 2751 if (!page) { 2752 put_ref_page(pfn, flags); 2753 return -EIO; 2754 } 2755 2756 mutex_lock(&mf_mutex); 2757 2758 if (PageHWPoison(page)) { 2759 pr_info("%s: %#lx page already poisoned\n", __func__, pfn); 2760 put_ref_page(pfn, flags); 2761 mutex_unlock(&mf_mutex); 2762 return 0; 2763 } 2764 2765 retry: 2766 get_online_mems(); 2767 ret = get_hwpoison_page(page, flags | MF_SOFT_OFFLINE); 2768 put_online_mems(); 2769 2770 if (hwpoison_filter(page)) { 2771 if (ret > 0) 2772 put_page(page); 2773 2774 mutex_unlock(&mf_mutex); 2775 return -EOPNOTSUPP; 2776 } 2777 2778 if (ret > 0) { 2779 ret = soft_offline_in_use_page(page); 2780 } else if (ret == 0) { 2781 if (!page_handle_poison(page, true, false)) { 2782 if (try_again) { 2783 try_again = false; 2784 flags &= ~MF_COUNT_INCREASED; 2785 goto retry; 2786 } 2787 ret = -EBUSY; 2788 } 2789 } 2790 2791 mutex_unlock(&mf_mutex); 2792 2793 return ret; 2794 } 2795