Line data Source code
1 : /* SPDX-License-Identifier: GPL-2.0 */
2 : #ifndef _LINUX_MM_TYPES_H
3 : #define _LINUX_MM_TYPES_H
4 :
5 : #include <linux/mm_types_task.h>
6 :
7 : #include <linux/auxvec.h>
8 : #include <linux/kref.h>
9 : #include <linux/list.h>
10 : #include <linux/spinlock.h>
11 : #include <linux/rbtree.h>
12 : #include <linux/maple_tree.h>
13 : #include <linux/rwsem.h>
14 : #include <linux/completion.h>
15 : #include <linux/cpumask.h>
16 : #include <linux/uprobes.h>
17 : #include <linux/rcupdate.h>
18 : #include <linux/page-flags-layout.h>
19 : #include <linux/workqueue.h>
20 : #include <linux/seqlock.h>
21 : #include <linux/percpu_counter.h>
22 :
23 : #include <asm/mmu.h>
24 :
25 : #ifndef AT_VECTOR_SIZE_ARCH
26 : #define AT_VECTOR_SIZE_ARCH 0
27 : #endif
28 : #define AT_VECTOR_SIZE (2*(AT_VECTOR_SIZE_ARCH + AT_VECTOR_SIZE_BASE + 1))
29 :
30 : #define INIT_PASID 0
31 :
32 : struct address_space;
33 : struct mem_cgroup;
34 :
35 : /*
36 : * Each physical page in the system has a struct page associated with
37 : * it to keep track of whatever it is we are using the page for at the
38 : * moment. Note that we have no way to track which tasks are using
39 : * a page, though if it is a pagecache page, rmap structures can tell us
40 : * who is mapping it.
41 : *
42 : * If you allocate the page using alloc_pages(), you can use some of the
43 : * space in struct page for your own purposes. The five words in the main
44 : * union are available, except for bit 0 of the first word which must be
45 : * kept clear. Many users use this word to store a pointer to an object
46 : * which is guaranteed to be aligned. If you use the same storage as
47 : * page->mapping, you must restore it to NULL before freeing the page.
48 : *
49 : * If your page will not be mapped to userspace, you can also use the four
50 : * bytes in the mapcount union, but you must call page_mapcount_reset()
51 : * before freeing it.
52 : *
53 : * If you want to use the refcount field, it must be used in such a way
54 : * that other CPUs temporarily incrementing and then decrementing the
55 : * refcount does not cause problems. On receiving the page from
56 : * alloc_pages(), the refcount will be positive.
57 : *
58 : * If you allocate pages of order > 0, you can use some of the fields
59 : * in each subpage, but you may need to restore some of their values
60 : * afterwards.
61 : *
62 : * SLUB uses cmpxchg_double() to atomically update its freelist and counters.
63 : * That requires that freelist & counters in struct slab be adjacent and
64 : * double-word aligned. Because struct slab currently just reinterprets the
65 : * bits of struct page, we align all struct pages to double-word boundaries,
66 : * and ensure that 'freelist' is aligned within struct slab.
67 : */
68 : #ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE
69 : #define _struct_page_alignment __aligned(2 * sizeof(unsigned long))
70 : #else
71 : #define _struct_page_alignment __aligned(sizeof(unsigned long))
72 : #endif
73 :
74 : struct page {
75 : unsigned long flags; /* Atomic flags, some possibly
76 : * updated asynchronously */
77 : /*
78 : * Five words (20/40 bytes) are available in this union.
79 : * WARNING: bit 0 of the first word is used for PageTail(). That
80 : * means the other users of this union MUST NOT use the bit to
81 : * avoid collision and false-positive PageTail().
82 : */
83 : union {
84 : struct { /* Page cache and anonymous pages */
85 : /**
86 : * @lru: Pageout list, eg. active_list protected by
87 : * lruvec->lru_lock. Sometimes used as a generic list
88 : * by the page owner.
89 : */
90 : union {
91 : struct list_head lru;
92 :
93 : /* Or, for the Unevictable "LRU list" slot */
94 : struct {
95 : /* Always even, to negate PageTail */
96 : void *__filler;
97 : /* Count page's or folio's mlocks */
98 : unsigned int mlock_count;
99 : };
100 :
101 : /* Or, free page */
102 : struct list_head buddy_list;
103 : struct list_head pcp_list;
104 : };
105 : /* See page-flags.h for PAGE_MAPPING_FLAGS */
106 : struct address_space *mapping;
107 : union {
108 : pgoff_t index; /* Our offset within mapping. */
109 : unsigned long share; /* share count for fsdax */
110 : };
111 : /**
112 : * @private: Mapping-private opaque data.
113 : * Usually used for buffer_heads if PagePrivate.
114 : * Used for swp_entry_t if PageSwapCache.
115 : * Indicates order in the buddy system if PageBuddy.
116 : */
117 : unsigned long private;
118 : };
119 : struct { /* page_pool used by netstack */
120 : /**
121 : * @pp_magic: magic value to avoid recycling non
122 : * page_pool allocated pages.
123 : */
124 : unsigned long pp_magic;
125 : struct page_pool *pp;
126 : unsigned long _pp_mapping_pad;
127 : unsigned long dma_addr;
128 : union {
129 : /**
130 : * dma_addr_upper: might require a 64-bit
131 : * value on 32-bit architectures.
132 : */
133 : unsigned long dma_addr_upper;
134 : /**
135 : * For frag page support, not supported in
136 : * 32-bit architectures with 64-bit DMA.
137 : */
138 : atomic_long_t pp_frag_count;
139 : };
140 : };
141 : struct { /* Tail pages of compound page */
142 : unsigned long compound_head; /* Bit zero is set */
143 : };
144 : struct { /* Page table pages */
145 : unsigned long _pt_pad_1; /* compound_head */
146 : pgtable_t pmd_huge_pte; /* protected by page->ptl */
147 : unsigned long _pt_pad_2; /* mapping */
148 : union {
149 : struct mm_struct *pt_mm; /* x86 pgds only */
150 : atomic_t pt_frag_refcount; /* powerpc */
151 : };
152 : #if ALLOC_SPLIT_PTLOCKS
153 : spinlock_t *ptl;
154 : #else
155 : spinlock_t ptl;
156 : #endif
157 : };
158 : struct { /* ZONE_DEVICE pages */
159 : /** @pgmap: Points to the hosting device page map. */
160 : struct dev_pagemap *pgmap;
161 : void *zone_device_data;
162 : /*
163 : * ZONE_DEVICE private pages are counted as being
164 : * mapped so the next 3 words hold the mapping, index,
165 : * and private fields from the source anonymous or
166 : * page cache page while the page is migrated to device
167 : * private memory.
168 : * ZONE_DEVICE MEMORY_DEVICE_FS_DAX pages also
169 : * use the mapping, index, and private fields when
170 : * pmem backed DAX files are mapped.
171 : */
172 : };
173 :
174 : /** @rcu_head: You can use this to free a page by RCU. */
175 : struct rcu_head rcu_head;
176 : };
177 :
178 : union { /* This union is 4 bytes in size. */
179 : /*
180 : * If the page can be mapped to userspace, encodes the number
181 : * of times this page is referenced by a page table.
182 : */
183 : atomic_t _mapcount;
184 :
185 : /*
186 : * If the page is neither PageSlab nor mappable to userspace,
187 : * the value stored here may help determine what this page
188 : * is used for. See page-flags.h for a list of page types
189 : * which are currently stored here.
190 : */
191 : unsigned int page_type;
192 : };
193 :
194 : /* Usage count. *DO NOT USE DIRECTLY*. See page_ref.h */
195 : atomic_t _refcount;
196 :
197 : #ifdef CONFIG_MEMCG
198 : unsigned long memcg_data;
199 : #endif
200 :
201 : /*
202 : * On machines where all RAM is mapped into kernel address space,
203 : * we can simply calculate the virtual address. On machines with
204 : * highmem some memory is mapped into kernel virtual memory
205 : * dynamically, so we need a place to store that address.
206 : * Note that this field could be 16 bits on x86 ... ;)
207 : *
208 : * Architectures with slow multiplication can define
209 : * WANT_PAGE_VIRTUAL in asm/page.h
210 : */
211 : #if defined(WANT_PAGE_VIRTUAL)
212 : void *virtual; /* Kernel virtual address (NULL if
213 : not kmapped, ie. highmem) */
214 : #endif /* WANT_PAGE_VIRTUAL */
215 :
216 : #ifdef CONFIG_KMSAN
217 : /*
218 : * KMSAN metadata for this page:
219 : * - shadow page: every bit indicates whether the corresponding
220 : * bit of the original page is initialized (0) or not (1);
221 : * - origin page: every 4 bytes contain an id of the stack trace
222 : * where the uninitialized value was created.
223 : */
224 : struct page *kmsan_shadow;
225 : struct page *kmsan_origin;
226 : #endif
227 :
228 : #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
229 : int _last_cpupid;
230 : #endif
231 : } _struct_page_alignment;
232 :
233 : /*
234 : * struct encoded_page - a nonexistent type marking this pointer
235 : *
236 : * An 'encoded_page' pointer is a pointer to a regular 'struct page', but
237 : * with the low bits of the pointer indicating extra context-dependent
238 : * information. Not super-common, but happens in mmu_gather and mlock
239 : * handling, and this acts as a type system check on that use.
240 : *
241 : * We only really have two guaranteed bits in general, although you could
242 : * play with 'struct page' alignment (see CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
243 : * for more.
244 : *
245 : * Use the supplied helper functions to endcode/decode the pointer and bits.
246 : */
247 : struct encoded_page;
248 : #define ENCODE_PAGE_BITS 3ul
249 : static __always_inline struct encoded_page *encode_page(struct page *page, unsigned long flags)
250 : {
251 : BUILD_BUG_ON(flags > ENCODE_PAGE_BITS);
252 : return (struct encoded_page *)(flags | (unsigned long)page);
253 : }
254 :
255 : static inline unsigned long encoded_page_flags(struct encoded_page *page)
256 : {
257 : return ENCODE_PAGE_BITS & (unsigned long)page;
258 : }
259 :
260 : static inline struct page *encoded_page_ptr(struct encoded_page *page)
261 : {
262 0 : return (struct page *)(~ENCODE_PAGE_BITS & (unsigned long)page);
263 : }
264 :
265 : /**
266 : * struct folio - Represents a contiguous set of bytes.
267 : * @flags: Identical to the page flags.
268 : * @lru: Least Recently Used list; tracks how recently this folio was used.
269 : * @mlock_count: Number of times this folio has been pinned by mlock().
270 : * @mapping: The file this page belongs to, or refers to the anon_vma for
271 : * anonymous memory.
272 : * @index: Offset within the file, in units of pages. For anonymous memory,
273 : * this is the index from the beginning of the mmap.
274 : * @private: Filesystem per-folio data (see folio_attach_private()).
275 : * Used for swp_entry_t if folio_test_swapcache().
276 : * @_mapcount: Do not access this member directly. Use folio_mapcount() to
277 : * find out how many times this folio is mapped by userspace.
278 : * @_refcount: Do not access this member directly. Use folio_ref_count()
279 : * to find how many references there are to this folio.
280 : * @memcg_data: Memory Control Group data.
281 : * @_folio_dtor: Which destructor to use for this folio.
282 : * @_folio_order: Do not use directly, call folio_order().
283 : * @_entire_mapcount: Do not use directly, call folio_entire_mapcount().
284 : * @_nr_pages_mapped: Do not use directly, call folio_mapcount().
285 : * @_pincount: Do not use directly, call folio_maybe_dma_pinned().
286 : * @_folio_nr_pages: Do not use directly, call folio_nr_pages().
287 : * @_hugetlb_subpool: Do not use directly, use accessor in hugetlb.h.
288 : * @_hugetlb_cgroup: Do not use directly, use accessor in hugetlb_cgroup.h.
289 : * @_hugetlb_cgroup_rsvd: Do not use directly, use accessor in hugetlb_cgroup.h.
290 : * @_hugetlb_hwpoison: Do not use directly, call raw_hwp_list_head().
291 : * @_deferred_list: Folios to be split under memory pressure.
292 : *
293 : * A folio is a physically, virtually and logically contiguous set
294 : * of bytes. It is a power-of-two in size, and it is aligned to that
295 : * same power-of-two. It is at least as large as %PAGE_SIZE. If it is
296 : * in the page cache, it is at a file offset which is a multiple of that
297 : * power-of-two. It may be mapped into userspace at an address which is
298 : * at an arbitrary page offset, but its kernel virtual address is aligned
299 : * to its size.
300 : */
301 : struct folio {
302 : /* private: don't document the anon union */
303 : union {
304 : struct {
305 : /* public: */
306 : unsigned long flags;
307 : union {
308 : struct list_head lru;
309 : /* private: avoid cluttering the output */
310 : struct {
311 : void *__filler;
312 : /* public: */
313 : unsigned int mlock_count;
314 : /* private: */
315 : };
316 : /* public: */
317 : };
318 : struct address_space *mapping;
319 : pgoff_t index;
320 : void *private;
321 : atomic_t _mapcount;
322 : atomic_t _refcount;
323 : #ifdef CONFIG_MEMCG
324 : unsigned long memcg_data;
325 : #endif
326 : /* private: the union with struct page is transitional */
327 : };
328 : struct page page;
329 : };
330 : union {
331 : struct {
332 : unsigned long _flags_1;
333 : unsigned long _head_1;
334 : /* public: */
335 : unsigned char _folio_dtor;
336 : unsigned char _folio_order;
337 : atomic_t _entire_mapcount;
338 : atomic_t _nr_pages_mapped;
339 : atomic_t _pincount;
340 : #ifdef CONFIG_64BIT
341 : unsigned int _folio_nr_pages;
342 : #endif
343 : /* private: the union with struct page is transitional */
344 : };
345 : struct page __page_1;
346 : };
347 : union {
348 : struct {
349 : unsigned long _flags_2;
350 : unsigned long _head_2;
351 : /* public: */
352 : void *_hugetlb_subpool;
353 : void *_hugetlb_cgroup;
354 : void *_hugetlb_cgroup_rsvd;
355 : void *_hugetlb_hwpoison;
356 : /* private: the union with struct page is transitional */
357 : };
358 : struct {
359 : unsigned long _flags_2a;
360 : unsigned long _head_2a;
361 : /* public: */
362 : struct list_head _deferred_list;
363 : /* private: the union with struct page is transitional */
364 : };
365 : struct page __page_2;
366 : };
367 : };
368 :
369 : #define FOLIO_MATCH(pg, fl) \
370 : static_assert(offsetof(struct page, pg) == offsetof(struct folio, fl))
371 : FOLIO_MATCH(flags, flags);
372 : FOLIO_MATCH(lru, lru);
373 : FOLIO_MATCH(mapping, mapping);
374 : FOLIO_MATCH(compound_head, lru);
375 : FOLIO_MATCH(index, index);
376 : FOLIO_MATCH(private, private);
377 : FOLIO_MATCH(_mapcount, _mapcount);
378 : FOLIO_MATCH(_refcount, _refcount);
379 : #ifdef CONFIG_MEMCG
380 : FOLIO_MATCH(memcg_data, memcg_data);
381 : #endif
382 : #undef FOLIO_MATCH
383 : #define FOLIO_MATCH(pg, fl) \
384 : static_assert(offsetof(struct folio, fl) == \
385 : offsetof(struct page, pg) + sizeof(struct page))
386 : FOLIO_MATCH(flags, _flags_1);
387 : FOLIO_MATCH(compound_head, _head_1);
388 : #undef FOLIO_MATCH
389 : #define FOLIO_MATCH(pg, fl) \
390 : static_assert(offsetof(struct folio, fl) == \
391 : offsetof(struct page, pg) + 2 * sizeof(struct page))
392 : FOLIO_MATCH(flags, _flags_2);
393 : FOLIO_MATCH(compound_head, _head_2);
394 : #undef FOLIO_MATCH
395 :
396 : /*
397 : * Used for sizing the vmemmap region on some architectures
398 : */
399 : #define STRUCT_PAGE_MAX_SHIFT (order_base_2(sizeof(struct page)))
400 :
401 : #define PAGE_FRAG_CACHE_MAX_SIZE __ALIGN_MASK(32768, ~PAGE_MASK)
402 : #define PAGE_FRAG_CACHE_MAX_ORDER get_order(PAGE_FRAG_CACHE_MAX_SIZE)
403 :
404 : /*
405 : * page_private can be used on tail pages. However, PagePrivate is only
406 : * checked by the VM on the head page. So page_private on the tail pages
407 : * should be used for data that's ancillary to the head page (eg attaching
408 : * buffer heads to tail pages after attaching buffer heads to the head page)
409 : */
410 : #define page_private(page) ((page)->private)
411 :
412 : static inline void set_page_private(struct page *page, unsigned long private)
413 : {
414 51716 : page->private = private;
415 : }
416 :
417 : static inline void *folio_get_private(struct folio *folio)
418 : {
419 : return folio->private;
420 : }
421 :
422 : struct page_frag_cache {
423 : void * va;
424 : #if (PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE)
425 : __u16 offset;
426 : __u16 size;
427 : #else
428 : __u32 offset;
429 : #endif
430 : /* we maintain a pagecount bias, so that we dont dirty cache line
431 : * containing page->_refcount every time we allocate a fragment.
432 : */
433 : unsigned int pagecnt_bias;
434 : bool pfmemalloc;
435 : };
436 :
437 : typedef unsigned long vm_flags_t;
438 :
439 : /*
440 : * A region containing a mapping of a non-memory backed file under NOMMU
441 : * conditions. These are held in a global tree and are pinned by the VMAs that
442 : * map parts of them.
443 : */
444 : struct vm_region {
445 : struct rb_node vm_rb; /* link in global region tree */
446 : vm_flags_t vm_flags; /* VMA vm_flags */
447 : unsigned long vm_start; /* start address of region */
448 : unsigned long vm_end; /* region initialised to here */
449 : unsigned long vm_top; /* region allocated to here */
450 : unsigned long vm_pgoff; /* the offset in vm_file corresponding to vm_start */
451 : struct file *vm_file; /* the backing file or NULL */
452 :
453 : int vm_usage; /* region usage count (access under nommu_region_sem) */
454 : bool vm_icache_flushed : 1; /* true if the icache has been flushed for
455 : * this region */
456 : };
457 :
458 : #ifdef CONFIG_USERFAULTFD
459 : #define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) { NULL, })
460 : struct vm_userfaultfd_ctx {
461 : struct userfaultfd_ctx *ctx;
462 : };
463 : #else /* CONFIG_USERFAULTFD */
464 : #define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) {})
465 : struct vm_userfaultfd_ctx {};
466 : #endif /* CONFIG_USERFAULTFD */
467 :
468 : struct anon_vma_name {
469 : struct kref kref;
470 : /* The name needs to be at the end because it is dynamically sized. */
471 : char name[];
472 : };
473 :
474 : struct vma_lock {
475 : struct rw_semaphore lock;
476 : };
477 :
478 : struct vma_numab_state {
479 : unsigned long next_scan;
480 : unsigned long next_pid_reset;
481 : unsigned long access_pids[2];
482 : };
483 :
484 : /*
485 : * This struct describes a virtual memory area. There is one of these
486 : * per VM-area/task. A VM area is any part of the process virtual memory
487 : * space that has a special rule for the page-fault handlers (ie a shared
488 : * library, the executable area etc).
489 : */
490 : struct vm_area_struct {
491 : /* The first cache line has the info for VMA tree walking. */
492 :
493 : union {
494 : struct {
495 : /* VMA covers [vm_start; vm_end) addresses within mm */
496 : unsigned long vm_start;
497 : unsigned long vm_end;
498 : };
499 : #ifdef CONFIG_PER_VMA_LOCK
500 : struct rcu_head vm_rcu; /* Used for deferred freeing. */
501 : #endif
502 : };
503 :
504 : struct mm_struct *vm_mm; /* The address space we belong to. */
505 : pgprot_t vm_page_prot; /* Access permissions of this VMA. */
506 :
507 : /*
508 : * Flags, see mm.h.
509 : * To modify use vm_flags_{init|reset|set|clear|mod} functions.
510 : */
511 : union {
512 : const vm_flags_t vm_flags;
513 : vm_flags_t __private __vm_flags;
514 : };
515 :
516 : #ifdef CONFIG_PER_VMA_LOCK
517 : int vm_lock_seq;
518 : struct vma_lock *vm_lock;
519 :
520 : /* Flag to indicate areas detached from the mm->mm_mt tree */
521 : bool detached;
522 : #endif
523 :
524 : /*
525 : * For areas with an address space and backing store,
526 : * linkage into the address_space->i_mmap interval tree.
527 : *
528 : */
529 : struct {
530 : struct rb_node rb;
531 : unsigned long rb_subtree_last;
532 : } shared;
533 :
534 : /*
535 : * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
536 : * list, after a COW of one of the file pages. A MAP_SHARED vma
537 : * can only be in the i_mmap tree. An anonymous MAP_PRIVATE, stack
538 : * or brk vma (with NULL file) can only be in an anon_vma list.
539 : */
540 : struct list_head anon_vma_chain; /* Serialized by mmap_lock &
541 : * page_table_lock */
542 : struct anon_vma *anon_vma; /* Serialized by page_table_lock */
543 :
544 : /* Function pointers to deal with this struct. */
545 : const struct vm_operations_struct *vm_ops;
546 :
547 : /* Information about our backing store: */
548 : unsigned long vm_pgoff; /* Offset (within vm_file) in PAGE_SIZE
549 : units */
550 : struct file * vm_file; /* File we map to (can be NULL). */
551 : void * vm_private_data; /* was vm_pte (shared mem) */
552 :
553 : #ifdef CONFIG_ANON_VMA_NAME
554 : /*
555 : * For private and shared anonymous mappings, a pointer to a null
556 : * terminated string containing the name given to the vma, or NULL if
557 : * unnamed. Serialized by mmap_lock. Use anon_vma_name to access.
558 : */
559 : struct anon_vma_name *anon_name;
560 : #endif
561 : #ifdef CONFIG_SWAP
562 : atomic_long_t swap_readahead_info;
563 : #endif
564 : #ifndef CONFIG_MMU
565 : struct vm_region *vm_region; /* NOMMU mapping region */
566 : #endif
567 : #ifdef CONFIG_NUMA
568 : struct mempolicy *vm_policy; /* NUMA policy for the VMA */
569 : #endif
570 : #ifdef CONFIG_NUMA_BALANCING
571 : struct vma_numab_state *numab_state; /* NUMA Balancing state */
572 : #endif
573 : struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
574 : } __randomize_layout;
575 :
576 : #ifdef CONFIG_SCHED_MM_CID
577 : struct mm_cid {
578 : u64 time;
579 : int cid;
580 : };
581 : #endif
582 :
583 : struct kioctx_table;
584 : struct mm_struct {
585 : struct {
586 : struct maple_tree mm_mt;
587 : #ifdef CONFIG_MMU
588 : unsigned long (*get_unmapped_area) (struct file *filp,
589 : unsigned long addr, unsigned long len,
590 : unsigned long pgoff, unsigned long flags);
591 : #endif
592 : unsigned long mmap_base; /* base of mmap area */
593 : unsigned long mmap_legacy_base; /* base of mmap area in bottom-up allocations */
594 : #ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
595 : /* Base addresses for compatible mmap() */
596 : unsigned long mmap_compat_base;
597 : unsigned long mmap_compat_legacy_base;
598 : #endif
599 : unsigned long task_size; /* size of task vm space */
600 : pgd_t * pgd;
601 :
602 : #ifdef CONFIG_MEMBARRIER
603 : /**
604 : * @membarrier_state: Flags controlling membarrier behavior.
605 : *
606 : * This field is close to @pgd to hopefully fit in the same
607 : * cache-line, which needs to be touched by switch_mm().
608 : */
609 : atomic_t membarrier_state;
610 : #endif
611 :
612 : /**
613 : * @mm_users: The number of users including userspace.
614 : *
615 : * Use mmget()/mmget_not_zero()/mmput() to modify. When this
616 : * drops to 0 (i.e. when the task exits and there are no other
617 : * temporary reference holders), we also release a reference on
618 : * @mm_count (which may then free the &struct mm_struct if
619 : * @mm_count also drops to 0).
620 : */
621 : atomic_t mm_users;
622 :
623 : /**
624 : * @mm_count: The number of references to &struct mm_struct
625 : * (@mm_users count as 1).
626 : *
627 : * Use mmgrab()/mmdrop() to modify. When this drops to 0, the
628 : * &struct mm_struct is freed.
629 : */
630 : atomic_t mm_count;
631 : #ifdef CONFIG_SCHED_MM_CID
632 : /**
633 : * @pcpu_cid: Per-cpu current cid.
634 : *
635 : * Keep track of the currently allocated mm_cid for each cpu.
636 : * The per-cpu mm_cid values are serialized by their respective
637 : * runqueue locks.
638 : */
639 : struct mm_cid __percpu *pcpu_cid;
640 : /*
641 : * @mm_cid_next_scan: Next mm_cid scan (in jiffies).
642 : *
643 : * When the next mm_cid scan is due (in jiffies).
644 : */
645 : unsigned long mm_cid_next_scan;
646 : #endif
647 : #ifdef CONFIG_MMU
648 : atomic_long_t pgtables_bytes; /* size of all page tables */
649 : #endif
650 : int map_count; /* number of VMAs */
651 :
652 : spinlock_t page_table_lock; /* Protects page tables and some
653 : * counters
654 : */
655 : /*
656 : * With some kernel config, the current mmap_lock's offset
657 : * inside 'mm_struct' is at 0x120, which is very optimal, as
658 : * its two hot fields 'count' and 'owner' sit in 2 different
659 : * cachelines, and when mmap_lock is highly contended, both
660 : * of the 2 fields will be accessed frequently, current layout
661 : * will help to reduce cache bouncing.
662 : *
663 : * So please be careful with adding new fields before
664 : * mmap_lock, which can easily push the 2 fields into one
665 : * cacheline.
666 : */
667 : struct rw_semaphore mmap_lock;
668 :
669 : struct list_head mmlist; /* List of maybe swapped mm's. These
670 : * are globally strung together off
671 : * init_mm.mmlist, and are protected
672 : * by mmlist_lock
673 : */
674 : #ifdef CONFIG_PER_VMA_LOCK
675 : int mm_lock_seq;
676 : #endif
677 :
678 :
679 : unsigned long hiwater_rss; /* High-watermark of RSS usage */
680 : unsigned long hiwater_vm; /* High-water virtual memory usage */
681 :
682 : unsigned long total_vm; /* Total pages mapped */
683 : unsigned long locked_vm; /* Pages that have PG_mlocked set */
684 : atomic64_t pinned_vm; /* Refcount permanently increased */
685 : unsigned long data_vm; /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
686 : unsigned long exec_vm; /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
687 : unsigned long stack_vm; /* VM_STACK */
688 : unsigned long def_flags;
689 :
690 : /**
691 : * @write_protect_seq: Locked when any thread is write
692 : * protecting pages mapped by this mm to enforce a later COW,
693 : * for instance during page table copying for fork().
694 : */
695 : seqcount_t write_protect_seq;
696 :
697 : spinlock_t arg_lock; /* protect the below fields */
698 :
699 : unsigned long start_code, end_code, start_data, end_data;
700 : unsigned long start_brk, brk, start_stack;
701 : unsigned long arg_start, arg_end, env_start, env_end;
702 :
703 : unsigned long saved_auxv[AT_VECTOR_SIZE]; /* for /proc/PID/auxv */
704 :
705 : struct percpu_counter rss_stat[NR_MM_COUNTERS];
706 :
707 : struct linux_binfmt *binfmt;
708 :
709 : /* Architecture-specific MM context */
710 : mm_context_t context;
711 :
712 : unsigned long flags; /* Must use atomic bitops to access */
713 :
714 : #ifdef CONFIG_AIO
715 : spinlock_t ioctx_lock;
716 : struct kioctx_table __rcu *ioctx_table;
717 : #endif
718 : #ifdef CONFIG_MEMCG
719 : /*
720 : * "owner" points to a task that is regarded as the canonical
721 : * user/owner of this mm. All of the following must be true in
722 : * order for it to be changed:
723 : *
724 : * current == mm->owner
725 : * current->mm != mm
726 : * new_owner->mm == mm
727 : * new_owner->alloc_lock is held
728 : */
729 : struct task_struct __rcu *owner;
730 : #endif
731 : struct user_namespace *user_ns;
732 :
733 : /* store ref to file /proc/<pid>/exe symlink points to */
734 : struct file __rcu *exe_file;
735 : #ifdef CONFIG_MMU_NOTIFIER
736 : struct mmu_notifier_subscriptions *notifier_subscriptions;
737 : #endif
738 : #if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
739 : pgtable_t pmd_huge_pte; /* protected by page_table_lock */
740 : #endif
741 : #ifdef CONFIG_NUMA_BALANCING
742 : /*
743 : * numa_next_scan is the next time that PTEs will be remapped
744 : * PROT_NONE to trigger NUMA hinting faults; such faults gather
745 : * statistics and migrate pages to new nodes if necessary.
746 : */
747 : unsigned long numa_next_scan;
748 :
749 : /* Restart point for scanning and remapping PTEs. */
750 : unsigned long numa_scan_offset;
751 :
752 : /* numa_scan_seq prevents two threads remapping PTEs. */
753 : int numa_scan_seq;
754 : #endif
755 : /*
756 : * An operation with batched TLB flushing is going on. Anything
757 : * that can move process memory needs to flush the TLB when
758 : * moving a PROT_NONE mapped page.
759 : */
760 : atomic_t tlb_flush_pending;
761 : #ifdef CONFIG_ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
762 : /* See flush_tlb_batched_pending() */
763 : atomic_t tlb_flush_batched;
764 : #endif
765 : struct uprobes_state uprobes_state;
766 : #ifdef CONFIG_PREEMPT_RT
767 : struct rcu_head delayed_drop;
768 : #endif
769 : #ifdef CONFIG_HUGETLB_PAGE
770 : atomic_long_t hugetlb_usage;
771 : #endif
772 : struct work_struct async_put_work;
773 :
774 : #ifdef CONFIG_IOMMU_SVA
775 : u32 pasid;
776 : #endif
777 : #ifdef CONFIG_KSM
778 : /*
779 : * Represent how many pages of this process are involved in KSM
780 : * merging.
781 : */
782 : unsigned long ksm_merging_pages;
783 : /*
784 : * Represent how many pages are checked for ksm merging
785 : * including merged and not merged.
786 : */
787 : unsigned long ksm_rmap_items;
788 : #endif
789 : #ifdef CONFIG_LRU_GEN
790 : struct {
791 : /* this mm_struct is on lru_gen_mm_list */
792 : struct list_head list;
793 : /*
794 : * Set when switching to this mm_struct, as a hint of
795 : * whether it has been used since the last time per-node
796 : * page table walkers cleared the corresponding bits.
797 : */
798 : unsigned long bitmap;
799 : #ifdef CONFIG_MEMCG
800 : /* points to the memcg of "owner" above */
801 : struct mem_cgroup *memcg;
802 : #endif
803 : } lru_gen;
804 : #endif /* CONFIG_LRU_GEN */
805 : } __randomize_layout;
806 :
807 : /*
808 : * The mm_cpumask needs to be at the end of mm_struct, because it
809 : * is dynamically sized based on nr_cpu_ids.
810 : */
811 : unsigned long cpu_bitmap[];
812 : };
813 :
814 : #define MM_MT_FLAGS (MT_FLAGS_ALLOC_RANGE | MT_FLAGS_LOCK_EXTERN | \
815 : MT_FLAGS_USE_RCU)
816 : extern struct mm_struct init_mm;
817 :
818 : /* Pointer magic because the dynamic array size confuses some compilers. */
819 : static inline void mm_init_cpumask(struct mm_struct *mm)
820 : {
821 0 : unsigned long cpu_bitmap = (unsigned long)mm;
822 :
823 0 : cpu_bitmap += offsetof(struct mm_struct, cpu_bitmap);
824 0 : cpumask_clear((struct cpumask *)cpu_bitmap);
825 : }
826 :
827 : /* Future-safe accessor for struct mm_struct's cpu_vm_mask. */
828 : static inline cpumask_t *mm_cpumask(struct mm_struct *mm)
829 : {
830 : return (struct cpumask *)&mm->cpu_bitmap;
831 : }
832 :
833 : #ifdef CONFIG_LRU_GEN
834 :
835 : struct lru_gen_mm_list {
836 : /* mm_struct list for page table walkers */
837 : struct list_head fifo;
838 : /* protects the list above */
839 : spinlock_t lock;
840 : };
841 :
842 : void lru_gen_add_mm(struct mm_struct *mm);
843 : void lru_gen_del_mm(struct mm_struct *mm);
844 : #ifdef CONFIG_MEMCG
845 : void lru_gen_migrate_mm(struct mm_struct *mm);
846 : #endif
847 :
848 : static inline void lru_gen_init_mm(struct mm_struct *mm)
849 : {
850 : INIT_LIST_HEAD(&mm->lru_gen.list);
851 : mm->lru_gen.bitmap = 0;
852 : #ifdef CONFIG_MEMCG
853 : mm->lru_gen.memcg = NULL;
854 : #endif
855 : }
856 :
857 : static inline void lru_gen_use_mm(struct mm_struct *mm)
858 : {
859 : /*
860 : * When the bitmap is set, page reclaim knows this mm_struct has been
861 : * used since the last time it cleared the bitmap. So it might be worth
862 : * walking the page tables of this mm_struct to clear the accessed bit.
863 : */
864 : WRITE_ONCE(mm->lru_gen.bitmap, -1);
865 : }
866 :
867 : #else /* !CONFIG_LRU_GEN */
868 :
869 : static inline void lru_gen_add_mm(struct mm_struct *mm)
870 : {
871 : }
872 :
873 : static inline void lru_gen_del_mm(struct mm_struct *mm)
874 : {
875 : }
876 :
877 : #ifdef CONFIG_MEMCG
878 : static inline void lru_gen_migrate_mm(struct mm_struct *mm)
879 : {
880 : }
881 : #endif
882 :
883 : static inline void lru_gen_init_mm(struct mm_struct *mm)
884 : {
885 : }
886 :
887 : static inline void lru_gen_use_mm(struct mm_struct *mm)
888 : {
889 : }
890 :
891 : #endif /* CONFIG_LRU_GEN */
892 :
893 : struct vma_iterator {
894 : struct ma_state mas;
895 : };
896 :
897 : #define VMA_ITERATOR(name, __mm, __addr) \
898 : struct vma_iterator name = { \
899 : .mas = { \
900 : .tree = &(__mm)->mm_mt, \
901 : .index = __addr, \
902 : .node = MAS_START, \
903 : }, \
904 : }
905 :
906 : static inline void vma_iter_init(struct vma_iterator *vmi,
907 : struct mm_struct *mm, unsigned long addr)
908 : {
909 0 : mas_init(&vmi->mas, &mm->mm_mt, addr);
910 : }
911 :
912 : #ifdef CONFIG_SCHED_MM_CID
913 :
914 : enum mm_cid_state {
915 : MM_CID_UNSET = -1U, /* Unset state has lazy_put flag set. */
916 : MM_CID_LAZY_PUT = (1U << 31),
917 : };
918 :
919 : static inline bool mm_cid_is_unset(int cid)
920 : {
921 : return cid == MM_CID_UNSET;
922 : }
923 :
924 : static inline bool mm_cid_is_lazy_put(int cid)
925 : {
926 : return !mm_cid_is_unset(cid) && (cid & MM_CID_LAZY_PUT);
927 : }
928 :
929 : static inline bool mm_cid_is_valid(int cid)
930 : {
931 : return !(cid & MM_CID_LAZY_PUT);
932 : }
933 :
934 : static inline int mm_cid_set_lazy_put(int cid)
935 : {
936 : return cid | MM_CID_LAZY_PUT;
937 : }
938 :
939 : static inline int mm_cid_clear_lazy_put(int cid)
940 : {
941 : return cid & ~MM_CID_LAZY_PUT;
942 : }
943 :
944 : /* Accessor for struct mm_struct's cidmask. */
945 : static inline cpumask_t *mm_cidmask(struct mm_struct *mm)
946 : {
947 : unsigned long cid_bitmap = (unsigned long)mm;
948 :
949 : cid_bitmap += offsetof(struct mm_struct, cpu_bitmap);
950 : /* Skip cpu_bitmap */
951 : cid_bitmap += cpumask_size();
952 : return (struct cpumask *)cid_bitmap;
953 : }
954 :
955 : static inline void mm_init_cid(struct mm_struct *mm)
956 : {
957 : int i;
958 :
959 : for_each_possible_cpu(i) {
960 : struct mm_cid *pcpu_cid = per_cpu_ptr(mm->pcpu_cid, i);
961 :
962 : pcpu_cid->cid = MM_CID_UNSET;
963 : pcpu_cid->time = 0;
964 : }
965 : cpumask_clear(mm_cidmask(mm));
966 : }
967 :
968 : static inline int mm_alloc_cid(struct mm_struct *mm)
969 : {
970 : mm->pcpu_cid = alloc_percpu(struct mm_cid);
971 : if (!mm->pcpu_cid)
972 : return -ENOMEM;
973 : mm_init_cid(mm);
974 : return 0;
975 : }
976 :
977 : static inline void mm_destroy_cid(struct mm_struct *mm)
978 : {
979 : free_percpu(mm->pcpu_cid);
980 : mm->pcpu_cid = NULL;
981 : }
982 :
983 : static inline unsigned int mm_cid_size(void)
984 : {
985 : return cpumask_size();
986 : }
987 : #else /* CONFIG_SCHED_MM_CID */
988 : static inline void mm_init_cid(struct mm_struct *mm) { }
989 : static inline int mm_alloc_cid(struct mm_struct *mm) { return 0; }
990 : static inline void mm_destroy_cid(struct mm_struct *mm) { }
991 : static inline unsigned int mm_cid_size(void)
992 : {
993 : return 0;
994 : }
995 : #endif /* CONFIG_SCHED_MM_CID */
996 :
997 : struct mmu_gather;
998 : extern void tlb_gather_mmu(struct mmu_gather *tlb, struct mm_struct *mm);
999 : extern void tlb_gather_mmu_fullmm(struct mmu_gather *tlb, struct mm_struct *mm);
1000 : extern void tlb_finish_mmu(struct mmu_gather *tlb);
1001 :
1002 : struct vm_fault;
1003 :
1004 : /**
1005 : * typedef vm_fault_t - Return type for page fault handlers.
1006 : *
1007 : * Page fault handlers return a bitmask of %VM_FAULT values.
1008 : */
1009 : typedef __bitwise unsigned int vm_fault_t;
1010 :
1011 : /**
1012 : * enum vm_fault_reason - Page fault handlers return a bitmask of
1013 : * these values to tell the core VM what happened when handling the
1014 : * fault. Used to decide whether a process gets delivered SIGBUS or
1015 : * just gets major/minor fault counters bumped up.
1016 : *
1017 : * @VM_FAULT_OOM: Out Of Memory
1018 : * @VM_FAULT_SIGBUS: Bad access
1019 : * @VM_FAULT_MAJOR: Page read from storage
1020 : * @VM_FAULT_HWPOISON: Hit poisoned small page
1021 : * @VM_FAULT_HWPOISON_LARGE: Hit poisoned large page. Index encoded
1022 : * in upper bits
1023 : * @VM_FAULT_SIGSEGV: segmentation fault
1024 : * @VM_FAULT_NOPAGE: ->fault installed the pte, not return page
1025 : * @VM_FAULT_LOCKED: ->fault locked the returned page
1026 : * @VM_FAULT_RETRY: ->fault blocked, must retry
1027 : * @VM_FAULT_FALLBACK: huge page fault failed, fall back to small
1028 : * @VM_FAULT_DONE_COW: ->fault has fully handled COW
1029 : * @VM_FAULT_NEEDDSYNC: ->fault did not modify page tables and needs
1030 : * fsync() to complete (for synchronous page faults
1031 : * in DAX)
1032 : * @VM_FAULT_COMPLETED: ->fault completed, meanwhile mmap lock released
1033 : * @VM_FAULT_HINDEX_MASK: mask HINDEX value
1034 : *
1035 : */
1036 : enum vm_fault_reason {
1037 : VM_FAULT_OOM = (__force vm_fault_t)0x000001,
1038 : VM_FAULT_SIGBUS = (__force vm_fault_t)0x000002,
1039 : VM_FAULT_MAJOR = (__force vm_fault_t)0x000004,
1040 : VM_FAULT_HWPOISON = (__force vm_fault_t)0x000010,
1041 : VM_FAULT_HWPOISON_LARGE = (__force vm_fault_t)0x000020,
1042 : VM_FAULT_SIGSEGV = (__force vm_fault_t)0x000040,
1043 : VM_FAULT_NOPAGE = (__force vm_fault_t)0x000100,
1044 : VM_FAULT_LOCKED = (__force vm_fault_t)0x000200,
1045 : VM_FAULT_RETRY = (__force vm_fault_t)0x000400,
1046 : VM_FAULT_FALLBACK = (__force vm_fault_t)0x000800,
1047 : VM_FAULT_DONE_COW = (__force vm_fault_t)0x001000,
1048 : VM_FAULT_NEEDDSYNC = (__force vm_fault_t)0x002000,
1049 : VM_FAULT_COMPLETED = (__force vm_fault_t)0x004000,
1050 : VM_FAULT_HINDEX_MASK = (__force vm_fault_t)0x0f0000,
1051 : };
1052 :
1053 : /* Encode hstate index for a hwpoisoned large page */
1054 : #define VM_FAULT_SET_HINDEX(x) ((__force vm_fault_t)((x) << 16))
1055 : #define VM_FAULT_GET_HINDEX(x) (((__force unsigned int)(x) >> 16) & 0xf)
1056 :
1057 : #define VM_FAULT_ERROR (VM_FAULT_OOM | VM_FAULT_SIGBUS | \
1058 : VM_FAULT_SIGSEGV | VM_FAULT_HWPOISON | \
1059 : VM_FAULT_HWPOISON_LARGE | VM_FAULT_FALLBACK)
1060 :
1061 : #define VM_FAULT_RESULT_TRACE \
1062 : { VM_FAULT_OOM, "OOM" }, \
1063 : { VM_FAULT_SIGBUS, "SIGBUS" }, \
1064 : { VM_FAULT_MAJOR, "MAJOR" }, \
1065 : { VM_FAULT_HWPOISON, "HWPOISON" }, \
1066 : { VM_FAULT_HWPOISON_LARGE, "HWPOISON_LARGE" }, \
1067 : { VM_FAULT_SIGSEGV, "SIGSEGV" }, \
1068 : { VM_FAULT_NOPAGE, "NOPAGE" }, \
1069 : { VM_FAULT_LOCKED, "LOCKED" }, \
1070 : { VM_FAULT_RETRY, "RETRY" }, \
1071 : { VM_FAULT_FALLBACK, "FALLBACK" }, \
1072 : { VM_FAULT_DONE_COW, "DONE_COW" }, \
1073 : { VM_FAULT_NEEDDSYNC, "NEEDDSYNC" }
1074 :
1075 : struct vm_special_mapping {
1076 : const char *name; /* The name, e.g. "[vdso]". */
1077 :
1078 : /*
1079 : * If .fault is not provided, this points to a
1080 : * NULL-terminated array of pages that back the special mapping.
1081 : *
1082 : * This must not be NULL unless .fault is provided.
1083 : */
1084 : struct page **pages;
1085 :
1086 : /*
1087 : * If non-NULL, then this is called to resolve page faults
1088 : * on the special mapping. If used, .pages is not checked.
1089 : */
1090 : vm_fault_t (*fault)(const struct vm_special_mapping *sm,
1091 : struct vm_area_struct *vma,
1092 : struct vm_fault *vmf);
1093 :
1094 : int (*mremap)(const struct vm_special_mapping *sm,
1095 : struct vm_area_struct *new_vma);
1096 : };
1097 :
1098 : enum tlb_flush_reason {
1099 : TLB_FLUSH_ON_TASK_SWITCH,
1100 : TLB_REMOTE_SHOOTDOWN,
1101 : TLB_LOCAL_SHOOTDOWN,
1102 : TLB_LOCAL_MM_SHOOTDOWN,
1103 : TLB_REMOTE_SEND_IPI,
1104 : NR_TLB_FLUSH_REASONS,
1105 : };
1106 :
1107 : /*
1108 : * A swap entry has to fit into a "unsigned long", as the entry is hidden
1109 : * in the "index" field of the swapper address space.
1110 : */
1111 : typedef struct {
1112 : unsigned long val;
1113 : } swp_entry_t;
1114 :
1115 : /**
1116 : * enum fault_flag - Fault flag definitions.
1117 : * @FAULT_FLAG_WRITE: Fault was a write fault.
1118 : * @FAULT_FLAG_MKWRITE: Fault was mkwrite of existing PTE.
1119 : * @FAULT_FLAG_ALLOW_RETRY: Allow to retry the fault if blocked.
1120 : * @FAULT_FLAG_RETRY_NOWAIT: Don't drop mmap_lock and wait when retrying.
1121 : * @FAULT_FLAG_KILLABLE: The fault task is in SIGKILL killable region.
1122 : * @FAULT_FLAG_TRIED: The fault has been tried once.
1123 : * @FAULT_FLAG_USER: The fault originated in userspace.
1124 : * @FAULT_FLAG_REMOTE: The fault is not for current task/mm.
1125 : * @FAULT_FLAG_INSTRUCTION: The fault was during an instruction fetch.
1126 : * @FAULT_FLAG_INTERRUPTIBLE: The fault can be interrupted by non-fatal signals.
1127 : * @FAULT_FLAG_UNSHARE: The fault is an unsharing request to break COW in a
1128 : * COW mapping, making sure that an exclusive anon page is
1129 : * mapped after the fault.
1130 : * @FAULT_FLAG_ORIG_PTE_VALID: whether the fault has vmf->orig_pte cached.
1131 : * We should only access orig_pte if this flag set.
1132 : * @FAULT_FLAG_VMA_LOCK: The fault is handled under VMA lock.
1133 : *
1134 : * About @FAULT_FLAG_ALLOW_RETRY and @FAULT_FLAG_TRIED: we can specify
1135 : * whether we would allow page faults to retry by specifying these two
1136 : * fault flags correctly. Currently there can be three legal combinations:
1137 : *
1138 : * (a) ALLOW_RETRY and !TRIED: this means the page fault allows retry, and
1139 : * this is the first try
1140 : *
1141 : * (b) ALLOW_RETRY and TRIED: this means the page fault allows retry, and
1142 : * we've already tried at least once
1143 : *
1144 : * (c) !ALLOW_RETRY and !TRIED: this means the page fault does not allow retry
1145 : *
1146 : * The unlisted combination (!ALLOW_RETRY && TRIED) is illegal and should never
1147 : * be used. Note that page faults can be allowed to retry for multiple times,
1148 : * in which case we'll have an initial fault with flags (a) then later on
1149 : * continuous faults with flags (b). We should always try to detect pending
1150 : * signals before a retry to make sure the continuous page faults can still be
1151 : * interrupted if necessary.
1152 : *
1153 : * The combination FAULT_FLAG_WRITE|FAULT_FLAG_UNSHARE is illegal.
1154 : * FAULT_FLAG_UNSHARE is ignored and treated like an ordinary read fault when
1155 : * applied to mappings that are not COW mappings.
1156 : */
1157 : enum fault_flag {
1158 : FAULT_FLAG_WRITE = 1 << 0,
1159 : FAULT_FLAG_MKWRITE = 1 << 1,
1160 : FAULT_FLAG_ALLOW_RETRY = 1 << 2,
1161 : FAULT_FLAG_RETRY_NOWAIT = 1 << 3,
1162 : FAULT_FLAG_KILLABLE = 1 << 4,
1163 : FAULT_FLAG_TRIED = 1 << 5,
1164 : FAULT_FLAG_USER = 1 << 6,
1165 : FAULT_FLAG_REMOTE = 1 << 7,
1166 : FAULT_FLAG_INSTRUCTION = 1 << 8,
1167 : FAULT_FLAG_INTERRUPTIBLE = 1 << 9,
1168 : FAULT_FLAG_UNSHARE = 1 << 10,
1169 : FAULT_FLAG_ORIG_PTE_VALID = 1 << 11,
1170 : FAULT_FLAG_VMA_LOCK = 1 << 12,
1171 : };
1172 :
1173 : typedef unsigned int __bitwise zap_flags_t;
1174 :
1175 : /*
1176 : * FOLL_PIN and FOLL_LONGTERM may be used in various combinations with each
1177 : * other. Here is what they mean, and how to use them:
1178 : *
1179 : *
1180 : * FIXME: For pages which are part of a filesystem, mappings are subject to the
1181 : * lifetime enforced by the filesystem and we need guarantees that longterm
1182 : * users like RDMA and V4L2 only establish mappings which coordinate usage with
1183 : * the filesystem. Ideas for this coordination include revoking the longterm
1184 : * pin, delaying writeback, bounce buffer page writeback, etc. As FS DAX was
1185 : * added after the problem with filesystems was found FS DAX VMAs are
1186 : * specifically failed. Filesystem pages are still subject to bugs and use of
1187 : * FOLL_LONGTERM should be avoided on those pages.
1188 : *
1189 : * In the CMA case: long term pins in a CMA region would unnecessarily fragment
1190 : * that region. And so, CMA attempts to migrate the page before pinning, when
1191 : * FOLL_LONGTERM is specified.
1192 : *
1193 : * FOLL_PIN indicates that a special kind of tracking (not just page->_refcount,
1194 : * but an additional pin counting system) will be invoked. This is intended for
1195 : * anything that gets a page reference and then touches page data (for example,
1196 : * Direct IO). This lets the filesystem know that some non-file-system entity is
1197 : * potentially changing the pages' data. In contrast to FOLL_GET (whose pages
1198 : * are released via put_page()), FOLL_PIN pages must be released, ultimately, by
1199 : * a call to unpin_user_page().
1200 : *
1201 : * FOLL_PIN is similar to FOLL_GET: both of these pin pages. They use different
1202 : * and separate refcounting mechanisms, however, and that means that each has
1203 : * its own acquire and release mechanisms:
1204 : *
1205 : * FOLL_GET: get_user_pages*() to acquire, and put_page() to release.
1206 : *
1207 : * FOLL_PIN: pin_user_pages*() to acquire, and unpin_user_pages to release.
1208 : *
1209 : * FOLL_PIN and FOLL_GET are mutually exclusive for a given function call.
1210 : * (The underlying pages may experience both FOLL_GET-based and FOLL_PIN-based
1211 : * calls applied to them, and that's perfectly OK. This is a constraint on the
1212 : * callers, not on the pages.)
1213 : *
1214 : * FOLL_PIN should be set internally by the pin_user_pages*() APIs, never
1215 : * directly by the caller. That's in order to help avoid mismatches when
1216 : * releasing pages: get_user_pages*() pages must be released via put_page(),
1217 : * while pin_user_pages*() pages must be released via unpin_user_page().
1218 : *
1219 : * Please see Documentation/core-api/pin_user_pages.rst for more information.
1220 : */
1221 :
1222 : enum {
1223 : /* check pte is writable */
1224 : FOLL_WRITE = 1 << 0,
1225 : /* do get_page on page */
1226 : FOLL_GET = 1 << 1,
1227 : /* give error on hole if it would be zero */
1228 : FOLL_DUMP = 1 << 2,
1229 : /* get_user_pages read/write w/o permission */
1230 : FOLL_FORCE = 1 << 3,
1231 : /*
1232 : * if a disk transfer is needed, start the IO and return without waiting
1233 : * upon it
1234 : */
1235 : FOLL_NOWAIT = 1 << 4,
1236 : /* do not fault in pages */
1237 : FOLL_NOFAULT = 1 << 5,
1238 : /* check page is hwpoisoned */
1239 : FOLL_HWPOISON = 1 << 6,
1240 : /* don't do file mappings */
1241 : FOLL_ANON = 1 << 7,
1242 : /*
1243 : * FOLL_LONGTERM indicates that the page will be held for an indefinite
1244 : * time period _often_ under userspace control. This is in contrast to
1245 : * iov_iter_get_pages(), whose usages are transient.
1246 : */
1247 : FOLL_LONGTERM = 1 << 8,
1248 : /* split huge pmd before returning */
1249 : FOLL_SPLIT_PMD = 1 << 9,
1250 : /* allow returning PCI P2PDMA pages */
1251 : FOLL_PCI_P2PDMA = 1 << 10,
1252 : /* allow interrupts from generic signals */
1253 : FOLL_INTERRUPTIBLE = 1 << 11,
1254 :
1255 : /* See also internal only FOLL flags in mm/internal.h */
1256 : };
1257 :
1258 : #endif /* _LINUX_MM_TYPES_H */
|
