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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_SCHED_MM_H
3#define _LINUX_SCHED_MM_H
4
5#include <linux/kernel.h>
6#include <linux/atomic.h>
7#include <linux/sched.h>
8#include <linux/mm_types.h>
9#include <linux/gfp.h>
10#include <linux/sync_core.h>
11#include <linux/sched/coredump.h>
12
13/*
14 * Routines for handling mm_structs
15 */
16extern struct mm_struct *mm_alloc(void);
17
18/**
19 * mmgrab() - Pin a &struct mm_struct.
20 * @mm: The &struct mm_struct to pin.
21 *
22 * Make sure that @mm will not get freed even after the owning task
23 * exits. This doesn't guarantee that the associated address space
24 * will still exist later on and mmget_not_zero() has to be used before
25 * accessing it.
26 *
27 * This is a preferred way to pin @mm for a longer/unbounded amount
28 * of time.
29 *
30 * Use mmdrop() to release the reference acquired by mmgrab().
31 *
32 * See also <Documentation/mm/active_mm.rst> for an in-depth explanation
33 * of &mm_struct.mm_count vs &mm_struct.mm_users.
34 */
35static inline void mmgrab(struct mm_struct *mm)
36{
37 atomic_inc(v: &mm->mm_count);
38}
39
40static inline void smp_mb__after_mmgrab(void)
41{
42 smp_mb__after_atomic();
43}
44
45extern void __mmdrop(struct mm_struct *mm);
46
47static inline void mmdrop(struct mm_struct *mm)
48{
49 /*
50 * The implicit full barrier implied by atomic_dec_and_test() is
51 * required by the membarrier system call before returning to
52 * user-space, after storing to rq->curr.
53 */
54 if (unlikely(atomic_dec_and_test(&mm->mm_count)))
55 __mmdrop(mm);
56}
57
58#ifdef CONFIG_PREEMPT_RT
59/*
60 * RCU callback for delayed mm drop. Not strictly RCU, but call_rcu() is
61 * by far the least expensive way to do that.
62 */
63static inline void __mmdrop_delayed(struct rcu_head *rhp)
64{
65 struct mm_struct *mm = container_of(rhp, struct mm_struct, delayed_drop);
66
67 __mmdrop(mm);
68}
69
70/*
71 * Invoked from finish_task_switch(). Delegates the heavy lifting on RT
72 * kernels via RCU.
73 */
74static inline void mmdrop_sched(struct mm_struct *mm)
75{
76 /* Provides a full memory barrier. See mmdrop() */
77 if (atomic_dec_and_test(&mm->mm_count))
78 call_rcu(&mm->delayed_drop, __mmdrop_delayed);
79}
80#else
81static inline void mmdrop_sched(struct mm_struct *mm)
82{
83 mmdrop(mm);
84}
85#endif
86
87/* Helpers for lazy TLB mm refcounting */
88static inline void mmgrab_lazy_tlb(struct mm_struct *mm)
89{
90 if (IS_ENABLED(CONFIG_MMU_LAZY_TLB_REFCOUNT))
91 mmgrab(mm);
92}
93
94static inline void mmdrop_lazy_tlb(struct mm_struct *mm)
95{
96 if (IS_ENABLED(CONFIG_MMU_LAZY_TLB_REFCOUNT)) {
97 mmdrop(mm);
98 } else {
99 /*
100 * mmdrop_lazy_tlb must provide a full memory barrier, see the
101 * membarrier comment finish_task_switch which relies on this.
102 */
103 smp_mb();
104 }
105}
106
107static inline void mmdrop_lazy_tlb_sched(struct mm_struct *mm)
108{
109 if (IS_ENABLED(CONFIG_MMU_LAZY_TLB_REFCOUNT))
110 mmdrop_sched(mm);
111 else
112 smp_mb(); /* see mmdrop_lazy_tlb() above */
113}
114
115/**
116 * mmget() - Pin the address space associated with a &struct mm_struct.
117 * @mm: The address space to pin.
118 *
119 * Make sure that the address space of the given &struct mm_struct doesn't
120 * go away. This does not protect against parts of the address space being
121 * modified or freed, however.
122 *
123 * Never use this function to pin this address space for an
124 * unbounded/indefinite amount of time.
125 *
126 * Use mmput() to release the reference acquired by mmget().
127 *
128 * See also <Documentation/mm/active_mm.rst> for an in-depth explanation
129 * of &mm_struct.mm_count vs &mm_struct.mm_users.
130 */
131static inline void mmget(struct mm_struct *mm)
132{
133 atomic_inc(v: &mm->mm_users);
134}
135
136static inline bool mmget_not_zero(struct mm_struct *mm)
137{
138 return atomic_inc_not_zero(v: &mm->mm_users);
139}
140
141/* mmput gets rid of the mappings and all user-space */
142extern void mmput(struct mm_struct *);
143#if defined(CONFIG_MMU) || defined(CONFIG_FUTEX_PRIVATE_HASH)
144/* same as above but performs the slow path from the async context. Can
145 * be called from the atomic context as well
146 */
147void mmput_async(struct mm_struct *);
148#endif
149
150/* Grab a reference to a task's mm, if it is not already going away */
151extern struct mm_struct *get_task_mm(struct task_struct *task);
152/*
153 * Grab a reference to a task's mm, if it is not already going away
154 * and ptrace_may_access with the mode parameter passed to it
155 * succeeds.
156 */
157extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode);
158/* Remove the current tasks stale references to the old mm_struct on exit() */
159extern void exit_mm_release(struct task_struct *, struct mm_struct *);
160/* Remove the current tasks stale references to the old mm_struct on exec() */
161extern void exec_mm_release(struct task_struct *, struct mm_struct *);
162
163#ifdef CONFIG_MEMCG
164extern void mm_update_next_owner(struct mm_struct *mm);
165#else
166static inline void mm_update_next_owner(struct mm_struct *mm)
167{
168}
169#endif /* CONFIG_MEMCG */
170
171#ifdef CONFIG_MMU
172#ifndef arch_get_mmap_end
173#define arch_get_mmap_end(addr, len, flags) (TASK_SIZE)
174#endif
175
176#ifndef arch_get_mmap_base
177#define arch_get_mmap_base(addr, base) (base)
178#endif
179
180extern void arch_pick_mmap_layout(struct mm_struct *mm,
181 const struct rlimit *rlim_stack);
182
183unsigned long
184arch_get_unmapped_area(struct file *filp, unsigned long addr,
185 unsigned long len, unsigned long pgoff,
186 unsigned long flags, vm_flags_t vm_flags);
187unsigned long
188arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
189 unsigned long len, unsigned long pgoff,
190 unsigned long flags, vm_flags_t);
191
192unsigned long mm_get_unmapped_area(struct file *filp, unsigned long addr,
193 unsigned long len, unsigned long pgoff,
194 unsigned long flags);
195
196unsigned long mm_get_unmapped_area_vmflags(struct file *filp,
197 unsigned long addr,
198 unsigned long len,
199 unsigned long pgoff,
200 unsigned long flags,
201 vm_flags_t vm_flags);
202
203unsigned long
204generic_get_unmapped_area(struct file *filp, unsigned long addr,
205 unsigned long len, unsigned long pgoff,
206 unsigned long flags, vm_flags_t vm_flags);
207unsigned long
208generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
209 unsigned long len, unsigned long pgoff,
210 unsigned long flags, vm_flags_t vm_flags);
211#else
212static inline void arch_pick_mmap_layout(struct mm_struct *mm,
213 const struct rlimit *rlim_stack) {}
214#endif
215
216static inline bool in_vfork(struct task_struct *tsk)
217{
218 bool ret;
219
220 /*
221 * need RCU to access ->real_parent if CLONE_VM was used along with
222 * CLONE_PARENT.
223 *
224 * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
225 * imply CLONE_VM
226 *
227 * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
228 * ->real_parent is not necessarily the task doing vfork(), so in
229 * theory we can't rely on task_lock() if we want to dereference it.
230 *
231 * And in this case we can't trust the real_parent->mm == tsk->mm
232 * check, it can be false negative. But we do not care, if init or
233 * another oom-unkillable task does this it should blame itself.
234 */
235 rcu_read_lock();
236 ret = tsk->vfork_done &&
237 rcu_dereference(tsk->real_parent)->mm == tsk->mm;
238 rcu_read_unlock();
239
240 return ret;
241}
242
243/*
244 * Applies per-task gfp context to the given allocation flags.
245 * PF_MEMALLOC_NOIO implies GFP_NOIO
246 * PF_MEMALLOC_NOFS implies GFP_NOFS
247 * PF_MEMALLOC_PIN implies !GFP_MOVABLE
248 */
249static inline gfp_t current_gfp_context(gfp_t flags)
250{
251 unsigned int pflags = READ_ONCE(current->flags);
252
253 if (unlikely(pflags & (PF_MEMALLOC_NOIO | PF_MEMALLOC_NOFS | PF_MEMALLOC_PIN))) {
254 /*
255 * NOIO implies both NOIO and NOFS and it is a weaker context
256 * so always make sure it makes precedence
257 */
258 if (pflags & PF_MEMALLOC_NOIO)
259 flags &= ~(__GFP_IO | __GFP_FS);
260 else if (pflags & PF_MEMALLOC_NOFS)
261 flags &= ~__GFP_FS;
262
263 if (pflags & PF_MEMALLOC_PIN)
264 flags &= ~__GFP_MOVABLE;
265 }
266 return flags;
267}
268
269#ifdef CONFIG_LOCKDEP
270extern void __fs_reclaim_acquire(unsigned long ip);
271extern void __fs_reclaim_release(unsigned long ip);
272extern void fs_reclaim_acquire(gfp_t gfp_mask);
273extern void fs_reclaim_release(gfp_t gfp_mask);
274#else
275static inline void __fs_reclaim_acquire(unsigned long ip) { }
276static inline void __fs_reclaim_release(unsigned long ip) { }
277static inline void fs_reclaim_acquire(gfp_t gfp_mask) { }
278static inline void fs_reclaim_release(gfp_t gfp_mask) { }
279#endif
280
281/* Any memory-allocation retry loop should use
282 * memalloc_retry_wait(), and pass the flags for the most
283 * constrained allocation attempt that might have failed.
284 * This provides useful documentation of where loops are,
285 * and a central place to fine tune the waiting as the MM
286 * implementation changes.
287 */
288static inline void memalloc_retry_wait(gfp_t gfp_flags)
289{
290 /* We use io_schedule_timeout because waiting for memory
291 * typically included waiting for dirty pages to be
292 * written out, which requires IO.
293 */
294 __set_current_state(TASK_UNINTERRUPTIBLE);
295 gfp_flags = current_gfp_context(flags: gfp_flags);
296 if (gfpflags_allow_blocking(gfp_flags) &&
297 !(gfp_flags & __GFP_NORETRY))
298 /* Probably waited already, no need for much more */
299 io_schedule_timeout(timeout: 1);
300 else
301 /* Probably didn't wait, and has now released a lock,
302 * so now is a good time to wait
303 */
304 io_schedule_timeout(HZ/50);
305}
306
307/**
308 * might_alloc - Mark possible allocation sites
309 * @gfp_mask: gfp_t flags that would be used to allocate
310 *
311 * Similar to might_sleep() and other annotations, this can be used in functions
312 * that might allocate, but often don't. Compiles to nothing without
313 * CONFIG_LOCKDEP. Includes a conditional might_sleep() if @gfp allows blocking.
314 */
315static inline void might_alloc(gfp_t gfp_mask)
316{
317 fs_reclaim_acquire(gfp_mask);
318 fs_reclaim_release(gfp_mask);
319
320 if (current->flags & PF_MEMALLOC)
321 return;
322
323 might_sleep_if(gfpflags_allow_blocking(gfp_mask));
324}
325
326/**
327 * memalloc_flags_save - Add a PF_* flag to current->flags, save old value
328 * @flags: Flags to add.
329 *
330 * This allows PF_* flags to be conveniently added, irrespective of current
331 * value, and then the old version restored with memalloc_flags_restore().
332 */
333static inline unsigned memalloc_flags_save(unsigned flags)
334{
335 unsigned oldflags = ~current->flags & flags;
336 current->flags |= flags;
337 return oldflags;
338}
339
340static inline void memalloc_flags_restore(unsigned flags)
341{
342 current->flags &= ~flags;
343}
344
345/**
346 * memalloc_noio_save - Marks implicit GFP_NOIO allocation scope.
347 *
348 * This functions marks the beginning of the GFP_NOIO allocation scope.
349 * All further allocations will implicitly drop __GFP_IO flag and so
350 * they are safe for the IO critical section from the allocation recursion
351 * point of view. Use memalloc_noio_restore to end the scope with flags
352 * returned by this function.
353 *
354 * Context: This function is safe to be used from any context.
355 * Return: The saved flags to be passed to memalloc_noio_restore.
356 */
357static inline unsigned int memalloc_noio_save(void)
358{
359 return memalloc_flags_save(PF_MEMALLOC_NOIO);
360}
361
362/**
363 * memalloc_noio_restore - Ends the implicit GFP_NOIO scope.
364 * @flags: Flags to restore.
365 *
366 * Ends the implicit GFP_NOIO scope started by memalloc_noio_save function.
367 * Always make sure that the given flags is the return value from the
368 * pairing memalloc_noio_save call.
369 */
370static inline void memalloc_noio_restore(unsigned int flags)
371{
372 memalloc_flags_restore(flags);
373}
374
375/**
376 * memalloc_nofs_save - Marks implicit GFP_NOFS allocation scope.
377 *
378 * This functions marks the beginning of the GFP_NOFS allocation scope.
379 * All further allocations will implicitly drop __GFP_FS flag and so
380 * they are safe for the FS critical section from the allocation recursion
381 * point of view. Use memalloc_nofs_restore to end the scope with flags
382 * returned by this function.
383 *
384 * Context: This function is safe to be used from any context.
385 * Return: The saved flags to be passed to memalloc_nofs_restore.
386 */
387static inline unsigned int memalloc_nofs_save(void)
388{
389 return memalloc_flags_save(PF_MEMALLOC_NOFS);
390}
391
392/**
393 * memalloc_nofs_restore - Ends the implicit GFP_NOFS scope.
394 * @flags: Flags to restore.
395 *
396 * Ends the implicit GFP_NOFS scope started by memalloc_nofs_save function.
397 * Always make sure that the given flags is the return value from the
398 * pairing memalloc_nofs_save call.
399 */
400static inline void memalloc_nofs_restore(unsigned int flags)
401{
402 memalloc_flags_restore(flags);
403}
404
405/**
406 * memalloc_noreclaim_save - Marks implicit __GFP_MEMALLOC scope.
407 *
408 * This function marks the beginning of the __GFP_MEMALLOC allocation scope.
409 * All further allocations will implicitly add the __GFP_MEMALLOC flag, which
410 * prevents entering reclaim and allows access to all memory reserves. This
411 * should only be used when the caller guarantees the allocation will allow more
412 * memory to be freed very shortly, i.e. it needs to allocate some memory in
413 * the process of freeing memory, and cannot reclaim due to potential recursion.
414 *
415 * Users of this scope have to be extremely careful to not deplete the reserves
416 * completely and implement a throttling mechanism which controls the
417 * consumption of the reserve based on the amount of freed memory. Usage of a
418 * pre-allocated pool (e.g. mempool) should be always considered before using
419 * this scope.
420 *
421 * Individual allocations under the scope can opt out using __GFP_NOMEMALLOC
422 *
423 * Context: This function should not be used in an interrupt context as that one
424 * does not give PF_MEMALLOC access to reserves.
425 * See __gfp_pfmemalloc_flags().
426 * Return: The saved flags to be passed to memalloc_noreclaim_restore.
427 */
428static inline unsigned int memalloc_noreclaim_save(void)
429{
430 return memalloc_flags_save(PF_MEMALLOC);
431}
432
433/**
434 * memalloc_noreclaim_restore - Ends the implicit __GFP_MEMALLOC scope.
435 * @flags: Flags to restore.
436 *
437 * Ends the implicit __GFP_MEMALLOC scope started by memalloc_noreclaim_save
438 * function. Always make sure that the given flags is the return value from the
439 * pairing memalloc_noreclaim_save call.
440 */
441static inline void memalloc_noreclaim_restore(unsigned int flags)
442{
443 memalloc_flags_restore(flags);
444}
445
446/**
447 * memalloc_pin_save - Marks implicit ~__GFP_MOVABLE scope.
448 *
449 * This function marks the beginning of the ~__GFP_MOVABLE allocation scope.
450 * All further allocations will implicitly remove the __GFP_MOVABLE flag, which
451 * will constraint the allocations to zones that allow long term pinning, i.e.
452 * not ZONE_MOVABLE zones.
453 *
454 * Return: The saved flags to be passed to memalloc_pin_restore.
455 */
456static inline unsigned int memalloc_pin_save(void)
457{
458 return memalloc_flags_save(PF_MEMALLOC_PIN);
459}
460
461/**
462 * memalloc_pin_restore - Ends the implicit ~__GFP_MOVABLE scope.
463 * @flags: Flags to restore.
464 *
465 * Ends the implicit ~__GFP_MOVABLE scope started by memalloc_pin_save function.
466 * Always make sure that the given flags is the return value from the pairing
467 * memalloc_pin_save call.
468 */
469static inline void memalloc_pin_restore(unsigned int flags)
470{
471 memalloc_flags_restore(flags);
472}
473
474#ifdef CONFIG_MEMCG
475DECLARE_PER_CPU(struct mem_cgroup *, int_active_memcg);
476/**
477 * set_active_memcg - Starts the remote memcg charging scope.
478 * @memcg: memcg to charge.
479 *
480 * This function marks the beginning of the remote memcg charging scope. All the
481 * __GFP_ACCOUNT allocations till the end of the scope will be charged to the
482 * given memcg.
483 *
484 * Please, make sure that caller has a reference to the passed memcg structure,
485 * so its lifetime is guaranteed to exceed the scope between two
486 * set_active_memcg() calls.
487 *
488 * NOTE: This function can nest. Users must save the return value and
489 * reset the previous value after their own charging scope is over.
490 */
491static inline struct mem_cgroup *
492set_active_memcg(struct mem_cgroup *memcg)
493{
494 struct mem_cgroup *old;
495
496 if (!in_task()) {
497 old = this_cpu_read(int_active_memcg);
498 this_cpu_write(int_active_memcg, memcg);
499 } else {
500 old = current->active_memcg;
501 current->active_memcg = memcg;
502 }
503
504 return old;
505}
506#else
507static inline struct mem_cgroup *
508set_active_memcg(struct mem_cgroup *memcg)
509{
510 return NULL;
511}
512#endif
513
514#ifdef CONFIG_MEMBARRIER
515enum {
516 MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY = (1U << 0),
517 MEMBARRIER_STATE_PRIVATE_EXPEDITED = (1U << 1),
518 MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY = (1U << 2),
519 MEMBARRIER_STATE_GLOBAL_EXPEDITED = (1U << 3),
520 MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY = (1U << 4),
521 MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE = (1U << 5),
522 MEMBARRIER_STATE_PRIVATE_EXPEDITED_RSEQ_READY = (1U << 6),
523 MEMBARRIER_STATE_PRIVATE_EXPEDITED_RSEQ = (1U << 7),
524};
525
526enum {
527 MEMBARRIER_FLAG_SYNC_CORE = (1U << 0),
528 MEMBARRIER_FLAG_RSEQ = (1U << 1),
529};
530
531#ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
532#include <asm/membarrier.h>
533#endif
534
535static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
536{
537 /*
538 * The atomic_read() below prevents CSE. The following should
539 * help the compiler generate more efficient code on architectures
540 * where sync_core_before_usermode() is a no-op.
541 */
542 if (!IS_ENABLED(CONFIG_ARCH_HAS_SYNC_CORE_BEFORE_USERMODE))
543 return;
544 if (current->mm != mm)
545 return;
546 if (likely(!(atomic_read(&mm->membarrier_state) &
547 MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE)))
548 return;
549 sync_core_before_usermode();
550}
551
552extern void membarrier_exec_mmap(struct mm_struct *mm);
553
554extern void membarrier_update_current_mm(struct mm_struct *next_mm);
555
556#else
557#ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
558static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
559 struct mm_struct *next,
560 struct task_struct *tsk)
561{
562}
563#endif
564static inline void membarrier_exec_mmap(struct mm_struct *mm)
565{
566}
567static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
568{
569}
570static inline void membarrier_update_current_mm(struct mm_struct *next_mm)
571{
572}
573#endif
574
575#endif /* _LINUX_SCHED_MM_H */
576

source code of linux/include/linux/sched/mm.h