Line data Source code
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 :
12 : /*
13 : * Routines for handling mm_structs
14 : */
15 : extern struct mm_struct *mm_alloc(void);
16 :
17 : /**
18 : * mmgrab() - Pin a &struct mm_struct.
19 : * @mm: The &struct mm_struct to pin.
20 : *
21 : * Make sure that @mm will not get freed even after the owning task
22 : * exits. This doesn't guarantee that the associated address space
23 : * will still exist later on and mmget_not_zero() has to be used before
24 : * accessing it.
25 : *
26 : * This is a preferred way to pin @mm for a longer/unbounded amount
27 : * of time.
28 : *
29 : * Use mmdrop() to release the reference acquired by mmgrab().
30 : *
31 : * See also <Documentation/mm/active_mm.rst> for an in-depth explanation
32 : * of &mm_struct.mm_count vs &mm_struct.mm_users.
33 : */
34 : static inline void mmgrab(struct mm_struct *mm)
35 : {
36 2 : atomic_inc(&mm->mm_count);
37 : }
38 :
39 : static inline void smp_mb__after_mmgrab(void)
40 : {
41 : smp_mb__after_atomic();
42 : }
43 :
44 : extern void __mmdrop(struct mm_struct *mm);
45 :
46 : static inline void mmdrop(struct mm_struct *mm)
47 : {
48 : /*
49 : * The implicit full barrier implied by atomic_dec_and_test() is
50 : * required by the membarrier system call before returning to
51 : * user-space, after storing to rq->curr.
52 : */
53 0 : if (unlikely(atomic_dec_and_test(&mm->mm_count)))
54 0 : __mmdrop(mm);
55 : }
56 :
57 : #ifdef CONFIG_PREEMPT_RT
58 : /*
59 : * RCU callback for delayed mm drop. Not strictly RCU, but call_rcu() is
60 : * by far the least expensive way to do that.
61 : */
62 : static inline void __mmdrop_delayed(struct rcu_head *rhp)
63 : {
64 : struct mm_struct *mm = container_of(rhp, struct mm_struct, delayed_drop);
65 :
66 : __mmdrop(mm);
67 : }
68 :
69 : /*
70 : * Invoked from finish_task_switch(). Delegates the heavy lifting on RT
71 : * kernels via RCU.
72 : */
73 : static inline void mmdrop_sched(struct mm_struct *mm)
74 : {
75 : /* Provides a full memory barrier. See mmdrop() */
76 : if (atomic_dec_and_test(&mm->mm_count))
77 : call_rcu(&mm->delayed_drop, __mmdrop_delayed);
78 : }
79 : #else
80 : static inline void mmdrop_sched(struct mm_struct *mm)
81 : {
82 : mmdrop(mm);
83 : }
84 : #endif
85 :
86 : /* Helpers for lazy TLB mm refcounting */
87 : static inline void mmgrab_lazy_tlb(struct mm_struct *mm)
88 : {
89 : if (IS_ENABLED(CONFIG_MMU_LAZY_TLB_REFCOUNT))
90 1 : mmgrab(mm);
91 : }
92 :
93 : static inline void mmdrop_lazy_tlb(struct mm_struct *mm)
94 : {
95 : if (IS_ENABLED(CONFIG_MMU_LAZY_TLB_REFCOUNT)) {
96 0 : mmdrop(mm);
97 : } else {
98 : /*
99 : * mmdrop_lazy_tlb must provide a full memory barrier, see the
100 : * membarrier comment finish_task_switch which relies on this.
101 : */
102 : smp_mb();
103 : }
104 : }
105 :
106 : static inline void mmdrop_lazy_tlb_sched(struct mm_struct *mm)
107 : {
108 : if (IS_ENABLED(CONFIG_MMU_LAZY_TLB_REFCOUNT))
109 : mmdrop_sched(mm);
110 : else
111 : smp_mb(); /* see mmdrop_lazy_tlb() above */
112 : }
113 :
114 : /**
115 : * mmget() - Pin the address space associated with a &struct mm_struct.
116 : * @mm: The address space to pin.
117 : *
118 : * Make sure that the address space of the given &struct mm_struct doesn't
119 : * go away. This does not protect against parts of the address space being
120 : * modified or freed, however.
121 : *
122 : * Never use this function to pin this address space for an
123 : * unbounded/indefinite amount of time.
124 : *
125 : * Use mmput() to release the reference acquired by mmget().
126 : *
127 : * See also <Documentation/mm/active_mm.rst> for an in-depth explanation
128 : * of &mm_struct.mm_count vs &mm_struct.mm_users.
129 : */
130 : static inline void mmget(struct mm_struct *mm)
131 : {
132 0 : atomic_inc(&mm->mm_users);
133 : }
134 :
135 : static inline bool mmget_not_zero(struct mm_struct *mm)
136 : {
137 0 : return atomic_inc_not_zero(&mm->mm_users);
138 : }
139 :
140 : /* mmput gets rid of the mappings and all user-space */
141 : extern void mmput(struct mm_struct *);
142 : #ifdef CONFIG_MMU
143 : /* same as above but performs the slow path from the async context. Can
144 : * be called from the atomic context as well
145 : */
146 : void mmput_async(struct mm_struct *);
147 : #endif
148 :
149 : /* Grab a reference to a task's mm, if it is not already going away */
150 : extern struct mm_struct *get_task_mm(struct task_struct *task);
151 : /*
152 : * Grab a reference to a task's mm, if it is not already going away
153 : * and ptrace_may_access with the mode parameter passed to it
154 : * succeeds.
155 : */
156 : extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode);
157 : /* Remove the current tasks stale references to the old mm_struct on exit() */
158 : extern void exit_mm_release(struct task_struct *, struct mm_struct *);
159 : /* Remove the current tasks stale references to the old mm_struct on exec() */
160 : extern void exec_mm_release(struct task_struct *, struct mm_struct *);
161 :
162 : #ifdef CONFIG_MEMCG
163 : extern void mm_update_next_owner(struct mm_struct *mm);
164 : #else
165 : static inline void mm_update_next_owner(struct mm_struct *mm)
166 : {
167 : }
168 : #endif /* CONFIG_MEMCG */
169 :
170 : #ifdef CONFIG_MMU
171 : #ifndef arch_get_mmap_end
172 : #define arch_get_mmap_end(addr, len, flags) (TASK_SIZE)
173 : #endif
174 :
175 : #ifndef arch_get_mmap_base
176 : #define arch_get_mmap_base(addr, base) (base)
177 : #endif
178 :
179 : extern void arch_pick_mmap_layout(struct mm_struct *mm,
180 : struct rlimit *rlim_stack);
181 : extern unsigned long
182 : arch_get_unmapped_area(struct file *, unsigned long, unsigned long,
183 : unsigned long, unsigned long);
184 : extern unsigned long
185 : arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
186 : unsigned long len, unsigned long pgoff,
187 : unsigned long flags);
188 :
189 : unsigned long
190 : generic_get_unmapped_area(struct file *filp, unsigned long addr,
191 : unsigned long len, unsigned long pgoff,
192 : unsigned long flags);
193 : unsigned long
194 : generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
195 : unsigned long len, unsigned long pgoff,
196 : unsigned long flags);
197 : #else
198 : static inline void arch_pick_mmap_layout(struct mm_struct *mm,
199 : struct rlimit *rlim_stack) {}
200 : #endif
201 :
202 : static inline bool in_vfork(struct task_struct *tsk)
203 : {
204 : bool ret;
205 :
206 : /*
207 : * need RCU to access ->real_parent if CLONE_VM was used along with
208 : * CLONE_PARENT.
209 : *
210 : * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
211 : * imply CLONE_VM
212 : *
213 : * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
214 : * ->real_parent is not necessarily the task doing vfork(), so in
215 : * theory we can't rely on task_lock() if we want to dereference it.
216 : *
217 : * And in this case we can't trust the real_parent->mm == tsk->mm
218 : * check, it can be false negative. But we do not care, if init or
219 : * another oom-unkillable task does this it should blame itself.
220 : */
221 : rcu_read_lock();
222 0 : ret = tsk->vfork_done &&
223 0 : rcu_dereference(tsk->real_parent)->mm == tsk->mm;
224 : rcu_read_unlock();
225 :
226 : return ret;
227 : }
228 :
229 : /*
230 : * Applies per-task gfp context to the given allocation flags.
231 : * PF_MEMALLOC_NOIO implies GFP_NOIO
232 : * PF_MEMALLOC_NOFS implies GFP_NOFS
233 : * PF_MEMALLOC_PIN implies !GFP_MOVABLE
234 : */
235 683 : static inline gfp_t current_gfp_context(gfp_t flags)
236 : {
237 683 : unsigned int pflags = READ_ONCE(current->flags);
238 :
239 683 : if (unlikely(pflags & (PF_MEMALLOC_NOIO | PF_MEMALLOC_NOFS | PF_MEMALLOC_PIN))) {
240 : /*
241 : * NOIO implies both NOIO and NOFS and it is a weaker context
242 : * so always make sure it makes precedence
243 : */
244 0 : if (pflags & PF_MEMALLOC_NOIO)
245 0 : flags &= ~(__GFP_IO | __GFP_FS);
246 0 : else if (pflags & PF_MEMALLOC_NOFS)
247 0 : flags &= ~__GFP_FS;
248 :
249 0 : if (pflags & PF_MEMALLOC_PIN)
250 0 : flags &= ~__GFP_MOVABLE;
251 : }
252 683 : return flags;
253 : }
254 :
255 : #ifdef CONFIG_LOCKDEP
256 : extern void __fs_reclaim_acquire(unsigned long ip);
257 : extern void __fs_reclaim_release(unsigned long ip);
258 : extern void fs_reclaim_acquire(gfp_t gfp_mask);
259 : extern void fs_reclaim_release(gfp_t gfp_mask);
260 : #else
261 : static inline void __fs_reclaim_acquire(unsigned long ip) { }
262 : static inline void __fs_reclaim_release(unsigned long ip) { }
263 : static inline void fs_reclaim_acquire(gfp_t gfp_mask) { }
264 : static inline void fs_reclaim_release(gfp_t gfp_mask) { }
265 : #endif
266 :
267 : /* Any memory-allocation retry loop should use
268 : * memalloc_retry_wait(), and pass the flags for the most
269 : * constrained allocation attempt that might have failed.
270 : * This provides useful documentation of where loops are,
271 : * and a central place to fine tune the waiting as the MM
272 : * implementation changes.
273 : */
274 : static inline void memalloc_retry_wait(gfp_t gfp_flags)
275 : {
276 : /* We use io_schedule_timeout because waiting for memory
277 : * typically included waiting for dirty pages to be
278 : * written out, which requires IO.
279 : */
280 : __set_current_state(TASK_UNINTERRUPTIBLE);
281 : gfp_flags = current_gfp_context(gfp_flags);
282 : if (gfpflags_allow_blocking(gfp_flags) &&
283 : !(gfp_flags & __GFP_NORETRY))
284 : /* Probably waited already, no need for much more */
285 : io_schedule_timeout(1);
286 : else
287 : /* Probably didn't wait, and has now released a lock,
288 : * so now is a good time to wait
289 : */
290 : io_schedule_timeout(HZ/50);
291 : }
292 :
293 : /**
294 : * might_alloc - Mark possible allocation sites
295 : * @gfp_mask: gfp_t flags that would be used to allocate
296 : *
297 : * Similar to might_sleep() and other annotations, this can be used in functions
298 : * that might allocate, but often don't. Compiles to nothing without
299 : * CONFIG_LOCKDEP. Includes a conditional might_sleep() if @gfp allows blocking.
300 : */
301 : static inline void might_alloc(gfp_t gfp_mask)
302 : {
303 17413 : fs_reclaim_acquire(gfp_mask);
304 17413 : fs_reclaim_release(gfp_mask);
305 :
306 17413 : might_sleep_if(gfpflags_allow_blocking(gfp_mask));
307 : }
308 :
309 : /**
310 : * memalloc_noio_save - Marks implicit GFP_NOIO allocation scope.
311 : *
312 : * This functions marks the beginning of the GFP_NOIO allocation scope.
313 : * All further allocations will implicitly drop __GFP_IO flag and so
314 : * they are safe for the IO critical section from the allocation recursion
315 : * point of view. Use memalloc_noio_restore to end the scope with flags
316 : * returned by this function.
317 : *
318 : * This function is safe to be used from any context.
319 : */
320 : static inline unsigned int memalloc_noio_save(void)
321 : {
322 5 : unsigned int flags = current->flags & PF_MEMALLOC_NOIO;
323 5 : current->flags |= PF_MEMALLOC_NOIO;
324 : return flags;
325 : }
326 :
327 : /**
328 : * memalloc_noio_restore - Ends the implicit GFP_NOIO scope.
329 : * @flags: Flags to restore.
330 : *
331 : * Ends the implicit GFP_NOIO scope started by memalloc_noio_save function.
332 : * Always make sure that the given flags is the return value from the
333 : * pairing memalloc_noio_save call.
334 : */
335 : static inline void memalloc_noio_restore(unsigned int flags)
336 : {
337 10 : current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
338 : }
339 :
340 : /**
341 : * memalloc_nofs_save - Marks implicit GFP_NOFS allocation scope.
342 : *
343 : * This functions marks the beginning of the GFP_NOFS allocation scope.
344 : * All further allocations will implicitly drop __GFP_FS flag and so
345 : * they are safe for the FS critical section from the allocation recursion
346 : * point of view. Use memalloc_nofs_restore to end the scope with flags
347 : * returned by this function.
348 : *
349 : * This function is safe to be used from any context.
350 : */
351 : static inline unsigned int memalloc_nofs_save(void)
352 : {
353 0 : unsigned int flags = current->flags & PF_MEMALLOC_NOFS;
354 0 : current->flags |= PF_MEMALLOC_NOFS;
355 : return flags;
356 : }
357 :
358 : /**
359 : * memalloc_nofs_restore - Ends the implicit GFP_NOFS scope.
360 : * @flags: Flags to restore.
361 : *
362 : * Ends the implicit GFP_NOFS scope started by memalloc_nofs_save function.
363 : * Always make sure that the given flags is the return value from the
364 : * pairing memalloc_nofs_save call.
365 : */
366 : static inline void memalloc_nofs_restore(unsigned int flags)
367 : {
368 0 : current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;
369 : }
370 :
371 : static inline unsigned int memalloc_noreclaim_save(void)
372 : {
373 0 : unsigned int flags = current->flags & PF_MEMALLOC;
374 0 : current->flags |= PF_MEMALLOC;
375 : return flags;
376 : }
377 :
378 : static inline void memalloc_noreclaim_restore(unsigned int flags)
379 : {
380 0 : current->flags = (current->flags & ~PF_MEMALLOC) | flags;
381 : }
382 :
383 : static inline unsigned int memalloc_pin_save(void)
384 : {
385 0 : unsigned int flags = current->flags & PF_MEMALLOC_PIN;
386 :
387 0 : current->flags |= PF_MEMALLOC_PIN;
388 : return flags;
389 : }
390 :
391 : static inline void memalloc_pin_restore(unsigned int flags)
392 : {
393 0 : current->flags = (current->flags & ~PF_MEMALLOC_PIN) | flags;
394 : }
395 :
396 : #ifdef CONFIG_MEMCG
397 : DECLARE_PER_CPU(struct mem_cgroup *, int_active_memcg);
398 : /**
399 : * set_active_memcg - Starts the remote memcg charging scope.
400 : * @memcg: memcg to charge.
401 : *
402 : * This function marks the beginning of the remote memcg charging scope. All the
403 : * __GFP_ACCOUNT allocations till the end of the scope will be charged to the
404 : * given memcg.
405 : *
406 : * NOTE: This function can nest. Users must save the return value and
407 : * reset the previous value after their own charging scope is over.
408 : */
409 : static inline struct mem_cgroup *
410 : set_active_memcg(struct mem_cgroup *memcg)
411 : {
412 : struct mem_cgroup *old;
413 :
414 : if (!in_task()) {
415 : old = this_cpu_read(int_active_memcg);
416 : this_cpu_write(int_active_memcg, memcg);
417 : } else {
418 : old = current->active_memcg;
419 : current->active_memcg = memcg;
420 : }
421 :
422 : return old;
423 : }
424 : #else
425 : static inline struct mem_cgroup *
426 : set_active_memcg(struct mem_cgroup *memcg)
427 : {
428 : return NULL;
429 : }
430 : #endif
431 :
432 : #ifdef CONFIG_MEMBARRIER
433 : enum {
434 : MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY = (1U << 0),
435 : MEMBARRIER_STATE_PRIVATE_EXPEDITED = (1U << 1),
436 : MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY = (1U << 2),
437 : MEMBARRIER_STATE_GLOBAL_EXPEDITED = (1U << 3),
438 : MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY = (1U << 4),
439 : MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE = (1U << 5),
440 : MEMBARRIER_STATE_PRIVATE_EXPEDITED_RSEQ_READY = (1U << 6),
441 : MEMBARRIER_STATE_PRIVATE_EXPEDITED_RSEQ = (1U << 7),
442 : };
443 :
444 : enum {
445 : MEMBARRIER_FLAG_SYNC_CORE = (1U << 0),
446 : MEMBARRIER_FLAG_RSEQ = (1U << 1),
447 : };
448 :
449 : #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
450 : #include <asm/membarrier.h>
451 : #endif
452 :
453 : static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
454 : {
455 0 : if (current->mm != mm)
456 : return;
457 0 : if (likely(!(atomic_read(&mm->membarrier_state) &
458 : MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE)))
459 : return;
460 : sync_core_before_usermode();
461 : }
462 :
463 : extern void membarrier_exec_mmap(struct mm_struct *mm);
464 :
465 : extern void membarrier_update_current_mm(struct mm_struct *next_mm);
466 :
467 : #else
468 : #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
469 : static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
470 : struct mm_struct *next,
471 : struct task_struct *tsk)
472 : {
473 : }
474 : #endif
475 : static inline void membarrier_exec_mmap(struct mm_struct *mm)
476 : {
477 : }
478 : static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
479 : {
480 : }
481 : static inline void membarrier_update_current_mm(struct mm_struct *next_mm)
482 : {
483 : }
484 : #endif
485 :
486 : #endif /* _LINUX_SCHED_MM_H */
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