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/ioasid.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(&mm->mm_count);
38}
39
40extern void __mmdrop(struct mm_struct *mm);
41
42static inline void mmdrop(struct mm_struct *mm)
43{
44 /*
45 * The implicit full barrier implied by atomic_dec_and_test() is
46 * required by the membarrier system call before returning to
47 * user-space, after storing to rq->curr.
48 */
49 if (unlikely(atomic_dec_and_test(&mm->mm_count)))
50 __mmdrop(mm);
51}
52
53#ifdef CONFIG_PREEMPT_RT
54/*
55 * RCU callback for delayed mm drop. Not strictly RCU, but call_rcu() is
56 * by far the least expensive way to do that.
57 */
58static inline void __mmdrop_delayed(struct rcu_head *rhp)
59{
60 struct mm_struct *mm = container_of(rhp, struct mm_struct, delayed_drop);
61
62 __mmdrop(mm);
63}
64
65/*
66 * Invoked from finish_task_switch(). Delegates the heavy lifting on RT
67 * kernels via RCU.
68 */
69static inline void mmdrop_sched(struct mm_struct *mm)
70{
71 /* Provides a full memory barrier. See mmdrop() */
72 if (atomic_dec_and_test(&mm->mm_count))
73 call_rcu(&mm->delayed_drop, __mmdrop_delayed);
74}
75#else
76static inline void mmdrop_sched(struct mm_struct *mm)
77{
78 mmdrop(mm);
79}
80#endif
81
82/**
83 * mmget() - Pin the address space associated with a &struct mm_struct.
84 * @mm: The address space to pin.
85 *
86 * Make sure that the address space of the given &struct mm_struct doesn't
87 * go away. This does not protect against parts of the address space being
88 * modified or freed, however.
89 *
90 * Never use this function to pin this address space for an
91 * unbounded/indefinite amount of time.
92 *
93 * Use mmput() to release the reference acquired by mmget().
94 *
95 * See also <Documentation/mm/active_mm.rst> for an in-depth explanation
96 * of &mm_struct.mm_count vs &mm_struct.mm_users.
97 */
98static inline void mmget(struct mm_struct *mm)
99{
100 atomic_inc(&mm->mm_users);
101}
102
103static inline bool mmget_not_zero(struct mm_struct *mm)
104{
105 return atomic_inc_not_zero(&mm->mm_users);
106}
107
108/* mmput gets rid of the mappings and all user-space */
109extern void mmput(struct mm_struct *);
110#ifdef CONFIG_MMU
111/* same as above but performs the slow path from the async context. Can
112 * be called from the atomic context as well
113 */
114void mmput_async(struct mm_struct *);
115#endif
116
117/* Grab a reference to a task's mm, if it is not already going away */
118extern struct mm_struct *get_task_mm(struct task_struct *task);
119/*
120 * Grab a reference to a task's mm, if it is not already going away
121 * and ptrace_may_access with the mode parameter passed to it
122 * succeeds.
123 */
124extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode);
125/* Remove the current tasks stale references to the old mm_struct on exit() */
126extern void exit_mm_release(struct task_struct *, struct mm_struct *);
127/* Remove the current tasks stale references to the old mm_struct on exec() */
128extern void exec_mm_release(struct task_struct *, struct mm_struct *);
129
130#ifdef CONFIG_MEMCG
131extern void mm_update_next_owner(struct mm_struct *mm);
132#else
133static inline void mm_update_next_owner(struct mm_struct *mm)
134{
135}
136#endif /* CONFIG_MEMCG */
137
138#ifdef CONFIG_MMU
139#ifndef arch_get_mmap_end
140#define arch_get_mmap_end(addr, len, flags) (TASK_SIZE)
141#endif
142
143#ifndef arch_get_mmap_base
144#define arch_get_mmap_base(addr, base) (base)
145#endif
146
147extern void arch_pick_mmap_layout(struct mm_struct *mm,
148 struct rlimit *rlim_stack);
149extern unsigned long
150arch_get_unmapped_area(struct file *, unsigned long, unsigned long,
151 unsigned long, unsigned long);
152extern unsigned long
153arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
154 unsigned long len, unsigned long pgoff,
155 unsigned long flags);
156
157unsigned long
158generic_get_unmapped_area(struct file *filp, unsigned long addr,
159 unsigned long len, unsigned long pgoff,
160 unsigned long flags);
161unsigned long
162generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
163 unsigned long len, unsigned long pgoff,
164 unsigned long flags);
165#else
166static inline void arch_pick_mmap_layout(struct mm_struct *mm,
167 struct rlimit *rlim_stack) {}
168#endif
169
170static inline bool in_vfork(struct task_struct *tsk)
171{
172 bool ret;
173
174 /*
175 * need RCU to access ->real_parent if CLONE_VM was used along with
176 * CLONE_PARENT.
177 *
178 * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
179 * imply CLONE_VM
180 *
181 * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
182 * ->real_parent is not necessarily the task doing vfork(), so in
183 * theory we can't rely on task_lock() if we want to dereference it.
184 *
185 * And in this case we can't trust the real_parent->mm == tsk->mm
186 * check, it can be false negative. But we do not care, if init or
187 * another oom-unkillable task does this it should blame itself.
188 */
189 rcu_read_lock();
190 ret = tsk->vfork_done &&
191 rcu_dereference(tsk->real_parent)->mm == tsk->mm;
192 rcu_read_unlock();
193
194 return ret;
195}
196
197/*
198 * Applies per-task gfp context to the given allocation flags.
199 * PF_MEMALLOC_NOIO implies GFP_NOIO
200 * PF_MEMALLOC_NOFS implies GFP_NOFS
201 * PF_MEMALLOC_PIN implies !GFP_MOVABLE
202 */
203static inline gfp_t current_gfp_context(gfp_t flags)
204{
205 unsigned int pflags = READ_ONCE(current->flags);
206
207 if (unlikely(pflags & (PF_MEMALLOC_NOIO | PF_MEMALLOC_NOFS | PF_MEMALLOC_PIN))) {
208 /*
209 * NOIO implies both NOIO and NOFS and it is a weaker context
210 * so always make sure it makes precedence
211 */
212 if (pflags & PF_MEMALLOC_NOIO)
213 flags &= ~(__GFP_IO | __GFP_FS);
214 else if (pflags & PF_MEMALLOC_NOFS)
215 flags &= ~__GFP_FS;
216
217 if (pflags & PF_MEMALLOC_PIN)
218 flags &= ~__GFP_MOVABLE;
219 }
220 return flags;
221}
222
223#ifdef CONFIG_LOCKDEP
224extern void __fs_reclaim_acquire(unsigned long ip);
225extern void __fs_reclaim_release(unsigned long ip);
226extern void fs_reclaim_acquire(gfp_t gfp_mask);
227extern void fs_reclaim_release(gfp_t gfp_mask);
228#else
229static inline void __fs_reclaim_acquire(unsigned long ip) { }
230static inline void __fs_reclaim_release(unsigned long ip) { }
231static inline void fs_reclaim_acquire(gfp_t gfp_mask) { }
232static inline void fs_reclaim_release(gfp_t gfp_mask) { }
233#endif
234
235/* Any memory-allocation retry loop should use
236 * memalloc_retry_wait(), and pass the flags for the most
237 * constrained allocation attempt that might have failed.
238 * This provides useful documentation of where loops are,
239 * and a central place to fine tune the waiting as the MM
240 * implementation changes.
241 */
242static inline void memalloc_retry_wait(gfp_t gfp_flags)
243{
244 /* We use io_schedule_timeout because waiting for memory
245 * typically included waiting for dirty pages to be
246 * written out, which requires IO.
247 */
248 __set_current_state(TASK_UNINTERRUPTIBLE);
249 gfp_flags = current_gfp_context(gfp_flags);
250 if (gfpflags_allow_blocking(gfp_flags) &&
251 !(gfp_flags & __GFP_NORETRY))
252 /* Probably waited already, no need for much more */
253 io_schedule_timeout(1);
254 else
255 /* Probably didn't wait, and has now released a lock,
256 * so now is a good time to wait
257 */
258 io_schedule_timeout(HZ/50);
259}
260
261/**
262 * might_alloc - Mark possible allocation sites
263 * @gfp_mask: gfp_t flags that would be used to allocate
264 *
265 * Similar to might_sleep() and other annotations, this can be used in functions
266 * that might allocate, but often don't. Compiles to nothing without
267 * CONFIG_LOCKDEP. Includes a conditional might_sleep() if @gfp allows blocking.
268 */
269static inline void might_alloc(gfp_t gfp_mask)
270{
271 fs_reclaim_acquire(gfp_mask);
272 fs_reclaim_release(gfp_mask);
273
274 might_sleep_if(gfpflags_allow_blocking(gfp_mask));
275}
276
277/**
278 * memalloc_noio_save - Marks implicit GFP_NOIO allocation scope.
279 *
280 * This functions marks the beginning of the GFP_NOIO allocation scope.
281 * All further allocations will implicitly drop __GFP_IO flag and so
282 * they are safe for the IO critical section from the allocation recursion
283 * point of view. Use memalloc_noio_restore to end the scope with flags
284 * returned by this function.
285 *
286 * This function is safe to be used from any context.
287 */
288static inline unsigned int memalloc_noio_save(void)
289{
290 unsigned int flags = current->flags & PF_MEMALLOC_NOIO;
291 current->flags |= PF_MEMALLOC_NOIO;
292 return flags;
293}
294
295/**
296 * memalloc_noio_restore - Ends the implicit GFP_NOIO scope.
297 * @flags: Flags to restore.
298 *
299 * Ends the implicit GFP_NOIO scope started by memalloc_noio_save function.
300 * Always make sure that the given flags is the return value from the
301 * pairing memalloc_noio_save call.
302 */
303static inline void memalloc_noio_restore(unsigned int flags)
304{
305 current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
306}
307
308/**
309 * memalloc_nofs_save - Marks implicit GFP_NOFS allocation scope.
310 *
311 * This functions marks the beginning of the GFP_NOFS allocation scope.
312 * All further allocations will implicitly drop __GFP_FS flag and so
313 * they are safe for the FS critical section from the allocation recursion
314 * point of view. Use memalloc_nofs_restore to end the scope with flags
315 * returned by this function.
316 *
317 * This function is safe to be used from any context.
318 */
319static inline unsigned int memalloc_nofs_save(void)
320{
321 unsigned int flags = current->flags & PF_MEMALLOC_NOFS;
322 current->flags |= PF_MEMALLOC_NOFS;
323 return flags;
324}
325
326/**
327 * memalloc_nofs_restore - Ends the implicit GFP_NOFS scope.
328 * @flags: Flags to restore.
329 *
330 * Ends the implicit GFP_NOFS scope started by memalloc_nofs_save function.
331 * Always make sure that the given flags is the return value from the
332 * pairing memalloc_nofs_save call.
333 */
334static inline void memalloc_nofs_restore(unsigned int flags)
335{
336 current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;
337}
338
339static inline unsigned int memalloc_noreclaim_save(void)
340{
341 unsigned int flags = current->flags & PF_MEMALLOC;
342 current->flags |= PF_MEMALLOC;
343 return flags;
344}
345
346static inline void memalloc_noreclaim_restore(unsigned int flags)
347{
348 current->flags = (current->flags & ~PF_MEMALLOC) | flags;
349}
350
351static inline unsigned int memalloc_pin_save(void)
352{
353 unsigned int flags = current->flags & PF_MEMALLOC_PIN;
354
355 current->flags |= PF_MEMALLOC_PIN;
356 return flags;
357}
358
359static inline void memalloc_pin_restore(unsigned int flags)
360{
361 current->flags = (current->flags & ~PF_MEMALLOC_PIN) | flags;
362}
363
364#ifdef CONFIG_MEMCG
365DECLARE_PER_CPU(struct mem_cgroup *, int_active_memcg);
366/**
367 * set_active_memcg - Starts the remote memcg charging scope.
368 * @memcg: memcg to charge.
369 *
370 * This function marks the beginning of the remote memcg charging scope. All the
371 * __GFP_ACCOUNT allocations till the end of the scope will be charged to the
372 * given memcg.
373 *
374 * NOTE: This function can nest. Users must save the return value and
375 * reset the previous value after their own charging scope is over.
376 */
377static inline struct mem_cgroup *
378set_active_memcg(struct mem_cgroup *memcg)
379{
380 struct mem_cgroup *old;
381
382 if (!in_task()) {
383 old = this_cpu_read(int_active_memcg);
384 this_cpu_write(int_active_memcg, memcg);
385 } else {
386 old = current->active_memcg;
387 current->active_memcg = memcg;
388 }
389
390 return old;
391}
392#else
393static inline struct mem_cgroup *
394set_active_memcg(struct mem_cgroup *memcg)
395{
396 return NULL;
397}
398#endif
399
400#ifdef CONFIG_MEMBARRIER
401enum {
402 MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY = (1U << 0),
403 MEMBARRIER_STATE_PRIVATE_EXPEDITED = (1U << 1),
404 MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY = (1U << 2),
405 MEMBARRIER_STATE_GLOBAL_EXPEDITED = (1U << 3),
406 MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY = (1U << 4),
407 MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE = (1U << 5),
408 MEMBARRIER_STATE_PRIVATE_EXPEDITED_RSEQ_READY = (1U << 6),
409 MEMBARRIER_STATE_PRIVATE_EXPEDITED_RSEQ = (1U << 7),
410};
411
412enum {
413 MEMBARRIER_FLAG_SYNC_CORE = (1U << 0),
414 MEMBARRIER_FLAG_RSEQ = (1U << 1),
415};
416
417#ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
418#include <asm/membarrier.h>
419#endif
420
421static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
422{
423 if (current->mm != mm)
424 return;
425 if (likely(!(atomic_read(&mm->membarrier_state) &
426 MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE)))
427 return;
428 sync_core_before_usermode();
429}
430
431extern void membarrier_exec_mmap(struct mm_struct *mm);
432
433extern void membarrier_update_current_mm(struct mm_struct *next_mm);
434
435#else
436#ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
437static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
438 struct mm_struct *next,
439 struct task_struct *tsk)
440{
441}
442#endif
443static inline void membarrier_exec_mmap(struct mm_struct *mm)
444{
445}
446static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
447{
448}
449static inline void membarrier_update_current_mm(struct mm_struct *next_mm)
450{
451}
452#endif
453
454#ifdef CONFIG_IOMMU_SVA
455static inline void mm_pasid_init(struct mm_struct *mm)
456{
457 mm->pasid = INVALID_IOASID;
458}
459
460/* Associate a PASID with an mm_struct: */
461static inline void mm_pasid_set(struct mm_struct *mm, u32 pasid)
462{
463 mm->pasid = pasid;
464}
465
466static inline void mm_pasid_drop(struct mm_struct *mm)
467{
468 if (pasid_valid(mm->pasid)) {
469 ioasid_free(mm->pasid);
470 mm->pasid = INVALID_IOASID;
471 }
472}
473#else
474static inline void mm_pasid_init(struct mm_struct *mm) {}
475static inline void mm_pasid_set(struct mm_struct *mm, u32 pasid) {}
476static inline void mm_pasid_drop(struct mm_struct *mm) {}
477#endif
478
479#endif /* _LINUX_SCHED_MM_H */
480

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