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