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 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.txt> 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 atomic_inc(&mm->mm_count);
37 }
38
39 extern void __mmdrop(struct mm_struct *mm);
40
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 /**
53 * mmget() - Pin the address space associated with a &struct mm_struct.
54 * @mm: The address space to pin.
55 *
56 * Make sure that the address space of the given &struct mm_struct doesn't
57 * go away. This does not protect against parts of the address space being
58 * modified or freed, however.
59 *
60 * Never use this function to pin this address space for an
61 * unbounded/indefinite amount of time.
62 *
63 * Use mmput() to release the reference acquired by mmget().
64 *
65 * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
66 * of &mm_struct.mm_count vs &mm_struct.mm_users.
67 */
68 static inline void mmget(struct mm_struct *mm)
69 {
70 atomic_inc(&mm->mm_users);
71 }
72
73 static inline bool mmget_not_zero(struct mm_struct *mm)
74 {
75 return atomic_inc_not_zero(&mm->mm_users);
76 }
77
78 /* mmput gets rid of the mappings and all user-space */
79 extern void mmput(struct mm_struct *);
80 #ifdef CONFIG_MMU
81 /* same as above but performs the slow path from the async context. Can
82 * be called from the atomic context as well
83 */
84 void mmput_async(struct mm_struct *);
85 #endif
86
87 /* Grab a reference to a task's mm, if it is not already going away */
88 extern struct mm_struct *get_task_mm(struct task_struct *task);
89 /*
90 * Grab a reference to a task's mm, if it is not already going away
91 * and ptrace_may_access with the mode parameter passed to it
92 * succeeds.
93 */
94 extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode);
95 /* Remove the current tasks stale references to the old mm_struct */
96 extern void mm_release(struct task_struct *, struct mm_struct *);
97
98 #ifdef CONFIG_MEMCG
99 extern void mm_update_next_owner(struct mm_struct *mm);
100 #else
101 static inline void mm_update_next_owner(struct mm_struct *mm)
102 {
103 }
104 #endif /* CONFIG_MEMCG */
105
106 #ifdef CONFIG_MMU
107 extern void arch_pick_mmap_layout(struct mm_struct *mm);
108 extern unsigned long
109 arch_get_unmapped_area(struct file *, unsigned long, unsigned long,
110 unsigned long, unsigned long);
111 extern unsigned long
112 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
113 unsigned long len, unsigned long pgoff,
114 unsigned long flags);
115 #else
116 static inline void arch_pick_mmap_layout(struct mm_struct *mm) {}
117 #endif
118
119 static inline bool in_vfork(struct task_struct *tsk)
120 {
121 bool ret;
122
123 /*
124 * need RCU to access ->real_parent if CLONE_VM was used along with
125 * CLONE_PARENT.
126 *
127 * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
128 * imply CLONE_VM
129 *
130 * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
131 * ->real_parent is not necessarily the task doing vfork(), so in
132 * theory we can't rely on task_lock() if we want to dereference it.
133 *
134 * And in this case we can't trust the real_parent->mm == tsk->mm
135 * check, it can be false negative. But we do not care, if init or
136 * another oom-unkillable task does this it should blame itself.
137 */
138 rcu_read_lock();
139 ret = tsk->vfork_done && tsk->real_parent->mm == tsk->mm;
140 rcu_read_unlock();
141
142 return ret;
143 }
144
145 /*
146 * Applies per-task gfp context to the given allocation flags.
147 * PF_MEMALLOC_NOIO implies GFP_NOIO
148 * PF_MEMALLOC_NOFS implies GFP_NOFS
149 */
150 static inline gfp_t current_gfp_context(gfp_t flags)
151 {
152 /*
153 * NOIO implies both NOIO and NOFS and it is a weaker context
154 * so always make sure it makes precendence
155 */
156 if (unlikely(current->flags & PF_MEMALLOC_NOIO))
157 flags &= ~(__GFP_IO | __GFP_FS);
158 else if (unlikely(current->flags & PF_MEMALLOC_NOFS))
159 flags &= ~__GFP_FS;
160 return flags;
161 }
162
163 #ifdef CONFIG_LOCKDEP
164 extern void fs_reclaim_acquire(gfp_t gfp_mask);
165 extern void fs_reclaim_release(gfp_t gfp_mask);
166 #else
167 static inline void fs_reclaim_acquire(gfp_t gfp_mask) { }
168 static inline void fs_reclaim_release(gfp_t gfp_mask) { }
169 #endif
170
171 static inline unsigned int memalloc_noio_save(void)
172 {
173 unsigned int flags = current->flags & PF_MEMALLOC_NOIO;
174 current->flags |= PF_MEMALLOC_NOIO;
175 return flags;
176 }
177
178 static inline void memalloc_noio_restore(unsigned int flags)
179 {
180 current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
181 }
182
183 static inline unsigned int memalloc_nofs_save(void)
184 {
185 unsigned int flags = current->flags & PF_MEMALLOC_NOFS;
186 current->flags |= PF_MEMALLOC_NOFS;
187 return flags;
188 }
189
190 static inline void memalloc_nofs_restore(unsigned int flags)
191 {
192 current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;
193 }
194
195 static inline unsigned int memalloc_noreclaim_save(void)
196 {
197 unsigned int flags = current->flags & PF_MEMALLOC;
198 current->flags |= PF_MEMALLOC;
199 return flags;
200 }
201
202 static inline void memalloc_noreclaim_restore(unsigned int flags)
203 {
204 current->flags = (current->flags & ~PF_MEMALLOC) | flags;
205 }
206
207 #ifdef CONFIG_MEMBARRIER
208 enum {
209 MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY = (1U << 0),
210 MEMBARRIER_STATE_PRIVATE_EXPEDITED = (1U << 1),
211 MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY = (1U << 2),
212 MEMBARRIER_STATE_GLOBAL_EXPEDITED = (1U << 3),
213 MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY = (1U << 4),
214 MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE = (1U << 5),
215 };
216
217 enum {
218 MEMBARRIER_FLAG_SYNC_CORE = (1U << 0),
219 };
220
221 #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
222 #include <asm/membarrier.h>
223 #endif
224
225 static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
226 {
227 if (likely(!(atomic_read(&mm->membarrier_state) &
228 MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE)))
229 return;
230 sync_core_before_usermode();
231 }
232
233 static inline void membarrier_execve(struct task_struct *t)
234 {
235 atomic_set(&t->mm->membarrier_state, 0);
236 }
237 #else
238 #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
239 static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
240 struct mm_struct *next,
241 struct task_struct *tsk)
242 {
243 }
244 #endif
245 static inline void membarrier_execve(struct task_struct *t)
246 {
247 }
248 static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
249 {
250 }
251 #endif
252
253 #endif /* _LINUX_SCHED_MM_H */
254
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