1 #ifndef _LINUX_SCHED_MM_H
2 #define _LINUX_SCHED_MM_H
3
4 #include <linux/kernel.h>
5 #include <linux/atomic.h>
6 #include <linux/sched.h>
7 #include <linux/mm_types.h>
8 #include <linux/gfp.h>
9
10 /*
11 * Routines for handling mm_structs
12 */
13 extern struct mm_struct * mm_alloc(void);
14
15 /**
16 * mmgrab() - Pin a &struct mm_struct.
17 * @mm: The &struct mm_struct to pin.
18 *
19 * Make sure that @mm will not get freed even after the owning task
20 * exits. This doesn't guarantee that the associated address space
21 * will still exist later on and mmget_not_zero() has to be used before
22 * accessing it.
23 *
24 * This is a preferred way to to pin @mm for a longer/unbounded amount
25 * of time.
26 *
27 * Use mmdrop() to release the reference acquired by mmgrab().
28 *
29 * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
30 * of &mm_struct.mm_count vs &mm_struct.mm_users.
31 */
32 static inline void mmgrab(struct mm_struct *mm)
33 {
34 atomic_inc(&mm->mm_count);
35 }
36
37 /* mmdrop drops the mm and the page tables */
38 extern void __mmdrop(struct mm_struct *);
39 static inline void mmdrop(struct mm_struct *mm)
40 {
41 if (unlikely(atomic_dec_and_test(&mm->mm_count)))
42 __mmdrop(mm);
43 }
44
45 static inline void mmdrop_async_fn(struct work_struct *work)
46 {
47 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
48 __mmdrop(mm);
49 }
50
51 static inline void mmdrop_async(struct mm_struct *mm)
52 {
53 if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
54 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
55 schedule_work(&mm->async_put_work);
56 }
57 }
58
59 /**
60 * mmget() - Pin the address space associated with a &struct mm_struct.
61 * @mm: The address space to pin.
62 *
63 * Make sure that the address space of the given &struct mm_struct doesn't
64 * go away. This does not protect against parts of the address space being
65 * modified or freed, however.
66 *
67 * Never use this function to pin this address space for an
68 * unbounded/indefinite amount of time.
69 *
70 * Use mmput() to release the reference acquired by mmget().
71 *
72 * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
73 * of &mm_struct.mm_count vs &mm_struct.mm_users.
74 */
75 static inline void mmget(struct mm_struct *mm)
76 {
77 atomic_inc(&mm->mm_users);
78 }
79
80 static inline bool mmget_not_zero(struct mm_struct *mm)
81 {
82 return atomic_inc_not_zero(&mm->mm_users);
83 }
84
85 /* mmput gets rid of the mappings and all user-space */
86 extern void mmput(struct mm_struct *);
87 #ifdef CONFIG_MMU
88 /* same as above but performs the slow path from the async context. Can
89 * be called from the atomic context as well
90 */
91 extern void mmput_async(struct mm_struct *);
92 #endif
93
94 /* Grab a reference to a task's mm, if it is not already going away */
95 extern struct mm_struct *get_task_mm(struct task_struct *task);
96 /*
97 * Grab a reference to a task's mm, if it is not already going away
98 * and ptrace_may_access with the mode parameter passed to it
99 * succeeds.
100 */
101 extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode);
102 /* Remove the current tasks stale references to the old mm_struct */
103 extern void mm_release(struct task_struct *, struct mm_struct *);
104
105 #ifdef CONFIG_MEMCG
106 extern void mm_update_next_owner(struct mm_struct *mm);
107 #else
108 static inline void mm_update_next_owner(struct mm_struct *mm)
109 {
110 }
111 #endif /* CONFIG_MEMCG */
112
113 #ifdef CONFIG_MMU
114 extern void arch_pick_mmap_layout(struct mm_struct *mm);
115 extern unsigned long
116 arch_get_unmapped_area(struct file *, unsigned long, unsigned long,
117 unsigned long, unsigned long);
118 extern unsigned long
119 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
120 unsigned long len, unsigned long pgoff,
121 unsigned long flags);
122 #else
123 static inline void arch_pick_mmap_layout(struct mm_struct *mm) {}
124 #endif
125
126 static inline bool in_vfork(struct task_struct *tsk)
127 {
128 bool ret;
129
130 /*
131 * need RCU to access ->real_parent if CLONE_VM was used along with
132 * CLONE_PARENT.
133 *
134 * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
135 * imply CLONE_VM
136 *
137 * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
138 * ->real_parent is not necessarily the task doing vfork(), so in
139 * theory we can't rely on task_lock() if we want to dereference it.
140 *
141 * And in this case we can't trust the real_parent->mm == tsk->mm
142 * check, it can be false negative. But we do not care, if init or
143 * another oom-unkillable task does this it should blame itself.
144 */
145 rcu_read_lock();
146 ret = tsk->vfork_done && tsk->real_parent->mm == tsk->mm;
147 rcu_read_unlock();
148
149 return ret;
150 }
151
152 /*
153 * Applies per-task gfp context to the given allocation flags.
154 * PF_MEMALLOC_NOIO implies GFP_NOIO
155 * PF_MEMALLOC_NOFS implies GFP_NOFS
156 */
157 static inline gfp_t current_gfp_context(gfp_t flags)
158 {
159 /*
160 * NOIO implies both NOIO and NOFS and it is a weaker context
161 * so always make sure it makes precendence
162 */
163 if (unlikely(current->flags & PF_MEMALLOC_NOIO))
164 flags &= ~(__GFP_IO | __GFP_FS);
165 else if (unlikely(current->flags & PF_MEMALLOC_NOFS))
166 flags &= ~__GFP_FS;
167 return flags;
168 }
169
170 static inline unsigned int memalloc_noio_save(void)
171 {
172 unsigned int flags = current->flags & PF_MEMALLOC_NOIO;
173 current->flags |= PF_MEMALLOC_NOIO;
174 return flags;
175 }
176
177 static inline void memalloc_noio_restore(unsigned int flags)
178 {
179 current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
180 }
181
182 static inline unsigned int memalloc_nofs_save(void)
183 {
184 unsigned int flags = current->flags & PF_MEMALLOC_NOFS;
185 current->flags |= PF_MEMALLOC_NOFS;
186 return flags;
187 }
188
189 static inline void memalloc_nofs_restore(unsigned int flags)
190 {
191 current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;
192 }
193
194 static inline unsigned int memalloc_noreclaim_save(void)
195 {
196 unsigned int flags = current->flags & PF_MEMALLOC;
197 current->flags |= PF_MEMALLOC;
198 return flags;
199 }
200
201 static inline void memalloc_noreclaim_restore(unsigned int flags)
202 {
203 current->flags = (current->flags & ~PF_MEMALLOC) | flags;
204 }
205
206 #endif /* _LINUX_SCHED_MM_H */
207
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