Linux kernel mirror (for testing)
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linux
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 */
13extern 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 */
32static 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 */
38extern void __mmdrop(struct mm_struct *);
39static inline void mmdrop(struct mm_struct *mm)
40{
41 if (unlikely(atomic_dec_and_test(&mm->mm_count)))
42 __mmdrop(mm);
43}
44
45static 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
51static 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 */
75static inline void mmget(struct mm_struct *mm)
76{
77 atomic_inc(&mm->mm_users);
78}
79
80static 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 */
86extern 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 */
91extern 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 */
95extern 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 */
101extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode);
102/* Remove the current tasks stale references to the old mm_struct */
103extern void mm_release(struct task_struct *, struct mm_struct *);
104
105#ifdef CONFIG_MEMCG
106extern void mm_update_next_owner(struct mm_struct *mm);
107#else
108static inline void mm_update_next_owner(struct mm_struct *mm)
109{
110}
111#endif /* CONFIG_MEMCG */
112
113#ifdef CONFIG_MMU
114extern void arch_pick_mmap_layout(struct mm_struct *mm);
115extern unsigned long
116arch_get_unmapped_area(struct file *, unsigned long, unsigned long,
117 unsigned long, unsigned long);
118extern unsigned long
119arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
120 unsigned long len, unsigned long pgoff,
121 unsigned long flags);
122#else
123static inline void arch_pick_mmap_layout(struct mm_struct *mm) {}
124#endif
125
126static 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 */
157static 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
170static 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
177static inline void memalloc_noio_restore(unsigned int flags)
178{
179 current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
180}
181
182static 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
189static inline void memalloc_nofs_restore(unsigned int flags)
190{
191 current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;
192}
193
194static 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
201static 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 */