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TOMOYO Linux Cross Reference
Linux/include/linux/sched/mm.h

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  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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