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

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  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 
 11 /*
 12  * Routines for handling mm_structs
 13  */
 14 extern struct mm_struct * mm_alloc(void);
 15 
 16 /**
 17  * mmgrab() - Pin a &struct mm_struct.
 18  * @mm: The &struct mm_struct to pin.
 19  *
 20  * Make sure that @mm will not get freed even after the owning task
 21  * exits. This doesn't guarantee that the associated address space
 22  * will still exist later on and mmget_not_zero() has to be used before
 23  * accessing it.
 24  *
 25  * This is a preferred way to to pin @mm for a longer/unbounded amount
 26  * of time.
 27  *
 28  * Use mmdrop() to release the reference acquired by mmgrab().
 29  *
 30  * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
 31  * of &mm_struct.mm_count vs &mm_struct.mm_users.
 32  */
 33 static inline void mmgrab(struct mm_struct *mm)
 34 {
 35         atomic_inc(&mm->mm_count);
 36 }
 37 
 38 /* mmdrop drops the mm and the page tables */
 39 extern void __mmdrop(struct mm_struct *);
 40 static inline void mmdrop(struct mm_struct *mm)
 41 {
 42         if (unlikely(atomic_dec_and_test(&mm->mm_count)))
 43                 __mmdrop(mm);
 44 }
 45 
 46 static inline void mmdrop_async_fn(struct work_struct *work)
 47 {
 48         struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
 49         __mmdrop(mm);
 50 }
 51 
 52 static inline void mmdrop_async(struct mm_struct *mm)
 53 {
 54         if (unlikely(atomic_dec_and_test(&mm->mm_count))) {
 55                 INIT_WORK(&mm->async_put_work, mmdrop_async_fn);
 56                 schedule_work(&mm->async_put_work);
 57         }
 58 }
 59 
 60 /**
 61  * mmget() - Pin the address space associated with a &struct mm_struct.
 62  * @mm: The address space to pin.
 63  *
 64  * Make sure that the address space of the given &struct mm_struct doesn't
 65  * go away. This does not protect against parts of the address space being
 66  * modified or freed, however.
 67  *
 68  * Never use this function to pin this address space for an
 69  * unbounded/indefinite amount of time.
 70  *
 71  * Use mmput() to release the reference acquired by mmget().
 72  *
 73  * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
 74  * of &mm_struct.mm_count vs &mm_struct.mm_users.
 75  */
 76 static inline void mmget(struct mm_struct *mm)
 77 {
 78         atomic_inc(&mm->mm_users);
 79 }
 80 
 81 static inline bool mmget_not_zero(struct mm_struct *mm)
 82 {
 83         return atomic_inc_not_zero(&mm->mm_users);
 84 }
 85 
 86 /* mmput gets rid of the mappings and all user-space */
 87 extern void mmput(struct mm_struct *);
 88 #ifdef CONFIG_MMU
 89 /* same as above but performs the slow path from the async context. Can
 90  * be called from the atomic context as well
 91  */
 92 void mmput_async(struct mm_struct *);
 93 #endif
 94 
 95 /* Grab a reference to a task's mm, if it is not already going away */
 96 extern struct mm_struct *get_task_mm(struct task_struct *task);
 97 /*
 98  * Grab a reference to a task's mm, if it is not already going away
 99  * and ptrace_may_access with the mode parameter passed to it
100  * succeeds.
101  */
102 extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode);
103 /* Remove the current tasks stale references to the old mm_struct */
104 extern void mm_release(struct task_struct *, struct mm_struct *);
105 
106 #ifdef CONFIG_MEMCG
107 extern void mm_update_next_owner(struct mm_struct *mm);
108 #else
109 static inline void mm_update_next_owner(struct mm_struct *mm)
110 {
111 }
112 #endif /* CONFIG_MEMCG */
113 
114 #ifdef CONFIG_MMU
115 extern void arch_pick_mmap_layout(struct mm_struct *mm);
116 extern unsigned long
117 arch_get_unmapped_area(struct file *, unsigned long, unsigned long,
118                        unsigned long, unsigned long);
119 extern unsigned long
120 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
121                           unsigned long len, unsigned long pgoff,
122                           unsigned long flags);
123 #else
124 static inline void arch_pick_mmap_layout(struct mm_struct *mm) {}
125 #endif
126 
127 static inline bool in_vfork(struct task_struct *tsk)
128 {
129         bool ret;
130 
131         /*
132          * need RCU to access ->real_parent if CLONE_VM was used along with
133          * CLONE_PARENT.
134          *
135          * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
136          * imply CLONE_VM
137          *
138          * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
139          * ->real_parent is not necessarily the task doing vfork(), so in
140          * theory we can't rely on task_lock() if we want to dereference it.
141          *
142          * And in this case we can't trust the real_parent->mm == tsk->mm
143          * check, it can be false negative. But we do not care, if init or
144          * another oom-unkillable task does this it should blame itself.
145          */
146         rcu_read_lock();
147         ret = tsk->vfork_done && tsk->real_parent->mm == tsk->mm;
148         rcu_read_unlock();
149 
150         return ret;
151 }
152 
153 /*
154  * Applies per-task gfp context to the given allocation flags.
155  * PF_MEMALLOC_NOIO implies GFP_NOIO
156  * PF_MEMALLOC_NOFS implies GFP_NOFS
157  */
158 static inline gfp_t current_gfp_context(gfp_t flags)
159 {
160         /*
161          * NOIO implies both NOIO and NOFS and it is a weaker context
162          * so always make sure it makes precendence
163          */
164         if (unlikely(current->flags & PF_MEMALLOC_NOIO))
165                 flags &= ~(__GFP_IO | __GFP_FS);
166         else if (unlikely(current->flags & PF_MEMALLOC_NOFS))
167                 flags &= ~__GFP_FS;
168         return flags;
169 }
170 
171 #ifdef CONFIG_LOCKDEP
172 extern void fs_reclaim_acquire(gfp_t gfp_mask);
173 extern void fs_reclaim_release(gfp_t gfp_mask);
174 #else
175 static inline void fs_reclaim_acquire(gfp_t gfp_mask) { }
176 static inline void fs_reclaim_release(gfp_t gfp_mask) { }
177 #endif
178 
179 static inline unsigned int memalloc_noio_save(void)
180 {
181         unsigned int flags = current->flags & PF_MEMALLOC_NOIO;
182         current->flags |= PF_MEMALLOC_NOIO;
183         return flags;
184 }
185 
186 static inline void memalloc_noio_restore(unsigned int flags)
187 {
188         current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
189 }
190 
191 static inline unsigned int memalloc_nofs_save(void)
192 {
193         unsigned int flags = current->flags & PF_MEMALLOC_NOFS;
194         current->flags |= PF_MEMALLOC_NOFS;
195         return flags;
196 }
197 
198 static inline void memalloc_nofs_restore(unsigned int flags)
199 {
200         current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;
201 }
202 
203 static inline unsigned int memalloc_noreclaim_save(void)
204 {
205         unsigned int flags = current->flags & PF_MEMALLOC;
206         current->flags |= PF_MEMALLOC;
207         return flags;
208 }
209 
210 static inline void memalloc_noreclaim_restore(unsigned int flags)
211 {
212         current->flags = (current->flags & ~PF_MEMALLOC) | flags;
213 }
214 
215 #ifdef CONFIG_MEMBARRIER
216 enum {
217         MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY        = (1U << 0),
218         MEMBARRIER_STATE_SWITCH_MM                      = (1U << 1),
219 };
220 
221 static inline void membarrier_execve(struct task_struct *t)
222 {
223         atomic_set(&t->mm->membarrier_state, 0);
224 }
225 #else
226 static inline void membarrier_execve(struct task_struct *t)
227 {
228 }
229 #endif
230 
231 #endif /* _LINUX_SCHED_MM_H */
232 

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