1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_SCHED_MM_H
3 #define _LINUX_SCHED_MM_H
5 #include <linux/kernel.h>
6 #include <linux/atomic.h>
7 #include <linux/sched.h>
8 #include <linux/mm_types.h>
12 * Routines for handling mm_structs
14 extern struct mm_struct * mm_alloc(void);
17 * mmgrab() - Pin a &struct mm_struct.
18 * @mm: The &struct mm_struct to pin.
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
25 * This is a preferred way to to pin @mm for a longer/unbounded amount
28 * Use mmdrop() to release the reference acquired by mmgrab().
30 * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
31 * of &mm_struct.mm_count vs &mm_struct.mm_users.
33 static inline void mmgrab(struct mm_struct *mm)
35 atomic_inc(&mm->mm_count);
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)
42 if (unlikely(atomic_dec_and_test(&mm->mm_count)))
46 static inline void mmdrop_async_fn(struct work_struct *work)
48 struct mm_struct *mm = container_of(work, struct mm_struct, async_put_work);
52 static inline void mmdrop_async(struct mm_struct *mm)
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);
61 * This has to be called after a get_task_mm()/mmget_not_zero()
62 * followed by taking the mmap_sem for writing before modifying the
63 * vmas or anything the coredump pretends not to change from under it.
65 * It also has to be called when mmgrab() is used in the context of
66 * the process, but then the mm_count refcount is transferred outside
67 * the context of the process to run down_write() on that pinned mm.
69 * NOTE: find_extend_vma() called from GUP context is the only place
70 * that can modify the "mm" (notably the vm_start/end) under mmap_sem
71 * for reading and outside the context of the process, so it is also
72 * the only case that holds the mmap_sem for reading that must call
73 * this function. Generally if the mmap_sem is hold for reading
74 * there's no need of this check after get_task_mm()/mmget_not_zero().
76 * This function can be obsoleted and the check can be removed, after
77 * the coredump code will hold the mmap_sem for writing before
78 * invoking the ->core_dump methods.
80 static inline bool mmget_still_valid(struct mm_struct *mm)
82 return likely(!mm->core_state);
86 * mmget() - Pin the address space associated with a &struct mm_struct.
87 * @mm: The address space to pin.
89 * Make sure that the address space of the given &struct mm_struct doesn't
90 * go away. This does not protect against parts of the address space being
91 * modified or freed, however.
93 * Never use this function to pin this address space for an
94 * unbounded/indefinite amount of time.
96 * Use mmput() to release the reference acquired by mmget().
98 * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
99 * of &mm_struct.mm_count vs &mm_struct.mm_users.
101 static inline void mmget(struct mm_struct *mm)
103 atomic_inc(&mm->mm_users);
106 static inline bool mmget_not_zero(struct mm_struct *mm)
108 return atomic_inc_not_zero(&mm->mm_users);
111 /* mmput gets rid of the mappings and all user-space */
112 extern void mmput(struct mm_struct *);
114 /* same as above but performs the slow path from the async context. Can
115 * be called from the atomic context as well
117 void mmput_async(struct mm_struct *);
120 /* Grab a reference to a task's mm, if it is not already going away */
121 extern struct mm_struct *get_task_mm(struct task_struct *task);
123 * Grab a reference to a task's mm, if it is not already going away
124 * and ptrace_may_access with the mode parameter passed to it
127 extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode);
128 /* Remove the current tasks stale references to the old mm_struct on exit() */
129 extern void exit_mm_release(struct task_struct *, struct mm_struct *);
130 /* Remove the current tasks stale references to the old mm_struct on exec() */
131 extern void exec_mm_release(struct task_struct *, struct mm_struct *);
134 extern void mm_update_next_owner(struct mm_struct *mm);
136 static inline void mm_update_next_owner(struct mm_struct *mm)
139 #endif /* CONFIG_MEMCG */
142 extern void arch_pick_mmap_layout(struct mm_struct *mm);
144 arch_get_unmapped_area(struct file *, unsigned long, unsigned long,
145 unsigned long, unsigned long);
147 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
148 unsigned long len, unsigned long pgoff,
149 unsigned long flags);
151 static inline void arch_pick_mmap_layout(struct mm_struct *mm) {}
154 static inline bool in_vfork(struct task_struct *tsk)
159 * need RCU to access ->real_parent if CLONE_VM was used along with
162 * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
165 * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
166 * ->real_parent is not necessarily the task doing vfork(), so in
167 * theory we can't rely on task_lock() if we want to dereference it.
169 * And in this case we can't trust the real_parent->mm == tsk->mm
170 * check, it can be false negative. But we do not care, if init or
171 * another oom-unkillable task does this it should blame itself.
174 ret = tsk->vfork_done &&
175 rcu_dereference(tsk->real_parent)->mm == tsk->mm;
182 * Applies per-task gfp context to the given allocation flags.
183 * PF_MEMALLOC_NOIO implies GFP_NOIO
184 * PF_MEMALLOC_NOFS implies GFP_NOFS
186 static inline gfp_t current_gfp_context(gfp_t flags)
189 * NOIO implies both NOIO and NOFS and it is a weaker context
190 * so always make sure it makes precendence
192 if (unlikely(current->flags & PF_MEMALLOC_NOIO))
193 flags &= ~(__GFP_IO | __GFP_FS);
194 else if (unlikely(current->flags & PF_MEMALLOC_NOFS))
199 #ifdef CONFIG_LOCKDEP
200 extern void fs_reclaim_acquire(gfp_t gfp_mask);
201 extern void fs_reclaim_release(gfp_t gfp_mask);
203 static inline void fs_reclaim_acquire(gfp_t gfp_mask) { }
204 static inline void fs_reclaim_release(gfp_t gfp_mask) { }
207 static inline unsigned int memalloc_noio_save(void)
209 unsigned int flags = current->flags & PF_MEMALLOC_NOIO;
210 current->flags |= PF_MEMALLOC_NOIO;
214 static inline void memalloc_noio_restore(unsigned int flags)
216 current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
219 static inline unsigned int memalloc_nofs_save(void)
221 unsigned int flags = current->flags & PF_MEMALLOC_NOFS;
222 current->flags |= PF_MEMALLOC_NOFS;
226 static inline void memalloc_nofs_restore(unsigned int flags)
228 current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;
231 static inline unsigned int memalloc_noreclaim_save(void)
233 unsigned int flags = current->flags & PF_MEMALLOC;
234 current->flags |= PF_MEMALLOC;
238 static inline void memalloc_noreclaim_restore(unsigned int flags)
240 current->flags = (current->flags & ~PF_MEMALLOC) | flags;
243 #ifdef CONFIG_MEMBARRIER
245 MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY = (1U << 0),
246 MEMBARRIER_STATE_SWITCH_MM = (1U << 1),
249 static inline void membarrier_execve(struct task_struct *t)
251 atomic_set(&t->mm->membarrier_state, 0);
254 static inline void membarrier_execve(struct task_struct *t)
259 #endif /* _LINUX_SCHED_MM_H */