include/linux/sched/mm.h

   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 */