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 #include <linux/sync_core.h>
  11
  12 /*
  13  * Routines for handling mm_structs
  14  */
  15 extern struct mm_struct *mm_alloc(void);
  16
  17 /**
  18  * mmgrab() - Pin a &struct mm_struct.
  19  * @mm: The &struct mm_struct to pin.
  20  *
  21  * Make sure that @mm will not get freed even after the owning task
  22  * exits. This doesn't guarantee that the associated address space
  23  * will still exist later on and mmget_not_zero() has to be used before
  24  * accessing it.
  25  *
  26  * This is a preferred way to to pin @mm for a longer/unbounded amount
  27  * of time.
  28  *
  29  * Use mmdrop() to release the reference acquired by mmgrab().
  30  *
  31  * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
  32  * of &mm_struct.mm_count vs &mm_struct.mm_users.
  33  */
  34 static inline void mmgrab(struct mm_struct *mm)
  35 {
  36         atomic_inc(&mm->mm_count);
  37 }
  38
  39 extern void __mmdrop(struct mm_struct *mm);
  40
  41 static inline void mmdrop(struct mm_struct *mm)
  42 {
  43         /*
  44          * The implicit full barrier implied by atomic_dec_and_test() is
  45          * required by the membarrier system call before returning to
  46          * user-space, after storing to rq->curr.
  47          */
  48         if (unlikely(atomic_dec_and_test(&mm->mm_count)))
  49                 __mmdrop(mm);
  50 }
  51
  52 /**
  53  * mmget() - Pin the address space associated with a &struct mm_struct.
  54  * @mm: The address space to pin.
  55  *
  56  * Make sure that the address space of the given &struct mm_struct doesn't
  57  * go away. This does not protect against parts of the address space being
  58  * modified or freed, however.
  59  *
  60  * Never use this function to pin this address space for an
  61  * unbounded/indefinite amount of time.
  62  *
  63  * Use mmput() to release the reference acquired by mmget().
  64  *
  65  * See also <Documentation/vm/active_mm.txt> for an in-depth explanation
  66  * of &mm_struct.mm_count vs &mm_struct.mm_users.
  67  */
  68 static inline void mmget(struct mm_struct *mm)
  69 {
  70         atomic_inc(&mm->mm_users);
  71 }
  72
  73 static inline bool mmget_not_zero(struct mm_struct *mm)
  74 {
  75         return atomic_inc_not_zero(&mm->mm_users);
  76 }
  77
  78 /* mmput gets rid of the mappings and all user-space */
  79 extern void mmput(struct mm_struct *);
  80 #ifdef CONFIG_MMU
  81 /* same as above but performs the slow path from the async context. Can
  82  * be called from the atomic context as well
  83  */
  84 void mmput_async(struct mm_struct *);
  85 #endif
  86
  87 /* Grab a reference to a task's mm, if it is not already going away */
  88 extern struct mm_struct *get_task_mm(struct task_struct *task);
  89 /*
  90  * Grab a reference to a task's mm, if it is not already going away
  91  * and ptrace_may_access with the mode parameter passed to it
  92  * succeeds.
  93  */
  94 extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode);
  95 /* Remove the current tasks stale references to the old mm_struct */
  96 extern void mm_release(struct task_struct *, struct mm_struct *);
  97
  98 #ifdef CONFIG_MEMCG
  99 extern void mm_update_next_owner(struct mm_struct *mm);
 100 #else
 101 static inline void mm_update_next_owner(struct mm_struct *mm)
 102 {
 103 }
 104 #endif /* CONFIG_MEMCG */
 105
 106 #ifdef CONFIG_MMU
 107 extern void arch_pick_mmap_layout(struct mm_struct *mm);
 108 extern unsigned long
 109 arch_get_unmapped_area(struct file *, unsigned long, unsigned long,
 110                        unsigned long, unsigned long);
 111 extern unsigned long
 112 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
 113                           unsigned long len, unsigned long pgoff,
 114                           unsigned long flags);
 115 #else
 116 static inline void arch_pick_mmap_layout(struct mm_struct *mm) {}
 117 #endif
 118
 119 static inline bool in_vfork(struct task_struct *tsk)
 120 {
 121         bool ret;
 122
 123         /*
 124          * need RCU to access ->real_parent if CLONE_VM was used along with
 125          * CLONE_PARENT.
 126          *
 127          * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
 128          * imply CLONE_VM
 129          *
 130          * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
 131          * ->real_parent is not necessarily the task doing vfork(), so in
 132          * theory we can't rely on task_lock() if we want to dereference it.
 133          *
 134          * And in this case we can't trust the real_parent->mm == tsk->mm
 135          * check, it can be false negative. But we do not care, if init or
 136          * another oom-unkillable task does this it should blame itself.
 137          */
 138         rcu_read_lock();
 139         ret = tsk->vfork_done && tsk->real_parent->mm == tsk->mm;
 140         rcu_read_unlock();
 141
 142         return ret;
 143 }
 144
 145 /*
 146  * Applies per-task gfp context to the given allocation flags.
 147  * PF_MEMALLOC_NOIO implies GFP_NOIO
 148  * PF_MEMALLOC_NOFS implies GFP_NOFS
 149  */
 150 static inline gfp_t current_gfp_context(gfp_t flags)
 151 {
 152         /*
 153          * NOIO implies both NOIO and NOFS and it is a weaker context
 154          * so always make sure it makes precendence
 155          */
 156         if (unlikely(current->flags & PF_MEMALLOC_NOIO))
 157                 flags &= ~(__GFP_IO | __GFP_FS);
 158         else if (unlikely(current->flags & PF_MEMALLOC_NOFS))
 159                 flags &= ~__GFP_FS;
 160         return flags;
 161 }
 162
 163 #ifdef CONFIG_LOCKDEP
 164 extern void fs_reclaim_acquire(gfp_t gfp_mask);
 165 extern void fs_reclaim_release(gfp_t gfp_mask);
 166 #else
 167 static inline void fs_reclaim_acquire(gfp_t gfp_mask) { }
 168 static inline void fs_reclaim_release(gfp_t gfp_mask) { }
 169 #endif
 170
 171 static inline unsigned int memalloc_noio_save(void)
 172 {
 173         unsigned int flags = current->flags & PF_MEMALLOC_NOIO;
 174         current->flags |= PF_MEMALLOC_NOIO;
 175         return flags;
 176 }
 177
 178 static inline void memalloc_noio_restore(unsigned int flags)
 179 {
 180         current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
 181 }
 182
 183 static inline unsigned int memalloc_nofs_save(void)
 184 {
 185         unsigned int flags = current->flags & PF_MEMALLOC_NOFS;
 186         current->flags |= PF_MEMALLOC_NOFS;
 187         return flags;
 188 }
 189
 190 static inline void memalloc_nofs_restore(unsigned int flags)
 191 {
 192         current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;
 193 }
 194
 195 static inline unsigned int memalloc_noreclaim_save(void)
 196 {
 197         unsigned int flags = current->flags & PF_MEMALLOC;
 198         current->flags |= PF_MEMALLOC;
 199         return flags;
 200 }
 201
 202 static inline void memalloc_noreclaim_restore(unsigned int flags)
 203 {
 204         current->flags = (current->flags & ~PF_MEMALLOC) | flags;
 205 }
 206
 207 #ifdef CONFIG_MEMBARRIER
 208 enum {
 209         MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY                = (1U << 0),
 210         MEMBARRIER_STATE_PRIVATE_EXPEDITED                      = (1U << 1),
 211         MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY                 = (1U << 2),
 212         MEMBARRIER_STATE_GLOBAL_EXPEDITED                       = (1U << 3),
 213         MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY      = (1U << 4),
 214         MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE            = (1U << 5),
 215 };
 216
 217 enum {
 218         MEMBARRIER_FLAG_SYNC_CORE       = (1U << 0),
 219 };
 220
 221 #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
 222 #include <asm/membarrier.h>
 223 #endif
 224
 225 static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
 226 {
 227         if (likely(!(atomic_read(&mm->membarrier_state) &
 228                      MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE)))
 229                 return;
 230         sync_core_before_usermode();
 231 }
 232
 233 static inline void membarrier_execve(struct task_struct *t)
 234 {
 235         atomic_set(&t->mm->membarrier_state, 0);
 236 }
 237 #else
 238 #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
 239 static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
 240                                              struct mm_struct *next,
 241                                              struct task_struct *tsk)
 242 {
 243 }
 244 #endif
 245 static inline void membarrier_execve(struct task_struct *t)
 246 {
 247 }
 248 static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
 249 {
 250 }
 251 #endif
 252
 253 #endif /* _LINUX_SCHED_MM_H */