root/include/linux/sched/mm.h

INCLUDED FROM

DEFINITIONS

1. mmgrab
2. mmdrop
3. mmget_still_valid
4. mmget
5. mmget_not_zero
6. mm_update_next_owner
7. arch_pick_mmap_layout
8. in_vfork
9. current_gfp_context
10. __fs_reclaim_acquire
11. __fs_reclaim_release
12. fs_reclaim_acquire
13. fs_reclaim_release
14. memalloc_noio_save
15. memalloc_noio_restore
16. memalloc_nofs_save
17. memalloc_nofs_restore
18. memalloc_noreclaim_save
19. memalloc_noreclaim_restore
20. memalloc_nocma_save
21. memalloc_nocma_restore
22. memalloc_nocma_save
23. memalloc_nocma_restore
24. memalloc_use_memcg
25. memalloc_unuse_memcg
26. memalloc_use_memcg
27. memalloc_unuse_memcg
28. membarrier_mm_sync_core_before_usermode
29. membarrier_arch_switch_mm
30. membarrier_exec_mmap
31. membarrier_mm_sync_core_before_usermode

   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.rst> 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  * This has to be called after a get_task_mm()/mmget_not_zero()
  54  * followed by taking the mmap_sem for writing before modifying the
  55  * vmas or anything the coredump pretends not to change from under it.
  56  *
  57  * It also has to be called when mmgrab() is used in the context of
  58  * the process, but then the mm_count refcount is transferred outside
  59  * the context of the process to run down_write() on that pinned mm.
  60  *
  61  * NOTE: find_extend_vma() called from GUP context is the only place
  62  * that can modify the "mm" (notably the vm_start/end) under mmap_sem
  63  * for reading and outside the context of the process, so it is also
  64  * the only case that holds the mmap_sem for reading that must call
  65  * this function. Generally if the mmap_sem is hold for reading
  66  * there's no need of this check after get_task_mm()/mmget_not_zero().
  67  *
  68  * This function can be obsoleted and the check can be removed, after
  69  * the coredump code will hold the mmap_sem for writing before
  70  * invoking the ->core_dump methods.
  71  */
  72 static inline bool mmget_still_valid(struct mm_struct *mm)
  73 {
  74         return likely(!mm->core_state);
  75 }
  76 
  77 /**
  78  * mmget() - Pin the address space associated with a &struct mm_struct.
  79  * @mm: The address space to pin.
  80  *
  81  * Make sure that the address space of the given &struct mm_struct doesn't
  82  * go away. This does not protect against parts of the address space being
  83  * modified or freed, however.
  84  *
  85  * Never use this function to pin this address space for an
  86  * unbounded/indefinite amount of time.
  87  *
  88  * Use mmput() to release the reference acquired by mmget().
  89  *
  90  * See also <Documentation/vm/active_mm.rst> for an in-depth explanation
  91  * of &mm_struct.mm_count vs &mm_struct.mm_users.
  92  */
  93 static inline void mmget(struct mm_struct *mm)
  94 {
  95         atomic_inc(&mm->mm_users);
  96 }
  97 
  98 static inline bool mmget_not_zero(struct mm_struct *mm)
  99 {
 100         return atomic_inc_not_zero(&mm->mm_users);
 101 }
 102 
 103 /* mmput gets rid of the mappings and all user-space */
 104 extern void mmput(struct mm_struct *);
 105 #ifdef CONFIG_MMU
 106 /* same as above but performs the slow path from the async context. Can
 107  * be called from the atomic context as well
 108  */
 109 void mmput_async(struct mm_struct *);
 110 #endif
 111 
 112 /* Grab a reference to a task's mm, if it is not already going away */
 113 extern struct mm_struct *get_task_mm(struct task_struct *task);
 114 /*
 115  * Grab a reference to a task's mm, if it is not already going away
 116  * and ptrace_may_access with the mode parameter passed to it
 117  * succeeds.
 118  */
 119 extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode);
 120 /* Remove the current tasks stale references to the old mm_struct on exit() */
 121 extern void exit_mm_release(struct task_struct *, struct mm_struct *);
 122 /* Remove the current tasks stale references to the old mm_struct on exec() */
 123 extern void exec_mm_release(struct task_struct *, struct mm_struct *);
 124 
 125 #ifdef CONFIG_MEMCG
 126 extern void mm_update_next_owner(struct mm_struct *mm);
 127 #else
 128 static inline void mm_update_next_owner(struct mm_struct *mm)
 129 {
 130 }
 131 #endif /* CONFIG_MEMCG */
 132 
 133 #ifdef CONFIG_MMU
 134 extern void arch_pick_mmap_layout(struct mm_struct *mm,
 135                                   struct rlimit *rlim_stack);
 136 extern unsigned long
 137 arch_get_unmapped_area(struct file *, unsigned long, unsigned long,
 138                        unsigned long, unsigned long);
 139 extern unsigned long
 140 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
 141                           unsigned long len, unsigned long pgoff,
 142                           unsigned long flags);
 143 #else
 144 static inline void arch_pick_mmap_layout(struct mm_struct *mm,
 145                                          struct rlimit *rlim_stack) {}
 146 #endif
 147 
 148 static inline bool in_vfork(struct task_struct *tsk)
 149 {
 150         bool ret;
 151 
 152         /*
 153          * need RCU to access ->real_parent if CLONE_VM was used along with
 154          * CLONE_PARENT.
 155          *
 156          * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
 157          * imply CLONE_VM
 158          *
 159          * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
 160          * ->real_parent is not necessarily the task doing vfork(), so in
 161          * theory we can't rely on task_lock() if we want to dereference it.
 162          *
 163          * And in this case we can't trust the real_parent->mm == tsk->mm
 164          * check, it can be false negative. But we do not care, if init or
 165          * another oom-unkillable task does this it should blame itself.
 166          */
 167         rcu_read_lock();
 168         ret = tsk->vfork_done && tsk->real_parent->mm == tsk->mm;
 169         rcu_read_unlock();
 170 
 171         return ret;
 172 }
 173 
 174 /*
 175  * Applies per-task gfp context to the given allocation flags.
 176  * PF_MEMALLOC_NOIO implies GFP_NOIO
 177  * PF_MEMALLOC_NOFS implies GFP_NOFS
 178  * PF_MEMALLOC_NOCMA implies no allocation from CMA region.
 179  */
 180 static inline gfp_t current_gfp_context(gfp_t flags)
 181 {
 182         if (unlikely(current->flags &
 183                      (PF_MEMALLOC_NOIO | PF_MEMALLOC_NOFS | PF_MEMALLOC_NOCMA))) {
 184                 /*
 185                  * NOIO implies both NOIO and NOFS and it is a weaker context
 186                  * so always make sure it makes precedence
 187                  */
 188                 if (current->flags & PF_MEMALLOC_NOIO)
 189                         flags &= ~(__GFP_IO | __GFP_FS);
 190                 else if (current->flags & PF_MEMALLOC_NOFS)
 191                         flags &= ~__GFP_FS;
 192 #ifdef CONFIG_CMA
 193                 if (current->flags & PF_MEMALLOC_NOCMA)
 194                         flags &= ~__GFP_MOVABLE;
 195 #endif
 196         }
 197         return flags;
 198 }
 199 
 200 #ifdef CONFIG_LOCKDEP
 201 extern void __fs_reclaim_acquire(void);
 202 extern void __fs_reclaim_release(void);
 203 extern void fs_reclaim_acquire(gfp_t gfp_mask);
 204 extern void fs_reclaim_release(gfp_t gfp_mask);
 205 #else
 206 static inline void __fs_reclaim_acquire(void) { }
 207 static inline void __fs_reclaim_release(void) { }
 208 static inline void fs_reclaim_acquire(gfp_t gfp_mask) { }
 209 static inline void fs_reclaim_release(gfp_t gfp_mask) { }
 210 #endif
 211 
 212 /**
 213  * memalloc_noio_save - Marks implicit GFP_NOIO allocation scope.
 214  *
 215  * This functions marks the beginning of the GFP_NOIO allocation scope.
 216  * All further allocations will implicitly drop __GFP_IO flag and so
 217  * they are safe for the IO critical section from the allocation recursion
 218  * point of view. Use memalloc_noio_restore to end the scope with flags
 219  * returned by this function.
 220  *
 221  * This function is safe to be used from any context.
 222  */
 223 static inline unsigned int memalloc_noio_save(void)
 224 {
 225         unsigned int flags = current->flags & PF_MEMALLOC_NOIO;
 226         current->flags |= PF_MEMALLOC_NOIO;
 227         return flags;
 228 }
 229 
 230 /**
 231  * memalloc_noio_restore - Ends the implicit GFP_NOIO scope.
 232  * @flags: Flags to restore.
 233  *
 234  * Ends the implicit GFP_NOIO scope started by memalloc_noio_save function.
 235  * Always make sure that that the given flags is the return value from the
 236  * pairing memalloc_noio_save call.
 237  */
 238 static inline void memalloc_noio_restore(unsigned int flags)
 239 {
 240         current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
 241 }
 242 
 243 /**
 244  * memalloc_nofs_save - Marks implicit GFP_NOFS allocation scope.
 245  *
 246  * This functions marks the beginning of the GFP_NOFS allocation scope.
 247  * All further allocations will implicitly drop __GFP_FS flag and so
 248  * they are safe for the FS critical section from the allocation recursion
 249  * point of view. Use memalloc_nofs_restore to end the scope with flags
 250  * returned by this function.
 251  *
 252  * This function is safe to be used from any context.
 253  */
 254 static inline unsigned int memalloc_nofs_save(void)
 255 {
 256         unsigned int flags = current->flags & PF_MEMALLOC_NOFS;
 257         current->flags |= PF_MEMALLOC_NOFS;
 258         return flags;
 259 }
 260 
 261 /**
 262  * memalloc_nofs_restore - Ends the implicit GFP_NOFS scope.
 263  * @flags: Flags to restore.
 264  *
 265  * Ends the implicit GFP_NOFS scope started by memalloc_nofs_save function.
 266  * Always make sure that that the given flags is the return value from the
 267  * pairing memalloc_nofs_save call.
 268  */
 269 static inline void memalloc_nofs_restore(unsigned int flags)
 270 {
 271         current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;
 272 }
 273 
 274 static inline unsigned int memalloc_noreclaim_save(void)
 275 {
 276         unsigned int flags = current->flags & PF_MEMALLOC;
 277         current->flags |= PF_MEMALLOC;
 278         return flags;
 279 }
 280 
 281 static inline void memalloc_noreclaim_restore(unsigned int flags)
 282 {
 283         current->flags = (current->flags & ~PF_MEMALLOC) | flags;
 284 }
 285 
 286 #ifdef CONFIG_CMA
 287 static inline unsigned int memalloc_nocma_save(void)
 288 {
 289         unsigned int flags = current->flags & PF_MEMALLOC_NOCMA;
 290 
 291         current->flags |= PF_MEMALLOC_NOCMA;
 292         return flags;
 293 }
 294 
 295 static inline void memalloc_nocma_restore(unsigned int flags)
 296 {
 297         current->flags = (current->flags & ~PF_MEMALLOC_NOCMA) | flags;
 298 }
 299 #else
 300 static inline unsigned int memalloc_nocma_save(void)
 301 {
 302         return 0;
 303 }
 304 
 305 static inline void memalloc_nocma_restore(unsigned int flags)
 306 {
 307 }
 308 #endif
 309 
 310 #ifdef CONFIG_MEMCG
 311 /**
 312  * memalloc_use_memcg - Starts the remote memcg charging scope.
 313  * @memcg: memcg to charge.
 314  *
 315  * This function marks the beginning of the remote memcg charging scope. All the
 316  * __GFP_ACCOUNT allocations till the end of the scope will be charged to the
 317  * given memcg.
 318  *
 319  * NOTE: This function is not nesting safe.
 320  */
 321 static inline void memalloc_use_memcg(struct mem_cgroup *memcg)
 322 {
 323         WARN_ON_ONCE(current->active_memcg);
 324         current->active_memcg = memcg;
 325 }
 326 
 327 /**
 328  * memalloc_unuse_memcg - Ends the remote memcg charging scope.
 329  *
 330  * This function marks the end of the remote memcg charging scope started by
 331  * memalloc_use_memcg().
 332  */
 333 static inline void memalloc_unuse_memcg(void)
 334 {
 335         current->active_memcg = NULL;
 336 }
 337 #else
 338 static inline void memalloc_use_memcg(struct mem_cgroup *memcg)
 339 {
 340 }
 341 
 342 static inline void memalloc_unuse_memcg(void)
 343 {
 344 }
 345 #endif
 346 
 347 #ifdef CONFIG_MEMBARRIER
 348 enum {
 349         MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY                = (1U << 0),
 350         MEMBARRIER_STATE_PRIVATE_EXPEDITED                      = (1U << 1),
 351         MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY                 = (1U << 2),
 352         MEMBARRIER_STATE_GLOBAL_EXPEDITED                       = (1U << 3),
 353         MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY      = (1U << 4),
 354         MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE            = (1U << 5),
 355 };
 356 
 357 enum {
 358         MEMBARRIER_FLAG_SYNC_CORE       = (1U << 0),
 359 };
 360 
 361 #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
 362 #include <asm/membarrier.h>
 363 #endif
 364 
 365 static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
 366 {
 367         if (current->mm != mm)
 368                 return;
 369         if (likely(!(atomic_read(&mm->membarrier_state) &
 370                      MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE)))
 371                 return;
 372         sync_core_before_usermode();
 373 }
 374 
 375 extern void membarrier_exec_mmap(struct mm_struct *mm);
 376 
 377 #else
 378 #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
 379 static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
 380                                              struct mm_struct *next,
 381                                              struct task_struct *tsk)
 382 {
 383 }
 384 #endif
 385 static inline void membarrier_exec_mmap(struct mm_struct *mm)
 386 {
 387 }
 388 static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
 389 {
 390 }
 391 #endif
 392 
 393 #endif /* _LINUX_SCHED_MM_H */