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 #include <linux/sched/coredump.h> 12 13 /* 14 * Routines for handling mm_structs 15 */ 16 extern struct mm_struct *mm_alloc(void); 17 18 /** 19 * mmgrab() - Pin a &struct mm_struct. 20 * @mm: The &struct mm_struct to pin. 21 * 22 * Make sure that @mm will not get freed even after the owning task 23 * exits. This doesn't guarantee that the associated address space 24 * will still exist later on and mmget_not_zero() has to be used before 25 * accessing it. 26 * 27 * This is a preferred way to pin @mm for a longer/unbounded amount 28 * of time. 29 * 30 * Use mmdrop() to release the reference acquired by mmgrab(). 31 * 32 * See also <Documentation/mm/active_mm.rst> for an in-depth explanation 33 * of &mm_struct.mm_count vs &mm_struct.mm_users. 34 */ 35 static inline void mmgrab(struct mm_struct *mm) 36 { 37 atomic_inc(&mm->mm_count); 38 } 39 40 static inline void smp_mb__after_mmgrab(void) 41 { 42 smp_mb__after_atomic(); 43 } 44 45 extern void __mmdrop(struct mm_struct *mm); 46 47 static inline void mmdrop(struct mm_struct *mm) 48 { 49 /* 50 * The implicit full barrier implied by atomic_dec_and_test() is 51 * required by the membarrier system call before returning to 52 * user-space, after storing to rq->curr. 53 */ 54 if (unlikely(atomic_dec_and_test(&mm->mm_count))) 55 __mmdrop(mm); 56 } 57 58 #ifdef CONFIG_PREEMPT_RT 59 /* 60 * RCU callback for delayed mm drop. Not strictly RCU, but call_rcu() is 61 * by far the least expensive way to do that. 62 */ 63 static inline void __mmdrop_delayed(struct rcu_head *rhp) 64 { 65 struct mm_struct *mm = container_of(rhp, struct mm_struct, delayed_drop); 66 67 __mmdrop(mm); 68 } 69 70 /* 71 * Invoked from finish_task_switch(). Delegates the heavy lifting on RT 72 * kernels via RCU. 73 */ 74 static inline void mmdrop_sched(struct mm_struct *mm) 75 { 76 /* Provides a full memory barrier. See mmdrop() */ 77 if (atomic_dec_and_test(&mm->mm_count)) 78 call_rcu(&mm->delayed_drop, __mmdrop_delayed); 79 } 80 #else 81 static inline void mmdrop_sched(struct mm_struct *mm) 82 { 83 mmdrop(mm); 84 } 85 #endif 86 87 /* Helpers for lazy TLB mm refcounting */ 88 static inline void mmgrab_lazy_tlb(struct mm_struct *mm) 89 { 90 if (IS_ENABLED(CONFIG_MMU_LAZY_TLB_REFCOUNT)) 91 mmgrab(mm); 92 } 93 94 static inline void mmdrop_lazy_tlb(struct mm_struct *mm) 95 { 96 if (IS_ENABLED(CONFIG_MMU_LAZY_TLB_REFCOUNT)) { 97 mmdrop(mm); 98 } else { 99 /* 100 * mmdrop_lazy_tlb must provide a full memory barrier, see the 101 * membarrier comment finish_task_switch which relies on this. 102 */ 103 smp_mb(); 104 } 105 } 106 107 static inline void mmdrop_lazy_tlb_sched(struct mm_struct *mm) 108 { 109 if (IS_ENABLED(CONFIG_MMU_LAZY_TLB_REFCOUNT)) 110 mmdrop_sched(mm); 111 else 112 smp_mb(); /* see mmdrop_lazy_tlb() above */ 113 } 114 115 /** 116 * mmget() - Pin the address space associated with a &struct mm_struct. 117 * @mm: The address space to pin. 118 * 119 * Make sure that the address space of the given &struct mm_struct doesn't 120 * go away. This does not protect against parts of the address space being 121 * modified or freed, however. 122 * 123 * Never use this function to pin this address space for an 124 * unbounded/indefinite amount of time. 125 * 126 * Use mmput() to release the reference acquired by mmget(). 127 * 128 * See also <Documentation/mm/active_mm.rst> for an in-depth explanation 129 * of &mm_struct.mm_count vs &mm_struct.mm_users. 130 */ 131 static inline void mmget(struct mm_struct *mm) 132 { 133 atomic_inc(&mm->mm_users); 134 } 135 136 static inline bool mmget_not_zero(struct mm_struct *mm) 137 { 138 return atomic_inc_not_zero(&mm->mm_users); 139 } 140 141 /* mmput gets rid of the mappings and all user-space */ 142 extern void mmput(struct mm_struct *); 143 #ifdef CONFIG_MMU 144 /* same as above but performs the slow path from the async context. Can 145 * be called from the atomic context as well 146 */ 147 void mmput_async(struct mm_struct *); 148 #endif 149 150 /* Grab a reference to a task's mm, if it is not already going away */ 151 extern struct mm_struct *get_task_mm(struct task_struct *task); 152 /* 153 * Grab a reference to a task's mm, if it is not already going away 154 * and ptrace_may_access with the mode parameter passed to it 155 * succeeds. 156 */ 157 extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode); 158 /* Remove the current tasks stale references to the old mm_struct on exit() */ 159 extern void exit_mm_release(struct task_struct *, struct mm_struct *); 160 /* Remove the current tasks stale references to the old mm_struct on exec() */ 161 extern void exec_mm_release(struct task_struct *, struct mm_struct *); 162 163 #ifdef CONFIG_MEMCG 164 extern void mm_update_next_owner(struct mm_struct *mm); 165 #else 166 static inline void mm_update_next_owner(struct mm_struct *mm) 167 { 168 } 169 #endif /* CONFIG_MEMCG */ 170 171 #ifdef CONFIG_MMU 172 #ifndef arch_get_mmap_end 173 #define arch_get_mmap_end(addr, len, flags) (TASK_SIZE) 174 #endif 175 176 #ifndef arch_get_mmap_base 177 #define arch_get_mmap_base(addr, base) (base) 178 #endif 179 180 extern void arch_pick_mmap_layout(struct mm_struct *mm, 181 struct rlimit *rlim_stack); 182 extern unsigned long 183 arch_get_unmapped_area(struct file *, unsigned long, unsigned long, 184 unsigned long, unsigned long); 185 extern unsigned long 186 arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr, 187 unsigned long len, unsigned long pgoff, 188 unsigned long flags); 189 190 unsigned long mm_get_unmapped_area(struct mm_struct *mm, struct file *filp, 191 unsigned long addr, unsigned long len, 192 unsigned long pgoff, unsigned long flags); 193 194 unsigned long 195 arch_get_unmapped_area_vmflags(struct file *filp, unsigned long addr, 196 unsigned long len, unsigned long pgoff, 197 unsigned long flags, vm_flags_t vm_flags); 198 unsigned long 199 arch_get_unmapped_area_topdown_vmflags(struct file *filp, unsigned long addr, 200 unsigned long len, unsigned long pgoff, 201 unsigned long flags, vm_flags_t); 202 203 unsigned long mm_get_unmapped_area_vmflags(struct mm_struct *mm, 204 struct file *filp, 205 unsigned long addr, 206 unsigned long len, 207 unsigned long pgoff, 208 unsigned long flags, 209 vm_flags_t vm_flags); 210 211 unsigned long 212 generic_get_unmapped_area(struct file *filp, unsigned long addr, 213 unsigned long len, unsigned long pgoff, 214 unsigned long flags); 215 unsigned long 216 generic_get_unmapped_area_topdown(struct file *filp, unsigned long addr, 217 unsigned long len, unsigned long pgoff, 218 unsigned long flags); 219 #else 220 static inline void arch_pick_mmap_layout(struct mm_struct *mm, 221 struct rlimit *rlim_stack) {} 222 #endif 223 224 static inline bool in_vfork(struct task_struct *tsk) 225 { 226 bool ret; 227 228 /* 229 * need RCU to access ->real_parent if CLONE_VM was used along with 230 * CLONE_PARENT. 231 * 232 * We check real_parent->mm == tsk->mm because CLONE_VFORK does not 233 * imply CLONE_VM 234 * 235 * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus 236 * ->real_parent is not necessarily the task doing vfork(), so in 237 * theory we can't rely on task_lock() if we want to dereference it. 238 * 239 * And in this case we can't trust the real_parent->mm == tsk->mm 240 * check, it can be false negative. But we do not care, if init or 241 * another oom-unkillable task does this it should blame itself. 242 */ 243 rcu_read_lock(); 244 ret = tsk->vfork_done && 245 rcu_dereference(tsk->real_parent)->mm == tsk->mm; 246 rcu_read_unlock(); 247 248 return ret; 249 } 250 251 /* 252 * Applies per-task gfp context to the given allocation flags. 253 * PF_MEMALLOC_NOIO implies GFP_NOIO 254 * PF_MEMALLOC_NOFS implies GFP_NOFS 255 * PF_MEMALLOC_PIN implies !GFP_MOVABLE 256 */ 257 static inline gfp_t current_gfp_context(gfp_t flags) 258 { 259 unsigned int pflags = READ_ONCE(current->flags); 260 261 if (unlikely(pflags & (PF_MEMALLOC_NOIO | 262 PF_MEMALLOC_NOFS | 263 PF_MEMALLOC_NORECLAIM | 264 PF_MEMALLOC_NOWARN | 265 PF_MEMALLOC_PIN))) { 266 /* 267 * Stronger flags before weaker flags: 268 * NORECLAIM implies NOIO, which in turn implies NOFS 269 */ 270 if (pflags & PF_MEMALLOC_NORECLAIM) 271 flags &= ~__GFP_DIRECT_RECLAIM; 272 else if (pflags & PF_MEMALLOC_NOIO) 273 flags &= ~(__GFP_IO | __GFP_FS); 274 else if (pflags & PF_MEMALLOC_NOFS) 275 flags &= ~__GFP_FS; 276 277 if (pflags & PF_MEMALLOC_NOWARN) 278 flags |= __GFP_NOWARN; 279 280 if (pflags & PF_MEMALLOC_PIN) 281 flags &= ~__GFP_MOVABLE; 282 } 283 return flags; 284 } 285 286 #ifdef CONFIG_LOCKDEP 287 extern void __fs_reclaim_acquire(unsigned long ip); 288 extern void __fs_reclaim_release(unsigned long ip); 289 extern void fs_reclaim_acquire(gfp_t gfp_mask); 290 extern void fs_reclaim_release(gfp_t gfp_mask); 291 #else 292 static inline void __fs_reclaim_acquire(unsigned long ip) { } 293 static inline void __fs_reclaim_release(unsigned long ip) { } 294 static inline void fs_reclaim_acquire(gfp_t gfp_mask) { } 295 static inline void fs_reclaim_release(gfp_t gfp_mask) { } 296 #endif 297 298 /* Any memory-allocation retry loop should use 299 * memalloc_retry_wait(), and pass the flags for the most 300 * constrained allocation attempt that might have failed. 301 * This provides useful documentation of where loops are, 302 * and a central place to fine tune the waiting as the MM 303 * implementation changes. 304 */ 305 static inline void memalloc_retry_wait(gfp_t gfp_flags) 306 { 307 /* We use io_schedule_timeout because waiting for memory 308 * typically included waiting for dirty pages to be 309 * written out, which requires IO. 310 */ 311 __set_current_state(TASK_UNINTERRUPTIBLE); 312 gfp_flags = current_gfp_context(gfp_flags); 313 if (gfpflags_allow_blocking(gfp_flags) && 314 !(gfp_flags & __GFP_NORETRY)) 315 /* Probably waited already, no need for much more */ 316 io_schedule_timeout(1); 317 else 318 /* Probably didn't wait, and has now released a lock, 319 * so now is a good time to wait 320 */ 321 io_schedule_timeout(HZ/50); 322 } 323 324 /** 325 * might_alloc - Mark possible allocation sites 326 * @gfp_mask: gfp_t flags that would be used to allocate 327 * 328 * Similar to might_sleep() and other annotations, this can be used in functions 329 * that might allocate, but often don't. Compiles to nothing without 330 * CONFIG_LOCKDEP. Includes a conditional might_sleep() if @gfp allows blocking. 331 */ 332 static inline void might_alloc(gfp_t gfp_mask) 333 { 334 fs_reclaim_acquire(gfp_mask); 335 fs_reclaim_release(gfp_mask); 336 337 might_sleep_if(gfpflags_allow_blocking(gfp_mask)); 338 } 339 340 /** 341 * memalloc_flags_save - Add a PF_* flag to current->flags, save old value 342 * 343 * This allows PF_* flags to be conveniently added, irrespective of current 344 * value, and then the old version restored with memalloc_flags_restore(). 345 */ 346 static inline unsigned memalloc_flags_save(unsigned flags) 347 { 348 unsigned oldflags = ~current->flags & flags; 349 current->flags |= flags; 350 return oldflags; 351 } 352 353 static inline void memalloc_flags_restore(unsigned flags) 354 { 355 current->flags &= ~flags; 356 } 357 358 /** 359 * memalloc_noio_save - Marks implicit GFP_NOIO allocation scope. 360 * 361 * This functions marks the beginning of the GFP_NOIO allocation scope. 362 * All further allocations will implicitly drop __GFP_IO flag and so 363 * they are safe for the IO critical section from the allocation recursion 364 * point of view. Use memalloc_noio_restore to end the scope with flags 365 * returned by this function. 366 * 367 * Context: This function is safe to be used from any context. 368 * Return: The saved flags to be passed to memalloc_noio_restore. 369 */ 370 static inline unsigned int memalloc_noio_save(void) 371 { 372 return memalloc_flags_save(PF_MEMALLOC_NOIO); 373 } 374 375 /** 376 * memalloc_noio_restore - Ends the implicit GFP_NOIO scope. 377 * @flags: Flags to restore. 378 * 379 * Ends the implicit GFP_NOIO scope started by memalloc_noio_save function. 380 * Always make sure that the given flags is the return value from the 381 * pairing memalloc_noio_save call. 382 */ 383 static inline void memalloc_noio_restore(unsigned int flags) 384 { 385 memalloc_flags_restore(flags); 386 } 387 388 /** 389 * memalloc_nofs_save - Marks implicit GFP_NOFS allocation scope. 390 * 391 * This functions marks the beginning of the GFP_NOFS allocation scope. 392 * All further allocations will implicitly drop __GFP_FS flag and so 393 * they are safe for the FS critical section from the allocation recursion 394 * point of view. Use memalloc_nofs_restore to end the scope with flags 395 * returned by this function. 396 * 397 * Context: This function is safe to be used from any context. 398 * Return: The saved flags to be passed to memalloc_nofs_restore. 399 */ 400 static inline unsigned int memalloc_nofs_save(void) 401 { 402 return memalloc_flags_save(PF_MEMALLOC_NOFS); 403 } 404 405 /** 406 * memalloc_nofs_restore - Ends the implicit GFP_NOFS scope. 407 * @flags: Flags to restore. 408 * 409 * Ends the implicit GFP_NOFS scope started by memalloc_nofs_save function. 410 * Always make sure that the given flags is the return value from the 411 * pairing memalloc_nofs_save call. 412 */ 413 static inline void memalloc_nofs_restore(unsigned int flags) 414 { 415 memalloc_flags_restore(flags); 416 } 417 418 /** 419 * memalloc_noreclaim_save - Marks implicit __GFP_MEMALLOC scope. 420 * 421 * This function marks the beginning of the __GFP_MEMALLOC allocation scope. 422 * All further allocations will implicitly add the __GFP_MEMALLOC flag, which 423 * prevents entering reclaim and allows access to all memory reserves. This 424 * should only be used when the caller guarantees the allocation will allow more 425 * memory to be freed very shortly, i.e. it needs to allocate some memory in 426 * the process of freeing memory, and cannot reclaim due to potential recursion. 427 * 428 * Users of this scope have to be extremely careful to not deplete the reserves 429 * completely and implement a throttling mechanism which controls the 430 * consumption of the reserve based on the amount of freed memory. Usage of a 431 * pre-allocated pool (e.g. mempool) should be always considered before using 432 * this scope. 433 * 434 * Individual allocations under the scope can opt out using __GFP_NOMEMALLOC 435 * 436 * Context: This function should not be used in an interrupt context as that one 437 * does not give PF_MEMALLOC access to reserves. 438 * See __gfp_pfmemalloc_flags(). 439 * Return: The saved flags to be passed to memalloc_noreclaim_restore. 440 */ 441 static inline unsigned int memalloc_noreclaim_save(void) 442 { 443 return memalloc_flags_save(PF_MEMALLOC); 444 } 445 446 /** 447 * memalloc_noreclaim_restore - Ends the implicit __GFP_MEMALLOC scope. 448 * @flags: Flags to restore. 449 * 450 * Ends the implicit __GFP_MEMALLOC scope started by memalloc_noreclaim_save 451 * function. Always make sure that the given flags is the return value from the 452 * pairing memalloc_noreclaim_save call. 453 */ 454 static inline void memalloc_noreclaim_restore(unsigned int flags) 455 { 456 memalloc_flags_restore(flags); 457 } 458 459 /** 460 * memalloc_pin_save - Marks implicit ~__GFP_MOVABLE scope. 461 * 462 * This function marks the beginning of the ~__GFP_MOVABLE allocation scope. 463 * All further allocations will implicitly remove the __GFP_MOVABLE flag, which 464 * will constraint the allocations to zones that allow long term pinning, i.e. 465 * not ZONE_MOVABLE zones. 466 * 467 * Return: The saved flags to be passed to memalloc_pin_restore. 468 */ 469 static inline unsigned int memalloc_pin_save(void) 470 { 471 return memalloc_flags_save(PF_MEMALLOC_PIN); 472 } 473 474 /** 475 * memalloc_pin_restore - Ends the implicit ~__GFP_MOVABLE scope. 476 * @flags: Flags to restore. 477 * 478 * Ends the implicit ~__GFP_MOVABLE scope started by memalloc_pin_save function. 479 * Always make sure that the given flags is the return value from the pairing 480 * memalloc_pin_save call. 481 */ 482 static inline void memalloc_pin_restore(unsigned int flags) 483 { 484 memalloc_flags_restore(flags); 485 } 486 487 #ifdef CONFIG_MEMCG 488 DECLARE_PER_CPU(struct mem_cgroup *, int_active_memcg); 489 /** 490 * set_active_memcg - Starts the remote memcg charging scope. 491 * @memcg: memcg to charge. 492 * 493 * This function marks the beginning of the remote memcg charging scope. All the 494 * __GFP_ACCOUNT allocations till the end of the scope will be charged to the 495 * given memcg. 496 * 497 * Please, make sure that caller has a reference to the passed memcg structure, 498 * so its lifetime is guaranteed to exceed the scope between two 499 * set_active_memcg() calls. 500 * 501 * NOTE: This function can nest. Users must save the return value and 502 * reset the previous value after their own charging scope is over. 503 */ 504 static inline struct mem_cgroup * 505 set_active_memcg(struct mem_cgroup *memcg) 506 { 507 struct mem_cgroup *old; 508 509 if (!in_task()) { 510 old = this_cpu_read(int_active_memcg); 511 this_cpu_write(int_active_memcg, memcg); 512 } else { 513 old = current->active_memcg; 514 current->active_memcg = memcg; 515 } 516 517 return old; 518 } 519 #else 520 static inline struct mem_cgroup * 521 set_active_memcg(struct mem_cgroup *memcg) 522 { 523 return NULL; 524 } 525 #endif 526 527 #ifdef CONFIG_MEMBARRIER 528 enum { 529 MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY = (1U << 0), 530 MEMBARRIER_STATE_PRIVATE_EXPEDITED = (1U << 1), 531 MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY = (1U << 2), 532 MEMBARRIER_STATE_GLOBAL_EXPEDITED = (1U << 3), 533 MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY = (1U << 4), 534 MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE = (1U << 5), 535 MEMBARRIER_STATE_PRIVATE_EXPEDITED_RSEQ_READY = (1U << 6), 536 MEMBARRIER_STATE_PRIVATE_EXPEDITED_RSEQ = (1U << 7), 537 }; 538 539 enum { 540 MEMBARRIER_FLAG_SYNC_CORE = (1U << 0), 541 MEMBARRIER_FLAG_RSEQ = (1U << 1), 542 }; 543 544 #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS 545 #include <asm/membarrier.h> 546 #endif 547 548 static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm) 549 { 550 if (current->mm != mm) 551 return; 552 if (likely(!(atomic_read(&mm->membarrier_state) & 553 MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE))) 554 return; 555 sync_core_before_usermode(); 556 } 557 558 extern void membarrier_exec_mmap(struct mm_struct *mm); 559 560 extern void membarrier_update_current_mm(struct mm_struct *next_mm); 561 562 #else 563 #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS 564 static inline void membarrier_arch_switch_mm(struct mm_struct *prev, 565 struct mm_struct *next, 566 struct task_struct *tsk) 567 { 568 } 569 #endif 570 static inline void membarrier_exec_mmap(struct mm_struct *mm) 571 { 572 } 573 static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm) 574 { 575 } 576 static inline void membarrier_update_current_mm(struct mm_struct *next_mm) 577 { 578 } 579 #endif 580 581 #endif /* _LINUX_SCHED_MM_H */ 582