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