text: /* SPDX-License-Identifier: GPL-2.0 */
  #ifndef _LINUX_SCHED_MM_H
  #define _LINUX_SCHED_MM_H
  
  #include <linux/kernel.h>
  #include <linux/atomic.h>
  #include <linux/sched.h>
  #include <linux/mm_types.h>
  #include <linux/gfp.h>
  #include <linux/sync_core.h>
  #include <linux/ioasid.h>
  
  /*
   * Routines for handling mm_structs
   */
  extern struct mm_struct *mm_alloc(void);
  
  /**
   * mmgrab() - Pin a &struct mm_struct.
   * @mm: The &struct mm_struct to pin.
   *
   * Make sure that @mm will not get freed even after the owning task
   * exits. This doesn't guarantee that the associated address space
   * will still exist later on and mmget_not_zero() has to be used before
   * accessing it.
   *
   * This is a preferred way to pin @mm for a longer/unbounded amount
   * of time.
   *
   * Use mmdrop() to release the reference acquired by mmgrab().
   *
   * See also <Documentation/vm/active_mm.rst> for an in-depth explanation
   * of &mm_struct.mm_count vs &mm_struct.mm_users.
   */
  static inline void mmgrab(struct mm_struct *mm)
  {
  	atomic_inc(&mm->mm_count);
  }
  
  extern void __mmdrop(struct mm_struct *mm);
  
  static inline void mmdrop(struct mm_struct *mm)
  {
  	/*
  	 * The implicit full barrier implied by atomic_dec_and_test() is
  	 * required by the membarrier system call before returning to
  	 * user-space, after storing to rq->curr.
  	 */
  	if (unlikely(atomic_dec_and_test(&mm->mm_count)))
  		__mmdrop(mm);
  }
  
  #ifdef CONFIG_PREEMPT_RT
  /*
   * RCU callback for delayed mm drop. Not strictly RCU, but call_rcu() is
   * by far the least expensive way to do that.
   */
  static inline void __mmdrop_delayed(struct rcu_head *rhp)
  {
  	struct mm_struct *mm = container_of(rhp, struct mm_struct, delayed_drop);
  
  	__mmdrop(mm);
  }
  
  /*
   * Invoked from finish_task_switch(). Delegates the heavy lifting on RT
   * kernels via RCU.
   */
  static inline void mmdrop_sched(struct mm_struct *mm)
  {
  	/* Provides a full memory barrier. See mmdrop() */
  	if (atomic_dec_and_test(&mm->mm_count))
  		call_rcu(&mm->delayed_drop, __mmdrop_delayed);
  }
  #else
  static inline void mmdrop_sched(struct mm_struct *mm)
  {
  	mmdrop(mm);
  }
  #endif
  
  /**
   * mmget() - Pin the address space associated with a &struct mm_struct.
   * @mm: The address space to pin.
   *
   * Make sure that the address space of the given &struct mm_struct doesn't
   * go away. This does not protect against parts of the address space being
   * modified or freed, however.
   *
   * Never use this function to pin this address space for an
   * unbounded/indefinite amount of time.
   *
   * Use mmput() to release the reference acquired by mmget().
   *
   * See also <Documentation/vm/active_mm.rst> for an in-depth explanation
   * of &mm_struct.mm_count vs &mm_struct.mm_users.
   */
  static inline void mmget(struct mm_struct *mm)
  {
  	atomic_inc(&mm->mm_users);
  }
  
  static inline bool mmget_not_zero(struct mm_struct *mm)
  {
  	return atomic_inc_not_zero(&mm->mm_users);
  }
  
  /* mmput gets rid of the mappings and all user-space */
  extern void mmput(struct mm_struct *);
  #ifdef CONFIG_MMU
  /* same as above but performs the slow path from the async context. Can
   * be called from the atomic context as well
   */
  void mmput_async(struct mm_struct *);
  #endif
  
  /* Grab a reference to a task's mm, if it is not already going away */
  extern struct mm_struct *get_task_mm(struct task_struct *task);
  /*
   * Grab a reference to a task's mm, if it is not already going away
   * and ptrace_may_access with the mode parameter passed to it
   * succeeds.
   */
  extern struct mm_struct *mm_access(struct task_struct *task, unsigned int mode);
  /* Remove the current tasks stale references to the old mm_struct on exit() */
  extern void exit_mm_release(struct task_struct *, struct mm_struct *);
  /* Remove the current tasks stale references to the old mm_struct on exec() */
  extern void exec_mm_release(struct task_struct *, struct mm_struct *);
  
  #ifdef CONFIG_MEMCG
  extern void mm_update_next_owner(struct mm_struct *mm);
  #else
  static inline void mm_update_next_owner(struct mm_struct *mm)
  {
  }
  #endif /* CONFIG_MEMCG */
  
  #ifdef CONFIG_MMU
  extern void arch_pick_mmap_layout(struct mm_struct *mm,
  				  struct rlimit *rlim_stack);
  extern unsigned long
  arch_get_unmapped_area(struct file *, unsigned long, unsigned long,
  		       unsigned long, unsigned long);
  extern unsigned long
  arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
  			  unsigned long len, unsigned long pgoff,
  			  unsigned long flags);
  #else
  static inline void arch_pick_mmap_layout(struct mm_struct *mm,
  					 struct rlimit *rlim_stack) {}
  #endif
  
  static inline bool in_vfork(struct task_struct *tsk)
  {
  	bool ret;
  
  	/*
  	 * need RCU to access ->real_parent if CLONE_VM was used along with
  	 * CLONE_PARENT.
  	 *
  	 * We check real_parent->mm == tsk->mm because CLONE_VFORK does not
  	 * imply CLONE_VM
  	 *
  	 * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus
  	 * ->real_parent is not necessarily the task doing vfork(), so in
  	 * theory we can't rely on task_lock() if we want to dereference it.
  	 *
  	 * And in this case we can't trust the real_parent->mm == tsk->mm
  	 * check, it can be false negative. But we do not care, if init or
  	 * another oom-unkillable task does this it should blame itself.
  	 */
  	rcu_read_lock();
  	ret = tsk->vfork_done &&
  			rcu_dereference(tsk->real_parent)->mm == tsk->mm;
  	rcu_read_unlock();
  
  	return ret;
  }
  
  /*
   * Applies per-task gfp context to the given allocation flags.
   * PF_MEMALLOC_NOIO implies GFP_NOIO
   * PF_MEMALLOC_NOFS implies GFP_NOFS
   * PF_MEMALLOC_PIN  implies !GFP_MOVABLE
   */
  static inline gfp_t current_gfp_context(gfp_t flags)
  {
  	unsigned int pflags = READ_ONCE(current->flags);
  
  	if (unlikely(pflags & (PF_MEMALLOC_NOIO | PF_MEMALLOC_NOFS | PF_MEMALLOC_PIN))) {
  		/*
  		 * NOIO implies both NOIO and NOFS and it is a weaker context
  		 * so always make sure it makes precedence
  		 */
  		if (pflags & PF_MEMALLOC_NOIO)
  			flags &= ~(__GFP_IO | __GFP_FS);
  		else if (pflags & PF_MEMALLOC_NOFS)
  			flags &= ~__GFP_FS;
  
  		if (pflags & PF_MEMALLOC_PIN)
  			flags &= ~__GFP_MOVABLE;
  	}
  	return flags;
  }
  
  #ifdef CONFIG_LOCKDEP
  extern void __fs_reclaim_acquire(unsigned long ip);
  extern void __fs_reclaim_release(unsigned long ip);
  extern void fs_reclaim_acquire(gfp_t gfp_mask);
  extern void fs_reclaim_release(gfp_t gfp_mask);
  #else
  static inline void __fs_reclaim_acquire(unsigned long ip) { }
  static inline void __fs_reclaim_release(unsigned long ip) { }
  static inline void fs_reclaim_acquire(gfp_t gfp_mask) { }
  static inline void fs_reclaim_release(gfp_t gfp_mask) { }
  #endif
  
  /* Any memory-allocation retry loop should use
   * memalloc_retry_wait(), and pass the flags for the most
   * constrained allocation attempt that might have failed.
   * This provides useful documentation of where loops are,
   * and a central place to fine tune the waiting as the MM
   * implementation changes.
   */
  static inline void memalloc_retry_wait(gfp_t gfp_flags)
  {
  	/* We use io_schedule_timeout because waiting for memory
  	 * typically included waiting for dirty pages to be
  	 * written out, which requires IO.
  	 */
  	__set_current_state(TASK_UNINTERRUPTIBLE);
  	gfp_flags = current_gfp_context(gfp_flags);
  	if (gfpflags_allow_blocking(gfp_flags) &&
  	    !(gfp_flags & __GFP_NORETRY))
  		/* Probably waited already, no need for much more */
  		io_schedule_timeout(1);
  	else
  		/* Probably didn't wait, and has now released a lock,
  		 * so now is a good time to wait
  		 */
  		io_schedule_timeout(HZ/50);
  }
  
  /**
   * might_alloc - Mark possible allocation sites
   * @gfp_mask: gfp_t flags that would be used to allocate
   *
   * Similar to might_sleep() and other annotations, this can be used in functions
   * that might allocate, but often don't. Compiles to nothing without
   * CONFIG_LOCKDEP. Includes a conditional might_sleep() if @gfp allows blocking.
   */
  static inline void might_alloc(gfp_t gfp_mask)
  {
  	fs_reclaim_acquire(gfp_mask);
  	fs_reclaim_release(gfp_mask);
  
  	might_sleep_if(gfpflags_allow_blocking(gfp_mask));
  }
  
  /**
   * memalloc_noio_save - Marks implicit GFP_NOIO allocation scope.
   *
   * This functions marks the beginning of the GFP_NOIO allocation scope.
   * All further allocations will implicitly drop __GFP_IO flag and so
   * they are safe for the IO critical section from the allocation recursion
   * point of view. Use memalloc_noio_restore to end the scope with flags
   * returned by this function.
   *
   * This function is safe to be used from any context.
   */
  static inline unsigned int memalloc_noio_save(void)
  {
  	unsigned int flags = current->flags & PF_MEMALLOC_NOIO;
  	current->flags |= PF_MEMALLOC_NOIO;
  	return flags;
  }
  
  /**
   * memalloc_noio_restore - Ends the implicit GFP_NOIO scope.
   * @flags: Flags to restore.
   *
   * Ends the implicit GFP_NOIO scope started by memalloc_noio_save function.
   * Always make sure that the given flags is the return value from the
   * pairing memalloc_noio_save call.
   */
  static inline void memalloc_noio_restore(unsigned int flags)
  {
  	current->flags = (current->flags & ~PF_MEMALLOC_NOIO) | flags;
  }
  
  /**
   * memalloc_nofs_save - Marks implicit GFP_NOFS allocation scope.
   *
   * This functions marks the beginning of the GFP_NOFS allocation scope.
   * All further allocations will implicitly drop __GFP_FS flag and so
   * they are safe for the FS critical section from the allocation recursion
   * point of view. Use memalloc_nofs_restore to end the scope with flags
   * returned by this function.
   *
   * This function is safe to be used from any context.
   */
  static inline unsigned int memalloc_nofs_save(void)
  {
  	unsigned int flags = current->flags & PF_MEMALLOC_NOFS;
  	current->flags |= PF_MEMALLOC_NOFS;
  	return flags;
  }
  
  /**
   * memalloc_nofs_restore - Ends the implicit GFP_NOFS scope.
   * @flags: Flags to restore.
   *
   * Ends the implicit GFP_NOFS scope started by memalloc_nofs_save function.
   * Always make sure that the given flags is the return value from the
   * pairing memalloc_nofs_save call.
   */
  static inline void memalloc_nofs_restore(unsigned int flags)
  {
  	current->flags = (current->flags & ~PF_MEMALLOC_NOFS) | flags;
  }
  
  static inline unsigned int memalloc_noreclaim_save(void)
  {
  	unsigned int flags = current->flags & PF_MEMALLOC;
  	current->flags |= PF_MEMALLOC;
  	return flags;
  }
  
  static inline void memalloc_noreclaim_restore(unsigned int flags)
  {
  	current->flags = (current->flags & ~PF_MEMALLOC) | flags;
  }
  
  static inline unsigned int memalloc_pin_save(void)
  {
  	unsigned int flags = current->flags & PF_MEMALLOC_PIN;
  
  	current->flags |= PF_MEMALLOC_PIN;
  	return flags;
  }
  
  static inline void memalloc_pin_restore(unsigned int flags)
  {
  	current->flags = (current->flags & ~PF_MEMALLOC_PIN) | flags;
  }
  
  #ifdef CONFIG_MEMCG
  DECLARE_PER_CPU(struct mem_cgroup *, int_active_memcg);
  /**
   * set_active_memcg - Starts the remote memcg charging scope.
   * @memcg: memcg to charge.
   *
   * This function marks the beginning of the remote memcg charging scope. All the
   * __GFP_ACCOUNT allocations till the end of the scope will be charged to the
   * given memcg.
   *
   * NOTE: This function can nest. Users must save the return value and
   * reset the previous value after their own charging scope is over.
   */
  static inline struct mem_cgroup *
  set_active_memcg(struct mem_cgroup *memcg)
  {
  	struct mem_cgroup *old;
  
  	if (!in_task()) {
  		old = this_cpu_read(int_active_memcg);
  		this_cpu_write(int_active_memcg, memcg);
  	} else {
  		old = current->active_memcg;
  		current->active_memcg = memcg;
  	}
  
  	return old;
  }
  #else
  static inline struct mem_cgroup *
  set_active_memcg(struct mem_cgroup *memcg)
  {
  	return NULL;
  }
  #endif
  
  #ifdef CONFIG_MEMBARRIER
  enum {
  	MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY		= (1U << 0),
  	MEMBARRIER_STATE_PRIVATE_EXPEDITED			= (1U << 1),
  	MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY			= (1U << 2),
  	MEMBARRIER_STATE_GLOBAL_EXPEDITED			= (1U << 3),
  	MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY	= (1U << 4),
  	MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE		= (1U << 5),
  	MEMBARRIER_STATE_PRIVATE_EXPEDITED_RSEQ_READY		= (1U << 6),
  	MEMBARRIER_STATE_PRIVATE_EXPEDITED_RSEQ			= (1U << 7),
  };
  
  enum {
  	MEMBARRIER_FLAG_SYNC_CORE	= (1U << 0),
  	MEMBARRIER_FLAG_RSEQ		= (1U << 1),
  };
  
  #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
  #include <asm/membarrier.h>
  #endif
  
  static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
  {
  	if (current->mm != mm)
  		return;
  	if (likely(!(atomic_read(&mm->membarrier_state) &
  		     MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE)))
  		return;
  	sync_core_before_usermode();
  }
  
  extern void membarrier_exec_mmap(struct mm_struct *mm);
  
  extern void membarrier_update_current_mm(struct mm_struct *next_mm);
  
  #else
  #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS
  static inline void membarrier_arch_switch_mm(struct mm_struct *prev,
  					     struct mm_struct *next,
  					     struct task_struct *tsk)
  {
  }
  #endif
  static inline void membarrier_exec_mmap(struct mm_struct *mm)
  {
  }
  static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
  {
  }
  static inline void membarrier_update_current_mm(struct mm_struct *next_mm)
  {
  }
  #endif
  
  #ifdef CONFIG_IOMMU_SVA
  static inline void mm_pasid_init(struct mm_struct *mm)
  {
  	mm->pasid = INVALID_IOASID;
  }
  
  /* Associate a PASID with an mm_struct: */
  static inline void mm_pasid_set(struct mm_struct *mm, u32 pasid)
  {
  	mm->pasid = pasid;
  }
  
  static inline void mm_pasid_drop(struct mm_struct *mm)
  {
  	if (pasid_valid(mm->pasid)) {
  		ioasid_free(mm->pasid);
  		mm->pasid = INVALID_IOASID;
  	}
  }
  #else
  static inline void mm_pasid_init(struct mm_struct *mm) {}
  static inline void mm_pasid_set(struct mm_struct *mm, u32 pasid) {}
  static inline void mm_pasid_drop(struct mm_struct *mm) {}
  #endif
  
  #endif /* _LINUX_SCHED_MM_H */
  