/* 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>

/*
 * 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

/**
 * 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

#endif /* _LINUX_SCHED_MM_H */