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/* 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/mm/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);
}
static inline void smp_mb__after_mmgrab(void)
{
smp_mb__after_atomic();
}
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
/* Helpers for lazy TLB mm refcounting */
static inline void mmgrab_lazy_tlb(struct mm_struct *mm)
{
if (IS_ENABLED(CONFIG_MMU_LAZY_TLB_REFCOUNT))
mmgrab(mm);
}
static inline void mmdrop_lazy_tlb(struct mm_struct *mm)
{
if (IS_ENABLED(CONFIG_MMU_LAZY_TLB_REFCOUNT)) {
mmdrop(mm);
} else {
/*
* mmdrop_lazy_tlb must provide a full memory barrier, see the
* membarrier comment finish_task_switch which relies on this.
*/
smp_mb();
}
}
static inline void mmdrop_lazy_tlb_sched(struct mm_struct *mm)
{
if (IS_ENABLED(CONFIG_MMU_LAZY_TLB_REFCOUNT))
mmdrop_sched(mm);
else
smp_mb(); /* see mmdrop_lazy_tlb() above */
}
/**
* 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/mm/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
#ifndef arch_get_mmap_end
#define arch_get_mmap_end(addr, len, flags) (TASK_SIZE)
#endif
#ifndef arch_get_mmap_base
#define arch_get_mmap_base(addr, base) (base)
#endif
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);
unsigned long
generic_get_unmapped_area(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff,
unsigned long flags);
unsigned long
generic_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.
*
* Please, make sure that caller has a reference to the passed memcg structure,
* so its lifetime is guaranteed to exceed the scope between two
* set_active_memcg() calls.
*
* 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 */