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mm/vmacache.c
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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2014 Davidlohr Bueso.
*/
#include <linux/sched/signal.h>
#include <linux/sched/task.h>
#include <linux/mm.h>
#include <linux/vmacache.h>
/*
* This task may be accessing a foreign mm via (for example)
* get_user_pages()->find_vma(). The vmacache is task-local and this
* task's vmacache pertains to a different mm (ie, its own). There is
* nothing we can do here.
*
* Also handle the case where a kernel thread has adopted this mm via use_mm().
* That kernel thread's vmacache is not applicable to this mm.
*/
static inline bool vmacache_valid_mm(struct mm_struct *mm)
{
return current->mm == mm && !(current->flags & PF_KTHREAD);
}
void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
{
if (vmacache_valid_mm(newvma->vm_mm))
current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma;
}
static bool vmacache_valid(struct mm_struct *mm)
{
struct task_struct *curr;
if (!vmacache_valid_mm(mm))
return false;
curr = current;
if (mm->vmacache_seqnum != curr->vmacache.seqnum) {
/*
* First attempt will always be invalid, initialize
* the new cache for this task here.
*/
curr->vmacache.seqnum = mm->vmacache_seqnum;
vmacache_flush(curr);
return false;
}
return true;
}
struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
{
int i;
count_vm_vmacache_event(VMACACHE_FIND_CALLS);
if (!vmacache_valid(mm))
return NULL;
for (i = 0; i < VMACACHE_SIZE; i++) {
struct vm_area_struct *vma = current->vmacache.vmas[i];
if (!vma)
continue;
if (WARN_ON_ONCE(vma->vm_mm != mm))
break;
if (vma->vm_start <= addr && vma->vm_end > addr) {
count_vm_vmacache_event(VMACACHE_FIND_HITS);
return vma;
}
}
return NULL;
}
#ifndef CONFIG_MMU
struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
unsigned long start,
unsigned long end)
{
int i;
count_vm_vmacache_event(VMACACHE_FIND_CALLS);
if (!vmacache_valid(mm))
return NULL;
for (i = 0; i < VMACACHE_SIZE; i++) {
struct vm_area_struct *vma = current->vmacache.vmas[i];
if (vma && vma->vm_start == start && vma->vm_end == end) {
count_vm_vmacache_event(VMACACHE_FIND_HITS);
return vma;
}
}
return NULL;
}
#endif
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