Line data    Source code

       1             : // SPDX-License-Identifier: GPL-2.0
       2             : /*
       3             :  * Copyright (C) 2014 Davidlohr Bueso.
       4             :  */
       5             : #include <linux/sched/signal.h>
       6             : #include <linux/sched/task.h>
       7             : #include <linux/mm.h>
       8             : #include <linux/vmacache.h>
       9             : 
      10             : /*
      11             :  * Hash based on the pmd of addr if configured with MMU, which provides a good
      12             :  * hit rate for workloads with spatial locality.  Otherwise, use pages.
      13             :  */
      14             : #ifdef CONFIG_MMU
      15             : #define VMACACHE_SHIFT  PMD_SHIFT
      16             : #else
      17             : #define VMACACHE_SHIFT  PAGE_SHIFT
      18             : #endif
      19             : #define VMACACHE_HASH(addr) ((addr >> VMACACHE_SHIFT) & VMACACHE_MASK)
      20             : 
      21             : /*
      22             :  * This task may be accessing a foreign mm via (for example)
      23             :  * get_user_pages()->find_vma().  The vmacache is task-local and this
      24             :  * task's vmacache pertains to a different mm (ie, its own).  There is
      25             :  * nothing we can do here.
      26             :  *
      27             :  * Also handle the case where a kernel thread has adopted this mm via
      28             :  * kthread_use_mm(). That kernel thread's vmacache is not applicable to this mm.
      29             :  */
      30      349050 : static inline bool vmacache_valid_mm(struct mm_struct *mm)
      31             : {
      32      333694 :         return current->mm == mm && !(current->flags & PF_KTHREAD);
      33             : }
      34             : 
      35      125095 : void vmacache_update(unsigned long addr, struct vm_area_struct *newvma)
      36             : {
      37      242515 :         if (vmacache_valid_mm(newvma->vm_mm))
      38      117422 :                 current->vmacache.vmas[VMACACHE_HASH(addr)] = newvma;
      39      125095 : }
      40             : 
      41      223955 : static bool vmacache_valid(struct mm_struct *mm)
      42             : {
      43      223955 :         struct task_struct *curr;
      44             : 
      45      440229 :         if (!vmacache_valid_mm(mm))
      46             :                 return false;
      47             : 
      48      216277 :         curr = current;
      49      216277 :         if (mm->vmacache_seqnum != curr->vmacache.seqnum) {
      50             :                 /*
      51             :                  * First attempt will always be invalid, initialize
      52             :                  * the new cache for this task here.
      53             :                  */
      54       17552 :                 curr->vmacache.seqnum = mm->vmacache_seqnum;
      55       17552 :                 vmacache_flush(curr);
      56       17552 :                 return false;
      57             :         }
      58             :         return true;
      59             : }
      60             : 
      61      223945 : struct vm_area_struct *vmacache_find(struct mm_struct *mm, unsigned long addr)
      62             : {
      63      223945 :         int idx = VMACACHE_HASH(addr);
      64      223945 :         int i;
      65             : 
      66      223945 :         count_vm_vmacache_event(VMACACHE_FIND_CALLS);
      67             : 
      68      223945 :         if (!vmacache_valid(mm))
      69             :                 return NULL;
      70             : 
      71      642251 :         for (i = 0; i < VMACACHE_SIZE; i++) {
      72      541509 :                 struct vm_area_struct *vma = current->vmacache.vmas[idx];
      73             : 
      74      541509 :                 if (vma) {
      75             : #ifdef CONFIG_DEBUG_VM_VMACACHE
      76             :                         if (WARN_ON_ONCE(vma->vm_mm != mm))
      77             :                                 break;
      78             : #endif
      79      362834 :                         if (vma->vm_start <= addr && vma->vm_end > addr) {
      80       97952 :                                 count_vm_vmacache_event(VMACACHE_FIND_HITS);
      81       97952 :                                 return vma;
      82             :                         }
      83             :                 }
      84      443557 :                 if (++idx == VMACACHE_SIZE)
      85      110789 :                         idx = 0;
      86             :         }
      87             : 
      88             :         return NULL;
      89             : }
      90             : 
      91             : #ifndef CONFIG_MMU
      92             : struct vm_area_struct *vmacache_find_exact(struct mm_struct *mm,
      93             :                                            unsigned long start,
      94             :                                            unsigned long end)
      95             : {
      96             :         int idx = VMACACHE_HASH(start);
      97             :         int i;
      98             : 
      99             :         count_vm_vmacache_event(VMACACHE_FIND_CALLS);
     100             : 
     101             :         if (!vmacache_valid(mm))
     102             :                 return NULL;
     103             : 
     104             :         for (i = 0; i < VMACACHE_SIZE; i++) {
     105             :                 struct vm_area_struct *vma = current->vmacache.vmas[idx];
     106             : 
     107             :                 if (vma && vma->vm_start == start && vma->vm_end == end) {
     108             :                         count_vm_vmacache_event(VMACACHE_FIND_HITS);
     109             :                         return vma;
     110             :                 }
     111             :                 if (++idx == VMACACHE_SIZE)
     112             :                         idx = 0;
     113             :         }
     114             : 
     115             :         return NULL;
     116             : }
     117             : #endif