1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 | /* * Copyright (C) 2014 Davidlohr Bueso. */ #include <linux/sched.h> #include <linux/mm.h> #include <linux/vmacache.h> /* * Flush vma caches for threads that share a given mm. * * The operation is safe because the caller holds the mmap_sem * exclusively and other threads accessing the vma cache will * have mmap_sem held at least for read, so no extra locking * is required to maintain the vma cache. */ void vmacache_flush_all(struct mm_struct *mm) { struct task_struct *g, *p; count_vm_vmacache_event(VMACACHE_FULL_FLUSHES); /* * Single threaded tasks need not iterate the entire * list of process. We can avoid the flushing as well * since the mm's seqnum was increased and don't have * to worry about other threads' seqnum. Current's * flush will occur upon the next lookup. */ if (atomic_read(&mm->mm_users) == 1) return; rcu_read_lock(); for_each_process_thread(g, p) { /* * Only flush the vmacache pointers as the * mm seqnum is already set and curr's will * be set upon invalidation when the next * lookup is done. */ if (mm == p->mm) vmacache_flush(p); } rcu_read_unlock(); } /* * 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[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[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 [31mCONFIG_MMU[0m 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[i]; if (vma && vma->vm_start == start && vma->vm_end == end) { count_vm_vmacache_event(VMACACHE_FIND_HITS); return vma; } } return NULL; } #endif |