static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
unsigned long old_addr, unsigned long old_end,
struct vm_area_struct *new_vma, pmd_t *new_pmd,
- unsigned long new_addr)
+ unsigned long new_addr, bool need_rmap_locks)
{
struct address_space *mapping = NULL;
+ struct anon_vma *anon_vma = NULL;
struct mm_struct *mm = vma->vm_mm;
pte_t *old_pte, *new_pte, pte;
spinlock_t *old_ptl, *new_ptl;
- if (vma->vm_file) {
- /*
- * Subtle point from Rajesh Venkatasubramanian: before
- * moving file-based ptes, we must lock truncate_pagecache
- * out, since it might clean the dst vma before the src vma,
- * and we propagate stale pages into the dst afterward.
- */
- mapping = vma->vm_file->f_mapping;
- mutex_lock(&mapping->i_mmap_mutex);
+ /*
+ * When need_rmap_locks is true, we take the i_mmap_mutex and anon_vma
+ * locks to ensure that rmap will always observe either the old or the
+ * new ptes. This is the easiest way to avoid races with
+ * truncate_pagecache(), page migration, etc...
+ *
+ * When need_rmap_locks is false, we use other ways to avoid
+ * such races:
+ *
+ * - During exec() shift_arg_pages(), we use a specially tagged vma
+ * which rmap call sites look for using is_vma_temporary_stack().
+ *
+ * - During mremap(), new_vma is often known to be placed after vma
+ * in rmap traversal order. This ensures rmap will always observe
+ * either the old pte, or the new pte, or both (the page table locks
+ * serialize access to individual ptes, but only rmap traversal
+ * order guarantees that we won't miss both the old and new ptes).
+ */
+ if (need_rmap_locks) {
+ if (vma->vm_file) {
+ mapping = vma->vm_file->f_mapping;
+ mutex_lock(&mapping->i_mmap_mutex);
+ }
+ if (vma->anon_vma) {
+ anon_vma = vma->anon_vma;
+ anon_vma_lock(anon_vma);
+ }
}
/*
spin_unlock(new_ptl);
pte_unmap(new_pte - 1);
pte_unmap_unlock(old_pte - 1, old_ptl);
+ if (anon_vma)
+ anon_vma_unlock(anon_vma);
if (mapping)
mutex_unlock(&mapping->i_mmap_mutex);
}
unsigned long move_page_tables(struct vm_area_struct *vma,
unsigned long old_addr, struct vm_area_struct *new_vma,
- unsigned long new_addr, unsigned long len)
+ unsigned long new_addr, unsigned long len,
+ bool need_rmap_locks)
{
unsigned long extent, next, old_end;
pmd_t *old_pmd, *new_pmd;
bool need_flush = false;
+ unsigned long mmun_start; /* For mmu_notifiers */
+ unsigned long mmun_end; /* For mmu_notifiers */
old_end = old_addr + len;
flush_cache_range(vma, old_addr, old_end);
- mmu_notifier_invalidate_range_start(vma->vm_mm, old_addr, old_end);
+ mmun_start = old_addr;
+ mmun_end = old_end;
+ mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
cond_resched();
if (extent > LATENCY_LIMIT)
extent = LATENCY_LIMIT;
move_ptes(vma, old_pmd, old_addr, old_addr + extent,
- new_vma, new_pmd, new_addr);
+ new_vma, new_pmd, new_addr, need_rmap_locks);
need_flush = true;
}
if (likely(need_flush))
flush_tlb_range(vma, old_end-len, old_addr);
- mmu_notifier_invalidate_range_end(vma->vm_mm, old_end-len, old_end);
+ mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
return len + old_addr - old_end; /* how much done */
}
unsigned long hiwater_vm;
int split = 0;
int err;
+ bool need_rmap_locks;
/*
* We'd prefer to avoid failure later on in do_munmap:
return err;
new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
- new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff);
+ new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
+ &need_rmap_locks);
if (!new_vma)
return -ENOMEM;
- moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len);
+ moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
+ need_rmap_locks);
if (moved_len < old_len) {
- /*
- * Before moving the page tables from the new vma to
- * the old vma, we need to be sure the old vma is
- * queued after new vma in the same_anon_vma list to
- * prevent SMP races with rmap_walk (that could lead
- * rmap_walk to miss some page table).
- */
- anon_vma_moveto_tail(vma);
-
/*
* On error, move entries back from new area to old,
* which will succeed since page tables still there,
* and then proceed to unmap new area instead of old.
*/
- move_page_tables(new_vma, new_addr, vma, old_addr, moved_len);
+ move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
+ true);
vma = new_vma;
old_len = new_len;
old_addr = new_addr;
git.openpandora.org / pandora-kernel.git / blobdiff