diff options
| -rw-r--r-- | include/linux/mm.h | 1 | ||||
| -rw-r--r-- | mm/memory.c | 41 |
2 files changed, 33 insertions, 9 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 9bee7ec0c31f..47a93928b90f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -224,6 +224,7 @@ struct vm_fault { pgoff_t pgoff; /* Logical page offset based on vma */ void __user *virtual_address; /* Faulting virtual address */ + struct page *cow_page; /* Handler may choose to COW */ struct page *page; /* ->fault handlers should return a * page here, unless VM_FAULT_NOPAGE * is set (which is also implied by diff --git a/mm/memory.c b/mm/memory.c index 1b04e13b9993..8068893697bb 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1965,6 +1965,7 @@ static int do_page_mkwrite(struct vm_area_struct *vma, struct page *page, vmf.pgoff = page->index; vmf.flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE; vmf.page = page; + vmf.cow_page = NULL; ret = vma->vm_ops->page_mkwrite(vma, &vmf); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE))) @@ -2639,7 +2640,8 @@ oom: * See filemap_fault() and __lock_page_retry(). */ static int __do_fault(struct vm_area_struct *vma, unsigned long address, - pgoff_t pgoff, unsigned int flags, struct page **page) + pgoff_t pgoff, unsigned int flags, + struct page *cow_page, struct page **page) { struct vm_fault vmf; int ret; @@ -2648,10 +2650,13 @@ static int __do_fault(struct vm_area_struct *vma, unsigned long address, vmf.pgoff = pgoff; vmf.flags = flags; vmf.page = NULL; + vmf.cow_page = cow_page; ret = vma->vm_ops->fault(vma, &vmf); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; + if (!vmf.page) + goto out; if (unlikely(PageHWPoison(vmf.page))) { if (ret & VM_FAULT_LOCKED) @@ -2665,6 +2670,7 @@ static int __do_fault(struct vm_area_struct *vma, unsigned long address, else VM_BUG_ON_PAGE(!PageLocked(vmf.page), vmf.page); + out: *page = vmf.page; return ret; } @@ -2835,7 +2841,7 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma, pte_unmap_unlock(pte, ptl); } - ret = __do_fault(vma, address, pgoff, flags, &fault_page); + ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; @@ -2875,26 +2881,43 @@ static int do_cow_fault(struct mm_struct *mm, struct vm_area_struct *vma, return VM_FAULT_OOM; } - ret = __do_fault(vma, address, pgoff, flags, &fault_page); + ret = __do_fault(vma, address, pgoff, flags, new_page, &fault_page); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) goto uncharge_out; - copy_user_highpage(new_page, fault_page, address, vma); + if (fault_page) + copy_user_highpage(new_page, fault_page, address, vma); __SetPageUptodate(new_page); pte = pte_offset_map_lock(mm, pmd, address, &ptl); if (unlikely(!pte_same(*pte, orig_pte))) { pte_unmap_unlock(pte, ptl); - unlock_page(fault_page); - page_cache_release(fault_page); + if (fault_page) { + unlock_page(fault_page); + page_cache_release(fault_page); + } else { + /* + * The fault handler has no page to lock, so it holds + * i_mmap_lock for read to protect against truncate. + */ + i_mmap_unlock_read(vma->vm_file->f_mapping); + } goto uncharge_out; } do_set_pte(vma, address, new_page, pte, true, true); mem_cgroup_commit_charge(new_page, memcg, false); lru_cache_add_active_or_unevictable(new_page, vma); pte_unmap_unlock(pte, ptl); - unlock_page(fault_page); - page_cache_release(fault_page); + if (fault_page) { + unlock_page(fault_page); + page_cache_release(fault_page); + } else { + /* + * The fault handler has no page to lock, so it holds + * i_mmap_lock for read to protect against truncate. + */ + i_mmap_unlock_read(vma->vm_file->f_mapping); + } return ret; uncharge_out: mem_cgroup_cancel_charge(new_page, memcg); @@ -2913,7 +2936,7 @@ static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma, int dirtied = 0; int ret, tmp; - ret = __do_fault(vma, address, pgoff, flags, &fault_page); + ret = __do_fault(vma, address, pgoff, flags, NULL, &fault_page); if (unlikely(ret & (VM_FAULT_ERROR | VM_FAULT_NOPAGE | VM_FAULT_RETRY))) return ret; |