mm: page_mapped: don't assume compound page is huge or THP

[linux-2.6-block.git] / mm / mincore.c

diff --git a/mm/mincore.c b/mm/mincore.c
index 4985965aa20a56fbafeaff20096d1fddbbb0d51f..f0f91461a9f45c350fd8fccc0ccaf6c9578e4b3a 100644 (file)
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -42,72 +42,14 @@ static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
        return 0;
 }
 
-/*
- * Later we can get more picky about what "in core" means precisely.
- * For now, simply check to see if the page is in the page cache,
- * and is up to date; i.e. that no page-in operation would be required
- * at this time if an application were to map and access this page.
- */
-static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
-{
-       unsigned char present = 0;
-       struct page *page;
-
-       /*
-        * When tmpfs swaps out a page from a file, any process mapping that
-        * file will not get a swp_entry_t in its pte, but rather it is like
-        * any other file mapping (ie. marked !present and faulted in with
-        * tmpfs's .fault). So swapped out tmpfs mappings are tested here.
-        */
-#ifdef CONFIG_SWAP
-       if (shmem_mapping(mapping)) {
-               page = find_get_entry(mapping, pgoff);
-               /*
-                * shmem/tmpfs may return swap: account for swapcache
-                * page too.
-                */
-               if (xa_is_value(page)) {
-                       swp_entry_t swp = radix_to_swp_entry(page);
-                       page = find_get_page(swap_address_space(swp),
-                                            swp_offset(swp));
-               }
-       } else
-               page = find_get_page(mapping, pgoff);
-#else
-       page = find_get_page(mapping, pgoff);
-#endif
-       if (page) {
-               present = PageUptodate(page);
-               put_page(page);
-       }
-
-       return present;
-}
-
-static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
-                               struct vm_area_struct *vma, unsigned char *vec)
-{
-       unsigned long nr = (end - addr) >> PAGE_SHIFT;
-       int i;
-
-       if (vma->vm_file) {
-               pgoff_t pgoff;
-
-               pgoff = linear_page_index(vma, addr);
-               for (i = 0; i < nr; i++, pgoff++)
-                       vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
-       } else {
-               for (i = 0; i < nr; i++)
-                       vec[i] = 0;
-       }
-       return nr;
-}
-
 static int mincore_unmapped_range(unsigned long addr, unsigned long end,
                                   struct mm_walk *walk)
 {
-       walk->private += __mincore_unmapped_range(addr, end,
-                                                 walk->vma, walk->private);
+       unsigned char *vec = walk->private;
+       unsigned long nr = (end - addr) >> PAGE_SHIFT;
+
+       memset(vec, 0, nr);
+       walk->private += nr;
        return 0;
 }
 
@@ -127,8 +69,9 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
                goto out;
        }
 
+       /* We'll consider a THP page under construction to be there */
        if (pmd_trans_unstable(pmd)) {
-               __mincore_unmapped_range(addr, end, vma, vec);
+               memset(vec, 1, nr);
                goto out;
        }
 
@@ -137,28 +80,17 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
                pte_t pte = *ptep;
 
                if (pte_none(pte))
-                       __mincore_unmapped_range(addr, addr + PAGE_SIZE,
-                                                vma, vec);
+                       *vec = 0;
                else if (pte_present(pte))
                        *vec = 1;
                else { /* pte is a swap entry */
                        swp_entry_t entry = pte_to_swp_entry(pte);
 
-                       if (non_swap_entry(entry)) {
-                               /*
-                                * migration or hwpoison entries are always
-                                * uptodate
-                                */
-                               *vec = 1;
-                       } else {
-#ifdef CONFIG_SWAP
-                               *vec = mincore_page(swap_address_space(entry),
-                                                   swp_offset(entry));
-#else
-                               WARN_ON(1);
-                               *vec = 1;
-#endif
-                       }
+                       /*
+                        * migration or hwpoison entries are always
+                        * uptodate
+                        */
+                       *vec = !!non_swap_entry(entry);
                }
                vec++;
        }
@@ -233,14 +165,14 @@ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
                return -EINVAL;
 
        /* ..and we need to be passed a valid user-space range */
-       if (!access_ok(VERIFY_READ, (void __user *) start, len))
+       if (!access_ok((void __user *) start, len))
                return -ENOMEM;
 
        /* This also avoids any overflows on PAGE_ALIGN */
        pages = len >> PAGE_SHIFT;
        pages += (offset_in_page(len)) != 0;
 
-       if (!access_ok(VERIFY_WRITE, vec, pages))
+       if (!access_ok(vec, pages))
                return -EFAULT;
 
        tmp = (void *) __get_free_page(GFP_USER);