[PATCH] mm: page fault handlers tidyup

Impose a little more consistency on the page fault handlers do_wp_page,
do_swap_page, do_anonymous_page, do_no_page, do_file_page: why not pass their
arguments in the same order, called the same names?

break_cow is all very well, but what it did was inlined elsewhere: easier to
compare if it's brought back into do_wp_page.

do_file_page's fallback to do_no_page dates from a time when we were testing
pte_file by using it wherever possible: currently it's peculiar to nonlinear
vmas, so just check that.  BUG_ON if not?  Better not, it's probably page
table corruption, so just show the pte: hmm, there's a pte_ERROR macro, let's
use that for do_wp_page's invalid pfn too.

Hah!  Someone in the ppc64 world noticed pte_ERROR was unused so removed it:
restored (and say "pud" not "pmd" in its pud_ERROR).
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/asm-ppc64/pgtable.h

@@ -478,10 +478,12 @@ extern pgprot_t phys_mem_access_prot(struct file *file, unsigned long addr,
 #define __HAVE_ARCH_PTE_SAME
 #define pte_same(A,B)	(((pte_val(A) ^ pte_val(B)) & ~_PAGE_HPTEFLAGS) == 0)
 
+#define pte_ERROR(e) \
+	printk("%s:%d: bad pte %08lx.\n", __FILE__, __LINE__, pte_val(e))
 #define pmd_ERROR(e) \
 	printk("%s:%d: bad pmd %08lx.\n", __FILE__, __LINE__, pmd_val(e))
 #define pud_ERROR(e) \
-	printk("%s:%d: bad pmd %08lx.\n", __FILE__, __LINE__, pud_val(e))
+	printk("%s:%d: bad pud %08lx.\n", __FILE__, __LINE__, pud_val(e))
 #define pgd_ERROR(e) \
 	printk("%s:%d: bad pgd %08lx.\n", __FILE__, __LINE__, pgd_val(e))
 

mm/filemap.c

@@ -1520,7 +1520,7 @@ int filemap_populate(struct vm_area_struct *vma, unsigned long addr,
 			page_cache_release(page);
 			return err;
 		}
-	} else {
+	} else if (vma->vm_flags & VM_NONLINEAR) {
 		/* No page was found just because we can't read it in now (being
 		 * here implies nonblock != 0), but the page may exist, so set
 		 * the PTE to fault it in later. */

mm/shmem.c

@@ -1201,7 +1201,7 @@ static int shmem_populate(struct vm_area_struct *vma,
 				page_cache_release(page);
 				return err;
 			}
-		} else {
+		} else if (vma->vm_flags & VM_NONLINEAR) {
 			/* No page was found just because we can't read it in
 			 * now (being here implies nonblock != 0), but the page
 			 * may exist, so set the PTE to fault it in later. */