mm: drop support of non-linear mapping from fault codepath

We don't create non-linear mappings anymore.  Let's drop code which
handles them on page fault.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 16 insertions, 65 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 600ef5ed4698..376e5c325dee 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -206,21 +206,19 @@ extern unsigned int kobjsize(const void *objp);
 extern pgprot_t protection_map[16];
 
 #define FAULT_FLAG_WRITE        0x01    /* Fault was a write access */
-#define FAULT_FLAG_NONLINEAR    0x02    /* Fault was via a nonlinear mapping */
-#define FAULT_FLAG_MKWRITE      0x04    /* Fault was mkwrite of existing pte */
-#define FAULT_FLAG_ALLOW_RETRY  0x08    /* Retry fault if blocking */
-#define FAULT_FLAG_RETRY_NOWAIT 0x10    /* Don't drop mmap_sem and wait when retrying */
-#define FAULT_FLAG_KILLABLE     0x20    /* The fault task is in SIGKILL killable region */
-#define FAULT_FLAG_TRIED        0x40    /* second try */
-#define FAULT_FLAG_USER         0x80    /* The fault originated in userspace */
+#define FAULT_FLAG_MKWRITE      0x02    /* Fault was mkwrite of existing pte */
+#define FAULT_FLAG_ALLOW_RETRY  0x04    /* Retry fault if blocking */
+#define FAULT_FLAG_RETRY_NOWAIT 0x08    /* Don't drop mmap_sem and wait when retrying */
+#define FAULT_FLAG_KILLABLE     0x10    /* The fault task is in SIGKILL killable region */
+#define FAULT_FLAG_TRIED        0x20    /* Second try */
+#define FAULT_FLAG_USER         0x40    /* The fault originated in userspace */
 
 /*
  * vm_fault is filled by the the pagefault handler and passed to the vma's
  * ->fault function. The vma's ->fault is responsible for returning a bitmask
  * of VM_FAULT_xxx flags that give details about how the fault was handled.
  *
- * pgoff should be used in favour of virtual_address, if possible. If pgoff
- * is used, one may implement ->remap_pages to get nonlinear mapping support.
+ * pgoff should be used in favour of virtual_address, if possible.
  */
 struct vm_fault {
         unsigned int flags;             /* FAULT_FLAG_xxx flags */
diff --git a/mm/memory.c b/mm/memory.c
index 9a3e73b69dad..43a53743cbb4 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1899,12 +1899,11 @@ int apply_to_page_range(struct mm_struct *mm, unsigned long addr,
 EXPORT_SYMBOL_GPL(apply_to_page_range);
 
 /*
- * handle_pte_fault chooses page fault handler according to an entry
- * which was read non-atomically.  Before making any commitment, on
- * those architectures or configurations (e.g. i386 with PAE) which
- * might give a mix of unmatched parts, do_swap_page and do_nonlinear_fault
- * must check under lock before unmapping the pte and proceeding
- * (but do_wp_page is only called after already making such a check;
+ * handle_pte_fault chooses page fault handler according to an entry which was
+ * read non-atomically.  Before making any commitment, on those architectures
+ * or configurations (e.g. i386 with PAE) which might give a mix of unmatched
+ * parts, do_swap_page must check under lock before unmapping the pte and
+ * proceeding (but do_wp_page is only called after already making such a check;
  * and do_anonymous_page can safely check later on).
  */
 static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,
@@ -2710,8 +2709,6 @@ void do_set_pte(struct vm_area_struct *vma, unsigned long address,
         entry = mk_pte(page, vma->vm_page_prot);
         if (write)
                 entry = maybe_mkwrite(pte_mkdirty(entry), vma);
-        else if (pte_file(*pte) && pte_file_soft_dirty(*pte))
-                entry = pte_mksoft_dirty(entry);
         if (anon) {
                 inc_mm_counter_fast(vma->vm_mm, MM_ANONPAGES);
                 page_add_new_anon_rmap(page, vma, address);
@@ -2846,8 +2843,7 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
          * if page by the offset is not ready to be mapped (cold cache or
          * something).
          */
-        if (vma->vm_ops->map_pages && !(flags & FAULT_FLAG_NONLINEAR) &&
-            fault_around_bytes >> PAGE_SHIFT > 1) {
+        if (vma->vm_ops->map_pages && fault_around_bytes >> PAGE_SHIFT > 1) {
                 pte = pte_offset_map_lock(mm, pmd, address, &ptl);
                 do_fault_around(vma, address, pte, pgoff, flags);
                 if (!pte_same(*pte, orig_pte))
@@ -2992,7 +2988,7 @@ static int do_shared_fault(struct mm_struct *mm, struct vm_area_struct *vma,
  * The mmap_sem may have been released depending on flags and our
  * return value.  See filemap_fault() and __lock_page_or_retry().
  */
-static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
+static int do_fault(struct mm_struct *mm, struct vm_area_struct *vma,
                 unsigned long address, pte_t *page_table, pmd_t *pmd,
                 unsigned int flags, pte_t orig_pte)
 {
@@ -3009,46 +3005,6 @@ static int do_linear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
         return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
 }
 
-/*
- * Fault of a previously existing named mapping. Repopulate the pte
- * from the encoded file_pte if possible. This enables swappable
- * nonlinear vmas.
- *
- * We enter with non-exclusive mmap_sem (to exclude vma changes,
- * but allow concurrent faults), and pte mapped but not yet locked.
- * We return with pte unmapped and unlocked.
- * The mmap_sem may have been released depending on flags and our
- * return value.  See filemap_fault() and __lock_page_or_retry().
- */
-static int do_nonlinear_fault(struct mm_struct *mm, struct vm_area_struct *vma,
-                unsigned long address, pte_t *page_table, pmd_t *pmd,
-                unsigned int flags, pte_t orig_pte)
-{
-        pgoff_t pgoff;
-
-        flags |= FAULT_FLAG_NONLINEAR;
-
-        if (!pte_unmap_same(mm, pmd, page_table, orig_pte))
-                return 0;
-
-        if (unlikely(!(vma->vm_flags & VM_NONLINEAR))) {
-                /*
-                 * Page table corrupted: show pte and kill process.
-                 */
-                print_bad_pte(vma, address, orig_pte, NULL);
-                return VM_FAULT_SIGBUS;
-        }
-
-        pgoff = pte_to_pgoff(orig_pte);
-        if (!(flags & FAULT_FLAG_WRITE))
-                return do_read_fault(mm, vma, address, pmd, pgoff, flags,
-                                orig_pte);
-        if (!(vma->vm_flags & VM_SHARED))
-                return do_cow_fault(mm, vma, address, pmd, pgoff, flags,
-                                orig_pte);
-        return do_shared_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
-}
-
 static int numa_migrate_prep(struct page *page, struct vm_area_struct *vma,
                                 unsigned long addr, int page_nid,
                                 int *flags)
@@ -3176,15 +3132,12 @@ static int handle_pte_fault(struct mm_struct *mm,
                 if (pte_none(entry)) {
                         if (vma->vm_ops) {
                                 if (likely(vma->vm_ops->fault))
-                                        return do_linear_fault(mm, vma, address,
-                                                pte, pmd, flags, entry);
+                                        return do_fault(mm, vma, address, pte,
+                                                        pmd, flags, entry);
                         }
                         return do_anonymous_page(mm, vma, address,
                                                  pte, pmd, flags);
                 }
-                if (pte_file(entry))
-                        return do_nonlinear_fault(mm, vma, address,
-                                        pte, pmd, flags, entry);
                 return do_swap_page(mm, vma, address,
                                         pte, pmd, flags, entry);
         }