mm rmap: remove vma_address check for address inside vma

In file and anon rmap, we use interval trees to find potentially relevant
vmas and then call vma_address() to find the virtual address the given
page might be found at in these vmas.  vma_address() used to include a
check that the returned address falls within the limits of the vma, but
this check isn't necessary now that we always use interval trees in rmap:
the interval tree just doesn't return any vmas which this check would find
to be irrelevant.  As a result, we can replace the use of -EFAULT error
code (which then needed to be checked in every call site) with a
VM_BUG_ON().

Signed-off-by: Michel Lespinasse <walken@google.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Daniel Santos <daniel.santos@pobox.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 21 insertions, 27 deletions

diff --git a/mm/rmap.c b/mm/rmap.c
index 9c61bf387fd1..28777412de62 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -510,22 +510,26 @@ void page_unlock_anon_vma(struct anon_vma *anon_vma)
 
 /*
  * At what user virtual address is page expected in @vma?
- * Returns virtual address or -EFAULT if page's index/offset is not
- * within the range mapped the @vma.
  */
-inline unsigned long
-vma_address(struct page *page, struct vm_area_struct *vma)
+static inline unsigned long
+__vma_address(struct page *page, struct vm_area_struct *vma)
 {
         pgoff_t pgoff = page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
-        unsigned long address;
 
         if (unlikely(is_vm_hugetlb_page(vma)))
                 pgoff = page->index << huge_page_order(page_hstate(page));
-        address = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
-        if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
-                /* page should be within @vma mapping range */
-                return -EFAULT;
-        }
+
+        return vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
+}
+
+inline unsigned long
+vma_address(struct page *page, struct vm_area_struct *vma)
+{
+        unsigned long address = __vma_address(page, vma);
+
+        /* page should be within @vma mapping range */
+        VM_BUG_ON(address < vma->vm_start || address >= vma->vm_end);
+
         return address;
 }
 
@@ -535,6 +539,7 @@ vma_address(struct page *page, struct vm_area_struct *vma)
  */
 unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
 {
+        unsigned long address;
         if (PageAnon(page)) {
                 struct anon_vma *page__anon_vma = page_anon_vma(page);
                 /*
@@ -550,7 +555,10 @@ unsigned long page_address_in_vma(struct page *page, struct vm_area_struct *vma)
                         return -EFAULT;
         } else
                 return -EFAULT;
-        return vma_address(page, vma);
+        address = __vma_address(page, vma);
+        if (unlikely(address < vma->vm_start || address >= vma->vm_end))
+                return -EFAULT;
+        return address;
 }
 
 /*
@@ -624,8 +632,8 @@ int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma)
         pte_t *pte;
         spinlock_t *ptl;
 
-        address = vma_address(page, vma);
-        if (address == -EFAULT)         /* out of vma range */
+        address = __vma_address(page, vma);
+        if (unlikely(address < vma->vm_start || address >= vma->vm_end))
                 return 0;
         pte = page_check_address(page, vma->vm_mm, address, &ptl, 1);
         if (!pte)                       /* the page is not in this mm */
@@ -732,8 +740,6 @@ static int page_referenced_anon(struct page *page,
         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
                 struct vm_area_struct *vma = avc->vma;
                 unsigned long address = vma_address(page, vma);
-                if (address == -EFAULT)
-                        continue;
                 /*
                  * If we are reclaiming on behalf of a cgroup, skip
                  * counting on behalf of references from different
@@ -799,8 +805,6 @@ static int page_referenced_file(struct page *page,
 
         vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
                 unsigned long address = vma_address(page, vma);
-                if (address == -EFAULT)
-                        continue;
                 /*
                  * If we are reclaiming on behalf of a cgroup, skip
                  * counting on behalf of references from different
@@ -904,8 +908,6 @@ static int page_mkclean_file(struct address_space *mapping, struct page *page)
         vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
                 if (vma->vm_flags & VM_SHARED) {
                         unsigned long address = vma_address(page, vma);
-                        if (address == -EFAULT)
-                                continue;
                         ret += page_mkclean_one(page, vma, address);
                 }
         }
@@ -1468,8 +1470,6 @@ static int try_to_unmap_anon(struct page *page, enum ttu_flags flags)
                         continue;
 
                 address = vma_address(page, vma);
-                if (address == -EFAULT)
-                        continue;
                 ret = try_to_unmap_one(page, vma, address, flags);
                 if (ret != SWAP_AGAIN || !page_mapped(page))
                         break;
@@ -1508,8 +1508,6 @@ static int try_to_unmap_file(struct page *page, enum ttu_flags flags)
         mutex_lock(&mapping->i_mmap_mutex);
         vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
                 unsigned long address = vma_address(page, vma);
-                if (address == -EFAULT)
-                        continue;
                 ret = try_to_unmap_one(page, vma, address, flags);
                 if (ret != SWAP_AGAIN || !page_mapped(page))
                         goto out;
@@ -1684,8 +1682,6 @@ static int rmap_walk_anon(struct page *page, int (*rmap_one)(struct page *,
         anon_vma_interval_tree_foreach(avc, &anon_vma->rb_root, pgoff, pgoff) {
                 struct vm_area_struct *vma = avc->vma;
                 unsigned long address = vma_address(page, vma);
-                if (address == -EFAULT)
-                        continue;
                 ret = rmap_one(page, vma, address, arg);
                 if (ret != SWAP_AGAIN)
                         break;
@@ -1707,8 +1703,6 @@ static int rmap_walk_file(struct page *page, int (*rmap_one)(struct page *,
         mutex_lock(&mapping->i_mmap_mutex);
         vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
                 unsigned long address = vma_address(page, vma);
-                if (address == -EFAULT)
-                        continue;
                 ret = rmap_one(page, vma, address, arg);
                 if (ret != SWAP_AGAIN)
                         break;