[PATCH] get_user_pages: kill get_page_map

Since its birth, get_user_pages has been calling a misguided get_page_map
function.  follow_page has already returned NULL if the pfn is invalid, we
cannot reach an invalid pfn from a validated struct page.

Remove get_page_map, and the messy rewind in get_user_pages to cope with
its failure.  Oh, and could we please call that "struct page *page" like
everywhere else, instead of "struct page *map"?

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/mm/memory.c b/mm/memory.c
index d209f745db7fbc3154e83cf04666770068986724..b8846cf2358a54fb9903568fc50dbd69ab3d2bce 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -840,23 +840,8 @@ check_user_page_readable(struct mm_struct *mm, unsigned long address)
 {
        return __follow_page(mm, address, /*read*/1, /*write*/0) != NULL;
 }
-
 EXPORT_SYMBOL(check_user_page_readable);
 
-/* 
- * Given a physical address, is there a useful struct page pointing to
- * it?  This may become more complex in the future if we start dealing
- * with IO-aperture pages for direct-IO.
- */
-
-static inline struct page *get_page_map(struct page *page)
-{
-       if (!pfn_valid(page_to_pfn(page)))
-               return NULL;
-       return page;
-}
-
-
 static inline int
 untouched_anonymous_page(struct mm_struct* mm, struct vm_area_struct *vma,
                         unsigned long address)
@@ -887,7 +872,6 @@ untouched_anonymous_page(struct mm_struct* mm, struct vm_area_struct *vma,
        return 0;
 }
 
-
 int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                unsigned long start, int len, int write, int force,
                struct page **pages, struct vm_area_struct **vmas)
@@ -951,21 +935,21 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                }
                spin_lock(&mm->page_table_lock);
                do {
-                       struct page *map;
+                       struct page *page;
                        int lookup_write = write;
 
                        cond_resched_lock(&mm->page_table_lock);
-                       while (!(map = follow_page(mm, start, lookup_write))) {
+                       while (!(page = follow_page(mm, start, lookup_write))) {
                                /*
                                 * Shortcut for anonymous pages. We don't want
                                 * to force the creation of pages tables for
-                                * insanly big anonymously mapped areas that
+                                * insanely big anonymously mapped areas that
                                 * nobody touched so far. This is important
                                 * for doing a core dump for these mappings.
                                 */
                                if (!lookup_write &&
                                    untouched_anonymous_page(mm,vma,start)) {
-                                       map = ZERO_PAGE(start);
+                                       page = ZERO_PAGE(start);
                                        break;
                                }
                                spin_unlock(&mm->page_table_lock);
@@ -994,30 +978,21 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                spin_lock(&mm->page_table_lock);
                        }
                        if (pages) {
-                               pages[i] = get_page_map(map);
-                               if (!pages[i]) {
-                                       spin_unlock(&mm->page_table_lock);
-                                       while (i--)
-                                               page_cache_release(pages[i]);
-                                       i = -EFAULT;
-                                       goto out;
-                               }
-                               flush_dcache_page(pages[i]);
-                               if (!PageReserved(pages[i]))
-                                       page_cache_get(pages[i]);
+                               pages[i] = page;
+                               flush_dcache_page(page);
+                               if (!PageReserved(page))
+                                       page_cache_get(page);
                        }
                        if (vmas)
                                vmas[i] = vma;
                        i++;
                        start += PAGE_SIZE;
                        len--;
-               } while(len && start < vma->vm_end);
+               } while (len && start < vma->vm_end);
                spin_unlock(&mm->page_table_lock);
-       } while(len);
-out:
+       } while (len);
        return i;
 }
-
 EXPORT_SYMBOL(get_user_pages);
 
 static int zeromap_pte_range(struct mm_struct *mm, pmd_t *pmd,