[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>

1 files changed, 10 insertions, 35 deletions

diff --git a/mm/memory.c b/mm/memory.c
index d209f745db7f..b8846cf2358a 100644
--- 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,