mm: don't vmalloc a huge page_to_node array for do_pages_stat()

do_pages_stat() does not need any page_to_node entry for real.  Just pass
the pointers to the user-space page address array and to the user-space
status array, and have do_pages_stat() traverse the former and fill the
latter directly.

Signed-off-by: Brice Goglin <Brice.Goglin@inria.fr>
Acked-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 25 insertions, 15 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index f233519f0453..a4c29081ebce 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -906,25 +906,33 @@ set_status:
 }
 
 /*
- * Determine the nodes of a list of pages. The addr in the pm array
- * must have been set to the virtual address of which we want to determine
- * the node number.
+ * Determine the nodes of an array of pages and store it in an array of status.
  */
-static int do_pages_stat(struct mm_struct *mm, struct page_to_node *pm)
+static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages,
+                         const void __user * __user *pages,
+                         int __user *status)
 {
+        unsigned long i;
+        int err;
+
         down_read(&mm->mmap_sem);
 
-        for ( ; pm->node != MAX_NUMNODES; pm++) {
+        for (i = 0; i < nr_pages; i++) {
+                const void __user *p;
+                unsigned long addr;
                 struct vm_area_struct *vma;
                 struct page *page;
-                int err;
 
                 err = -EFAULT;
-                vma = find_vma(mm, pm->addr);
+                if (get_user(p, pages+i))
+                        goto out;
+                addr = (unsigned long) p;
+
+                vma = find_vma(mm, addr);
                 if (!vma)
                         goto set_status;
 
-                page = follow_page(vma, pm->addr, 0);
+                page = follow_page(vma, addr, 0);
 
                 err = PTR_ERR(page);
                 if (IS_ERR(page))
@@ -937,11 +945,13 @@ static int do_pages_stat(struct mm_struct *mm, struct page_to_node *pm)
 
                 err = page_to_nid(page);
 set_status:
-                pm->status = err;
+                put_user(err, status+i);
         }
+        err = 0;
 
+out:
         up_read(&mm->mmap_sem);
-        return 0;
+        return err;
 }
 
 /*
@@ -997,6 +1007,10 @@ asmlinkage long sys_move_pages(pid_t pid, unsigned long nr_pages,
         if (err)
                 goto out2;
 
+        if (!nodes) {
+                err = do_pages_stat(mm, nr_pages, pages, status);
+                goto out2;
+        }
 
         task_nodes = cpuset_mems_allowed(task);
 
@@ -1045,11 +1059,7 @@ asmlinkage long sys_move_pages(pid_t pid, unsigned long nr_pages,
         /* End marker */
         pm[nr_pages].node = MAX_NUMNODES;
 
-        if (nodes)
-                err = do_move_pages(mm, pm, flags & MPOL_MF_MOVE_ALL);
-        else
-                err = do_pages_stat(mm, pm);
-
+        err = do_move_pages(mm, pm, flags & MPOL_MF_MOVE_ALL);
         if (err >= 0)
                 /* Return status information */
                 for (i = 0; i < nr_pages; i++)