[PATCH] swap: correct swapfile nr_good_pages

If a regular swapfile lies on a filesystem whose blocksize is less than
PAGE_SIZE, then setup_swap_extents may have to cut the number of usable swap
pages; but sys_swapon's nr_good_pages was not expecting that.  Also,
setup_swap_extents takes no account of badpages listed in the swap header: not
worth doing so, but ensure nr_badpages is 0 for a regular swapfile.

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/swapfile.c b/mm/swapfile.c
index 9f46d83..5ac5333 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1008,8 +1008,9 @@ reprobe:
        }
        ret = 0;
        if (page_no == 0)
-               ret = -EINVAL;
+               page_no = 1;    /* force Empty message */
        sis->max = page_no;
+       sis->pages = page_no - 1;
        sis->highest_bit = page_no - 1;
 done:
        sis->curr_swap_extent = list_entry(sis->extent_list.prev,
@@ -1446,6 +1447,10 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
                p->highest_bit = maxpages - 1;
 
                error = -EINVAL;
+               if (!maxpages)
+                       goto bad_swap;
+               if (swap_header->info.nr_badpages && S_ISREG(inode->i_mode))
+                       goto bad_swap;
                if (swap_header->info.nr_badpages > MAX_SWAP_BADPAGES)
                        goto bad_swap;
                
@@ -1470,25 +1475,27 @@ asmlinkage long sys_swapon(const char __user * specialfile, int swap_flags)
                if (error) 
                        goto bad_swap;
        }
-       
+
        if (swapfilesize && maxpages > swapfilesize) {
                printk(KERN_WARNING
                       "Swap area shorter than signature indicates\n");
                error = -EINVAL;
                goto bad_swap;
        }
+       if (nr_good_pages) {
+               p->swap_map[0] = SWAP_MAP_BAD;
+               p->max = maxpages;
+               p->pages = nr_good_pages;
+               error = setup_swap_extents(p);
+               if (error)
+                       goto bad_swap;
+               nr_good_pages = p->pages;
+       }
        if (!nr_good_pages) {
                printk(KERN_WARNING "Empty swap-file\n");
                error = -EINVAL;
                goto bad_swap;
        }
-       p->swap_map[0] = SWAP_MAP_BAD;
-       p->max = maxpages;
-       p->pages = nr_good_pages;
-
-       error = setup_swap_extents(p);
-       if (error)
-               goto bad_swap;
 
        down(&swapon_sem);
        swap_list_lock();