[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>

1 files changed, 16 insertions, 9 deletions

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 9f46d83b4ece..5ac5333f37a0 100644
--- 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();