mm: replace some BUG_ONs by VM_BUG_ONs

The swap code is over-provisioned with BUG_ONs on assorted page flags,
mostly dating back to 2.3.  They're good documentation, and guard against
developer error, but a waste of space on most systems: change them to
VM_BUG_ONs, conditional on CONFIG_DEBUG_VM.  Just delete the PagePrivate
ones: they're later, from 2.5.69, but even less interesting now.

Signed-off-by: Hugh Dickins <hugh@veritas.com>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 9 insertions, 10 deletions

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 3353c9029cef..e793fdea275d 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -72,10 +72,10 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
 {
         int error;
 
-        BUG_ON(!PageLocked(page));
-        BUG_ON(PageSwapCache(page));
-        BUG_ON(PagePrivate(page));
-        BUG_ON(!PageSwapBacked(page));
+        VM_BUG_ON(!PageLocked(page));
+        VM_BUG_ON(PageSwapCache(page));
+        VM_BUG_ON(!PageSwapBacked(page));
+
         error = radix_tree_preload(gfp_mask);
         if (!error) {
                 page_cache_get(page);
@@ -108,10 +108,9 @@ int add_to_swap_cache(struct page *page, swp_entry_t entry, gfp_t gfp_mask)
  */
 void __delete_from_swap_cache(struct page *page)
 {
-        BUG_ON(!PageLocked(page));
-        BUG_ON(!PageSwapCache(page));
-        BUG_ON(PageWriteback(page));
-        BUG_ON(PagePrivate(page));
+        VM_BUG_ON(!PageLocked(page));
+        VM_BUG_ON(!PageSwapCache(page));
+        VM_BUG_ON(PageWriteback(page));
 
         radix_tree_delete(&swapper_space.page_tree, page_private(page));
         set_page_private(page, 0);
@@ -134,8 +133,8 @@ int add_to_swap(struct page * page, gfp_t gfp_mask)
         swp_entry_t entry;
         int err;
 
-        BUG_ON(!PageLocked(page));
-        BUG_ON(!PageUptodate(page));
+        VM_BUG_ON(!PageLocked(page));
+        VM_BUG_ON(!PageUptodate(page));
 
         for (;;) {
                 entry = get_swap_page();