mm: dump page when hitting a VM_BUG_ON using VM_BUG_ON_PAGE

Most of the VM_BUG_ON assertions are performed on a page.  Usually, when
one of these assertions fails we'll get a BUG_ON with a call stack and
the registers.

I've recently noticed based on the requests to add a small piece of code
that dumps the page to various VM_BUG_ON sites that the page dump is
quite useful to people debugging issues in mm.

This patch adds a VM_BUG_ON_PAGE(cond, page) which beyond doing what
VM_BUG_ON() does, also dumps the page before executing the actual
BUG_ON.

[akpm@linux-foundation.org: fix up includes]
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 6 deletions

diff --git a/mm/ksm.c b/mm/ksm.c
index 3df141e5f3e0..f91ddf5c3688 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1898,13 +1898,13 @@ int rmap_walk_ksm(struct page *page, struct rmap_walk_control *rwc)
         int ret = SWAP_AGAIN;
         int search_new_forks = 0;
 
-        VM_BUG_ON(!PageKsm(page));
+        VM_BUG_ON_PAGE(!PageKsm(page), page);
 
         /*
          * Rely on the page lock to protect against concurrent modifications
          * to that page's node of the stable tree.
          */
-        VM_BUG_ON(!PageLocked(page));
+        VM_BUG_ON_PAGE(!PageLocked(page), page);
 
         stable_node = page_stable_node(page);
         if (!stable_node)
@@ -1958,13 +1958,13 @@ void ksm_migrate_page(struct page *newpage, struct page *oldpage)
 {
         struct stable_node *stable_node;
 
-        VM_BUG_ON(!PageLocked(oldpage));
-        VM_BUG_ON(!PageLocked(newpage));
-        VM_BUG_ON(newpage->mapping != oldpage->mapping);
+        VM_BUG_ON_PAGE(!PageLocked(oldpage), oldpage);
+        VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
+        VM_BUG_ON_PAGE(newpage->mapping != oldpage->mapping, newpage);
 
         stable_node = page_stable_node(newpage);
         if (stable_node) {
-                VM_BUG_ON(stable_node->kpfn != page_to_pfn(oldpage));
+                VM_BUG_ON_PAGE(stable_node->kpfn != page_to_pfn(oldpage), oldpage);
                 stable_node->kpfn = page_to_pfn(newpage);
                 /*
                  * newpage->mapping was set in advance; now we need smp_wmb()