[PATCH] mm: more rmap debugging

Add more debugging in the rmap code in an attempt to locate to source of
the occasional "mapcount went negative" assertions.

Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

4 files changed, 14 insertions, 7 deletions

diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
index 8d667617f558..45b3553865cf 100644
--- a/mm/filemap_xip.c
+++ b/mm/filemap_xip.c
@@ -189,7 +189,7 @@ __xip_unmap (struct address_space * mapping,
                         /* Nuke the page table entry. */
                         flush_cache_page(vma, address, pte_pfn(*pte));
                         pteval = ptep_clear_flush(vma, address, pte);
-                        page_remove_rmap(page);
+                        page_remove_rmap(page, vma);
                         dec_mm_counter(mm, file_rss);
                         BUG_ON(pte_dirty(pteval));
                         pte_unmap_unlock(pte, ptl);
diff --git a/mm/fremap.c b/mm/fremap.c
index b77a002c3352..4e3f53dd5fd4 100644
--- a/mm/fremap.c
+++ b/mm/fremap.c
@@ -33,7 +33,7 @@ static int zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
                 if (page) {
                         if (pte_dirty(pte))
                                 set_page_dirty(page);
-                        page_remove_rmap(page);
+                        page_remove_rmap(page, vma);
                         page_cache_release(page);
                 }
         } else {
diff --git a/mm/memory.c b/mm/memory.c
index c00bac66ce9f..563792f4f687 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -681,7 +681,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
                                         mark_page_accessed(page);
                                 file_rss--;
                         }
-                        page_remove_rmap(page);
+                        page_remove_rmap(page, vma);
                         tlb_remove_page(tlb, page);
                         continue;
                 }
@@ -1586,7 +1586,7 @@ gotten:
         page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
         if (likely(pte_same(*page_table, orig_pte))) {
                 if (old_page) {
-                        page_remove_rmap(old_page);
+                        page_remove_rmap(old_page, vma);
                         if (!PageAnon(old_page)) {
                                 dec_mm_counter(mm, file_rss);
                                 inc_mm_counter(mm, anon_rss);
diff --git a/mm/rmap.c b/mm/rmap.c
index d8a842a586db..b3deda8b5019 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -47,6 +47,7 @@
 #include <linux/rmap.h>
 #include <linux/rcupdate.h>
 #include <linux/module.h>
+#include <linux/kallsyms.h>
 
 #include <asm/tlbflush.h>
 
@@ -567,14 +568,20 @@ void page_add_file_rmap(struct page *page)
  *
  * The caller needs to hold the pte lock.
  */
-void page_remove_rmap(struct page *page)
+void page_remove_rmap(struct page *page, struct vm_area_struct *vma)
 {
         if (atomic_add_negative(-1, &page->_mapcount)) {
                 if (unlikely(page_mapcount(page) < 0)) {
                         printk (KERN_EMERG "Eeek! page_mapcount(page) went negative! (%d)\n", page_mapcount(page));
+                        printk (KERN_EMERG "  page pfn = %lx\n", page_to_pfn(page));
                         printk (KERN_EMERG "  page->flags = %lx\n", page->flags);
                         printk (KERN_EMERG "  page->count = %x\n", page_count(page));
                         printk (KERN_EMERG "  page->mapping = %p\n", page->mapping);
+                        print_symbol (KERN_EMERG "  vma->vm_ops = %s\n", (unsigned long)vma->vm_ops);
+                        if (vma->vm_ops)
+                                print_symbol (KERN_EMERG "  vma->vm_ops->nopage = %s\n", (unsigned long)vma->vm_ops->nopage);
+                        if (vma->vm_file && vma->vm_file->f_op)
+                                print_symbol (KERN_EMERG "  vma->vm_file->f_op->mmap = %s\n", (unsigned long)vma->vm_file->f_op->mmap);
                         BUG();
                 }
 
@@ -679,7 +686,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
                 dec_mm_counter(mm, file_rss);
 
 
-        page_remove_rmap(page);
+        page_remove_rmap(page, vma);
         page_cache_release(page);
 
 out_unmap:
@@ -769,7 +776,7 @@ static void try_to_unmap_cluster(unsigned long cursor,
                 if (pte_dirty(pteval))
                         set_page_dirty(page);
 
-                page_remove_rmap(page);
+                page_remove_rmap(page, vma);
                 page_cache_release(page);
                 dec_mm_counter(mm, file_rss);
                 (*mapcount)--;