From 2909caa4119427b5b3c6c5724cfd630a45e6218e Mon Sep 17 00:00:00 2001
From: shadow <shadow>
Date: Tue, 17 Jun 2008 06:50:36 +0000
Subject: [PATCH] Branch HEAD b=15837 i=nikita i=green

---
 lustre/ChangeLog          |  6 ++++++
 lustre/llite/llite_mmap.c | 29 +++++++++++++++--------------
 2 files changed, 21 insertions(+), 14 deletions(-)

diff --git a/lustre/ChangeLog b/lustre/ChangeLog
index cd60758..2ad66ba 100644
--- a/lustre/ChangeLog
+++ b/lustre/ChangeLog
@@ -13,6 +13,12 @@ tbd  Sun Microsystems, Inc.
         removed cwd "./" (refer to Bugzilla 14399).
 
 Severity   : minor
+Bugzilla   : 15837
+Description: oops in page fault handler
+Details    : kernel page fault handler can return two special 'pages' in error case, don't
+             try dereference NOPAGE_SIGBUS and NOPAGE_OMM.
+
+Severity   : minor
 Bugzilla   : 15716
 Description: timeout with invalidate import.
 Details    : ptlrpcd_check call obd_zombie_impexp_cull and wait request which should be
diff --git a/lustre/llite/llite_mmap.c b/lustre/llite/llite_mmap.c
index 147a4d7..d6c2230 100644
--- a/lustre/llite/llite_mmap.c
+++ b/lustre/llite/llite_mmap.c
@@ -328,20 +328,16 @@ int lt_get_mmap_locks(struct ll_lock_tree *tree,
         RETURN(0);
 }
 
-/* FIXME: there is a pagefault race goes as follow (only 2.4):
- * 1. A user process on node A accesses a portion of a mapped file,
- *    resulting in a page fault.  The pagefault handler invokes the
- *    ll_nopage function, which reads the page into memory.
- * 2. A user process on node B writes to the same portion of the file
- *    (either via mmap or write()), that cause node A to cancel the
- *    lock and truncate the page.
- * 3. Node A then executes the rest of do_no_page(), entering the
- *    now-invalid page into the PTEs.
+/**
+ * Page fault handler.
  *
- * Make the whole do_no_page as a hook to cover both the page cache
- * and page mapping installing with dlm lock would eliminate this race.
+ * \param vma - is virtiual area struct related to page fault
+ * \param address - address when hit fault
+ * \param type - of fault
  *
- * In 2.6, the truncate_count of address_space can cover this race.
+ * \return allocated and filled page for address
+ * \retval NOPAGE_SIGBUS if page not exist on this address
+ * \retval NOPAGE_OOM not have memory for allocate new page
  */
 struct page *ll_nopage(struct vm_area_struct *vma, unsigned long address,
                        int *type)
@@ -442,8 +438,13 @@ struct page *ll_nopage(struct vm_area_struct *vma, unsigned long address,
         vma->vm_flags |= VM_RAND_READ;
 
         page = filemap_nopage(vma, address, type);
-        LL_CDEBUG_PAGE(D_PAGE, page, "got addr %lu type %lx\n", address,
-                       (long)type);
+        if (page != NOPAGE_SIGBUS && page != NOPAGE_OOM)
+                LL_CDEBUG_PAGE(D_PAGE, page, "got addr %lu type %lx\n", address,
+                               (long)type);
+        else
+                CDEBUG(D_PAGE, "got addr %lu type %lx - SIGBUS\n",  address,
+                               (long)type);
+
         vma->vm_flags &= ~VM_RAND_READ;
         vma->vm_flags |= (rand_read | seq_read);
 
-- 
1.8.3.1