mm: fix XFS oops due to dirty pages without buffers on s390

[karo-tx-linux.git] / mm / rmap.c

diff --git a/mm/rmap.c b/mm/rmap.c
index 7df7984d476c8661b900725c0e2c3f33c883a32d..2ee1ef0f317b7487bfb21b7a6717b1e12d1f7ef4 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -56,6 +56,7 @@
 #include <linux/mmu_notifier.h>
 #include <linux/migrate.h>
 #include <linux/hugetlb.h>
+#include <linux/backing-dev.h>
 
 #include <asm/tlbflush.h>
 
@@ -926,11 +927,8 @@ int page_mkclean(struct page *page)
 
        if (page_mapped(page)) {
                struct address_space *mapping = page_mapping(page);
-               if (mapping) {
+               if (mapping)
                        ret = page_mkclean_file(mapping, page);
-                       if (page_test_and_clear_dirty(page_to_pfn(page), 1))
-                               ret = 1;
-               }
        }
 
        return ret;
@@ -1116,6 +1114,7 @@ void page_add_file_rmap(struct page *page)
  */
 void page_remove_rmap(struct page *page)
 {
+       struct address_space *mapping = page_mapping(page);
        bool anon = PageAnon(page);
        bool locked;
        unsigned long flags;
@@ -1138,8 +1137,19 @@ void page_remove_rmap(struct page *page)
         * this if the page is anon, so about to be freed; but perhaps
         * not if it's in swapcache - there might be another pte slot
         * containing the swap entry, but page not yet written to swap.
+        *
+        * And we can skip it on file pages, so long as the filesystem
+        * participates in dirty tracking; but need to catch shm and tmpfs
+        * and ramfs pages which have been modified since creation by read
+        * fault.
+        *
+        * Note that mapping must be decided above, before decrementing
+        * mapcount (which luckily provides a barrier): once page is unmapped,
+        * it could be truncated and page->mapping reset to NULL at any moment.
+        * Note also that we are relying on page_mapping(page) to set mapping
+        * to &swapper_space when PageSwapCache(page).
         */
-       if ((!anon || PageSwapCache(page)) &&
+       if (mapping && !mapping_cap_account_dirty(mapping) &&
            page_test_and_clear_dirty(page_to_pfn(page), 1))
                set_page_dirty(page);
        /*