1 files changed, 65 insertions, 2 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 3dc712f29d2d..a9b399402007 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1022,6 +1022,7 @@ try_again:
 
                 bh->b_state = 0;
                 atomic_set(&bh->b_count, 0);
+                bh->b_private = NULL;
                 bh->b_size = size;
 
                 /* Link the buffer to its page */
@@ -2866,22 +2867,22 @@ void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
                 else if (test_set_buffer_locked(bh))
                         continue;
 
-                get_bh(bh);
                 if (rw == WRITE || rw == SWRITE) {
                         if (test_clear_buffer_dirty(bh)) {
                                 bh->b_end_io = end_buffer_write_sync;
+                                get_bh(bh);
                                 submit_bh(WRITE, bh);
                                 continue;
                         }
                 } else {
                         if (!buffer_uptodate(bh)) {
                                 bh->b_end_io = end_buffer_read_sync;
+                                get_bh(bh);
                                 submit_bh(rw, bh);
                                 continue;
                         }
                 }
                 unlock_buffer(bh);
-                put_bh(bh);
         }
 }
 
@@ -3050,6 +3051,68 @@ asmlinkage long sys_bdflush(int func, long data)
 }
 
 /*
+ * Migration function for pages with buffers. This function can only be used
+ * if the underlying filesystem guarantees that no other references to "page"
+ * exist.
+ */
+#ifdef CONFIG_MIGRATION
+int buffer_migrate_page(struct page *newpage, struct page *page)
+{
+        struct address_space *mapping = page->mapping;
+        struct buffer_head *bh, *head;
+        int rc;
+
+        if (!mapping)
+                return -EAGAIN;
+
+        if (!page_has_buffers(page))
+                return migrate_page(newpage, page);
+
+        head = page_buffers(page);
+
+        rc = migrate_page_remove_references(newpage, page, 3);
+        if (rc)
+                return rc;
+
+        bh = head;
+        do {
+                get_bh(bh);
+                lock_buffer(bh);
+                bh = bh->b_this_page;
+
+        } while (bh != head);
+
+        ClearPagePrivate(page);
+        set_page_private(newpage, page_private(page));
+        set_page_private(page, 0);
+        put_page(page);
+        get_page(newpage);
+
+        bh = head;
+        do {
+                set_bh_page(bh, newpage, bh_offset(bh));
+                bh = bh->b_this_page;
+
+        } while (bh != head);
+
+        SetPagePrivate(newpage);
+
+        migrate_page_copy(newpage, page);
+
+        bh = head;
+        do {
+                unlock_buffer(bh);
+                put_bh(bh);
+                bh = bh->b_this_page;
+
+        } while (bh != head);
+
+        return 0;
+}
+EXPORT_SYMBOL(buffer_migrate_page);
+#endif
+
+/*
  * Buffer-head allocation
  */
 static kmem_cache_t *bh_cachep;