Merge tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux

fix 1 mysterious divide error
fix 3 NULL dereference bugs in writeback tracing, on SD card removal w/o umount

* tag 'writeback-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/wfg/linux:
  writeback: fix dereferencing NULL bdi->dev on trace_writeback_queue
  lib: proportion: lower PROP_MAX_SHIFT to 32 on 64-bit kernel
  writeback: fix NULL bdi->dev in trace writeback_single_inode
  backing-dev: fix wakeup timer races with bdi_unregister()

2 files changed, 9 insertions, 2 deletions

diff --git a/include/linux/proportions.h b/include/linux/proportions.h
index ef35bb73f69b..26a8a4ed9b07 100644
--- a/include/linux/proportions.h
+++ b/include/linux/proportions.h
@@ -81,7 +81,11 @@ void prop_inc_percpu(struct prop_descriptor *pd, struct prop_local_percpu *pl)
  * Limit the time part in order to ensure there are some bits left for the
  * cycle counter and fraction multiply.
  */
+#if BITS_PER_LONG == 32
 #define PROP_MAX_SHIFT (3*BITS_PER_LONG/4)
+#else
+#define PROP_MAX_SHIFT (BITS_PER_LONG/2)
+#endif
 
 #define PROP_FRAC_SHIFT         (BITS_PER_LONG - PROP_MAX_SHIFT - 1)
 #define PROP_FRAC_BASE          (1UL << PROP_FRAC_SHIFT)
diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
index 8588a8918023..5973410e8f8c 100644
--- a/include/trace/events/writeback.h
+++ b/include/trace/events/writeback.h
@@ -47,7 +47,10 @@ DECLARE_EVENT_CLASS(writeback_work_class,
                 __field(int, reason)
         ),
         TP_fast_assign(
-                strncpy(__entry->name, dev_name(bdi->dev), 32);
+                struct device *dev = bdi->dev;
+                if (!dev)
+                        dev = default_backing_dev_info.dev;
+                strncpy(__entry->name, dev_name(dev), 32);
                 __entry->nr_pages = work->nr_pages;
                 __entry->sb_dev = work->sb ? work->sb->s_dev : 0;
                 __entry->sync_mode = work->sync_mode;
@@ -426,7 +429,7 @@ DECLARE_EVENT_CLASS(writeback_single_inode_template,
 
         TP_fast_assign(
                 strncpy(__entry->name,
-                        dev_name(inode->i_mapping->backing_dev_info->dev), 32);
+                        dev_name(inode_to_bdi(inode)->dev), 32);
                 __entry->ino            = inode->i_ino;
                 __entry->state          = inode->i_state;
                 __entry->dirtied_when   = inode->dirtied_when;