Merge branch 'for-linus' of git://git.kernel.dk/linux-block

Pull block layer fixes from Jens Axboe:
 "A small collection of fixes that has been gathered over the last few
  weeks.  This contains:

   - A one-liner fix for NVMe, fixing a missing list_head init that
     could makes us oops on hitting recovery at load time.

   - Two small blk-mq fixes:
        - Fixup a bad goto jump on error handling.
        - Fix for oopsing if running out of reserved tags.

   - A memory leak fix for NBD.

   - Two small writeback fixes from Tejun, fixing a missing init to
     INITIAL_JIFFIES, and a possible underflow introduced recently.

   - A core merge fixup in sg gap detection, where rq->biotail was
     indexed with the count of rq->bio"

* 'for-linus' of git://git.kernel.dk/linux-block:
  writeback: fix possible underflow in write bandwidth calculation
  NVMe: Initialize device list head before starting
  Fix bug in blk_rq_merge_ok
  blkmq: Fix NULL pointer deref when all reserved tags in
  blk-mq: fix use of incorrect goto label in blk_mq_init_queue error path
  nbd: fix possible memory leak
  writeback: add missing INITIAL_JIFFIES init in global_update_bandwidth()

1 files changed, 5 insertions, 2 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 45e187b2d971..644bcb665773 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -857,8 +857,11 @@ static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
          *                   bw * elapsed + write_bandwidth * (period - elapsed)
          * write_bandwidth = ---------------------------------------------------
          *                                          period
+         *
+         * @written may have decreased due to account_page_redirty().
+         * Avoid underflowing @bw calculation.
          */
-        bw = written - bdi->written_stamp;
+        bw = written - min(written, bdi->written_stamp);
         bw *= HZ;
         if (unlikely(elapsed > period)) {
                 do_div(bw, elapsed);
@@ -922,7 +925,7 @@ static void global_update_bandwidth(unsigned long thresh,
                                     unsigned long now)
 {
         static DEFINE_SPINLOCK(dirty_lock);
-        static unsigned long update_time;
+        static unsigned long update_time = INITIAL_JIFFIES;
 
         /*
          * check locklessly first to optimize away locking for the most time