rt-patches/0149-fs-jbd2-pull-your-plug-when-waiting-for-space.patch

   1 From f14c9bf89b1ea5e50bc7da05b26885e060f311cb Mon Sep 17 00:00:00 2001
   2 From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
   3 Date: Mon, 17 Feb 2014 17:30:03 +0100
   4 Subject: [PATCH 149/366] fs: jbd2: pull your plug when waiting for space
   5
   6 Two cps in parallel managed to stall the the ext4 fs. It seems that
   7 journal code is either waiting for locks or sleeping waiting for
   8 something to happen. This seems similar to what Mike observed on ext3,
   9 here is his description:
  10
  11 |With an -rt kernel, and a heavy sync IO load, tasks can jam
  12 |up on journal locks without unplugging, which can lead to
  13 |terminal IO starvation.  Unplug and schedule when waiting
  14 |for space.
  15
  16 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
  17 ---
  18  fs/jbd2/checkpoint.c | 2 ++
  19  1 file changed, 2 insertions(+)
  20
  21 diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
  22 index 684996c..6e18a06 100644
  23 --- a/fs/jbd2/checkpoint.c
  24 +++ b/fs/jbd2/checkpoint.c
  25 @@ -116,6 +116,8 @@ void __jbd2_log_wait_for_space(journal_t *journal)
  26         nblocks = jbd2_space_needed(journal);
  27         while (jbd2_log_space_left(journal) < nblocks) {
  28                 write_unlock(&journal->j_state_lock);
  29 +               if (current->plug)
  30 +                       io_schedule();
  31                 mutex_lock(&journal->j_checkpoint_mutex);
  32
  33                 /*
  34 --
  35 1.9.1
  36