fs, jbd: pull your plug when waiting for space

With an -rt kernel, and a heavy sync IO load, tasks can jam
up on journal locks without unplugging, which can lead to
terminal IO starvation.  Unplug and schedule when waiting for space.

Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Theodore Tso <tytso@mit.edu>
Link: http://lkml.kernel.org/r/1341812414.7370.73.camel@marge.simpson.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/fs/jbd/checkpoint.c b/fs/jbd/checkpoint.c
index 08c03044abddbc216d5c8904295631d11c4b6c1b..95debd71e5faeb725aabe8a33d92f6e990b7628c 100644 (file)
--- a/fs/jbd/checkpoint.c
+++ b/fs/jbd/checkpoint.c
@@ -129,6 +129,8 @@ void __log_wait_for_space(journal_t *journal)
                if (journal->j_flags & JFS_ABORT)
                        return;
                spin_unlock(&journal->j_state_lock);
+               if (current->plug)
+                       io_schedule();
                mutex_lock(&journal->j_checkpoint_mutex);
 
                /*