Merge commit '8700c95adb03' into timers/nohz

The full dynticks tree needs the latest RCU and sched
upstream updates in order to fix some dependencies.

Merge a common upstream merge point that has these
updates.

Conflicts:
	include/linux/perf_event.h
	kernel/rcutree.h
	kernel/rcutree_plugin.h

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

1 files changed, 22 insertions, 3 deletions

diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index 86b39b167c23..11bb11f48b3a 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -162,8 +162,17 @@ static void journal_do_submit_data(struct buffer_head **wbuf, int bufs,
 
 	for (i = 0; i < bufs; i++) {
 		wbuf[i]->b_end_io = end_buffer_write_sync;
-		/* We use-up our safety reference in submit_bh() */
-		submit_bh(write_op, wbuf[i]);
+		/*
+		 * Here we write back pagecache data that may be mmaped. Since
+		 * we cannot afford to clean the page and set PageWriteback
+		 * here due to lock ordering (page lock ranks above transaction
+		 * start), the data can change while IO is in flight. Tell the
+		 * block layer it should bounce the bio pages if stable data
+		 * during write is required.
+		 *
+		 * We use up our safety reference in submit_bh().
+		 */
+		_submit_bh(write_op, wbuf[i], 1 << BIO_SNAP_STABLE);
 	}
 }
 
@@ -667,7 +676,17 @@ start_journal_io:
 				clear_buffer_dirty(bh);
 				set_buffer_uptodate(bh);
 				bh->b_end_io = journal_end_buffer_io_sync;
-				submit_bh(write_op, bh);
+				/*
+				 * In data=journal mode, here we can end up
+				 * writing pagecache data that might be
+				 * mmapped. Since we can't afford to clean the
+				 * page and set PageWriteback (see the comment
+				 * near the other use of _submit_bh()), the
+				 * data can change while the write is in
+				 * flight.  Tell the block layer to bounce the
+				 * bio pages if stable pages are required.
+				 */
+				_submit_bh(write_op, bh, 1 << BIO_SNAP_STABLE);
 			}
 			cond_resched();