jbd2: make the whole kjournald2 kthread NOFS safe

kjournald2 is central to the transaction commit processing.  As such any
potential allocation from this kernel thread has to be GFP_NOFS.  Make
sure to mark the whole kernel thread GFP_NOFS by the memalloc_nofs_save.

[[email protected]: coding-style fixes]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Michal Hocko <[email protected]>
Suggested-by: Jan Kara <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Theodore Ts'o <[email protected]>
Cc: Chris Mason <[email protected]>
Cc: David Sterba <[email protected]>
Cc: Brian Foster <[email protected]>
Cc: Darrick J. Wong <[email protected]>
Cc: Nikolay Borisov <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

1 files changed, 9 insertions, 0 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 5adc2fb62b0f..c43fe83ee708 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -43,6 +43,7 @@
 #include <linux/backing-dev.h>
 #include <linux/bitops.h>
 #include <linux/ratelimit.h>
+#include <linux/sched/mm.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/jbd2.h>
@@ -206,6 +207,14 @@ static int kjournald2(void *arg)
 	wake_up(&journal->j_wait_done_commit);
 
 	/*
+	 * Make sure that no allocations from this kernel thread will ever
+	 * recurse to the fs layer because we are responsible for the
+	 * transaction commit and any fs involvement might get stuck waiting for
+	 * the trasn. commit.
+	 */
+	memalloc_nofs_save();
+
+	/*
 	 * And now, wait forever for commit wakeup events.
 	 */
 	write_lock(&journal->j_state_lock);