jbd: remove dependency on __GFP_NOFAIL

The callers of start_this_handle() (or better ext3_journal_start()) are not
really prepared to handle allocation failures. Such failures can for example
result in silent data loss when it happens in ext3_..._writepage().  OTOH
__GFP_NOFAIL is going away so we just retry allocation in start_this_handle().

This loop is potentially dangerous because the oom killer cannot be invoked
for GFP_NOFS allocation, so there is a potential for infinitely looping.
But still this is better than silent data loss.
Signed-off-by: Jan Kara <jack@suse.cz>

fs/jbd/transaction.c

@@ -26,6 +26,7 @@
 #include <linux/mm.h>
 #include <linux/highmem.h>
 #include <linux/hrtimer.h>
+#include <linux/backing-dev.h>
 
 static void __journal_temp_unlink_buffer(struct journal_head *jh);
 
@@ -99,11 +100,10 @@ static int start_this_handle(journal_t *journal, handle_t *handle)
 
 alloc_transaction:
 	if (!journal->j_running_transaction) {
-		new_transaction = kzalloc(sizeof(*new_transaction),
-						GFP_NOFS|__GFP_NOFAIL);
+		new_transaction = kzalloc(sizeof(*new_transaction), GFP_NOFS);
 		if (!new_transaction) {
-			ret = -ENOMEM;
-			goto out;
+			congestion_wait(BLK_RW_ASYNC, HZ/50);
+			goto alloc_transaction;
 		}
 	}