block: use an on-stack bio in blkdev_issue_flush

There is no point in allocating memory for a synchronous flush.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Acked-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index b121d7d..3cc4ab2 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -825,7 +825,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 	if (commit_transaction->t_need_data_flush &&
 	    (journal->j_fs_dev != journal->j_dev) &&
 	    (journal->j_flags & JBD2_BARRIER))
-		blkdev_issue_flush(journal->j_fs_dev, GFP_NOFS);
+		blkdev_issue_flush(journal->j_fs_dev);
 
 	/* Done it all: now write the commit record asynchronously. */
 	if (jbd2_has_feature_async_commit(journal)) {
@@ -932,7 +932,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 	stats.run.rs_blocks_logged++;
 	if (jbd2_has_feature_async_commit(journal) &&
 	    journal->j_flags & JBD2_BARRIER) {
-		blkdev_issue_flush(journal->j_dev, GFP_NOFS);
+		blkdev_issue_flush(journal->j_dev);
 	}
 
 	if (err)