jbd2: Add ENOMEM checking in and for jbd2_journal_write_metadata_buffer()

OOM happens.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index d4cfd6d..8896c1d 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -636,6 +636,10 @@
 		JBUFFER_TRACE(jh, "ph3: write metadata");
 		flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 						      jh, &new_jh, blocknr);
+		if (flags < 0) {
+			jbd2_journal_abort(journal, flags);
+			continue;
+		}
 		set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 		wbuf[bufs++] = jh2bh(new_jh);