[PATCH 9/9] ext3: do not throttle metadata and journal IO

[Andrea Righi <righi.andrea-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Delaying journal IO can unnecessarily delay other independent IO
operations from different cgroups.

Add BIO_RW_META flag to the ext3 journal IO that informs the io-throttle
subsystem to account but not delay journal IO and avoid potential
priority inversion problems.

Signed-off-by: Andrea Righi <righi.andrea-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 fs/jbd/commit.c  |    4 ++--
 fs/jbd2/commit.c |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index a8e8513..2e444af 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -318,7 +318,7 @@ void journal_commit_transaction(journal_t *journal)
 	int first_tag = 0;
 	int tag_flag;
 	int i;
-	int write_op = WRITE;
+	int write_op = WRITE | (1 << BIO_RW_META);
 
 	/*
 	 * First job: lock down the current transaction and wait for
@@ -357,7 +357,7 @@ void journal_commit_transaction(journal_t *journal)
 	 * instead we rely on sync_buffer() doing the unplug for us.
 	 */
 	if (commit_transaction->t_synchronous_commit)
-		write_op = WRITE_SYNC_PLUG;
+		write_op = WRITE_SYNC_PLUG | (1 << BIO_RW_META);
 	spin_lock(&commit_transaction->t_handle_lock);
 	while (commit_transaction->t_updates) {
 		DEFINE_WAIT(wait);
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 073c8c3..61484d0 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -367,7 +367,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 	int tag_bytes = journal_tag_bytes(journal);
 	struct buffer_head *cbh = NULL; /* For transactional checksums */
 	__u32 crc32_sum = ~0;
-	int write_op = WRITE;
+	int write_op = WRITE | (1 << BIO_RW_META);
 
 	/*
 	 * First job: lock down the current transaction and wait for
@@ -408,7 +408,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 	 * instead we rely on sync_buffer() doing the unplug for us.
 	 */
 	if (commit_transaction->t_synchronous_commit)
-		write_op = WRITE_SYNC_PLUG;
+		write_op = WRITE_SYNC_PLUG | (1 << BIO_RW_META);
 	stats.u.run.rs_wait = commit_transaction->t_max_wait;
 	stats.u.run.rs_locked = jiffies;
 	stats.u.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
-- 
1.5.6.3