jbd2: Change j_state_lock to be a rwlock_t
Lockstat reports have shown that j_state_lock is a major source of
lock contention, especially on systems with more than 4 CPU cores. So
change it to be a read/write spinlock.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 533b607..ab2247d 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5066,7 +5066,7 @@
transaction_t *transaction;
tid_t tid;
- spin_lock(&journal->j_state_lock);
+ read_lock(&journal->j_state_lock);
if (journal->j_running_transaction)
transaction = journal->j_running_transaction;
else
@@ -5075,7 +5075,7 @@
tid = transaction->t_tid;
else
tid = journal->j_commit_sequence;
- spin_unlock(&journal->j_state_lock);
+ read_unlock(&journal->j_state_lock);
ei->i_sync_tid = tid;
ei->i_datasync_tid = tid;
}