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>

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 533b607f9cb5..ab2247d642c6 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5066,7 +5066,7 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
                 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 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
                         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;
         }