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>

2 files changed, 4 insertions, 4 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;
         }
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 3fd65eb66ccd..81cb3fc1218e 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3232,7 +3232,7 @@ static void ext4_init_journal_params(struct super_block *sb, journal_t *journal)
         journal->j_min_batch_time = sbi->s_min_batch_time;
         journal->j_max_batch_time = sbi->s_max_batch_time;
 
-        spin_lock(&journal->j_state_lock);
+        write_lock(&journal->j_state_lock);
         if (test_opt(sb, BARRIER))
                 journal->j_flags |= JBD2_BARRIER;
         else
@@ -3241,7 +3241,7 @@ static void ext4_init_journal_params(struct super_block *sb, journal_t *journal)
                 journal->j_flags |= JBD2_ABORT_ON_SYNCDATA_ERR;
         else
                 journal->j_flags &= ~JBD2_ABORT_ON_SYNCDATA_ERR;
-        spin_unlock(&journal->j_state_lock);
+        write_unlock(&journal->j_state_lock);
 }
 
 static journal_t *ext4_get_journal(struct super_block *sb,