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, 46 insertions, 48 deletions

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index a79d3345b55..e7bf0fd9cec 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -142,7 +142,7 @@ static int kjournald2(void *arg)
 	/*
 	 * And now, wait forever for commit wakeup events.
 	 */
-	spin_lock(&journal->j_state_lock);
+	write_lock(&journal->j_state_lock);
 
 loop:
 	if (journal->j_flags & JBD2_UNMOUNT)
@@ -153,10 +153,10 @@ loop:
 
 	if (journal->j_commit_sequence != journal->j_commit_request) {
 		jbd_debug(1, "OK, requests differ\n");
-		spin_unlock(&journal->j_state_lock);
+		write_unlock(&journal->j_state_lock);
 		del_timer_sync(&journal->j_commit_timer);
 		jbd2_journal_commit_transaction(journal);
-		spin_lock(&journal->j_state_lock);
+		write_lock(&journal->j_state_lock);
 		goto loop;
 	}
 
@@ -168,9 +168,9 @@ loop:
 		 * be already stopped.
 		 */
 		jbd_debug(1, "Now suspending kjournald2\n");
-		spin_unlock(&journal->j_state_lock);
+		write_unlock(&journal->j_state_lock);
 		refrigerator();
-		spin_lock(&journal->j_state_lock);
+		write_lock(&journal->j_state_lock);
 	} else {
 		/*
 		 * We assume on resume that commits are already there,
@@ -190,9 +190,9 @@ loop:
 		if (journal->j_flags & JBD2_UNMOUNT)
 			should_sleep = 0;
 		if (should_sleep) {
-			spin_unlock(&journal->j_state_lock);
+			write_unlock(&journal->j_state_lock);
 			schedule();
-			spin_lock(&journal->j_state_lock);
+			write_lock(&journal->j_state_lock);
 		}
 		finish_wait(&journal->j_wait_commit, &wait);
 	}
@@ -210,7 +210,7 @@ loop:
 	goto loop;
 
 end_loop:
-	spin_unlock(&journal->j_state_lock);
+	write_unlock(&journal->j_state_lock);
 	del_timer_sync(&journal->j_commit_timer);
 	journal->j_task = NULL;
 	wake_up(&journal->j_wait_done_commit);
@@ -233,16 +233,16 @@ static int jbd2_journal_start_thread(journal_t *journal)
 
 static void journal_kill_thread(journal_t *journal)
 {
-	spin_lock(&journal->j_state_lock);
+	write_lock(&journal->j_state_lock);
 	journal->j_flags |= JBD2_UNMOUNT;
 
 	while (journal->j_task) {
 		wake_up(&journal->j_wait_commit);
-		spin_unlock(&journal->j_state_lock);
+		write_unlock(&journal->j_state_lock);
 		wait_event(journal->j_wait_done_commit, journal->j_task == NULL);
-		spin_lock(&journal->j_state_lock);
+		write_lock(&journal->j_state_lock);
 	}
-	spin_unlock(&journal->j_state_lock);
+	write_unlock(&journal->j_state_lock);
 }
 
 /*
@@ -452,7 +452,7 @@ int __jbd2_log_space_left(journal_t *journal)
 {
 	int left = journal->j_free;
 
-	assert_spin_locked(&journal->j_state_lock);
+	/* assert_spin_locked(&journal->j_state_lock); */
 
 	/*
 	 * Be pessimistic here about the number of those free blocks which
@@ -497,9 +497,9 @@ int jbd2_log_start_commit(journal_t *journal, tid_t tid)
 {
 	int ret;
 
-	spin_lock(&journal->j_state_lock);
+	write_lock(&journal->j_state_lock);
 	ret = __jbd2_log_start_commit(journal, tid);
-	spin_unlock(&journal->j_state_lock);
+	write_unlock(&journal->j_state_lock);
 	return ret;
 }
 
@@ -518,7 +518,7 @@ int jbd2_journal_force_commit_nested(journal_t *journal)
 	transaction_t *transaction = NULL;
 	tid_t tid;
 
-	spin_lock(&journal->j_state_lock);
+	read_lock(&journal->j_state_lock);
 	if (journal->j_running_transaction && !current->journal_info) {
 		transaction = journal->j_running_transaction;
 		__jbd2_log_start_commit(journal, transaction->t_tid);
@@ -526,12 +526,12 @@ int jbd2_journal_force_commit_nested(journal_t *journal)
 		transaction = journal->j_committing_transaction;
 
 	if (!transaction) {
-		spin_unlock(&journal->j_state_lock);
+		read_unlock(&journal->j_state_lock);
 		return 0;	/* Nothing to retry */
 	}
 
 	tid = transaction->t_tid;
-	spin_unlock(&journal->j_state_lock);
+	read_unlock(&journal->j_state_lock);
 	jbd2_log_wait_commit(journal, tid);
 	return 1;
 }
@@ -545,7 +545,7 @@ int jbd2_journal_start_commit(journal_t *journal, tid_t *ptid)
 {
 	int ret = 0;
 
-	spin_lock(&journal->j_state_lock);
+	write_lock(&journal->j_state_lock);
 	if (journal->j_running_transaction) {
 		tid_t tid = journal->j_running_transaction->t_tid;
 
@@ -564,7 +564,7 @@ int jbd2_journal_start_commit(journal_t *journal, tid_t *ptid)
 			*ptid = journal->j_committing_transaction->t_tid;
 		ret = 1;
 	}
-	spin_unlock(&journal->j_state_lock);
+	write_unlock(&journal->j_state_lock);
 	return ret;
 }
 
@@ -576,26 +576,24 @@ int jbd2_log_wait_commit(journal_t *journal, tid_t tid)
 {
 	int err = 0;
 
+	read_lock(&journal->j_state_lock);
 #ifdef CONFIG_JBD2_DEBUG
-	spin_lock(&journal->j_state_lock);
 	if (!tid_geq(journal->j_commit_request, tid)) {
 		printk(KERN_EMERG
 		       "%s: error: j_commit_request=%d, tid=%d\n",
 		       __func__, journal->j_commit_request, tid);
 	}
-	spin_unlock(&journal->j_state_lock);
 #endif
-	spin_lock(&journal->j_state_lock);
 	while (tid_gt(tid, journal->j_commit_sequence)) {
 		jbd_debug(1, "JBD: want %d, j_commit_sequence=%d\n",
 				  tid, journal->j_commit_sequence);
 		wake_up(&journal->j_wait_commit);
-		spin_unlock(&journal->j_state_lock);
+		read_unlock(&journal->j_state_lock);
 		wait_event(journal->j_wait_done_commit,
 				!tid_gt(tid, journal->j_commit_sequence));
-		spin_lock(&journal->j_state_lock);
+		read_lock(&journal->j_state_lock);
 	}
-	spin_unlock(&journal->j_state_lock);
+	read_unlock(&journal->j_state_lock);
 
 	if (unlikely(is_journal_aborted(journal))) {
 		printk(KERN_EMERG "journal commit I/O error\n");
@@ -612,7 +610,7 @@ int jbd2_journal_next_log_block(journal_t *journal, unsigned long long *retp)
 {
 	unsigned long blocknr;
 
-	spin_lock(&journal->j_state_lock);
+	write_lock(&journal->j_state_lock);
 	J_ASSERT(journal->j_free > 1);
 
 	blocknr = journal->j_head;
@@ -620,7 +618,7 @@ int jbd2_journal_next_log_block(journal_t *journal, unsigned long long *retp)
 	journal->j_free--;
 	if (journal->j_head == journal->j_last)
 		journal->j_head = journal->j_first;
-	spin_unlock(&journal->j_state_lock);
+	write_unlock(&journal->j_state_lock);
 	return jbd2_journal_bmap(journal, blocknr, retp);
 }
 
@@ -840,7 +838,7 @@ static journal_t * journal_init_common (void)
 	mutex_init(&journal->j_checkpoint_mutex);
 	spin_lock_init(&journal->j_revoke_lock);
 	spin_lock_init(&journal->j_list_lock);
-	spin_lock_init(&journal->j_state_lock);
+	rwlock_init(&journal->j_state_lock);
 
 	journal->j_commit_interval = (HZ * JBD2_DEFAULT_MAX_COMMIT_AGE);
 	journal->j_min_batch_time = 0;
@@ -1106,14 +1104,14 @@ void jbd2_journal_update_superblock(journal_t *journal, int wait)
 		set_buffer_uptodate(bh);
 	}
 
-	spin_lock(&journal->j_state_lock);
+	read_lock(&journal->j_state_lock);
 	jbd_debug(1,"JBD: updating superblock (start %ld, seq %d, errno %d)\n",
 		  journal->j_tail, journal->j_tail_sequence, journal->j_errno);
 
 	sb->s_sequence = cpu_to_be32(journal->j_tail_sequence);
 	sb->s_start    = cpu_to_be32(journal->j_tail);
 	sb->s_errno    = cpu_to_be32(journal->j_errno);
-	spin_unlock(&journal->j_state_lock);
+	read_unlock(&journal->j_state_lock);
 
 	BUFFER_TRACE(bh, "marking dirty");
 	mark_buffer_dirty(bh);
@@ -1134,12 +1132,12 @@ out:
 	 * any future commit will have to be careful to update the
 	 * superblock again to re-record the true start of the log. */
 
-	spin_lock(&journal->j_state_lock);
+	write_lock(&journal->j_state_lock);
 	if (sb->s_start)
 		journal->j_flags &= ~JBD2_FLUSHED;
 	else
 		journal->j_flags |= JBD2_FLUSHED;
-	spin_unlock(&journal->j_state_lock);
+	write_unlock(&journal->j_state_lock);
 }
 
 /*
@@ -1551,7 +1549,7 @@ int jbd2_journal_flush(journal_t *journal)
 	transaction_t *transaction = NULL;
 	unsigned long old_tail;
 
-	spin_lock(&journal->j_state_lock);
+	write_lock(&journal->j_state_lock);
 
 	/* Force everything buffered to the log... */
 	if (journal->j_running_transaction) {
@@ -1564,10 +1562,10 @@ int jbd2_journal_flush(journal_t *journal)
 	if (transaction) {
 		tid_t tid = transaction->t_tid;
 
-		spin_unlock(&journal->j_state_lock);
+		write_unlock(&journal->j_state_lock);
 		jbd2_log_wait_commit(journal, tid);
 	} else {
-		spin_unlock(&journal->j_state_lock);
+		write_unlock(&journal->j_state_lock);
 	}
 
 	/* ...and flush everything in the log out to disk. */
@@ -1591,12 +1589,12 @@ int jbd2_journal_flush(journal_t *journal)
 	 * the magic code for a fully-recovered superblock.  Any future
 	 * commits of data to the journal will restore the current
 	 * s_start value. */
-	spin_lock(&journal->j_state_lock);
+	write_lock(&journal->j_state_lock);
 	old_tail = journal->j_tail;
 	journal->j_tail = 0;
-	spin_unlock(&journal->j_state_lock);
+	write_unlock(&journal->j_state_lock);
 	jbd2_journal_update_superblock(journal, 1);
-	spin_lock(&journal->j_state_lock);
+	write_lock(&journal->j_state_lock);
 	journal->j_tail = old_tail;
 
 	J_ASSERT(!journal->j_running_transaction);
@@ -1604,7 +1602,7 @@ int jbd2_journal_flush(journal_t *journal)
 	J_ASSERT(!journal->j_checkpoint_transactions);
 	J_ASSERT(journal->j_head == journal->j_tail);
 	J_ASSERT(journal->j_tail_sequence == journal->j_transaction_sequence);
-	spin_unlock(&journal->j_state_lock);
+	write_unlock(&journal->j_state_lock);
 	return 0;
 }
 
@@ -1668,12 +1666,12 @@ void __jbd2_journal_abort_hard(journal_t *journal)
 	printk(KERN_ERR "Aborting journal on device %s.\n",
 	       journal->j_devname);
 
-	spin_lock(&journal->j_state_lock);
+	write_lock(&journal->j_state_lock);
 	journal->j_flags |= JBD2_ABORT;
 	transaction = journal->j_running_transaction;
 	if (transaction)
 		__jbd2_log_start_commit(journal, transaction->t_tid);
-	spin_unlock(&journal->j_state_lock);
+	write_unlock(&journal->j_state_lock);
 }
 
 /* Soft abort: record the abort error status in the journal superblock,
@@ -1758,12 +1756,12 @@ int jbd2_journal_errno(journal_t *journal)
 {
 	int err;
 
-	spin_lock(&journal->j_state_lock);
+	read_lock(&journal->j_state_lock);
 	if (journal->j_flags & JBD2_ABORT)
 		err = -EROFS;
 	else
 		err = journal->j_errno;
-	spin_unlock(&journal->j_state_lock);
+	read_unlock(&journal->j_state_lock);
 	return err;
 }
 
@@ -1778,12 +1776,12 @@ int jbd2_journal_clear_err(journal_t *journal)
 {
 	int err = 0;
 
-	spin_lock(&journal->j_state_lock);
+	write_lock(&journal->j_state_lock);
 	if (journal->j_flags & JBD2_ABORT)
 		err = -EROFS;
 	else
 		journal->j_errno = 0;
-	spin_unlock(&journal->j_state_lock);
+	write_unlock(&journal->j_state_lock);
 	return err;
 }
 
@@ -1796,10 +1794,10 @@ int jbd2_journal_clear_err(journal_t *journal)
  */
 void jbd2_journal_ack_err(journal_t *journal)
 {
-	spin_lock(&journal->j_state_lock);
+	write_lock(&journal->j_state_lock);
 	if (journal->j_errno)
 		journal->j_flags |= JBD2_ACK_ERR;
-	spin_unlock(&journal->j_state_lock);
+	write_unlock(&journal->j_state_lock);
 }
 
 int jbd2_journal_blocks_per_page(struct inode *inode)