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>

4 files changed, 107 insertions, 103 deletions

diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
index f8cdc02520f9..1c23a0f4e8a3 100644
--- a/fs/jbd2/checkpoint.c
+++ b/fs/jbd2/checkpoint.c
@@ -118,13 +118,13 @@ static int __try_to_free_cp_buf(struct journal_head *jh)
 void __jbd2_log_wait_for_space(journal_t *journal)
 {
         int nblocks, space_left;
-        assert_spin_locked(&journal->j_state_lock);
+        /* assert_spin_locked(&journal->j_state_lock); */
 
         nblocks = jbd_space_needed(journal);
         while (__jbd2_log_space_left(journal) < nblocks) {
                 if (journal->j_flags & JBD2_ABORT)
                         return;
-                spin_unlock(&journal->j_state_lock);
+                write_unlock(&journal->j_state_lock);
                 mutex_lock(&journal->j_checkpoint_mutex);
 
                 /*
@@ -138,7 +138,7 @@ void __jbd2_log_wait_for_space(journal_t *journal)
                  * filesystem, so abort the journal and leave a stack
                  * trace for forensic evidence.
                  */
-                spin_lock(&journal->j_state_lock);
+                write_lock(&journal->j_state_lock);
                 spin_lock(&journal->j_list_lock);
                 nblocks = jbd_space_needed(journal);
                 space_left = __jbd2_log_space_left(journal);
@@ -149,7 +149,7 @@ void __jbd2_log_wait_for_space(journal_t *journal)
                         if (journal->j_committing_transaction)
                                 tid = journal->j_committing_transaction->t_tid;
                         spin_unlock(&journal->j_list_lock);
-                        spin_unlock(&journal->j_state_lock);
+                        write_unlock(&journal->j_state_lock);
                         if (chkpt) {
                                 jbd2_log_do_checkpoint(journal);
                         } else if (jbd2_cleanup_journal_tail(journal) == 0) {
@@ -167,7 +167,7 @@ void __jbd2_log_wait_for_space(journal_t *journal)
                                 WARN_ON(1);
                                 jbd2_journal_abort(journal, 0);
                         }
-                        spin_lock(&journal->j_state_lock);
+                        write_lock(&journal->j_state_lock);
                 } else {
                         spin_unlock(&journal->j_list_lock);
                 }
@@ -474,7 +474,7 @@ int jbd2_cleanup_journal_tail(journal_t *journal)
          * next transaction ID we will write, and where it will
          * start. */
 
-        spin_lock(&journal->j_state_lock);
+        write_lock(&journal->j_state_lock);
         spin_lock(&journal->j_list_lock);
         transaction = journal->j_checkpoint_transactions;
         if (transaction) {
@@ -496,7 +496,7 @@ int jbd2_cleanup_journal_tail(journal_t *journal)
         /* If the oldest pinned transaction is at the tail of the log
            already then there's not much we can do right now. */
         if (journal->j_tail_sequence == first_tid) {
-                spin_unlock(&journal->j_state_lock);
+                write_unlock(&journal->j_state_lock);
                 return 1;
         }
 
@@ -516,7 +516,7 @@ int jbd2_cleanup_journal_tail(journal_t *journal)
         journal->j_free += freed;
         journal->j_tail_sequence = first_tid;
         journal->j_tail = blocknr;
-        spin_unlock(&journal->j_state_lock);
+        write_unlock(&journal->j_state_lock);
 
         /*
          * If there is an external journal, we need to make sure that
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index fbd2c564e916..67bb0a2f35e5 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -152,9 +152,9 @@ static int journal_submit_commit_record(journal_t *journal,
                 printk(KERN_WARNING
                        "JBD2: Disabling barriers on %s, "
                        "not supported by device\n", journal->j_devname);
-                spin_lock(&journal->j_state_lock);
+                write_lock(&journal->j_state_lock);
                 journal->j_flags &= ~JBD2_BARRIER;
-                spin_unlock(&journal->j_state_lock);
+                write_unlock(&journal->j_state_lock);
 
                 /* And try again, without the barrier */
                 lock_buffer(bh);
@@ -182,9 +182,9 @@ retry:
                 printk(KERN_WARNING
                        "JBD2: %s: disabling barries on %s - not supported "
                        "by device\n", __func__, journal->j_devname);
-                spin_lock(&journal->j_state_lock);
+                write_lock(&journal->j_state_lock);
                 journal->j_flags &= ~JBD2_BARRIER;
-                spin_unlock(&journal->j_state_lock);
+                write_unlock(&journal->j_state_lock);
 
                 lock_buffer(bh);
                 clear_buffer_dirty(bh);
@@ -400,7 +400,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
         jbd_debug(1, "JBD: starting commit of transaction %d\n",
                         commit_transaction->t_tid);
 
-        spin_lock(&journal->j_state_lock);
+        write_lock(&journal->j_state_lock);
         commit_transaction->t_state = T_LOCKED;
 
         /*
@@ -424,9 +424,9 @@ void jbd2_journal_commit_transaction(journal_t *journal)
                                         TASK_UNINTERRUPTIBLE);
                 if (atomic_read(&commit_transaction->t_updates)) {
                         spin_unlock(&commit_transaction->t_handle_lock);
-                        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);
                         spin_lock(&commit_transaction->t_handle_lock);
                 }
                 finish_wait(&journal->j_wait_updates, &wait);
@@ -497,7 +497,7 @@ void jbd2_journal_commit_transaction(journal_t *journal)
         start_time = ktime_get();
         commit_transaction->t_log_start = journal->j_head;
         wake_up(&journal->j_wait_transaction_locked);
-        spin_unlock(&journal->j_state_lock);
+        write_unlock(&journal->j_state_lock);
 
         jbd_debug (3, "JBD: commit phase 2\n");
 
@@ -519,9 +519,9 @@ void jbd2_journal_commit_transaction(journal_t *journal)
          * transaction!  Now comes the tricky part: we need to write out
          * metadata.  Loop over the transaction's entire buffer list:
          */
-        spin_lock(&journal->j_state_lock);
+        write_lock(&journal->j_state_lock);
         commit_transaction->t_state = T_COMMIT;
-        spin_unlock(&journal->j_state_lock);
+        write_unlock(&journal->j_state_lock);
 
         trace_jbd2_commit_logging(journal, commit_transaction);
         stats.run.rs_logging = jiffies;
@@ -978,7 +978,7 @@ restart_loop:
          * __jbd2_journal_drop_transaction(). Otherwise we could race with
          * other checkpointing code processing the transaction...
          */
-        spin_lock(&journal->j_state_lock);
+        write_lock(&journal->j_state_lock);
         spin_lock(&journal->j_list_lock);
         /*
          * Now recheck if some buffers did not get attached to the transaction
@@ -986,7 +986,7 @@ restart_loop:
          */
         if (commit_transaction->t_forget) {
                 spin_unlock(&journal->j_list_lock);
-                spin_unlock(&journal->j_state_lock);
+                write_unlock(&journal->j_state_lock);
                 goto restart_loop;
         }
 
@@ -1038,7 +1038,7 @@ restart_loop:
                                 journal->j_average_commit_time*3) / 4;
         else
                 journal->j_average_commit_time = commit_time;
-        spin_unlock(&journal->j_state_lock);
+        write_unlock(&journal->j_state_lock);
 
         if (commit_transaction->t_checkpoint_list == NULL &&
             commit_transaction->t_checkpoint_io_list == NULL) {
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index a79d3345b55a..e7bf0fd9cec7 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)
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 9c64c7ec48d4..663065142b42 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -124,36 +124,38 @@ alloc_transaction:
 
         jbd_debug(3, "New handle %p going live.\n", handle);
 
-repeat:
-
         /*
          * We need to hold j_state_lock until t_updates has been incremented,
          * for proper journal barrier handling
          */
-        spin_lock(&journal->j_state_lock);
-repeat_locked:
+repeat:
+        read_lock(&journal->j_state_lock);
         if (is_journal_aborted(journal) ||
             (journal->j_errno != 0 && !(journal->j_flags & JBD2_ACK_ERR))) {
-                spin_unlock(&journal->j_state_lock);
+                read_unlock(&journal->j_state_lock);
                 kfree(new_transaction);
                 return -EROFS;
         }
 
         /* Wait on the journal's transaction barrier if necessary */
         if (journal->j_barrier_count) {
-                spin_unlock(&journal->j_state_lock);
+                read_unlock(&journal->j_state_lock);
                 wait_event(journal->j_wait_transaction_locked,
                                 journal->j_barrier_count == 0);
                 goto repeat;
         }
 
         if (!journal->j_running_transaction) {
-                if (!new_transaction) {
-                        spin_unlock(&journal->j_state_lock);
+                read_unlock(&journal->j_state_lock);
+                if (!new_transaction)
                         goto alloc_transaction;
+                write_lock(&journal->j_state_lock);
+                if (!journal->j_running_transaction) {
+                        jbd2_get_transaction(journal, new_transaction);
+                        new_transaction = NULL;
                 }
-                jbd2_get_transaction(journal, new_transaction);
-                new_transaction = NULL;
+                write_unlock(&journal->j_state_lock);
+                goto repeat;
         }
 
         transaction = journal->j_running_transaction;
@@ -167,7 +169,7 @@ repeat_locked:
 
                 prepare_to_wait(&journal->j_wait_transaction_locked,
                                         &wait, TASK_UNINTERRUPTIBLE);
-                spin_unlock(&journal->j_state_lock);
+                read_unlock(&journal->j_state_lock);
                 schedule();
                 finish_wait(&journal->j_wait_transaction_locked, &wait);
                 goto repeat;
@@ -194,7 +196,7 @@ repeat_locked:
                 prepare_to_wait(&journal->j_wait_transaction_locked, &wait,
                                 TASK_UNINTERRUPTIBLE);
                 __jbd2_log_start_commit(journal, transaction->t_tid);
-                spin_unlock(&journal->j_state_lock);
+                read_unlock(&journal->j_state_lock);
                 schedule();
                 finish_wait(&journal->j_wait_transaction_locked, &wait);
                 goto repeat;
@@ -228,8 +230,12 @@ repeat_locked:
         if (__jbd2_log_space_left(journal) < jbd_space_needed(journal)) {
                 jbd_debug(2, "Handle %p waiting for checkpoint...\n", handle);
                 spin_unlock(&transaction->t_handle_lock);
-                __jbd2_log_wait_for_space(journal);
-                goto repeat_locked;
+                read_unlock(&journal->j_state_lock);
+                write_lock(&journal->j_state_lock);
+                if (__jbd2_log_space_left(journal) < jbd_space_needed(journal))
+                        __jbd2_log_wait_for_space(journal);
+                write_unlock(&journal->j_state_lock);
+                goto repeat;
         }
 
         /* OK, account for the buffers that this operation expects to
@@ -250,7 +256,7 @@ repeat_locked:
                   atomic_read(&transaction->t_outstanding_credits),
                   __jbd2_log_space_left(journal));
         spin_unlock(&transaction->t_handle_lock);
-        spin_unlock(&journal->j_state_lock);
+        read_unlock(&journal->j_state_lock);
 
         lock_map_acquire(&handle->h_lockdep_map);
         kfree(new_transaction);
@@ -362,7 +368,7 @@ int jbd2_journal_extend(handle_t *handle, int nblocks)
 
         result = 1;
 
-        spin_lock(&journal->j_state_lock);
+        read_lock(&journal->j_state_lock);
 
         /* Don't extend a locked-down transaction! */
         if (handle->h_transaction->t_state != T_RUNNING) {
@@ -394,7 +400,7 @@ int jbd2_journal_extend(handle_t *handle, int nblocks)
 unlock:
         spin_unlock(&transaction->t_handle_lock);
 error_out:
-        spin_unlock(&journal->j_state_lock);
+        read_unlock(&journal->j_state_lock);
 out:
         return result;
 }
@@ -432,7 +438,7 @@ int jbd2__journal_restart(handle_t *handle, int nblocks, int gfp_mask)
         J_ASSERT(atomic_read(&transaction->t_updates) > 0);
         J_ASSERT(journal_current_handle() == handle);
 
-        spin_lock(&journal->j_state_lock);
+        read_lock(&journal->j_state_lock);
         spin_lock(&transaction->t_handle_lock);
         atomic_sub(handle->h_buffer_credits,
                    &transaction->t_outstanding_credits);
@@ -442,7 +448,7 @@ int jbd2__journal_restart(handle_t *handle, int nblocks, int gfp_mask)
 
         jbd_debug(2, "restarting handle %p\n", handle);
         __jbd2_log_start_commit(journal, transaction->t_tid);
-        spin_unlock(&journal->j_state_lock);
+        read_unlock(&journal->j_state_lock);
 
         lock_map_release(&handle->h_lockdep_map);
         handle->h_buffer_credits = nblocks;
@@ -472,7 +478,7 @@ void jbd2_journal_lock_updates(journal_t *journal)
 {
         DEFINE_WAIT(wait);
 
-        spin_lock(&journal->j_state_lock);
+        write_lock(&journal->j_state_lock);
         ++journal->j_barrier_count;
 
         /* Wait until there are no running updates */
@@ -490,12 +496,12 @@ void jbd2_journal_lock_updates(journal_t *journal)
                 prepare_to_wait(&journal->j_wait_updates, &wait,
                                 TASK_UNINTERRUPTIBLE);
                 spin_unlock(&transaction->t_handle_lock);
-                spin_unlock(&journal->j_state_lock);
+                write_unlock(&journal->j_state_lock);
                 schedule();
                 finish_wait(&journal->j_wait_updates, &wait);
-                spin_lock(&journal->j_state_lock);
+                write_lock(&journal->j_state_lock);
         }
-        spin_unlock(&journal->j_state_lock);
+        write_unlock(&journal->j_state_lock);
 
         /*
          * We have now established a barrier against other normal updates, but
@@ -519,9 +525,9 @@ void jbd2_journal_unlock_updates (journal_t *journal)
         J_ASSERT(journal->j_barrier_count != 0);
 
         mutex_unlock(&journal->j_barrier);
-        spin_lock(&journal->j_state_lock);
+        write_lock(&journal->j_state_lock);
         --journal->j_barrier_count;
-        spin_unlock(&journal->j_state_lock);
+        write_unlock(&journal->j_state_lock);
         wake_up(&journal->j_wait_transaction_locked);
 }
 
@@ -1314,9 +1320,9 @@ int jbd2_journal_stop(handle_t *handle)
 
                 journal->j_last_sync_writer = pid;
 
-                spin_lock(&journal->j_state_lock);
+                read_lock(&journal->j_state_lock);
                 commit_time = journal->j_average_commit_time;
-                spin_unlock(&journal->j_state_lock);
+                read_unlock(&journal->j_state_lock);
 
                 trans_time = ktime_to_ns(ktime_sub(ktime_get(),
                                                    transaction->t_start_time));
@@ -1748,7 +1754,7 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
                 goto zap_buffer_unlocked;
 
         /* OK, we have data buffer in journaled mode */
-        spin_lock(&journal->j_state_lock);
+        write_lock(&journal->j_state_lock);
         jbd_lock_bh_state(bh);
         spin_lock(&journal->j_list_lock);
 
@@ -1801,7 +1807,7 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
                         jbd2_journal_put_journal_head(jh);
                         spin_unlock(&journal->j_list_lock);
                         jbd_unlock_bh_state(bh);
-                        spin_unlock(&journal->j_state_lock);
+                        write_unlock(&journal->j_state_lock);
                         return ret;
                 } else {
                         /* There is no currently-running transaction. So the
@@ -1815,7 +1821,7 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
                                 jbd2_journal_put_journal_head(jh);
                                 spin_unlock(&journal->j_list_lock);
                                 jbd_unlock_bh_state(bh);
-                                spin_unlock(&journal->j_state_lock);
+                                write_unlock(&journal->j_state_lock);
                                 return ret;
                         } else {
                                 /* The orphan record's transaction has
@@ -1839,7 +1845,7 @@ static int journal_unmap_buffer(journal_t *journal, struct buffer_head *bh)
                 jbd2_journal_put_journal_head(jh);
                 spin_unlock(&journal->j_list_lock);
                 jbd_unlock_bh_state(bh);
-                spin_unlock(&journal->j_state_lock);
+                write_unlock(&journal->j_state_lock);
                 return 0;
         } else {
                 /* Good, the buffer belongs to the running transaction.
@@ -1858,7 +1864,7 @@ zap_buffer:
 zap_buffer_no_jh:
         spin_unlock(&journal->j_list_lock);
         jbd_unlock_bh_state(bh);
-        spin_unlock(&journal->j_state_lock);
+        write_unlock(&journal->j_state_lock);
 zap_buffer_unlocked:
         clear_buffer_dirty(bh);
         J_ASSERT_BH(bh, !buffer_jbddirty(bh));
@@ -2165,9 +2171,9 @@ int jbd2_journal_begin_ordered_truncate(journal_t *journal,
         /* Locks are here just to force reading of recent values, it is
          * enough that the transaction was not committing before we started
          * a transaction adding the inode to orphan list */
-        spin_lock(&journal->j_state_lock);
+        read_lock(&journal->j_state_lock);
         commit_trans = journal->j_committing_transaction;
-        spin_unlock(&journal->j_state_lock);
+        read_unlock(&journal->j_state_lock);
         spin_lock(&journal->j_list_lock);
         inode_trans = jinode->i_transaction;
         spin_unlock(&journal->j_list_lock);