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, 40 insertions, 34 deletions

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);