jbd2: fix lockdep annotation in add_transaction_credits()

Thomas has reported a lockdep splat hitting in
add_transaction_credits(). The problem is that that function calls
jbd2_might_wait_for_commit() while holding j_state_lock which is wrong
(we do not really wait for transaction commit while holding that lock).

Fix the problem by moving jbd2_might_wait_for_commit() into places where
we are ready to wait for transaction commit and thus j_state_lock is
unlocked.

Cc: stable@vger.kernel.org
Fixes: 1eaa566d368b214d99cbb973647c1b0b8102a9ae
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 4 insertions, 2 deletions

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index b5bc3e249163..3d8246a9faa4 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -159,6 +159,7 @@ static void wait_transaction_locked(journal_t *journal)
         read_unlock(&journal->j_state_lock);
         if (need_to_start)
                 jbd2_log_start_commit(journal, tid);
+        jbd2_might_wait_for_commit(journal);
         schedule();
         finish_wait(&journal->j_wait_transaction_locked, &wait);
 }
@@ -182,8 +183,6 @@ static int add_transaction_credits(journal_t *journal, int blocks,
         int needed;
         int total = blocks + rsv_blocks;
 
-        jbd2_might_wait_for_commit(journal);
-
         /*
          * If the current transaction is locked down for commit, wait
          * for the lock to be released.
@@ -214,6 +213,7 @@ static int add_transaction_credits(journal_t *journal, int blocks,
                 if (atomic_read(&journal->j_reserved_credits) + total >
                     journal->j_max_transaction_buffers) {
                         read_unlock(&journal->j_state_lock);
+                        jbd2_might_wait_for_commit(journal);
                         wait_event(journal->j_wait_reserved,
                                    atomic_read(&journal->j_reserved_credits) + total <=
                                    journal->j_max_transaction_buffers);
@@ -238,6 +238,7 @@ static int add_transaction_credits(journal_t *journal, int blocks,
         if (jbd2_log_space_left(journal) < jbd2_space_needed(journal)) {
                 atomic_sub(total, &t->t_outstanding_credits);
                 read_unlock(&journal->j_state_lock);
+                jbd2_might_wait_for_commit(journal);
                 write_lock(&journal->j_state_lock);
                 if (jbd2_log_space_left(journal) < jbd2_space_needed(journal))
                         __jbd2_log_wait_for_space(journal);
@@ -255,6 +256,7 @@ static int add_transaction_credits(journal_t *journal, int blocks,
                 sub_reserved_credits(journal, rsv_blocks);
                 atomic_sub(total, &t->t_outstanding_credits);
                 read_unlock(&journal->j_state_lock);
+                jbd2_might_wait_for_commit(journal);
                 wait_event(journal->j_wait_reserved,
                          atomic_read(&journal->j_reserved_credits) + rsv_blocks
                          <= journal->j_max_transaction_buffers / 2);