fix-lockdep-annotation-in-add_transaction_credits

   1 jbd2: fix lockdep annotation in add_transaction_credits()
   2
   3 From: Jan Kara <jack@suse.cz>
   4
   5 Thomas has reported a lockdep splat hitting in
   6 add_transaction_credits(). The problem is that that function calls
   7 jbd2_might_wait_for_commit() while holding j_state_lock which is wrong
   8 (we do not really wait for transaction commit while holding that lock).
   9
  10 Fix the problem by moving jbd2_might_wait_for_commit() into places where
  11 we are ready to wait for transaction commit and thus j_state_lock is
  12 unlocked.
  13
  14 Cc: stable@vger.kernel.org
  15 Fixes: 1eaa566d368b214d99cbb973647c1b0b8102a9ae
  16 Reported-by: Thomas Gleixner <tglx@linutronix.de>
  17 Signed-off-by: Jan Kara <jack@suse.cz>
  18 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  19 ---
  20  fs/jbd2/transaction.c | 6 ++++--
  21  1 file changed, 4 insertions(+), 2 deletions(-)
  22
  23 diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
  24 index b5bc3e249163..3d8246a9faa4 100644
  25 --- a/fs/jbd2/transaction.c
  26 +++ b/fs/jbd2/transaction.c
  27 @@ -159,6 +159,7 @@ static void wait_transaction_locked(journal_t *journal)
  28         read_unlock(&journal->j_state_lock);
  29         if (need_to_start)
  30                 jbd2_log_start_commit(journal, tid);
  31 +       jbd2_might_wait_for_commit(journal);
  32         schedule();
  33         finish_wait(&journal->j_wait_transaction_locked, &wait);
  34  }
  35 @@ -182,8 +183,6 @@ static int add_transaction_credits(journal_t *journal, int blocks,
  36         int needed;
  37         int total = blocks + rsv_blocks;
  38
  39 -       jbd2_might_wait_for_commit(journal);
  40 -
  41         /*
  42          * If the current transaction is locked down for commit, wait
  43          * for the lock to be released.
  44 @@ -214,6 +213,7 @@ static int add_transaction_credits(journal_t *journal, int blocks,
  45                 if (atomic_read(&journal->j_reserved_credits) + total >
  46                     journal->j_max_transaction_buffers) {
  47                         read_unlock(&journal->j_state_lock);
  48 +                       jbd2_might_wait_for_commit(journal);
  49                         wait_event(journal->j_wait_reserved,
  50                                    atomic_read(&journal->j_reserved_credits) + total <=
  51                                    journal->j_max_transaction_buffers);
  52 @@ -238,6 +238,7 @@ static int add_transaction_credits(journal_t *journal, int blocks,
  53         if (jbd2_log_space_left(journal) < jbd2_space_needed(journal)) {
  54                 atomic_sub(total, &t->t_outstanding_credits);
  55                 read_unlock(&journal->j_state_lock);
  56 +               jbd2_might_wait_for_commit(journal);
  57                 write_lock(&journal->j_state_lock);
  58                 if (jbd2_log_space_left(journal) < jbd2_space_needed(journal))
  59                         __jbd2_log_wait_for_space(journal);
  60 @@ -255,6 +256,7 @@ static int add_transaction_credits(journal_t *journal, int blocks,
  61                 sub_reserved_credits(journal, rsv_blocks);
  62                 atomic_sub(total, &t->t_outstanding_credits);
  63                 read_unlock(&journal->j_state_lock);
  64 +               jbd2_might_wait_for_commit(journal);
  65                 wait_event(journal->j_wait_reserved,
  66                          atomic_read(&journal->j_reserved_credits) + rsv_blocks
  67                          <= journal->j_max_transaction_buffers / 2);
  68 --
  69 2.6.6
  70
  71