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>

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index b5bc3e2..3d8246a 100644 (file)
--- 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);