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.
Fixes: 1eaa566d368b214d99cbb973647c1b0b8102a9ae
Reported-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/jbd2/transaction.c | 6 ++++--
1 file 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);
--
2.6.6
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