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jbd2: Fix lockdep splat with generic/270 test

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I've hit a lockdep splat with generic/270 test complaining that:

3216.fsstress.b/3533 is trying to acquire lock:
 (jbd2_handle){++++..}, at: [<ffffffff813152e0>] jbd2_log_wait_commit+0x0/0x150

but task is already holding lock:
 (jbd2_handle){++++..}, at: [<ffffffff8130bd3b>] start_this_handle+0x35b/0x850

The underlying problem is that jbd2_journal_force_commit_nested()
(called from ext4_should_retry_alloc()) may get called while a
transaction handle is started. In such case it takes care to not wait
for commit of the running transaction (which would deadlock) but only
for a commit of a transaction that is already committing (which is safe
as that doesn't wait for any filesystem locks).

In fact there are also other callers of jbd2_log_wait_commit() that take
care to pass tid of a transaction that is already committing and for
those cases, the lockdep instrumentation is too restrictive and leading
to false positive reports. Fix the problem by calling
jbd2_might_wait_for_commit() from jbd2_log_wait_commit() only if the
transaction isn't already committing.

Fixes: 1eaa566d36
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Jan Kara 2017-04-29 20:12:16 -04:00 committed by Theodore Ts'o
parent 80a2ea9f85
commit c52c47e4b4
1 changed files with 14 additions and 1 deletions
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15
fs/jbd2/journal.c
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@ -691,8 +691,21 @@ int jbd2_log_wait_commit(journal_t *journal, tid_t tid)
{
int err = 0;
jbd2_might_wait_for_commit(journal);
read_lock(&journal->j_state_lock);
#ifdef CONFIG_PROVE_LOCKING
/*
* Some callers make sure transaction is already committing and in that
* case we cannot block on open handles anymore. So don't warn in that
* case.
*/
if (tid_gt(tid, journal->j_commit_sequence) &&
(!journal->j_committing_transaction ||
journal->j_committing_transaction->t_tid != tid)) {
read_unlock(&journal->j_state_lock);
jbd2_might_wait_for_commit(journal);
read_lock(&journal->j_state_lock);
}
#endif
#ifdef CONFIG_JBD2_DEBUG
if (!tid_geq(journal->j_commit_request, tid)) {
printk(KERN_ERR