| Message ID | 1310664370-20091-1-git-send-email-josef@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 07/15/2011 01:26 AM, Josef Bacik wrote: > Hit this nice little deadlock. What happens is this > > __btrfs_end_transaction with throttle set, --use_count so it equals 0 > btrfs_commit_transaction > <somebody else actually manages to start the commit> > btrfs_end_transaction --use_count so now its -1 <== BAD > we just return and wait on the transaction > > This is bad because we just return after our use_count is -1 and don't let go > of our num_writer count on the transaction, so the guy committing the > transaction just sits there forever. Fix this by inc'ing our use_count if we're > going to call commit_transaction so that if we call btrfs_end_transaction it's > valid. Thanks, > > Signed-off-by: Josef Bacik <josef@redhat.com> > --- > fs/btrfs/transaction.c | 13 ++++++++++--- > 1 files changed, 10 insertions(+), 3 deletions(-) > > diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c > index 654755b..00b81fb5 100644 > --- a/fs/btrfs/transaction.c > +++ b/fs/btrfs/transaction.c > @@ -497,10 +497,17 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans, > } > > if (lock && cur_trans->blocked && !cur_trans->in_commit) { > - if (throttle) > + if (throttle) { > + /* > + * We may race with somebody else here so end up having > + * to call end_transaction on ourselves again, so inc > + * our use_count. > + */ > + trans->use_count++; > return btrfs_commit_transaction(trans, root); > - else > + } else { > wake_up_process(info->transaction_kthread); > + } > } > > WARN_ON(cur_trans != info->running_transaction); > @@ -1225,7 +1232,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans, > if (cur_trans->in_commit) { > spin_unlock(&cur_trans->commit_lock); > atomic_inc(&cur_trans->use_count); > - btrfs_end_transaction(trans, root); > + __btrfs_end_transaction(trans, root, 0, 1); > Looks good. BTW, btrfs_end_transaction(trans, root) is just __btrfs_end_transaction(trans, root, 0, 1). thanks, liubo > ret = wait_for_commit(root, cur_trans); > BUG_ON(ret); -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 07/14/2011 10:56 PM, liubo wrote: > On 07/15/2011 01:26 AM, Josef Bacik wrote: >> Hit this nice little deadlock. What happens is this >> >> __btrfs_end_transaction with throttle set, --use_count so it equals 0 >> btrfs_commit_transaction >> <somebody else actually manages to start the commit> >> btrfs_end_transaction --use_count so now its -1 <== BAD >> we just return and wait on the transaction >> >> This is bad because we just return after our use_count is -1 and don't let go >> of our num_writer count on the transaction, so the guy committing the >> transaction just sits there forever. Fix this by inc'ing our use_count if we're >> going to call commit_transaction so that if we call btrfs_end_transaction it's >> valid. Thanks, >> >> Signed-off-by: Josef Bacik <josef@redhat.com> >> --- >> fs/btrfs/transaction.c | 13 ++++++++++--- >> 1 files changed, 10 insertions(+), 3 deletions(-) >> >> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c >> index 654755b..00b81fb5 100644 >> --- a/fs/btrfs/transaction.c >> +++ b/fs/btrfs/transaction.c >> @@ -497,10 +497,17 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans, >> } >> >> if (lock && cur_trans->blocked && !cur_trans->in_commit) { >> - if (throttle) >> + if (throttle) { >> + /* >> + * We may race with somebody else here so end up having >> + * to call end_transaction on ourselves again, so inc >> + * our use_count. >> + */ >> + trans->use_count++; >> return btrfs_commit_transaction(trans, root); >> - else >> + } else { >> wake_up_process(info->transaction_kthread); >> + } >> } >> >> WARN_ON(cur_trans != info->running_transaction); >> @@ -1225,7 +1232,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans, >> if (cur_trans->in_commit) { >> spin_unlock(&cur_trans->commit_lock); >> atomic_inc(&cur_trans->use_count); >> - btrfs_end_transaction(trans, root); >> + __btrfs_end_transaction(trans, root, 0, 1); >> > > Looks good. > > BTW, btrfs_end_transaction(trans, root) is just __btrfs_end_transaction(trans, root, 0, 1). > Oops you're right, I saw the 1 for lock and thought it was for throttle. Thanks, Josef -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 654755b..00b81fb5 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -497,10 +497,17 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans, } if (lock && cur_trans->blocked && !cur_trans->in_commit) { - if (throttle) + if (throttle) { + /* + * We may race with somebody else here so end up having + * to call end_transaction on ourselves again, so inc + * our use_count. + */ + trans->use_count++; return btrfs_commit_transaction(trans, root); - else + } else { wake_up_process(info->transaction_kthread); + } } WARN_ON(cur_trans != info->running_transaction); @@ -1225,7 +1232,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans, if (cur_trans->in_commit) { spin_unlock(&cur_trans->commit_lock); atomic_inc(&cur_trans->use_count); - btrfs_end_transaction(trans, root); + __btrfs_end_transaction(trans, root, 0, 1); ret = wait_for_commit(root, cur_trans); BUG_ON(ret);
Hit this nice little deadlock. What happens is this __btrfs_end_transaction with throttle set, --use_count so it equals 0 btrfs_commit_transaction <somebody else actually manages to start the commit> btrfs_end_transaction --use_count so now its -1 <== BAD we just return and wait on the transaction This is bad because we just return after our use_count is -1 and don't let go of our num_writer count on the transaction, so the guy committing the transaction just sits there forever. Fix this by inc'ing our use_count if we're going to call commit_transaction so that if we call btrfs_end_transaction it's valid. Thanks, Signed-off-by: Josef Bacik <josef@redhat.com> --- fs/btrfs/transaction.c | 13 ++++++++++--- 1 files changed, 10 insertions(+), 3 deletions(-)