On Wed 10-02-21 10:57:39, Alexander Lochmann wrote: > Some members of transaction_t are allowed to be read without > any lock being held if consistency doesn't matter. > Based on LockDoc's findings, we extended the locking > documentation of those members. > Each one of them is marked with a short comment: > "no lock for quick racy checks". > > Signed-off-by: Alexander Lochmann <alexander.lochmann@xxxxxxxxxxxxxx> > Signed-off-by: Horst Schirmeier <horst.schirmeier@xxxxxxxxxxxxxx> Thanks for the patch! Some comments below... > --- > include/linux/jbd2.h | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h > index 99d3cd051ac3..18f77d9b1745 100644 > --- a/include/linux/jbd2.h > +++ b/include/linux/jbd2.h > @@ -594,18 +594,18 @@ struct transaction_s > */ > unsigned long t_log_start; > > - /* Number of buffers on the t_buffers list [j_list_lock] */ > + /* Number of buffers on the t_buffers list [j_list_lock, no lock for quick racy checks] */ > int t_nr_buffers; So this case is actually somewhat different now that I audited the uses. There are two types of users - commit code (fs/jbd2/commit.c) and others. Other users properly use j_list_lock to access t_nr_buffers. Commit code does not use any locks because committing transaction is fully in ownership of the jbd2 thread and all other users need to check & wait for commit to be finished before doing anything with the transaction's buffers. > /* > * Doubly-linked circular list of all buffers reserved but not yet > - * modified by this transaction [j_list_lock] > + * modified by this transaction [j_list_lock, no lock for quick racy checks] > */ > struct journal_head *t_reserved_list; > > /* > * Doubly-linked circular list of all metadata buffers owned by this > - * transaction [j_list_lock] > + * transaction [j_list_lock, no lock for quick racy checks] > */ > struct journal_head *t_buffers; > > @@ -631,7 +631,7 @@ struct transaction_s > /* > * Doubly-linked circular list of metadata buffers being shadowed by log > * IO. The IO buffers on the iobuf list and the shadow buffers on this > - * list match each other one for one at all times. [j_list_lock] > + * list match each other one for one at all times. [j_list_lock, no lock for quick racy checks] > */ > struct journal_head *t_shadow_list; The above three cases are the same as t_reserved_list. Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
