On Thu, Jun 04, 2020 at 05:01:30PM -0400, Waiman Long wrote: > --- > fs/xfs/xfs_log.c | 3 ++- > fs/xfs/xfs_trans.c | 8 +++++++- > 2 files changed, 9 insertions(+), 2 deletions(-) > > diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c > index 00fda2e8e738..d273d4e74ef8 100644 > --- a/fs/xfs/xfs_log.c > +++ b/fs/xfs/xfs_log.c > @@ -433,7 +433,8 @@ xfs_log_reserve( > XFS_STATS_INC(mp, xs_try_logspace); > > ASSERT(*ticp == NULL); > - tic = xlog_ticket_alloc(log, unit_bytes, cnt, client, permanent, 0); > + tic = xlog_ticket_alloc(log, unit_bytes, cnt, client, permanent, > + mp->m_super->s_writers.frozen ? KM_NOLOCKDEP : 0); > *ticp = tic; Hi Waiman, As I originally stated when you posted this the first time 6 months ago: we are not going to spread this sort of conditional gunk though the XFS codebase just to shut up lockdep false positives. I pointed you at the way to conditionally turn of lockdep for operations where we are doing transactions when the filesystem has already frozen the transaction subsystem. That is: > > xlog_grant_push_ail(log, tic->t_cnt ? tic->t_unit_res * tic->t_cnt > diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c > index 3c94e5ff4316..3a9f394a0f02 100644 > --- a/fs/xfs/xfs_trans.c > +++ b/fs/xfs/xfs_trans.c > @@ -261,8 +261,14 @@ xfs_trans_alloc( > * Allocate the handle before we do our freeze accounting and setting up > * GFP_NOFS allocation context so that we avoid lockdep false positives > * by doing GFP_KERNEL allocations inside sb_start_intwrite(). > + * > + * To prevent false positive lockdep warning of circular locking > + * dependency between sb_internal and fs_reclaim, disable the > + * acquisition of the fs_reclaim pseudo-lock when the superblock > + * has been frozen or in the process of being frozen. > */ > - tp = kmem_zone_zalloc(xfs_trans_zone, 0); > + tp = kmem_zone_zalloc(xfs_trans_zone, > + mp->m_super->s_writers.frozen ? KM_NOLOCKDEP : 0); > if (!(flags & XFS_TRANS_NO_WRITECOUNT)) We only should be setting KM_NOLOCKDEP when XFS_TRANS_NO_WRITECOUNT is set. That's the flag that transactions set when they run in a fully frozen context to avoid deadlocking with the freeze in progress, and that's the only case where we should be turning off lockdep. And, as I also mentioned, this should be done via a process flag - PF_MEMALLOC_NOLOCKDEP - so that it is automatically inherited by all subsequent memory allocations done in this path. That way we only need this wrapping code in xfs_trans_alloc(): if (flags & XFS_TRANS_NO_WRITECOUNT) memalloc_nolockdep_save() ..... if (flags & XFS_TRANS_NO_WRITECOUNT) memalloc_nolockdep_restore() and nothing else needs to change. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
