Messages in this thread | | | Date | Fri, 21 Feb 2020 12:34:51 +1100 | From | Dave Chinner <> | Subject | Re: [PATCH V4 02/13] fs/xfs: Clarify lockdep dependency for xfs_isilocked() |
| |
On Thu, Feb 20, 2020 at 04:41:23PM -0800, ira.weiny@intel.com wrote: > From: Ira Weiny <ira.weiny@intel.com> > > xfs_isilocked() can't work fully without CONFIG_LOCKDEP. However, > making xfs_isilocked() dependant on CONFIG_LOCKDEP is not feasible > because it is used for more than the i_rwsem. Therefore a short-circuit > was provided via debug_locks. However, this caused confusion while > working through the xfs locking. > > Rather than use debug_locks as a flag specify this clearly using > IS_ENABLED(CONFIG_LOCKDEP). > > Signed-off-by: Ira Weiny <ira.weiny@intel.com> > > --- > Changes from V3: > Reordered to be a "pre-cleanup" patch > > Changes from V2: > This patch is new for V3 > --- > fs/xfs/xfs_inode.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c > index c5077e6326c7..35df324875db 100644 > --- a/fs/xfs/xfs_inode.c > +++ b/fs/xfs/xfs_inode.c > @@ -364,7 +364,7 @@ xfs_isilocked( > > if (lock_flags & (XFS_IOLOCK_EXCL|XFS_IOLOCK_SHARED)) { > if (!(lock_flags & XFS_IOLOCK_SHARED)) > - return !debug_locks || > + return !IS_ENABLED(CONFIG_LOCKDEP) || > lockdep_is_held_type(&VFS_I(ip)->i_rwsem, 0);
This breaks expected lockdep behaviour.
We need to use debug_locks here because lockdep turns off lock checking via debug_locks when lockdep encounters a locking inconsistency. We only want to know about the first locking problem, not spew cascading lock problems over and over once we already know there is a locking problem.
IOWs, checking debug_locks is required here for the same reason it is used in lockdep_assert_held_{read/write}(). essentially we are open coding lockdep_assert_held_write() here because this function is only called from within ASSERT() statements and we don't want multiple WARN/BUGs being issued when this triggers....
Cheers,
Dave. -- Dave Chinner david@fromorbit.com
| |