On Thu, Jul 16, 2015 at 07:32:56PM +0200, Oleg Nesterov wrote: > > #ifdef CONFIG_LOCKDEP > /* > * We want lockdep to tell us about possible deadlocks with > freezing but > * it's it bit tricky to properly instrument it. Getting a > freeze protection > * works as getting a read lock but there are subtle problems. > XFS for example > * gets freeze protection on internal level twice in some > cases, which is OK
Sorry, I've missed something here - where is XFS nesting sb_start_intwrite() calls? XFS only has a call to sb_start_intwrite() in xfs_trans_alloc() and an open coded equivalent in xfs_iomap_write_unwritten(). However, we cannot create nested transaction contexts as doing so is *guaranteed to deadlock the journal*. (e.g. why we use PF_FSTRANS to trigger GFP_NOFS allocation as it prevents direct memory reclaim from causing nested transactions.) Hence if we taking multiple FREEZE_FS level references at a time then there is a bug that needs fixing.... Cheers, Dave. -- Dave Chinner da...@fromorbit.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
