On Wed, Jan 09, 2019 at 03:53:29PM -0500, Qian Cai wrote: > Easy to reproduce: > > 1. run LTP oom02 workload to let kswapd acquire this locking order: > fs_reclaim -> sb_internal. > > # grep -i fs_reclaim -C 3 /proc/lockdep_chains | grep -C 5 sb_internal > [00000000826b9172] &type->s_umount_key#27 > [000000005fa8b2ac] sb_pagefaults > [0000000033f1247e] sb_internal > [000000009e9a9664] fs_reclaim > > 2. freeze XFS. > # fsfreeze -f /home > > Dave mentioned that this is due to a lockdep limitation - "IOWs, this is > a false positive, caused by the fact that xfs_trans_alloc() is called > from both above and below memory reclaim as well as within /every level/ > of freeze processing. Lockdep is unable to describe the staged flush > logic in the freeze process that prevents deadlocks from occurring, and > hence we will pretty much always see false positives in the freeze > path....". Hence, just temporarily disable lockdep in that path. NACK. Turning off lockdep is not a solution, it just prevents lockdep from finding and reporting real issues. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
