[v2,0/2] sched, xfs: Add PF_MEMALLOC_NOLOCKDEP to fix lockdep problem in xfs

Message

Waiman Long June 17, 2020, 5:53 p.m. UTC

v2:
  - Update patch to add the frozen flag check as the XFS_TRANS_NO_WRITECOUNT
    check alone is insufficient.

There is a false positive lockdep warning in how the xfs code handle
filesystem freeze:

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(sb_internal);
                               lock(fs_reclaim);
                               lock(sb_internal);
  lock(fs_reclaim);

 *** DEADLOCK ***

This patch series works around this problem by adding a
PF_MEMALLOC_NOLOCKDEP flag and set during filesystem freeze to avoid
the lockdep splat.

Waiman Long (2):
  sched: Add PF_MEMALLOC_NOLOCKDEP flag
  xfs: Fix false positive lockdep warning with sb_internal & fs_reclaim

 fs/xfs/xfs_log.c         |  9 +++++++++
 fs/xfs/xfs_trans.c       | 31 +++++++++++++++++++++++++++----
 include/linux/sched.h    |  7 +++++++
 include/linux/sched/mm.h | 15 ++++++++++-----
 4 files changed, 53 insertions(+), 9 deletions(-)