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

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Message-Id: <20200617175310.20912-1-longman@redhat.com>
Date:   Wed, 17 Jun 2020 13:53:08 -0400
From:   Waiman Long <longman@...hat.com>
To:     "Darrick J. Wong" <darrick.wong@...cle.com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dave Chinner <david@...morbit.com>, Qian Cai <cai@....pw>,
        Eric Sandeen <sandeen@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Waiman Long <longman@...hat.com>
Subject: [PATCH v2 0/2] sched, xfs: Add PF_MEMALLOC_NOLOCKDEP to fix lockdep problem in xfs

 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(-)

-- 
2.18.1