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[PATCH 7/9] jbd2: make the whole kjournald2 kthread NOFS safe

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From: Michal Hocko <mhocko@suse.com>

kjournald2 is central to the transaction commit processing. As such any
potential allocation from this kernel thread has to be GFP_NOFS. Make
sure to mark the whole kernel thread GFP_NOFS by the memalloc_nofs_save.

Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Michal Hocko <mhocko@suse.com>
---
 fs/jbd2/journal.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 8ed971eeab44..6dad8c5d6ddf 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -206,6 +206,13 @@ static int kjournald2(void *arg)
 	wake_up(&journal->j_wait_done_commit);
 
 	/*
+	 * Make sure that no allocations from this kernel thread will ever recurse
+	 * to the fs layer because we are responsible for the transaction commit
+	 * and any fs involvement might get stuck waiting for the trasn. commit.
+	 */
+	memalloc_nofs_save();
+
+	/*
 	 * And now, wait forever for commit wakeup events.
 	 */
 	write_lock(&journal->j_state_lock);
-- 
2.10.2

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[PATCH 0/9 v2] scope GFP_NOFS api Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:10 +0100
  [PATCH 5/9] xfs: use memalloc_nofs_{save,restore} instead of memalloc_noio* Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:10 +0100
    Re: [PATCH 5/9] xfs: use memalloc_nofs_{save,restore} instead of  memalloc_noio* Brian Foster <bfoster@redhat.com> - 2016-12-16 17:40 +0100
      [PATCH 5/9 v2] xfs: use memalloc_nofs_{save,restore} instead of  memalloc_noio* Michal Hocko <mhocko@kernel.org> - 2016-12-16 23:10 +0100
  [PATCH 6/9] jbd2: mark the transaction context with the scope GFP_NOFS context Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:10 +0100
    Re: [PATCH 6/9] jbd2: mark the transaction context with the scope  GFP_NOFS context Jan Kara <jack@suse.cz> - 2016-12-19 10:40 +0100
  [PATCH 9/9] Revert "ext4: fix wrong gfp type under transaction" Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:10 +0100
    Re: [PATCH 9/9] Revert "ext4: fix wrong gfp type under transaction" Jan Kara <jack@suse.cz> - 2016-12-19 10:40 +0100
  [PATCH 3/9] xfs: abstract PF_FSTRANS to PF_MEMALLOC_NOFS Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:20 +0100
    Re: [PATCH 3/9] xfs: abstract PF_FSTRANS to PF_MEMALLOC_NOFS Brian Foster <bfoster@redhat.com> - 2016-12-16 17:40 +0100
  [PATCH 7/9] jbd2: make the whole kjournald2 kthread NOFS safe Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:20 +0100
    Re: [PATCH 7/9] jbd2: make the whole kjournald2 kthread NOFS safe Jan Kara <jack@suse.cz> - 2016-12-19 10:40 +0100
  [PATCH 4/9] mm: introduce memalloc_nofs_{save,restore} API Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:20 +0100
  [PATCH 2/9] xfs: introduce and use KM_NOLOCKDEP to silence reclaim lockdep false positives Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:20 +0100
    [PATCH 2/9 v2] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives Michal Hocko <mhocko@kernel.org> - 2016-12-16 16:50 +0100
      Re: [PATCH 2/9 v2] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives Brian Foster <bfoster@redhat.com> - 2016-12-16 17:40 +0100
        Re: [PATCH 2/9 v2] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives Michal Hocko <mhocko@kernel.org> - 2016-12-16 23:10 +0100
    Re: [PATCH 2/9] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives Dave Chinner <david@fromorbit.com> - 2016-12-19 22:30 +0100
      Re: [PATCH 2/9] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives "Darrick J. Wong" <darrick.wong@oracle.com> - 2016-12-19 23:10 +0100
        Re: [PATCH 2/9] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives Dave Chinner <david@fromorbit.com> - 2016-12-20 22:40 +0100
      Re: [PATCH 2/9] xfs: introduce and use KM_NOLOCKDEP to silence  reclaim lockdep false positives Michal Hocko <mhocko@kernel.org> - 2016-12-20 09:40 +0100
  [PATCH 1/9] lockdep: allow to disable reclaim lockup detection Michal Hocko <mhocko@kernel.org> - 2016-12-15 15:20 +0100
  [DEBUG PATCH 0/2] debug explicit GFP_NO{FS,IO} usage from the scope context Michal Hocko <mhocko@kernel.org> - 2016-12-16 13:50 +0100
    [DEBUG PATCH 2/2] silent warnings which we cannot do anything about Michal Hocko <mhocko@kernel.org> - 2016-12-16 13:50 +0100
    [DEBUG PATCH 1/2] mm, debug: report when GFP_NO{FS,IO} is used explicitly from memalloc_no{fs,io}_{save,restore} context Michal Hocko <mhocko@kernel.org> - 2016-12-16 13:50 +0100
  Re: [PATCH 0/9 v2] scope GFP_NOFS api Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-12-16 16:20 +0100
    Re: [PATCH 0/9 v2] scope GFP_NOFS api Michal Hocko <mhocko@kernel.org> - 2016-12-16 16:40 +0100
      Re: [PATCH 0/9 v2] scope GFP_NOFS api Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-12-16 17:30 +0100
        Re: [PATCH 0/9 v2] scope GFP_NOFS api Jan Kara <jack@suse.cz> - 2016-12-19 10:30 +0100
  Re: [PATCH 0/9 v2] scope GFP_NOFS api Michal Hocko <mhocko@kernel.org> - 2016-12-22 10:40 +0100

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