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[PATCH 6/8] 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>
Reviewed-by: Jan Kara <jack@suse.cz>
---
 fs/jbd2/journal.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index a097048ed1a3..3a449150f834 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);
-- 
2.11.0

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[PATCH 0/8 v3] scope GFP_NOFS api Michal Hocko <mhocko@kernel.org> - 2017-01-06 15:20 +0100
  [PATCH 4/8] xfs: use memalloc_nofs_{save,restore} instead of memalloc_noio* Michal Hocko <mhocko@kernel.org> - 2017-01-06 15:20 +0100
    Re: [PATCH 4/8] xfs: use memalloc_nofs_{save,restore} instead of  memalloc_noio* Vlastimil Babka <vbabka@suse.cz> - 2017-01-09 15:10 +0100
      Re: [PATCH 4/8] xfs: use memalloc_nofs_{save,restore} instead of  memalloc_noio* Michal Hocko <mhocko@kernel.org> - 2017-01-09 15:30 +0100
    Re: [PATCH 4/8] xfs: use memalloc_nofs_{save,restore} instead of  memalloc_noio* Brian Foster <bfoster@redhat.com> - 2017-01-09 17:00 +0100
    Re: [PATCH 4/8] xfs: use memalloc_nofs_{save,restore} instead of  memalloc_noio* "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-01-09 22:10 +0100
  [PATCH 1/8] lockdep: allow to disable reclaim lockup detection Michal Hocko <mhocko@kernel.org> - 2017-01-06 15:20 +0100
    Re: [PATCH 1/8] lockdep: allow to disable reclaim lockup detection Vlastimil Babka <vbabka@suse.cz> - 2017-01-09 14:00 +0100
  [PATCH 6/8] jbd2: make the whole kjournald2 kthread NOFS safe Michal Hocko <mhocko@kernel.org> - 2017-01-06 15:20 +0100
  [PATCH 8/8] Revert "ext4: fix wrong gfp type under transaction" Michal Hocko <mhocko@kernel.org> - 2017-01-06 15:20 +0100
  [PATCH 7/8] Revert "ext4: avoid deadlocks in the writeback path by using sb_getblk_gfp" Michal Hocko <mhocko@kernel.org> - 2017-01-06 15:20 +0100
  [PATCH 3/8] mm: introduce memalloc_nofs_{save,restore} API Michal Hocko <mhocko@kernel.org> - 2017-01-06 15:20 +0100
    Re: [PATCH 3/8] mm: introduce memalloc_nofs_{save,restore} API Vlastimil Babka <vbabka@suse.cz> - 2017-01-09 14:10 +0100
      Re: [PATCH 3/8] mm: introduce memalloc_nofs_{save,restore} API Michal Hocko <mhocko@kernel.org> - 2017-01-09 14:50 +0100
        Re: [PATCH 3/8] mm: introduce memalloc_nofs_{save,restore} API Michal Hocko <mhocko@kernel.org> - 2017-01-09 15:00 +0100
        Re: [PATCH 3/8] mm: introduce memalloc_nofs_{save,restore} API Vlastimil Babka <vbabka@suse.cz> - 2017-01-09 15:10 +0100
  [PATCH 2/8] xfs: abstract PF_FSTRANS to PF_MEMALLOC_NOFS Michal Hocko <mhocko@kernel.org> - 2017-01-06 15:20 +0100
    Re: [PATCH 2/8] xfs: abstract PF_FSTRANS to PF_MEMALLOC_NOFS Vlastimil Babka <vbabka@suse.cz> - 2017-01-09 14:00 +0100
      Re: [PATCH 2/8] xfs: abstract PF_FSTRANS to PF_MEMALLOC_NOFS Michal Hocko <mhocko@kernel.org> - 2017-01-09 15:40 +0100
    Re: [PATCH 2/8] xfs: abstract PF_FSTRANS to PF_MEMALLOC_NOFS "Darrick J. Wong" <darrick.wong@oracle.com> - 2017-01-09 22:10 +0100
  [DEBUG PATCH 0/2] debug explicit GFP_NO{FS,IO} usage from the scope context Michal Hocko <mhocko@kernel.org> - 2017-01-06 15:30 +0100
    [DEBUG PATCH 2/2] silent warnings which we cannot do anything about Michal Hocko <mhocko@kernel.org> - 2017-01-06 15:30 +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> - 2017-01-06 15:30 +0100

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