From ac09630d8b0bf6c92084a30fdaefd03fd0adbdc1 Mon Sep 17 00:00:00 2001
From: Brian Behlendorf <behlendorf1@llnl.gov>
Date: Wed, 11 Jul 2018 15:49:10 -0700
Subject: Fix zpl_mount() deadlock

Commit 93b43af10 inadvertently introduced the following scenario which
can result in a deadlock.  This issue was most easily reproduced by
LXD containers using a ZFS storage backend but should be reproducible
under any workload which is frequently mounting and unmounting.

-- THREAD A --
spa_sync()
  spa_sync_upgrades()
    rrw_enter(&dp->dp_config_rwlock, RW_WRITER, FTAG); <- Waiting on B

-- THREAD B --
mount_fs()
  zpl_mount()
    zpl_mount_impl()
      dmu_objset_hold()
        dmu_objset_hold_flags()
          dsl_pool_hold()
            dsl_pool_config_enter()
              rrw_enter(&dp->dp_config_rwlock, RW_READER, tag);
    sget()
      sget_userns()
        grab_super()
          down_write(&s->s_umount); <- Waiting on C

-- THREAD C --
cleanup_mnt()
  deactivate_super()
    down_write(&s->s_umount);
    deactivate_locked_super()
      zpl_kill_sb()
        kill_anon_super()
          generic_shutdown_super()
            sync_filesystem()
              zpl_sync_fs()
                zfs_sync()
                  zil_commit()
                    txg_wait_synced() <- Waiting on A

Reviewed by: Alek Pinchuk <apinchuk@datto.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #7598
Closes #7659
Closes #7691
Closes #7693
---
 include/sys/zfs_vfsops.h | 1 +
 1 file changed, 1 insertion(+)

(limited to 'include/sys')

diff --git a/include/sys/zfs_vfsops.h b/include/sys/zfs_vfsops.h
index febfdff97..31c9c6d7f 100644
--- a/include/sys/zfs_vfsops.h
+++ b/include/sys/zfs_vfsops.h
@@ -32,6 +32,7 @@
 #include <sys/zil.h>
 #include <sys/sa.h>
 #include <sys/rrwlock.h>
+#include <sys/dsl_dataset.h>
 #include <sys/zfs_ioctl.h>
 
 #ifdef	__cplusplus
-- 
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