• Johannes Thumshirn's avatar
    nvme: fix lockdep warning in nvme_mpath_clear_current_path · 978628ec
    Johannes Thumshirn authored
    When running blktest's nvme/005 with a lockdep enabled kernel the test
    case fails due to the following lockdep splat in dmesg:
    
     =============================
     WARNING: suspicious RCU usage
     4.17.0-rc5 #881 Not tainted
     -----------------------------
     drivers/nvme/host/nvme.h:457 suspicious rcu_dereference_check() usage!
    
     other info that might help us debug this:
    
     rcu_scheduler_active = 2, debug_locks = 1
     3 locks held by kworker/u32:5/1102:
      #0:         (ptrval) ((wq_completion)"nvme-wq"){+.+.}, at: process_one_work+0x152/0x5c0
      #1:         (ptrval) ((work_completion)(&ctrl->scan_work)){+.+.}, at: process_one_work+0x152/0x5c0
      #2:         (ptrval) (&subsys->lock#2){+.+.}, at: nvme_ns_remove+0x43/0x1c0 [nvme_core]
    
    The only caller of nvme_mpath_clear_current_path() is nvme_ns_remove()
    which holds the subsys lock so it's likely a false positive, but when
    using rcu_access_pointer(), we're telling rcu and lockdep that we're
    only after the pointer falue.
    
    Fixes: 32acab31 ("nvme: implement multipath access to nvme subsystems")
    Signed-off-by: default avatarJohannes Thumshirn <jthumshirn@suse.de>
    Suggested-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
    Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
    Signed-off-by: default avatarKeith Busch <keith.busch@intel.com>
    978628ec
nvme.h 14.2 KB