From: Johannes Thumshirn <jthumshirn@suse.de>
Date: Thu, 17 May 2018 13:52:50 +0200
Subject: nvme: fix lockdep warning in nvme_mpath_clear_current_path
Git-commit: 978628ec795b18179e74ef12cfcd35bae569d13e
Patch-mainline: v4.18-rc1
References: FATE#323952, FATE#322506
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: 32acab3181c7 ("nvme: implement multipath access to nvme subsystems")
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Suggested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <keith.busch@intel.com>
---
drivers/nvme/host/nvme.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -21,6 +21,7 @@
#include <linux/lightnvm.h>
#include <linux/sed-opal.h>
#include <linux/fault-inject.h>
+#include <linux/rcupdate.h>
extern unsigned int nvme_io_timeout;
#define NVME_IO_TIMEOUT (nvme_io_timeout * HZ)
@@ -420,7 +421,7 @@ static inline void nvme_mpath_clear_curr
{
struct nvme_ns_head *head = ns->head;
- if (head && ns == srcu_dereference(head->current_path, &head->srcu))
+ if (head && ns == rcu_access_pointer(head->current_path))
rcu_assign_pointer(head->current_path, NULL);
}
struct nvme_ns *nvme_find_path(struct nvme_ns_head *head);