[PATCH RFC tip/core/rcu 1/4] dax/super: Dynamically allocate dax_srcu

["Paul E. McKenney" <paulmck@linux.ibm.com>]

Having DEFINE_SRCU() or DEFINE_STATIC_SRCU() in a loadable module
requires that the size of the reserved region be increased, which is
not something we really want to be doing.  This commit therefore removes
the DEFINE_STATIC_SRCU() from drivers/dax/super.c in favor of defining
dax_srcu as a simple srcu_struct, initializing it in dax_core_init(),
and cleaning it up in dax_core_exit().

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: <linux-nvdimm@lists.01.org>
---
 drivers/dax/super.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 0a339b85133e..3b152db30c6b 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -25,7 +25,7 @@
 #include "dax-private.h"
 
 static dev_t dax_devt;
-DEFINE_STATIC_SRCU(dax_srcu);
+static struct srcu_struct dax_srcu;
 static struct vfsmount *dax_mnt;
 static DEFINE_IDA(dax_minor_ida);
 static struct kmem_cache *dax_cache __read_mostly;
@@ -665,6 +665,10 @@ static int __init dax_core_init(void)
 {
 	int rc;
 
+	rc = init_srcu_struct(&dax_srcu);
+	if (rc)
+		goto err_srcu;
+
 	rc = dax_fs_init();
 	if (rc)
 		return rc;
@@ -678,10 +682,13 @@ static int __init dax_core_init(void)
 		goto err_bus;
 	return 0;
 
+
 err_bus:
 	unregister_chrdev_region(dax_devt, MINORMASK+1);
 err_chrdev:
 	dax_fs_exit();
+	cleanup_srcu_struct(&dax_srcu);
+err_srcu:
 	return 0;
 }
 
@@ -690,6 +697,7 @@ static void __exit dax_core_exit(void)
 	unregister_chrdev_region(dax_devt, MINORMASK+1);
 	ida_destroy(&dax_minor_ida);
 	dax_fs_exit();
+	cleanup_srcu_struct(&dax_srcu);
 }
 
 MODULE_AUTHOR("Intel Corporation");
-- 
2.17.1