linux-kernel - [PATCH] lightnvm: prevent target type module removal when in use

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Date:   Fri, 8 Sep 2017 15:35:28 +0300
From:   Rakesh Pandit <rakesh@...era.com>
To:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     Matias Bjørling <mb@...htnvm.io>,
        Javier González <jg@...htnvm.io>
Subject: [PATCH] lightnvm: prevent target type module removal when in use

If target type module e.g. pblk here is unloaded (rmmod) while module
is in use (after creating target) system crashes.  We fix this by
using module API refcnt.

Signed-off-by: Rakesh Pandit <rakesh@...era.com>
---
 drivers/lightnvm/core.c      | 4 ++++
 drivers/lightnvm/pblk-init.c | 1 +
 include/linux/lightnvm.h     | 1 +
 3 files changed, 6 insertions(+)

diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
index bbea2c8..c39f87d 100644
--- a/drivers/lightnvm/core.c
+++ b/drivers/lightnvm/core.c
@@ -22,6 +22,7 @@
 #include <linux/types.h>
 #include <linux/sem.h>
 #include <linux/bitmap.h>
+#include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/miscdevice.h>
 #include <linux/lightnvm.h>
@@ -316,6 +317,8 @@ static int nvm_create_tgt(struct nvm_dev *dev, struct nvm_ioctl_create *create)
 	list_add_tail(&t->list, &dev->targets);
 	mutex_unlock(&dev->mlock);
 
+	__module_get(tt->owner);
+
 	return 0;
 err_sysfs:
 	if (tt->exit)
@@ -351,6 +354,7 @@ static void __nvm_remove_target(struct nvm_target *t)
 
 	nvm_remove_tgt_dev(t->dev, 1);
 	put_disk(tdisk);
+	module_put(t->type->owner);
 
 	list_del(&t->list);
 	kfree(t);
diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
index 5fe926b..77d6120 100644
--- a/drivers/lightnvm/pblk-init.c
+++ b/drivers/lightnvm/pblk-init.c
@@ -1059,6 +1059,7 @@ static struct nvm_tgt_type tt_pblk = {
 
 	.sysfs_init	= pblk_sysfs_init,
 	.sysfs_exit	= pblk_sysfs_exit,
+	.owner		= THIS_MODULE,
 };
 
 static int __init pblk_module_init(void)
diff --git a/include/linux/lightnvm.h b/include/linux/lightnvm.h
index 81b71c6d..78a22e0 100644
--- a/include/linux/lightnvm.h
+++ b/include/linux/lightnvm.h
@@ -461,6 +461,7 @@ struct nvm_tgt_type {
 
 	/* For internal use */
 	struct list_head list;
+	struct module *owner;
 };
 
 extern struct nvm_tgt_type *nvm_find_target_type(const char *, int);
-- 
2.7.4