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

[Rakesh Pandit]

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 <rak...@tuxera.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