[PATCH] tcmu: Oops in unmap_thread_fn()

[Dan Carpenter]

Calling list_del() on the iterator pointer in list_for_each_entry() will
cause an oops.  We need to user the _safe() version for that.

Fixes: c73d02f63c16 ("tcmu: Add fifo type waiter list support to avoid 
starvation")
Signed-off-by: Dan Carpenter <dan.carpen...@oracle.com>

diff --git a/drivers/target/target_core_user.c 
b/drivers/target/target_core_user.c
index 9258b7dd2c30..fd9fcea68d23 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -1985,7 +1985,7 @@ static struct target_backend_ops tcmu_ops = {
 
 static int unmap_thread_fn(void *data)
 {
-       struct tcmu_dev *udev;
+       struct tcmu_dev *udev, *tmp;
        loff_t off;
        uint32_t start, end, block;
        static uint32_t free_blocks;
@@ -2056,7 +2056,7 @@ static int unmap_thread_fn(void *data)
                 * for the global data pool blocks.
                 */
                mutex_lock(&root_udev_waiter_mutex);
-               list_for_each_entry(udev, &root_udev_waiter, waiter) {
+               list_for_each_entry_safe(udev, tmp, &root_udev_waiter, waiter) {
                        mutex_lock(&udev->cmdr_lock);
                        if (udev->waiting_blocks < free_blocks) {
                                mutex_unlock(&udev->cmdr_lock);