[PATCH] lightnvm: add a lock to prevent before the race condition on pblk remove

[Marcin Dziegielewski]

When we trigger nvm target remove during device hot unplug, we
have a chance to hit general protection fault caused by use of
nvm_dev which was freed from another (hot unplug) thread (in
nvm_unregister function).

This patch introduce lock in nvme_ioctl_dev_remove function to
prevent us before a situation like described above.

Signed-off-by: Marcin Dziegielewski <marcin.dziegielew...@intel.com>
---
 drivers/lightnvm/core.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
index 5f82036..84f0b9a 100644
--- a/drivers/lightnvm/core.c
+++ b/drivers/lightnvm/core.c
@@ -1335,11 +1335,13 @@ static long nvm_ioctl_dev_remove(struct file *file, 
void __user *arg)
                return -EINVAL;
        }
 
+       down_read(&nvm_lock);
        list_for_each_entry(dev, &nvm_devices, devices) {
                ret = nvm_remove_tgt(dev, &remove);
                if (!ret)
                        break;
        }
+       up_read(&nvm_lock);
 
        return ret;
 }
-- 
1.8.3.1