Re: [PATCH] lightnvm: missing nvm_lock acquire

[Matias BjÃrling]

On 11/25/2015 09:57 AM, Wenwei Tao wrote:
> Hi Matias
> I think list_for_each_entry_safe(pos, n, head, member) cannot avoid
> race condition
> the item point by ânâ can be deleted and freed in the same time we
> operate on 'pos'
> so lock is still necessary.
I've made the patch like this, ok?

To avoid race conditions, traverse dev, media manager,
and target lists and also register, unregister entries
to/from them, should be always under the nvm_lock control.

Signed-off-by: Wenwei Tao <ww.tao0320@xxxxxxxxx>
Signed-off-by: Matias BjÃrling <m@xxxxxxxxxxx>
---
 drivers/lightnvm/core.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/lightnvm/core.c b/drivers/lightnvm/core.c
index ea6dba5..9f901f6 100644
--- a/drivers/lightnvm/core.c
+++ b/drivers/lightnvm/core.c
@@ -127,9 +127,11 @@ static struct nvm_dev *nvm_find_nvm_dev(const char 
*name)
 {
 	struct nvm_dev *dev;

+	down_write(&nvm_lock);
 	list_for_each_entry(dev, &nvm_devices, devices)
 		if (!strcmp(name, dev->name))
 			return dev;
+	up_write(&nvm_lock);

 	return NULL;
 }
@@ -388,13 +390,14 @@ static int nvm_create_target(struct nvm_dev *dev,
 		}
 	}

+	down_write(&nvm_lock);
 	tt = nvm_find_target_type(create->tgttype);
 	if (!tt) {
 		pr_err("nvm: target type %s not found\n", create->tgttype);
+		up_write(&nvm_lock);
 		return -EINVAL;
 	}

-	down_write(&nvm_lock);
 	list_for_each_entry(t, &dev->online_targets, list) {
 		if (!strcmp(create->tgtname, t->disk->disk_name)) {
 			pr_err("nvm: target name already exists.\n");
--
2.1.4


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