Re: [PATCH] lightnvm: missing nvm_lock acquire

Matias Bjørling
2015-11-25T11:37:05Z

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 ‘n’ 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@gmail.com>
Signed-off-by: Matias Bjørling <m@bjorling.me>
---
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