linux-kernel - Re: [PATCH] lightnvm: missing nvm

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Message-ID: <56559D5C.6090004@lightnvm.io>
Date:	Wed, 25 Nov 2015 12:37:00 +0100
From:	Matias Bjørling <mb@...htnvm.io>
To:	Wenwei Tao <ww.tao0320@...il.com>
CC:	linux-kernel@...r.kernel.org, linux-block@...r.kernel.org
Subject: Re: [PATCH] lightnvm: missing nvm_lock acquire

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@...il.com>
Signed-off-by: Matias Bjørling <m@...rling.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


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