Re: [PATCH] vfs: Tighten up linkat(..., AT_EMPTY_PATH)

[Andy Lutomirski]

On Wed, Aug 21, 2013 at 11:20 AM, Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
> Can't really comment the patch, just a nit:
>
> On 08/21, Andy Lutomirski wrote:
>>
>> +static bool may_flink(const struct path *path)
>> +{
>> +     bool ret;
>> +     struct inode *inode = path->dentry->d_inode;
>> +
>> +     /*
>> +      * This is racy: I_LINKABLE could be cleared between this check
>> +      * and the actual link operation.
>
> OK,
>
>> +     spin_lock(&inode->i_lock);
>> +     ret = !!(inode->i_state & I_LINKABLE);
>> +     spin_unlock(&inode->i_lock);
>
> so why do we need to take a lock ?
>

We probably don't.  But other accesses to this field take that lock,
so it seemed safer.

(In principle, someone could take the lock, write I_LINKABLE, clear
it, and unlock, and we'd get confused if we didn't take the lock
ourselves.)

> Oleg.
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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