Hao Lee <haolee.swjtu@xxxxxxxxx> writes:
> On Tue, Sep 08, 2020 at 07:48:57PM +0100, Al Viro wrote:
>> On Tue, Sep 08, 2020 at 01:06:56PM +0000, Hao Lee wrote:
>> > ping
>> >
>> > On Wed, Jul 29, 2020 at 03:21:28PM +0000, Hao Lee wrote:
>> > > The dentry local variable is introduced in 'commit 84d17192d2afd ("get
>> > > rid of full-hash scan on detaching vfsmounts")' to reduce the length of
>> > > some long statements for example
>> > > mutex_lock(&path->dentry->d_inode->i_mutex). We have already used
>> > > inode_lock(dentry->d_inode) to do the same thing now, and its length is
>> > > acceptable. Furthermore, it seems not concise that assign path->dentry
>> > > to local variable dentry in the statement before goto. So, this function
>> > > would be more clear if we eliminate the local variable dentry.
>>
>> How does it make the function more clear? More specifically, what
>> analysis of behaviour is simplified by that?
>
> When I first read this function, it takes me a few seconds to think
> about if the local variable dentry is always equal to path->dentry and
> want to know if it has special purpose. This local variable may confuse
> other people too, so I think it would be better to eliminate it.
I tend to have the opposite reaction. I read your patch and wonder
why path->dentry needs to be reread what is changing path that I can not see.
my back.
Now for clarity it would probably help to do something like:
diff --git a/fs/namespace.c b/fs/namespace.c
index bae0e95b3713..430f3b4785e3 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2206,7 +2206,7 @@ static struct mountpoint *lock_mount(struct path *path)
return mp;
}
namespace_unlock();
- inode_unlock(path->dentry->d_inode);
+ inode_unlock(dentry->d_inode);
path_put(path);
path->mnt = mnt;
dentry = path->dentry = dget(mnt->mnt_root);
So at least the inode_lock and inode_unlock are properly paired.
At first glance inode_unlock using path->dentry instead of dentry
appears to be an oversight in 84d17192d2af ("get rid of full-hash scan
on detaching vfsmounts").
Eric
