Re: [PATCH] cifs: When "refer file directly", make new inode cache if "uniqueid is different"

[Nakajima Akira <nakajima.akira-o7dWnD6vFTHqq2nvvmkE/A@public.gmane.org>]

On 2015/04/07 23:39, Steve French wrote:
> On Tue, Apr 7, 2015 at 5:45 AM, Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org> wrote:
>> On Wed, 24 Dec 2014 11:27:38 +0900
>> Nakajima Akira <nakajima.akira-o7dWnD6vFTHqq2nvvmkE/A@public.gmane.org> wrote:
>>
>>> When refer file "directly" (e.g. ls -li <filename>),
>>>  if file is same name, old inode cache is used.
>>> This causes that client shows wrong(old) inode number.
>>> So this patch is that if uniqueid is different, return error.
>>>
>>> ## But this patch is applicable to when Server is UNIX.
>>> ## When Server is Windows, we need another new patch.
>>>
>>>
>>> Reproducible sample :
>>> 1. create file 'a' at cifs client.
>>> 2. rm 'a' and touch 'b a' at server.
>>> 3. ls -li 'a' at client, then client shows wrong(old) inode number.
>>>
>>> Bug link:
>>> https://bugzilla.kernel.org/show_bug.cgi?id=90021
>>>
>>>
>>>
>>> Signed-off-by: Nakajima Akira <nakajima.akira-o7dWnD6vFTHqq2nvvmkE/A@public.gmane.org>
>>> diff -uprN -X linux-3.18-vanilla/Documentation/dontdiff linux-3.18-vanilla/fs/cifs/inode.c linux-3.18/fs/cifs/inode.c
>>> --- linux-3.18-vanilla/fs/cifs/inode.c        2014-12-08 07:21:05.000000000 +0900
>>> +++ linux-3.18/fs/cifs/inode.c        2014-12-19 11:07:59.127000000 +0900
>>> @@ -402,9 +402,18 @@ int cifs_get_inode_info_unix(struct inod
>>>                       rc = -ENOMEM;
>>>       } else {
>>>               /* we already have inode, update it */
>>> +
>>> +             /* if uniqueid is different, return error */
>>> +             if (unlikely(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM &&
>>> +                 CIFS_I(*pinode)->uniqueid != fattr.cf_uniqueid)) {
>>> +                     rc = -ENOENT;
>>> +                     goto cgiiu_exit;
>>> +             }
>>> +
>>>               cifs_fattr_to_inode(*pinode, &fattr);
>>>       }
>>>
>>> +cgiiu_exit:
>>>       return rc;
>>>  }
>>>
>>
>> Returning ENOENT here seems like the wrong error to me. That path does
>> exist, it just no longer refers to the same file as before.
>>
>> Maybe ESTALE would be better as it would allow the VFS layer
>> to revalidate the dcache and invalidate the old dentry?
>>
>> --
>> Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>
> 
> Similar to what Jeff mentioned, isn't the nfs_relavidate_inode path
> roughly equivalent to what we want here (where nfs.ko returns ESTALE
> on various cases where we detect an inode that doesn't match what we
> expect)?

If uniqueid is different, return -ESTALE.
If filetype is different, return -ENOENT.
That's right?

+		/* if filetype is different, return error */
+		if (unlikely(((*pinode)->i_mode & S_IFMT) !=
+		    (fattr.cf_mode & S_IFMT))) {
+			rc = -ENOENT;
+			goto cgiiu_exit;
+		}