[PATCH] CIFS: Update CreationTime on every query info request

[Pavel Shilovsky]

2014-08-06 15:25 GMT+04:00 Jeff Layton <jlayton at samba.org>:
> On Wed,  6 Aug 2014 15:15:43 +0400
> Pavel Shilovsky <pshilovsky at samba.org> wrote:
>
>> Samba server can change a creation time of an inode in the default
>> configuration. The client sets this value during the inode initialization
>> only and uses it the inode search. In this case harlinked dentries may
>> link to different inodes. As the results the Cthon basic test #7 fails
>> on nounix Samba mounts.
>>
>> Fix this by making the client update the creation time on every
>> query info request.
>>
>> Cc: Jeff Layton <jlayton at samba.org>
>> Signed-off-by: Pavel Shilovsky <pshilovsky at samba.org>
>> ---
>>  fs/cifs/inode.c | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/fs/cifs/inode.c b/fs/cifs/inode.c
>> index a174605..2029e7c 100644
>> --- a/fs/cifs/inode.c
>> +++ b/fs/cifs/inode.c
>> @@ -173,6 +173,9 @@ cifs_fattr_to_inode(struct inode *inode, struct cifs_fattr *fattr)
>>
>>       cifs_i->cifsAttrs = fattr->cf_cifsattrs;
>>
>> +     /* Samba server changes this value in the default configuration */
>> +     cifs_i->createtime = fattr->cf_createtime;
>> +
>>       if (fattr->cf_flags & CIFS_FATTR_NEED_REVAL)
>>               cifs_i->time = 0;
>>       else
>
> NAK
>
> That really sounds more like a bug in Samba. The creation time is
> supposed to be immutable, and if it changes then that means that you
> have a new inode.
>
> We really *don't* want to go updating it like this.

If it is suppose to be immutable and the server does processing right,
the fix will not break things since the cifs_i->createtime value stays
the same.

But if this value was changed and we don't store this latest returned
value from the server and continue to use the old one, does things go
better? We'll end up relying on the value that is wrong...

If Samba server doesn't store the creation time attribute in xattrs
(that is restricted by underlying file system and switched off by
default), it can't return a right value to the client since POSIX file
systems store only access, modify and change timestamps.

So, in the result we have the CIFS client that doesn't work with the
default configuration of Samba. If we can't fix Samba due to POSIX
restrictions), we need to do something with the client, don't we?

-- 
Best regards,
Pavel Shilovsky.