linux-kernel - Re: [PATCH] cifs: Add information about noserverino

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <AANLkTi=KJa4w3bwDJgsfjPAH0Vi=oJb+psBB2731jnNG@mail.gmail.com>
Date:	Thu, 9 Dec 2010 22:58:20 -0600
From:	Steve French <smfrench@...il.com>
To:	Suresh Jayaraman <sjayaraman@...e.de>
Cc:	Jeff Layton <jlayton@...hat.com>,
	Bernhard Walle <bernhard@...lle.de>, sfrench@...ba.org,
	linux-cifs@...r.kernel.org, samba-technical@...ts.samba.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cifs: Add information about noserverino

On Thu, Dec 9, 2010 at 9:09 PM, Suresh Jayaraman <sjayaraman@...e.de> wrote:
> On 12/10/2010 02:14 AM, Steve French wrote:
>> On Thu, Dec 9, 2010 at 1:34 PM, Jeff Layton <jlayton@...hat.com> wrote:
>>> On Thu, 9 Dec 2010 12:26:39 -0600
>>> Steve French <smfrench@...il.com> wrote:
>>>
>>>> On Thu, Dec 9, 2010 at 6:09 AM, Jeff Layton <jlayton@...hat.com> wrote:
>>>>> On Thu, 09 Dec 2010 17:10:28 +0530
>>>>> Suresh Jayaraman <sjayaraman@...e.de> wrote:
>>>>>
>>>>>> On 12/06/2010 09:08 PM, Jeff Layton wrote:
>>>>>>> On Mon, 06 Dec 2010 16:35:06 +0100
>>>>>>> Bernhard Walle <bernhard@...lle.de> wrote:
>>>>>>>
>>>>>>>>
>>>>>>>> Zitat von Jeff Layton <jlayton@...hat.com>:
>>>>>>>>
>>>>>>>>>
>>>>>>>>> I'm still not sure I like this patch however. It potentially means a
>>>>>>>>> lot of printk spam since these things have no ratelimiting. It also
>>>>>>>>> doesn't tell me anything about which server might be giving me grief.
>>>>>>>>>
>>>>>>>>> Maybe this should be turned into a cFYI?
>>>>>>>>
>>>>>>>> Well, if I see it in the kernel log, it doesn't matter if it's info or
>>>>>>>> something else.
>>>>>>>>
>>>>>>>>> The bottom line though is that running 32-bit applications that were
>>>>>>>>> built without -D_FILE_OFFSET_BITS=64 on a 64-bit kernel is a very bad
>>>>>>>>> idea. It would be nice to be able to alert users that things aren't
>>>>>>>>> working the way they expect, but I'm not sure this is the right place
>>>>>>>>> to do that.
>>>>>>>>
>>>>>>>> Well, but there *are* such application (in my case it was Softmaker Office
>>>>>>>> which is a proprietary word processor) and it's quite nice if you know
>>>>>>>> how you can workaround it when you encounter such a problem. That's all.
>>>>>>>>
>>>>>>>
>>>>>>> Sure...but this problem is not limited to CIFS. Many modern filesystems
>>>>>>> use 64-bit inodes. Running this application on XFS or NFS for instance
>>>>>>> is likely to give you the same trouble. You just hit it on CIFS because
>>>>>>> the server happened to give you a very large inode number.
>>>>>>>
>>>>>>> If we're going to add printk's for this situation, it probably ought to
>>>>>>> be in a more generic place.
>>>>>>>
>>>>>>
>>>>>> By generic place, did you mean at the VFS level? I think at VFS level,
>>>>>> there is little information about the Server or underlying fs and this
>>>>>> information doesn't seem too critical that VFS should warn/care much about.
>>>>>>
>>>>>> May be sticking to a cFYI along with Server detail is a good idea?
>>>>>>
>>>>> My poing was mainly that there's nothing special about CIFS in this
>>>>> regard, other than the fact that servers regularly send us inodes that
>>>>> are larger than 2^32. Why should we do this for cifs but not for nfs,
>>>>> xfs, ext4, etc?
>>>>>
>>>>> The filldir function gets a dentry as an argument, so it could
>>>>> reasonably generate a printk for this. I'm also not keen on
>>>>> the printk recommending noserverino for this. That has its own
>>>>> drawbacks.
>>>>>
>>>>> A cFYI for this sort of thing seems reasonable however.
>>>>
>>>> I agree that a cFYI is reasonable. �The next obvious question is: do
>>>> we need to add code to generate unique 32 bit inode numbers
>>>> that don't collide (as IIRC Samba does by xor the high and low 32
>>>> bits of the inode number) when the app can't support ino64
>>>> I would prefer not to go back to noserverino since that has worse
>>>> drawbacks.
>>>>
>>>
>>> Right, the fact that noserverino works around this is really just due
>>> to an implementation detail of iunique(). That should probably be
>>> discouraged as a solution since it's not guaranteed to be a workaround
>>> in the future.
>>>
>>> If we did add such a switch, I'd suggest that we pattern it after what
>>> NFS did for this. They added an "enable_ino64" module parameter a
>>> couple of years ago that defaults to "true".
>
> What are the advantages we have by making it a module parameter as
> opposed to an mount option? XFS seems to have "inode64" mount option for
> quite sometime now, without much issues..

I prefer mount option, but with the default to support 64 bit inode numbers.

>> makes me uncomfortable to break ino64 for all mounts - when we
>> may have one application on one mount that needs it (might be
>> better to make a mount related)
>>
>>
>
>
> --
> Suresh Jayaraman
>



-- 
Thanks,

Steve
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/