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

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Message-ID: <AANLkTikKkOEO1gZFCD+aVwVTCEXmR9Q6jVndrX6Bd08V@mail.gmail.com>
Date:	Thu, 9 Dec 2010 14:44:27 -0600
From:	Steve French <smfrench@...il.com>
To:	Jeff Layton <jlayton@...hat.com>
Cc:	Suresh Jayaraman <sjayaraman@...e.de>,
	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 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".

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)



-- 
Thanks,

Steve
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