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

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Date:	Thu, 9 Dec 2010 14:34:48 -0500
From:	Jeff Layton <jlayton@...hat.com>
To:	Steve French <smfrench@...il.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, 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".

-- 
Jeff Layton <jlayton@...hat.com>
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