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Date: Fri, 11 May 2012 14:15:32 -0700
From: Jeremy Allison <jra AT samba DOT org>
To: cygwin AT cygwin DOT com, starlight DOT 2012q2 AT binnacle DOT cx, jra AT samba DOT org
Subject: Re: CYGWIN inode over Samba share not constructed from   IndexNumber
Message-ID: <20120511211532.GB2278@jeremy-laptop>
Reply-To: Jeremy Allison <jra AT samba DOT org>
References: <6 DOT 2 DOT 5 DOT 6 DOT 2 DOT 20120511125624 DOT 05cd1ff8 AT binnacle DOT cx> <20120511175843 DOT GL13090 AT calimero DOT vinschen DOT de>
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On Fri, May 11, 2012 at 07:58:43PM +0200, Corinna Vinschen wrote:
> On May 11 12:56, starlight DOT 2012q2 AT binnacle DOT cx wrote:
> > Here is the logic Samba uses for inode
> > determination, per Jermey Allison:
> > 
> > 
> > 
> > Ok, here's how we construct the 64-bit return
> > value for that field:
> > 
> > /********************************************************************
> >  Create a 64 bit FileIndex. If the file is on the same device as
> >  the root of the share, just return the 64-bit inode. If it isn't,
> >  mangle as we used to do.
> > ********************************************************************/
> > 
> > uint64_t get_FileIndex(connection_struct *conn, const SMB_STRUCT_STAT *psbuf)
> > {
> >    uint64_t file_index;
> >    if (conn->base_share_dev == psbuf->st_ex_dev) {
> >       return (uint64_t)psbuf->st_ex_ino;
> >    }
> >    file_index = ((psbuf->st_ex_ino) & UINT32_MAX); /* FileIndexLow */
> >    file_index |= ((uint64_t)((psbuf->st_ex_dev) & UINT32_MAX)) << 32; /* FileIndexHigh */
> >    return file_index;
> > }
> 
> Which Samba version introduced this behaviour?  Originally, way back
> when Samba 3.0.28 was new, the inode numbers were always mangled to be
> 64 bit numbers, AFAIK.  The code in Cygwin which doesn't trust 32 bit
> inode numbers on remote drives is there for ages, at least since 2007.
> 
> Fortunately we have an interface which allows to fetch the Samba version
> number from the server since Samba 3.0.28a.  So, if we know which Samba
> version started to return the real 32 bit inode number, we can adapt.
> 
> Btw., https://lists.samba.org/archive/samba/2012-May/167383.html is a
> bit of a disappointment.  There's nothing "oddball" in the decision not
> to trust remote inode numbers <= 0xffffffff.
> 
> It all started with the fact that remote NT4 servers returned ephemeral
> file IDs <= 0xfffffff.  And there was some problem with 2.x Samba shares
> as well, which also returned weird file IDs, but I don't recall the
> details.
> 
> This is old code, I grant you that, but we had our reason to do so at
> the time.  Here's the code in question including comment:
> 
> inline bool
> path_conv::isgood_inode (__ino64_t ino) const
> {
>   /* We can't trust remote inode numbers of only 32 bit.  That means,
>      remote NT4 NTFS, as well as shares of Samba version < 3.0.
>      The known exception are SFU NFS shares, which return the valid 32 bit
>      inode number from the remote file system unchanged. */
>   return hasgood_inode () && (ino > UINT32_MAX || !isremote () || fs_is_nfs ());
> }

The get_FileIndex() code has been there since at least 3.6.x, but
I'll try and track down when it was first introduced.

Jeremy.

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