Re: Samba symlinks and dcache collisions

[Jeremy Allison <jra@samba.org>]

On Mon, Sep 28, 2015 at 09:48:06PM -0500, Steve French wrote:
> directory listings of large directories on smb2/smb3 mounts to Samba
> sometimes shows the
> 
> "Autodisabling the use of server inode numbers ..." message in dmesg.
> 
> I have narrowed it down to cases where Samba is displaying symlink
> source and target with the same inode number (the client does not know
> they are symlinks since Samba does not set that file type when Unix
> Extensions are not available).  Interestingly small directories with
> either symlinks or hardlinks in them don't cause the client to detect
> the inode number collision (which causes the server inode message to
> be displayed).

Yes, that's going to happen if symlinks are within the share
without UNIX extensions I'm afraid. We report them as the same file
(as they are).

> cifs_find_inode in fs/cifs/inode.c has the following check (after
> making sure that the inode numbers and mode of the two are the same
> and that they are not directories and that their creation time is the
> same)
> 
>     /* if it's not a directory or has no dentries, then flag it */
>     if (S_ISDIR(inode->i_mode) && !hlist_empty(&inode->i_dentry))
>         fattr->cf_flags |= CIFS_FATTR_INO_COLLISION;
> 
> Not sure what causes the collision in the case of a larger directory
> but not a smaller one.  It is puzzling because the source and target
> look (to the SMB3 client) similar to hardlinks with the same metadata
> except for file name (Samba server does not emulate symlinks as SMB3
> symlink reparse points or apple style symlinks so they look more like
> hardlinks to the client)

Nothing to do with directory size. Any link is going to do this
if it points within the share.