Just-in-time mounts when following symlinks

Luke Kenneth Casson Leighton lkcl at switchboard.net
Thu Jun 4 14:19:12 GMT 1998

[cross-posted to samba-technical, samba-ntdom and samba].

On Thu, 4 Jun 1998, Albert Chin-A-Young wrote:

> This mail message follows from several discussions with Luke Leighton.
> It's mostly technical in nature but I'm submitting to all mailing
> lists anyway (Luke's suggestion).
> We have our Samba server running with the Berkeley AMD automounter
> (nothing peculiar here). In order for our Samba users to walk the
> automount tree, we created a program to create symbolic links from
> the local filesystem to the automounter keys. So, we have a tree
> that looks like the following:
> 	/amdlinks
> 	    d418		(tree created from amd.d418 map)
> 		PS2MIF -> /d418/PS2MIF
> 		adm -> /d418/adm
> 		bin -> /d418/bin
> 	    da
> 		abt		(tree created from amd.da.abt map)
> 		    dist
> 			nosw -> /da/abt/dist/nosw
> 			sw -> /da/abt/dist/sw
> 		adm		(tree created from amd.da.adm map)
> 		    dist
> 			sys -> /da/adm/dist/sys
> So, the user, using the File Manager/Explorer in windows, can
> map to \\samba\da or \\samba\d418 and walk the /amdlinks/da or
> /amdlinks/d418 tree and see all the directories that the automounter
> *might* mount (if we didn't do it this way, \\samba\da would map
> to the automounter /da directory which might not contain anything
> and this would make it impossible for them to "point-and-click"
> their way down the directory tree).
> The problem occurs when users descend into a directory with a list
> of symbolic links (such as \\samba\d418 above). When you descend
> into this directory, the Samba server will kick off the automounter
> in this directory and mount everything in /d418. This becomes a big
> problem when there are *many* symbolic links in a directory pointing
> to autmounted paths (which would then cause lots of NFS mount). So,
> what I would like is a "just in time links" option that returns the
> symbolic link to the File Manager and, not until the user "double
> clicks" on an entry that is a symbolic link, have it followed
> (and thus kick off the automounter on an "as-needed" basis).

my suggestion to solve this was to have a function that either calls lstat
or stat with a boolean switch.  then, identify _all_ SMB calls that make a
stat or lstat calls.  then, subdivide them into calls that need to have
the real file/directory time/date and those that could get away with the
file/directory link time/date.  this _may_ require an smb.conf file list

at a first guess, you could do lstat on directories, and stat on files.

my second guess is simply that stat is being accidentally called (which
triggers the automount lookup) in places where lstat should only be
called (under the control of lp_symlinks() whatever).

opinions / comments welcomed.


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