Re: [PATCH 1/7] autofs4: Save autofs trigger's vfsmount in super block info

["H. Peter Anvin" <hpa@zytor.com>]

On 01/18/2010 11:35 AM, Trond Myklebust wrote:
> On Mon, 2010-01-18 at 10:27 +0000, Al Viro wrote:
>> Back to another question: which syscalls should and which syscalls should not
>> trigger automount on the last component?  Note that it's something we'd better
>> be consistent about between autofs4 and cifs/afs/nfs...
>
> In addition to the ones that trigger automounts now:
>
> One syscall that we've had a lot of complaints about is 'stat()'. Since
> it doesn't follow symlinks, it will fail to trigger the automount, and
> will return bogus values for st_dev. This again confuses some versions
> of the 'du' utility that check the value of st_dev before and after
> entering the subdir.
> (see https://bugzilla.redhat.com/show_bug.cgi?id=431166 )
>

[Sorry for late comment]

I presume you mean lstat() here.  This is *exactly* the intended 
semantics -- this prevents a GUI from looking in /home with enumeration 
enabled, and mounting *every single subvolume* in that map.

Thus the semantic: "don't automount if you wouldn't follow a symlink". 
It's perhaps not *ideal*, but it is a pretty decent approximation, easy 
to describe, and serves the purpose.

	-hpa