From: "J. Bruce Fields" <bfields@fieldses.org>
Subject: Re: [NFS] nfs-utils crossmnt/fsid bug
Date: Mon, 26 Nov 2007 22:39:54 +0000
Message-ID: <20071126223954.GX5960@fieldses.org>
References: <20070905204628.GD29582@fieldses.org>
	<18246.16373.177320.570040@notabene.brown>
Mime-Version: 1.0
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Cc: nfs@lists.sourceforge.net, Steve Dickson <SteveD@redhat.com>
To: Neil Brown <neilb@suse.de>
In-Reply-To: <18246.16373.177320.570040-wvvUuzkyo1EYVZTmpyfIwg@public.gmane.org>
Sender: linux-nfs-owner@vger.kernel.org

On Fri, Nov 23, 2007 at 01:50:29PM +1100, Neil Brown wrote:
> On Wednesday September 5, bfields@fieldses.org wrote:
> > With an exports entry like
> > 
> > 	/exports *.citi.umich.edu(rw,crossmnt,fsid=0)
> > 
> > and some other stuff mounted under /exports, I get an odd situation
> > where listing /exports/submnt/ shows me the contents of /exports/.
> > 
> > I looks to me like what's happening is that the new code to
> > automatically export filesystems under crossmnt exports is exporting
> > those directories with the fsid option turned on, with the result that
> > the root of each of those subdirectories ends up with the same
> > filehandle as the root of /exports, and the hilarity ensues.  But I
> > haven't tried a patch yet.
> > 
> > Does that make sense?  I assume we should just clear the fsid flag on
> > submounts, as it's never going to make sense, and leave the logic
> > otherwise intact.
> > 
> > --b.
> 
> Thanks for noticing and reporting this.
> 
> Does this (untested, but it compiles) patch seem right?
> 
> NeilBrown
> 
> --------
> When exported a filesystems with option inherited (by the crossmnt
> option) from a higherlevel filesystem, ignore filesystem specific
> options like FSID and explicit UUID.

Looks right to me.  I'm confused about uuid's--how does the non-explicit
UUID case work?

--b.

> 
> Signed-off-by: NeilBrown <neilb@suse.de>
> 
> diff --git a/utils/mountd/cache.c b/utils/mountd/cache.c
> index fd317cd..ff56b9f 100644
> --- a/utils/mountd/cache.c
> +++ b/utils/mountd/cache.c
> @@ -565,20 +565,29 @@ static int dump_to_cache(FILE *f, char *domain, char *path, struct exportent *ex
>  	qword_print(f, path);
>  	qword_printint(f, time(0)+30*60);
>  	if (exp) {
> -		qword_printint(f, exp->e_flags);
> +		int different_fs = 0;
> +		struct stat stb1, stb2;
> +		if (stat(path, &stb1) == 0 &&
> +		    stat(exp->e_path, &stb2) == 0 &&
> +		    stb1.st_dev != stb2.st_dev)
> +			different_fs = 1;
> +		if (different_fs)
> +			qword_printint(f, exp->e_flags & ~NFSEXP_FSID);
> +		else
> +			qword_printint(f, exp->e_flags);
>  		qword_printint(f, exp->e_anonuid);
>  		qword_printint(f, exp->e_anongid);
>  		qword_printint(f, exp->e_fsid);
>  		write_fsloc(f, exp, path);
>  		write_secinfo(f, exp);
>  #if USE_BLKID
> - 		if (exp->e_uuid == NULL) {
> + 		if (exp->e_uuid == NULL || different_fs) {
>   			char u[16];
>   			if (get_uuid(path, NULL, 16, u)) {
>   				qword_print(f, "uuid");
>   				qword_printhex(f, u, 16);
>   			}
> - 		} else if (exp->e_uuid) {
> + 		} else {
>   			qword_print(f, "uuid");
>   			qword_printhex(f, exp->e_uuid, 16);
>   		}

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