From: Steve Dickson <SteveD@redhat.com>
Subject: Re: [PATCH nfs-utils 2/3] Correctly probe mount v2
Date: Mon, 05 Nov 2007 05:58:59 -0500
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Neil Brown wrote:
> diff --git a/utils/mount/network.c b/utils/mount/network.c
> index 2b09457..38d0135 100644
> --- a/utils/mount/network.c
> +++ b/utils/mount/network.c
> @@ -494,7 +494,7 @@ int probe_bothports(clnt_addr_t *mnt_server, clnt_addr_t *nfs_server)
>  	for (; *probe_vers; probe_vers++) {
>  		nfs_pmap->pm_vers = mntvers_to_nfs(*probe_vers);
>  		if ((res = probe_nfsport(nfs_server) != 0)) {
> -			mnt_pmap->pm_vers = nfsvers_to_mnt(nfs_pmap->pm_vers);
> +			mnt_pmap->pm_vers = *probe_vers;
>  			if ((res = probe_mntport(mnt_server)) != 0)
>  				return 1;
>  			memcpy(mnt_pmap, &save_mnt, sizeof(*mnt_pmap));

This patch does indeed fix mounts in the case where servers only support
version 2 of the mount protocol. Meaning "mount server:/export /mnt/v2"
now work when mountd only registers version 2 of the mnt protocol.

But I happen to also notice that when setting the nfsvers
    "mount -o vers=2 server:/export /mnt/v2"

the mount fails, because the mount command assumes version 1 (of the mnt
protocol) should be used and never tries any other versions. A similar
assumption is made on the umount side as well.

So I guess the question is, what correlation (if any) is there between
the mount version and nfs version that is used? Do nfsvers=2 mounts
have to use version 1 of the mnt protocol? What is the problem if
v3 mounts use version 2 of the mnt protocol?

My answers would be None, No and None to those questions, but maybe
I'm missing something...

Below is an RFC patch that removes these assumption:

  diff --git a/utils/mount/network.c b/utils/mount/network.c
index 38d0135..c929986 100644
--- a/utils/mount/network.c
+++ b/utils/mount/network.c
@@ -481,8 +481,12 @@ int probe_bothports(clnt_addr_t *mnt_server, 
clnt_addr_t *nfs_server)

  	if (mnt_pmap->pm_vers && !nfs_pmap->pm_vers)
  		nfs_pmap->pm_vers = mntvers_to_nfs(mnt_pmap->pm_vers);
-	else if (nfs_pmap->pm_vers && !mnt_pmap->pm_vers)
-		mnt_pmap->pm_vers = nfsvers_to_mnt(nfs_pmap->pm_vers);
+	else if (nfs_pmap->pm_vers && !mnt_pmap->pm_vers) {
+		/* Does it matter which mount version is used
+		 * when the nfs version is set ?
+		 */
+		mnt_pmap->pm_vers = 0;
+	}
  	if (nfs_pmap->pm_vers)
  		goto version_fixed;

diff --git a/utils/mount/nfsumount.c b/utils/mount/nfsumount.c
index 285273b..4209514 100644
--- a/utils/mount/nfsumount.c
+++ b/utils/mount/nfsumount.c
@@ -195,12 +195,6 @@ static int do_nfs_umount23(const char *spec, char 
*opts)
  		pmap->pm_prog = atoi(p+10);
  	if (opts && (p = strstr(opts, "mountport=")) && isdigit(*(p+10)))
  		pmap->pm_port = atoi(p+10);
-	if (opts && hasmntopt(&mnt, "v2"))
-		pmap->pm_vers = nfsvers_to_mnt(2);
-	if (opts && hasmntopt(&mnt, "v3"))
-		pmap->pm_vers = nfsvers_to_mnt(3);
-	if (opts && (p = strstr(opts, "vers=")) && isdigit(*(p+5)))
-		pmap->pm_vers = nfsvers_to_mnt(atoi(p+5));
  	if (opts && (p = strstr(opts, "mountvers=")) && isdigit(*(p+10)))
  		pmap->pm_vers = atoi(p+10);
  	if (opts && (hasmntopt(&mnt, "udp") || hasmntopt(&mnt, "proto=udp")))


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