Re: [PATCH] rpc.nfsd: mount up nfsdfs is it doesn't appear to be mounted yet (try #2)

[Steve Dickson <SteveD@redhat.com>]

On 09/14/2010 09:23 AM, Jeff Layton wrote:
> On Tue, 31 Aug 2010 15:32:40 -0400
> Jeff Layton <jlayton@redhat.com> wrote:
> 
> Hi Steve,
> 
> It's been a couple of weeks and this latest patch hasn't been committed...
> 
> IIRC, you wanted changes to the xlog messages and were going to send an
> alternate patch. I'd like to see this in the next release of nfs-utils.
> What do we need to do to move this to resolution?
Sorry for taking so long to get to this..  

What I was thinking is to simply make the error messages more definitive 
as to what the problem is and how to fix it.. Logging that we are 
falling back to the legacy probably would not mean much to mere 
mortals... IMHO... 

I still think at some point nfsd should fail to start up, but logging
an error message at this point is fine..

Comments?

steved.

commit 8a78cb2e651d55fc1aaacf1e4ca9c009d1cf9113
Author: Jeff Layton <jlayton@redhat.com>
Date:   Wed Sep 15 15:54:36 2010 -0400

    rpc.nfsd: mount up nfsdfs is it doesn't appear to be mounted yet (try #3)
    
    There's a bit of a chicken and egg problem when nfsd is run the first
    time. On Fedora/RHEL at least, /proc/fs/nfsd is mounted up whenever nfsd
    is plugged in via a modprobe.conf "install" directive.
    
    If someone runs rpc.nfsd without plugging in nfsd.ko first,
    /proc/fs/nfsd won't be mounted and rpc.nfsd will end up using the legacy
    nfsctl interface. After that, nfsd will be plugged in and subsequent
    rpc.nfsd invocations will use that instead.
    
    This is a problem as some nfsd command-line options are ignored when the
    legacy interface is used. It'll also be a problem for people who want
    IPv6 enabled servers. The upshot is that we really don't want to use the
    legacy interface unless there is no other option.
    
    To avoid this situation, have rpc.nfsd check to see if the "threads"
    file is already present. If it's not, then make an attempt to mount
    /proc/fs/nfsd.  This is a "best-effort" sort of thing, however so we
    just ignore the return code from the mount attempt and fall back to
    using nfsctl() if it fails.
    
    Signed-off-by: Steve Dickson <steved@redhat.com>

diff --git a/utils/nfsd/nfsd.c b/utils/nfsd/nfsd.c
index 1cda1e5..658b8fa 100644
--- a/utils/nfsd/nfsd.c
+++ b/utils/nfsd/nfsd.c
@@ -246,6 +246,9 @@ main(int argc, char **argv)
 		exit(1);
 	}
 
+	/* make sure nfsdfs is mounted if it's available */
+	nfssvc_mount_nfsdfs(progname);
+
 	/* can only change number of threads if nfsd is already up */
 	if (nfssvc_inuse()) {
 		socket_up = 1;
diff --git a/utils/nfsd/nfssvc.c b/utils/nfsd/nfssvc.c
index 34c67ca..f7edcba 100644
--- a/utils/nfsd/nfssvc.c
+++ b/utils/nfsd/nfssvc.c
@@ -15,9 +15,11 @@
 #include <netdb.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
+#include <sys/stat.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <errno.h>
+#include <stdlib.h>
 
 #include "nfslib.h"
 #include "xlog.h"
@@ -31,9 +33,13 @@
  */
 #undef IPV6_SUPPORTED
 
-#define NFSD_PORTS_FILE     "/proc/fs/nfsd/portlist"
-#define NFSD_VERS_FILE    "/proc/fs/nfsd/versions"
-#define NFSD_THREAD_FILE  "/proc/fs/nfsd/threads"
+#ifndef NFSD_FS_DIR
+#define NFSD_FS_DIR	  "/proc/fs/nfsd"
+#endif
+
+#define NFSD_PORTS_FILE   NFSD_FS_DIR "/portlist"
+#define NFSD_VERS_FILE    NFSD_FS_DIR "/versions"
+#define NFSD_THREAD_FILE  NFSD_FS_DIR "/threads"
 
 /*
  * declaring a common static scratch buffer here keeps us from having to
@@ -44,6 +50,45 @@
 char buf[128];
 
 /*
+ * Using the "new" interfaces for nfsd requires that /proc/fs/nfsd is
+ * actually mounted. Make an attempt to mount it here if it doesn't appear
+ * to be. If the mount attempt fails, no big deal -- fall back to using nfsctl
+ * instead.
+ */
+void
+nfssvc_mount_nfsdfs(char *progname)
+{
+	int err;
+	struct stat statbuf;
+
+	err = stat(NFSD_THREAD_FILE, &statbuf);
+	if (err == 0)
+		return;
+	else if (errno != ENOENT) {
+		xlog(L_ERROR, "Unable to stat %s: errno %d (%m)",
+				NFSD_THREAD_FILE, errno);
+		return;
+	}
+
+	/*
+	 * this call can return an error if modprobe is set up to automatically
+	 * mount nfsdfs when nfsd.ko is plugged in. So, ignore the return
+	 * code from it and just check for the "threads" file afterward.
+	 */
+	system("/bin/mount -t nfsd nfsd " NFSD_FS_DIR " >/dev/null 2>&1");
+
+	err = stat(NFSD_THREAD_FILE, &statbuf);
+	if (err == 0)
+		return;
+
+	xlog(L_ERROR, "Unable to access " NFSD_FS_DIR " errno %d (%m)." 
+		"\nPlease try, as root, 'mount -t nfsd nfsd " NFSD_FS_DIR 
+		"' and then restart %s to correct the problem", errno, progname);
+
+	return;
+}
+
+/*
  * Are there already sockets configured? If not, then it is safe to try to
  * open some and pass them through.
  *
diff --git a/utils/nfsd/nfssvc.h b/utils/nfsd/nfssvc.h
index 0c69bd6..1a01cec 100644
--- a/utils/nfsd/nfssvc.h
+++ b/utils/nfsd/nfssvc.h
@@ -20,6 +20,7 @@
  *
  */
 
+void	nfssvc_mount_nfsdfs(char *progname);
 int	nfssvc_inuse(void);
 int	nfssvc_set_sockets(const int family, const unsigned int protobits,
 			   const char *host, const char *port);