On Wed, Oct 03, 2012 at 08:40:29AM -0400, Jeff Layton wrote:
> Add a new client tracker upcall type that uses call_usermodehelper to
> call out to a program. This seems to be the preferred method of
> calling out to usermode these days for seldom-called upcalls. It's
> simple and doesn't require a running daemon, so it should "just work"
> as long as the binary is installed.
>
> The client tracking exit operation is also changed to check for a
> NULL pointer before running. The UMH upcall doesn't need to do anything
> at module teardown time.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
> fs/nfsd/nfs4recover.c | 139 +++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 138 insertions(+), 1 deletion(-)
>
> diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
> index 43295d4..481cb3e 100644
> --- a/fs/nfsd/nfs4recover.c
> +++ b/fs/nfsd/nfs4recover.c
> @@ -926,6 +926,142 @@ static struct nfsd4_client_tracking_ops nfsd4_cld_tracking_ops = {
> .grace_done = nfsd4_cld_grace_done,
> };
>
> +/* upcall via usermodehelper */
> +static char cltrack_prog[PATH_MAX] = "/sbin/nfsdcltrack";
> +module_param_string(cltrack_prog, cltrack_prog, sizeof(cltrack_prog),
> + S_IRUGO|S_IWUSR);
> +MODULE_PARM_DESC(cltrack_prog, "Path to the nfsdcltrack upcall program");
> +
> +static int
> +nfsd4_cltrack_upcall(char *cmd, char *arg)
> +{
> + char *envp[] = { "HOME=/",
> + "TERM=linux",
> + "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
Dumb question: why does the upcall program need these environment
variables?
--b.
> + NULL
> + };
> + char *argv[4];
> + int ret;
> +
> + if (unlikely(!cltrack_prog[0])) {
> + dprintk("%s: cltrack_prog is disabled\n", __func__);
> + return -EACCES;
> + }
> +
> + dprintk("%s: cmd: %s\n", __func__, cmd);
> + dprintk("%s: arg: %s\n", __func__, arg ? arg : "(null)");
> +
> + argv[0] = (char *)cltrack_prog;
> + argv[1] = cmd;
> + argv[2] = arg;
> + argv[3] = NULL;
> +
> + ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_PROC);
> + /*
> + * Disable the upcall mechanism if we're getting an ENOENT
> + * error. The admin can re-enable it on the fly by using sysfs
> + * once the problem has been fixed.
> + */
> + if (ret == -ENOENT || ret == -EACCES) {
> + printk(KERN_ERR "NFSD: %s was not found or isn't executable. "
> + "Please reset nfsd.cltrack_prog module parameter "
> + "once problem is resolved (%d)!\n",
> + cltrack_prog, ret);
> + cltrack_prog[0] = '\0';
> + }
> + dprintk("%s: %s return value: %d\n", __func__, cltrack_prog, ret);
> +
> + return ret;
> +}
> +
> +static char *
> +bin_to_hex_dup(const unsigned char *src, int srclen)
> +{
> + int i;
> + char *buf, *hex;
> +
> + /* +1 for terminating NULL */
> + buf = kmalloc((srclen * 2) + 1, GFP_KERNEL);
> + if (!buf)
> + return buf;
> +
> + hex = buf;
> + for (i = 0; i < srclen; i++) {
> + sprintf(hex, "%2.2x", *src++);
> + hex += 2;
> + }
> + return buf;
> +}
> +
> +static int
> +nfsd4_umh_cltrack_init(struct net __attribute__((unused)) *net)
> +{
> + return nfsd4_cltrack_upcall("init", NULL);
> +}
> +
> +static void
> +nfsd4_umh_cltrack_create(struct nfs4_client *clp)
> +{
> + char *hexid;
> +
> + hexid = bin_to_hex_dup(clp->cl_name.data, clp->cl_name.len);
> + if (!hexid) {
> + dprintk("%s: can't allocate memory for upcall!\n", __func__);
> + return;
> + }
> + nfsd4_cltrack_upcall("create", hexid);
> + kfree(hexid);
> +}
> +
> +static void
> +nfsd4_umh_cltrack_remove(struct nfs4_client *clp)
> +{
> + char *hexid;
> +
> + hexid = bin_to_hex_dup(clp->cl_name.data, clp->cl_name.len);
> + if (!hexid) {
> + dprintk("%s: can't allocate memory for upcall!\n", __func__);
> + return;
> + }
> + nfsd4_cltrack_upcall("remove", hexid);
> + kfree(hexid);
> +}
> +
> +static int
> +nfsd4_umh_cltrack_check(struct nfs4_client *clp)
> +{
> + int ret;
> + char *hexid;
> +
> + hexid = bin_to_hex_dup(clp->cl_name.data, clp->cl_name.len);
> + if (!hexid) {
> + dprintk("%s: can't allocate memory for upcall!\n", __func__);
> + return -ENOMEM;
> + }
> + ret = nfsd4_cltrack_upcall("check", hexid);
> + kfree(hexid);
> + return ret;
> +}
> +
> +static void
> +nfsd4_umh_cltrack_grace_done(struct net __attribute__((unused)) *net,
> + time_t boot_time)
> +{
> + char timestr[22]; /* FIXME: better way to determine max size? */
> +
> + sprintf(timestr, "%ld", boot_time);
> + nfsd4_cltrack_upcall("gracedone", timestr);
> +}
> +
> +static struct nfsd4_client_tracking_ops nfsd4_umh_tracking_ops = {
> + .init = nfsd4_umh_cltrack_init,
> + .exit = NULL,
> + .create = nfsd4_umh_cltrack_create,
> + .remove = nfsd4_umh_cltrack_remove,
> + .check = nfsd4_umh_cltrack_check,
> + .grace_done = nfsd4_umh_cltrack_grace_done,
> +};
> +
> int
> nfsd4_client_tracking_init(struct net *net)
> {
> @@ -956,7 +1092,8 @@ void
> nfsd4_client_tracking_exit(struct net *net)
> {
> if (client_tracking_ops) {
> - client_tracking_ops->exit(net);
> + if (client_tracking_ops->exit)
> + client_tracking_ops->exit(net);
> client_tracking_ops = NULL;
> }
> }
> --
> 1.7.11.4
>
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