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nfsd: add a usermodehelper upcall for NFSv4 client ID tracking 

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@redhat.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Jeff Layton 2012-11-12 15:00:48 -05:00 committed by J. Bruce Fields
parent a0af710a65
commit 2873d2147e
1 changed files with 133 additions and 1 deletions
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134
fs/nfsd/nfs4recover.c
View File

@ -927,6 +927,137 @@ 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_umh_cltrack_upcall(char *cmd, char *arg)
{
char *envp[] = { 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 or EACCES
* error. The admin can re-enable it on the fly by using sysfs
* once the problem has been fixed.
*/
if (ret == -ENOENT || ret == -EACCES) {
dprintk("NFSD: %s was not found or isn't executable (%d). "
"Setting cltrack_prog to blank string!",
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_umh_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_umh_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_umh_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_umh_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_umh_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)
{
@ -957,7 +1088,8 @@ 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;
}
}