Simplify hostid logic

There is plenty of compatibility code for a hw_hostid
that isn't used by anything. At the same time, there are apparently
issues with the current hostid logic. coredumb in #zfsonlinux on
freenode reported that Fedora 17 changes its hostid on every boot, which
required force importing his pool. A suggestion by wca was to adopt
FreeBSD's behavior, where it treats hostid as zero if /etc/hostid does
not exist

Adopting FreeBSD's behavior permits us to eliminate plenty of code,
including a userland helper that invokes the system's hostid as a
fallback.

Signed-off-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #224

include/sys/sysmacros.h

@@ -143,7 +143,6 @@
 /* Missing globals */
 extern char spl_version[32];
 extern unsigned long spl_hostid;
-extern char hw_serial[11];
 
 /* Missing misc functions */
 extern int highbit(unsigned long i);

include/sys/systeminfo.h

@@ -25,7 +25,6 @@
 #ifndef _SPL_SYSTEMINFO_H
 #define _SPL_SYSTEMINFO_H
 
-#define HW_INVALID_HOSTID	0xFFFFFFFF	/* an invalid hostid */
 #define HW_HOSTID_LEN		11		/* minimum buffer size needed */
 						/* to hold a decimal or hex */
 						/* hostid string */

module/spl/spl-generic.c

@@ -52,14 +52,11 @@
 char spl_version[32] = "SPL v" SPL_META_VERSION "-" SPL_META_RELEASE;
 EXPORT_SYMBOL(spl_version);
 
-unsigned long spl_hostid = HW_INVALID_HOSTID;
+unsigned long spl_hostid = 0;
 EXPORT_SYMBOL(spl_hostid);
 module_param(spl_hostid, ulong, 0644);
 MODULE_PARM_DESC(spl_hostid, "The system hostid.");
 
-char hw_serial[HW_HOSTID_LEN] = "<none>";
-EXPORT_SYMBOL(hw_serial);
-
 proc_t p0 = { 0 };
 EXPORT_SYMBOL(p0);
 
@@ -467,7 +464,7 @@ hostid_read(void)
 	int result;
 	uint64_t size;
 	struct _buf *file;
-	unsigned long hostid = 0;
+	uint32_t hostid = 0;
 
 	file = kobj_open_file(spl_hostid_path);
 
@@ -511,45 +508,10 @@ hostid_read(void)
 	return 0;
 }
 
-#define GET_HOSTID_CMD \
-	"exec 0</dev/null " \
-	"     1>/proc/sys/kernel/spl/hostid " \
-	"     2>/dev/null; " \
-	"hostid"
-
-static int
-hostid_exec(void)
-{
-	char *argv[] = { "/bin/sh",
-	                 "-c",
-	                 GET_HOSTID_CMD,
-	                 NULL };
-	char *envp[] = { "HOME=/",
-	                 "TERM=linux",
-	                 "PATH=/sbin:/usr/sbin:/bin:/usr/bin",
-	                 NULL };
-	int rc;
-
-	/* Doing address resolution in the kernel is tricky and just
-	 * not a good idea in general.  So to set the proper 'hw_serial'
-	 * use the usermodehelper support to ask '/bin/sh' to run
-	 * '/usr/bin/hostid' and redirect the result to /proc/sys/spl/hostid
-	 * for us to use.  It's a horrific solution but it will do for now.
-	 */
-	rc = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_PROC);
-	if (rc)
-		printk("SPL: Failed user helper '%s %s %s', rc = %d\n",
-		       argv[0], argv[1], argv[2], rc);
-
-	return rc;
-}
-
 uint32_t
 zone_get_hostid(void *zone)
 {
 	static int first = 1;
-	unsigned long hostid;
-	int rc;
 
 	/* Only the global zone is supported */
 	ASSERT(zone == NULL);
@@ -559,21 +521,16 @@ zone_get_hostid(void *zone)
 
 		/*
 		 * Get the hostid if it was not passed as a module parameter.
-		 * Try reading the /etc/hostid file directly, and then fall
-		 * back to calling the /usr/bin/hostid utility.
+		 * Try reading the /etc/hostid file directly.
 		 */
-		if ((spl_hostid == HW_INVALID_HOSTID) &&
-		    (rc = hostid_read()) && (rc = hostid_exec()))
-			return HW_INVALID_HOSTID;
+		if (hostid_read())
+			spl_hostid = 0;
 
 		printk(KERN_NOTICE "SPL: using hostid 0x%08x\n",
 			(unsigned int) spl_hostid);
 	}
 
-	if (ddi_strtoul(hw_serial, NULL, HW_HOSTID_LEN-1, &hostid) != 0)
-		return HW_INVALID_HOSTID;
-
-	return (uint32_t)hostid;
+	return spl_hostid;
 }
 EXPORT_SYMBOL(zone_get_hostid);
 

module/spl/spl-proc.c

@@ -72,7 +72,6 @@ struct proc_dir_entry *proc_spl_kstat = NULL;
 
 #define CTL_VERSION		CTL_UNNUMBERED /* Version */
 #define CTL_HOSTID		CTL_UNNUMBERED /* Host id by /usr/bin/hostid */
-#define CTL_HW_SERIAL		CTL_UNNUMBERED /* HW serial number by hostid */
 #define CTL_KALLSYMS		CTL_UNNUMBERED /* kallsyms_lookup_name addr */
 
 #define CTL_DEBUG_SUBSYS	CTL_UNNUMBERED /* Debug subsystem */
@@ -129,7 +128,6 @@ enum {
 enum {
 	CTL_VERSION = 1,		/* Version */
 	CTL_HOSTID,			/* Host id reported by /usr/bin/hostid */
-	CTL_HW_SERIAL,			/* Hardware serial number from hostid */
 	CTL_KALLSYMS,			/* Address of kallsyms_lookup_name */
 
 #ifdef DEBUG_LOG
@@ -513,9 +511,6 @@ SPL_PROC_HANDLER(proc_dohostid)
                 if (str == end)
                         SRETURN(-EINVAL);
 
-                (void) snprintf(hw_serial, HW_HOSTID_LEN, "%lu", spl_hostid);
-                hw_serial[HW_HOSTID_LEN - 1] = '\0';
-                *ppos += *lenp;
         } else {
                 len = snprintf(str, sizeof(str), "%lx", spl_hostid);
                 if (*ppos >= len)
@@ -1058,14 +1053,6 @@ static struct ctl_table spl_table[] = {
                 .mode     = 0644,
                 .proc_handler = &proc_dohostid,
         },
-        {
-                CTL_NAME    (CTL_HW_SERIAL)
-                .procname = "hw_serial",
-                .data     = hw_serial,
-                .maxlen   = sizeof(hw_serial),
-                .mode     = 0444,
-                .proc_handler = &proc_dostring,
-        },
 #ifndef HAVE_KALLSYMS_LOOKUP_NAME
         {
                 CTL_NAME    (CTL_KALLSYMS)