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Read the /etc/hostid file directly.

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Deprecate the /usr/bin/hostid call by reading the /etc/hostid file
directly. Add the spl_hostid_path parameter to override the default
/etc/hostid path.

Rename the set_hostid() function to hostid_exec() to better reflect
actual behavior and complement the new hostid_read() function.

Use HW_INVALID_HOSTID as the spl_hostid sentinel value because
zero seems to be a valid gethostid() result on Linux.
This commit is contained in:
Darik Horn 2011-06-20 14:53:56 -05:00 committed by Brian Behlendorf
parent bf0c60c060
commit 0d54dcb566
2 changed files with 109 additions and 5 deletions
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4
include/sys/systeminfo.h
View File

@ -30,4 +30,8 @@
/* to hold a decimal or hex */
/* hostid string */
/* Supplemental definitions for Linux. */
#define HW_HOSTID_PATH "/etc/hostid" /* binary configuration file */
#define HW_HOSTID_MASK 0xFFFFFFFF /* significant hostid bits */
#endif /* SPL_SYSTEMINFO_H */

110
module/spl/spl-generic.c
View File

@ -27,7 +27,7 @@
#include <sys/sysmacros.h>
#include <sys/systeminfo.h>
#include <sys/vmsystm.h>
#include <sys/vnode.h>
#include <sys/kobj.h>
#include <sys/kmem.h>
#include <sys/mutex.h>
#include <sys/rwlock.h>
@ -52,7 +52,7 @@
char spl_version[16] = "SPL v" SPL_META_VERSION;
EXPORT_SYMBOL(spl_version);
unsigned long spl_hostid = 0;
unsigned long spl_hostid = HW_INVALID_HOSTID;
EXPORT_SYMBOL(spl_hostid);
module_param(spl_hostid, ulong, 0644);
MODULE_PARM_DESC(spl_hostid, "The system hostid.");
@ -364,6 +364,100 @@ struct new_utsname *__utsname(void)
}
EXPORT_SYMBOL(__utsname);
/*
* Read the unique system identifier from the /etc/hostid file.
*
* The behavior of /usr/bin/hostid on Linux systems with the
* regular eglibc and coreutils is:
*
* 1. Generate the value if the /etc/hostid file does not exist
* or if the /etc/hostid file is less than four bytes in size.
*
* 2. If the /etc/hostid file is at least 4 bytes, then return
* the first four bytes [0..3] in native endian order.
*
* 3. Always ignore bytes [4..] if they exist in the file.
*
* Only the first four bytes are significant, even on systems that
* have a 64-bit word size.
*
* See:
*
* eglibc: sysdeps/unix/sysv/linux/gethostid.c
* coreutils: src/hostid.c
*
* Notes:
*
* The /etc/hostid file on Solaris is a text file that often reads:
*
* # DO NOT EDIT
* "0123456789"
*
* Directly copying this file to Linux results in a constant
* hostid of 4f442023 because the default comment constitutes
* the first four bytes of the file.
*
*/
char *spl_hostid_path = HW_HOSTID_PATH;
module_param(spl_hostid_path, charp, 0444);
MODULE_PARM_DESC(spl_hostid_path, "The system hostid file (/etc/hostid)");
static int
hostid_read(void)
{
int result;
uint64_t size;
struct _buf *file;
unsigned long hostid = 0;
file = kobj_open_file(spl_hostid_path);
if (file == (struct _buf *)-1) {
printk(KERN_WARNING
"SPL: The %s file is not found.\n",
spl_hostid_path);
return -1;
}
result = kobj_get_filesize(file, &size);
if (result != 0) {
printk(KERN_WARNING
"SPL: kobj_get_filesize returned %i on %s\n",
result, spl_hostid_path);
kobj_close_file(file);
return -2;
}
if (size < sizeof(HW_HOSTID_MASK)) {
printk(KERN_WARNING
"SPL: Ignoring the %s file because it is %llu bytes; "
"expecting %lu bytes instead.\n",
spl_hostid_path, size, sizeof(HW_HOSTID_MASK));
kobj_close_file(file);
return -3;
}
/* Read directly into the variable like eglibc does. */
/* Short reads are okay; native behavior is preserved. */
result = kobj_read_file(file, (char *)&hostid, sizeof(hostid), 0);
if (result < 0) {
printk(KERN_WARNING
"SPL: kobj_read_file returned %i on %s\n",
result, spl_hostid_path);
kobj_close_file(file);
return -4;
}
/* Mask down to 32 bits like coreutils does. */
spl_hostid = hostid & HW_HOSTID_MASK;
kobj_close_file(file);
return 0;
}
#define GET_HOSTID_CMD \
"exec 0</dev/null " \
" 1>/proc/sys/kernel/spl/hostid " \
@ -371,7 +465,7 @@ EXPORT_SYMBOL(__utsname);
"hostid"
static int
set_hostid(void)
hostid_exec(void)
{
char *argv[] = { "/bin/sh",
"-c",
@ -486,8 +580,14 @@ __init spl_init(void)
if ((rc = zlib_init()))
SGOTO(out9, rc);
/* Get the hostid if it was not passed as a module parameter. */
if (spl_hostid == 0 && (rc = set_hostid()))
/*
* 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.
*/
if (spl_hostid == HW_INVALID_HOSTID
&& (rc = hostid_read()) && (rc = hostid_exec()))
SGOTO(out10, rc = -EADDRNOTAVAIL);
#ifndef HAVE_KALLSYMS_LOOKUP_NAME