kernel/sys.c: improve code generation

utsname() is quite expensive to calculate.  Cache it in a local.

          text    data     bss     dec     hex filename
before:  11136     720      16   11872    2e60 kernel/sys.o
after:   11096     720      16   11832    2e38 kernel/sys.o

Acked-by: Vegard Nossum <vegard.nossum@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: "Serge E. Hallyn" <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/sys.c b/kernel/sys.c
index 558b035965aadc14736d0613b2e353e35548078c..0bc8fa3c2288110b49fad4e9eaab2326f52c69f7 100644 (file)
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1349,9 +1349,10 @@ asmlinkage long sys_sethostname(char __user *name, int len)
        down_write(&uts_sem);
        errno = -EFAULT;
        if (!copy_from_user(tmp, name, len)) {
-               memcpy(utsname()->nodename, tmp, len);
-               memset(utsname()->nodename + len, 0,
-                       sizeof(utsname()->nodename) - len);
+               struct new_utsname *u = utsname();
+
+               memcpy(u->nodename, tmp, len);
+               memset(u->nodename + len, 0, sizeof(u->nodename) - len);
                errno = 0;
        }
        up_write(&uts_sem);
@@ -1363,15 +1364,17 @@ asmlinkage long sys_sethostname(char __user *name, int len)
 asmlinkage long sys_gethostname(char __user *name, int len)
 {
        int i, errno;
+       struct new_utsname *u;
 
        if (len < 0)
                return -EINVAL;
        down_read(&uts_sem);
-       i = 1 + strlen(utsname()->nodename);
+       u = utsname();
+       i = 1 + strlen(u->nodename);
        if (i > len)
                i = len;
        errno = 0;
-       if (copy_to_user(name, utsname()->nodename, i))
+       if (copy_to_user(name, u->nodename, i))
                errno = -EFAULT;
        up_read(&uts_sem);
        return errno;
@@ -1396,9 +1399,10 @@ asmlinkage long sys_setdomainname(char __user *name, int len)
        down_write(&uts_sem);
        errno = -EFAULT;
        if (!copy_from_user(tmp, name, len)) {
-               memcpy(utsname()->domainname, tmp, len);
-               memset(utsname()->domainname + len, 0,
-                       sizeof(utsname()->domainname) - len);
+               struct new_utsname *u = utsname();
+
+               memcpy(u->domainname, tmp, len);
+               memset(u->domainname + len, 0, sizeof(u->domainname) - len);
                errno = 0;
        }
        up_write(&uts_sem);