[Devel] [PATCH 3/3] lutimesat: actual syscall and wire-up on i386

[Alexey Dobriyan]

On Sat, Jan 27, 2007 at 11:59:55PM -0800, H. Peter Anvin wrote:
> Alexey Dobriyan wrote:
> >+asmlinkage long sys_lutimesat(int dfd, char __user *filename, struct
> >timeval __user *utimes)
>
> Could we get these to take struct timespec instead of struct timeval?
>
> Right now we have a real problem in that the interfaces that *set* times
> take struct timeval (microsecond granularity) but the interfaces that
> *get* times return struct timespec (nanosecond granularity), which means
> information loss on any setting operations.

OK. XFS could use it.
---------------------

[PATCH 3/3] lutimesat: actual syscall and wire-up on i386

lutimesat(2) does everything futimesat(2) does except it doesn't follow
symlinks. It could be used by tar(1) and cp(1).

FreeBSD and NetBSD have lutimes(2) which can be emulated by C library.

lutimesat(2) accepts "struct timespec" which means timestamps with nanosecond
granularity. Tested on XFS which has nanosecond timestamps on-disk.

Changes to do_utimes() which is used by all existing utime* syscalls pass
LTP utime tests.

Closes http://bugme.osdl.org/show_bug.cgi?id=4433

Signed-off-by: Alexey Dobriyan <adobriyan at openvz.org>
---

 arch/i386/kernel/syscall_table.S |    1 +
 fs/utimes.c                      |   30 +++++++++++++++++++++++++-----
 include/asm-i386/unistd.h        |    4 ++--
 3 files changed, 28 insertions(+), 7 deletions(-)

--- a/arch/i386/kernel/syscall_table.S
+++ b/arch/i386/kernel/syscall_table.S
@@ -319,3 +319,4 @@ ENTRY(sys_call_table)
 	.long sys_move_pages
 	.long sys_getcpu
 	.long sys_epoll_pwait
+	.long sys_lutimesat		/* 320 */
--- a/fs/utimes.c
+++ b/fs/utimes.c
@@ -40,7 +40,7 @@ #endif
  * must be owner or have write permission.
  * Else, update from *times, must be owner or super user.
  */
-long do_utimes(int dfd, char __user *filename, struct timeval *times, int flags)
+static long do_utimes_nsec(int dfd, char __user *filename, struct timespec *times, int flags)
 {
 	int error = -EINVAL;
 	struct nameidata nd;
@@ -69,10 +69,8 @@ long do_utimes(int dfd, char __user *fil
                 if (IS_APPEND(inode) || IS_IMMUTABLE(inode))
                         goto dput_and_out;
 
-		newattrs.ia_atime.tv_sec = times[0].tv_sec;
-		newattrs.ia_atime.tv_nsec = times[0].tv_usec * 1000;
-		newattrs.ia_mtime.tv_sec = times[1].tv_sec;
-		newattrs.ia_mtime.tv_nsec = times[1].tv_usec * 1000;
+		newattrs.ia_atime = times[0];
+		newattrs.ia_mtime = times[1];
 		newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
 	} else {
 		error = -EACCES;
@@ -92,6 +90,19 @@ out:
 	return error;
 }
 
+long do_utimes(int dfd, char __user *filename, struct timeval *times, int flags)
+{
+	struct timespec ts[2];
+
+	if (times) {
+		ts[0].tv_sec = times[0].tv_sec;
+		ts[0].tv_nsec = times[0].tv_usec * 1000;
+		ts[1].tv_sec = times[1].tv_sec;
+		ts[1].tv_nsec = times[1].tv_usec * 1000;
+	}
+	return do_utimes_nsec(dfd, filename, times ? ts : NULL, flags);
+}
+
 asmlinkage long sys_futimesat(int dfd, char __user *filename, struct timeval __user *utimes)
 {
 	struct timeval times[2];
@@ -105,3 +116,12 @@ asmlinkage long sys_utimes(char __user *
 {
 	return sys_futimesat(AT_FDCWD, filename, utimes);
 }
+
+asmlinkage long sys_lutimesat(int dfd, char __user *filename, struct timespec __user *utimes)
+{
+	struct timespec times[2];
+
+	if (utimes && copy_from_user(&times, utimes, sizeof(times)))
+		return -EFAULT;
+	return do_utimes_nsec(dfd, filename, utimes ? times : NULL, AT_SYMLINK_NOFOLLOW);
+}
--- a/include/asm-i386/unistd.h
+++ b/include/asm-i386/unistd.h
@@ -325,10 +325,11 @@ #define __NR_vmsplice		316
 #define __NR_move_pages		317
 #define __NR_getcpu		318
 #define __NR_epoll_pwait	319
+#define __NR_lutimesat		320
 
 #ifdef __KERNEL__
 
-#define NR_syscalls 320
+#define NR_syscalls 321
 
 #define __ARCH_WANT_IPC_PARSE_VERSION
 #define __ARCH_WANT_OLD_READDIR