um: remove file sync for stub data

There is no need to sync the stub code to "disk" for the other process
to see the correct memory. Drop the fsync there and remove the helper
function.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241103150506.1367695-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Author: benzea

arch/um/include/shared/os.h

@@ -145,7 +145,6 @@ extern int os_ioctl_generic(int fd, unsigned int cmd, unsigned long arg);
 extern int os_get_ifname(int fd, char *namebuf);
 extern int os_set_slip(int fd);
 extern int os_mode_fd(int fd, int mode);
-extern int os_fsync_file(int fd);
 
 extern int os_seek_file(int fd, unsigned long long offset);
 extern int os_open_file(const char *file, struct openflags flags, int mode);

arch/um/kernel/physmem.c

@@ -101,7 +101,6 @@ void __init setup_physmem(unsigned long start, unsigned long reserve_end,
 	 */
 	os_seek_file(physmem_fd, __pa(__syscall_stub_start));
 	os_write_file(physmem_fd, __syscall_stub_start, PAGE_SIZE);
-	os_fsync_file(physmem_fd);
 
 	memblock_add(__pa(start), len);
 	memblock_reserve(__pa(start), reserve);

arch/um/os-Linux/file.c

@@ -255,12 +255,6 @@ void os_close_file(int fd)
 {
 	close(fd);
 }
-int os_fsync_file(int fd)
-{
-	if (fsync(fd) < 0)
-	    return -errno;
-	return 0;
-}
 
 int os_seek_file(int fd, unsigned long long offset)
 {