flag parameters: NONBLOCK in inotify_init

This patch adds non-blocking support for inotify_init1.  The
additional changes needed are minimal.

The following test must be adjusted for architectures other than x86 and
x86-64 and in case the syscall numbers changed.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/syscall.h>

#ifndef __NR_inotify_init1
# ifdef __x86_64__
#  define __NR_inotify_init1 294
# elif defined __i386__
#  define __NR_inotify_init1 332
# else
#  error "need __NR_inotify_init1"
# endif
#endif

#define IN_NONBLOCK O_NONBLOCK

int
main (void)
{
  int fd = syscall (__NR_inotify_init1, 0);
  if (fd == -1)
    {
      puts ("inotify_init1(0) failed");
      return 1;
    }
  int fl = fcntl (fd, F_GETFL);
  if (fl == -1)
    {
      puts ("fcntl failed");
      return 1;
    }
  if (fl & O_NONBLOCK)
    {
      puts ("inotify_init1(0) set non-blocking mode");
      return 1;
    }
  close (fd);

  fd = syscall (__NR_inotify_init1, IN_NONBLOCK);
  if (fd == -1)
    {
      puts ("inotify_init1(IN_NONBLOCK) failed");
      return 1;
    }
  fl = fcntl (fd, F_GETFL);
  if (fl == -1)
    {
      puts ("fcntl failed");
      return 1;
    }
  if ((fl & O_NONBLOCK) == 0)
    {
      puts ("inotify_init1(IN_NONBLOCK) set non-blocking mode");
      return 1;
    }
  close (fd);

  puts ("OK");

  return 0;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Signed-off-by: NUlrich Drepper <drepper@redhat.com>
Acked-by: NDavide Libenzi <davidel@xmailserver.org>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/inotify_user.c

@@ -574,7 +574,7 @@ asmlinkage long sys_inotify_init1(int flags)
 	struct file *filp;
 	int fd, ret;
 
-	if (flags & ~IN_CLOEXEC)
+	if (flags & ~(IN_CLOEXEC | IN_NONBLOCK))
 		return -EINVAL;
 
 	fd = get_unused_fd_flags(flags & O_CLOEXEC);
@@ -613,7 +613,7 @@ asmlinkage long sys_inotify_init1(int flags)
 	filp->f_path.dentry = dget(inotify_mnt->mnt_root);
 	filp->f_mapping = filp->f_path.dentry->d_inode->i_mapping;
 	filp->f_mode = FMODE_READ;
-	filp->f_flags = O_RDONLY;
+	filp->f_flags = O_RDONLY | (flags & O_NONBLOCK);
 	filp->private_data = dev;
 
 	INIT_LIST_HEAD(&dev->events);

include/linux/inotify.h

@@ -7,7 +7,7 @@
 #ifndef _LINUX_INOTIFY_H
 #define _LINUX_INOTIFY_H
 
-/* For O_CLOEXEC */
+/* For O_CLOEXEC and O_NONBLOCK */
 #include <linux/fcntl.h>
 #include <linux/types.h>
 
@@ -67,6 +67,7 @@ struct inotify_event {
 
 /* Flags for sys_inotify_init1.  */
 #define IN_CLOEXEC O_CLOEXEC
+#define IN_NONBLOCK O_NONBLOCK
 
 #ifdef __KERNEL__