flag parameters: NONBLOCK in pipe

This patch adds O_NONBLOCK support to pipe2.  It is minimally more involved
than the patches for eventfd et.al but still trivial.  The interfaces of the
create_write_pipe and create_read_pipe helper functions were changed and the
one other caller as well.

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_pipe2
# ifdef __x86_64__
#  define __NR_pipe2 293
# elif defined __i386__
#  define __NR_pipe2 331
# else
#  error "need __NR_pipe2"
# endif
#endif

int
main (void)
{
  int fds[2];
  if (syscall (__NR_pipe2, fds, 0) == -1)
    {
      puts ("pipe2(0) failed");
      return 1;
    }
  for (int i = 0; i < 2; ++i)
    {
      int fl = fcntl (fds[i], F_GETFL);
      if (fl == -1)
        {
          puts ("fcntl failed");
          return 1;
        }
      if (fl & O_NONBLOCK)
        {
          printf ("pipe2(0) set non-blocking mode for fds[%d]\n", i);
          return 1;
        }
      close (fds[i]);
    }

  if (syscall (__NR_pipe2, fds, O_NONBLOCK) == -1)
    {
      puts ("pipe2(O_NONBLOCK) failed");
      return 1;
    }
  for (int i = 0; i < 2; ++i)
    {
      int fl = fcntl (fds[i], F_GETFL);
      if (fl == -1)
        {
          puts ("fcntl failed");
          return 1;
        }
      if ((fl & O_NONBLOCK) == 0)
        {
          printf ("pipe2(O_NONBLOCK) does not set non-blocking mode for fds[%d]\n", i);
          return 1;
        }
      close (fds[i]);
    }

  puts ("OK");

  return 0;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Ulrich Drepper <drepper@redhat.com>
Acked-by: Davide Libenzi <davidel@xmailserver.org>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 11 insertions, 11 deletions

diff --git a/fs/pipe.c b/fs/pipe.c
index 68e82061070c..10c4e9aa5c49 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -950,7 +950,7 @@ fail_inode:
         return NULL;
 }
 
-struct file *create_write_pipe(void)
+struct file *create_write_pipe(int flags)
 {
         int err;
         struct inode *inode;
@@ -983,7 +983,7 @@ struct file *create_write_pipe(void)
                 goto err_dentry;
         f->f_mapping = inode->i_mapping;
 
-        f->f_flags = O_WRONLY;
+        f->f_flags = O_WRONLY | (flags & O_NONBLOCK);
         f->f_version = 0;
 
         return f;
@@ -1007,7 +1007,7 @@ void free_write_pipe(struct file *f)
         put_filp(f);
 }
 
-struct file *create_read_pipe(struct file *wrf)
+struct file *create_read_pipe(struct file *wrf, int flags)
 {
         struct file *f = get_empty_filp();
         if (!f)
@@ -1019,7 +1019,7 @@ struct file *create_read_pipe(struct file *wrf)
         f->f_mapping = wrf->f_path.dentry->d_inode->i_mapping;
 
         f->f_pos = 0;
-        f->f_flags = O_RDONLY;
+        f->f_flags = O_RDONLY | (flags & O_NONBLOCK);
         f->f_op = &read_pipe_fops;
         f->f_mode = FMODE_READ;
         f->f_version = 0;
@@ -1033,13 +1033,13 @@ int do_pipe_flags(int *fd, int flags)
         int error;
         int fdw, fdr;
 
-        if (flags & ~O_CLOEXEC)
+        if (flags & ~(O_CLOEXEC | O_NONBLOCK))
                 return -EINVAL;
 
-        fw = create_write_pipe();
+        fw = create_write_pipe(flags);
         if (IS_ERR(fw))
                 return PTR_ERR(fw);
-        fr = create_read_pipe(fw);
+        fr = create_read_pipe(fw, flags);
         error = PTR_ERR(fr);
         if (IS_ERR(fr))
                 goto err_write_pipe;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0e80cd717d32..4b86f806014c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1778,8 +1778,8 @@ static inline void allow_write_access(struct file *file)
 }
 extern int do_pipe(int *);
 extern int do_pipe_flags(int *, int);
-extern struct file *create_read_pipe(struct file *f);
-extern struct file *create_write_pipe(void);
+extern struct file *create_read_pipe(struct file *f, int flags);
+extern struct file *create_write_pipe(int flags);
 extern void free_write_pipe(struct file *);
 
 extern struct file *do_filp_open(int dfd, const char *pathname,
diff --git a/kernel/kmod.c b/kernel/kmod.c
index 90d7af1c1655..2989f67c4446 100644
--- a/kernel/kmod.c
+++ b/kernel/kmod.c
@@ -417,12 +417,12 @@ int call_usermodehelper_stdinpipe(struct subprocess_info *sub_info,
 {
         struct file *f;
 
-        f = create_write_pipe();
+        f = create_write_pipe(0);
         if (IS_ERR(f))
                 return PTR_ERR(f);
         *filp = f;
 
-        f = create_read_pipe(f);
+        f = create_read_pipe(f, 0);
         if (IS_ERR(f)) {
                 free_write_pipe(*filp);
                 return PTR_ERR(f);