[PATCH 16/18] flag parameters: NONBLOCK in pipe

Ulrich Drepper
2008-05-06T21:21:07Z

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;
}
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

fs/pipe.c | 14 +++++++-------
include/linux/fs.h | 4 ++--
kernel/kmod.c | 4 ++--
3 files changed, 11 insertions(+), 11 deletions(-)

Signed-off-by: Ulrich Drepper <drepper@redhat.com>

diff --git a/fs/pipe.c b/fs/pipe.c
index 059411e..796c0a0 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -949,7 +949,7 @@ fail_inode:
return NULL;
}

-struct file *create_write_pipe(void)
+struct file *create_write_pipe(int flags)
{
int err;
struct inode *inode;
@@ -982,7 +982,7 @@ 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 134d2d5..3694eeb 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1776,8 +1776,8 @@ 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 8df97d3..7356146 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);