Commit 7644c823 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'pipe-nonblock-2023-05-06' of git://git.kernel.dk/linux 

Pull nonblocking pipe io_uring support from Jens Axboe:
 "Here's the revised edition of the FMODE_NOWAIT support for pipes, in
  which we just flag it as such supporting FMODE_NOWAIT unconditionally,
  but clear it if we ever end up using splice/vmsplice on the pipe.

  The pipe read/write side is perfectly fine for nonblocking IO, however
  splice and vmsplice can potentially wait for IO with the pipe lock
  held"

* tag 'pipe-nonblock-2023-05-06' of git://git.kernel.dk/linux:
  pipe: set FMODE_NOWAIT on pipes
  splice: clear FMODE_NOWAIT on file if splice/vmsplice is used
parents 0021b532 afed6271

fs/pipe.c

+3 −0
Original line number Diff line number Diff line
@@ -976,6 +976,9 @@ static int __do_pipe_flags(int *fd, struct file **files, int flags) 
	audit_fd_pair(fdr, fdw);

	fd[0] = fdr;

	fd[1] = fdw;

	/* pipe groks IOCB_NOWAIT */

	files[0]->f_mode |= FMODE_NOWAIT;

	files[1]->f_mode |= FMODE_NOWAIT;

	return 0;



 err_fdr:

fs/splice.c

+30 −4
Original line number Diff line number Diff line
@@ -38,6 +38,22 @@ 


#include "internal.h"



/*

 * Splice doesn't support FMODE_NOWAIT. Since pipes may set this flag to

 * indicate they support non-blocking reads or writes, we must clear it

 * here if set to avoid blocking other users of this pipe if splice is

 * being done on it.

 */

static noinline void noinline pipe_clear_nowait(struct file *file)

{

	fmode_t fmode = READ_ONCE(file->f_mode);



	do {

		if (!(fmode & FMODE_NOWAIT))

			break;

	} while (!try_cmpxchg(&file->f_mode, &fmode, fmode & ~FMODE_NOWAIT));

}



/*

 * Attempt to steal a page from a pipe buffer. This should perhaps go into

 * a vm helper function, it's already simplified quite a bit by the
@@ -1219,10 +1235,16 @@ static long __do_splice(struct file *in, loff_t __user *off_in, 
	ipipe = get_pipe_info(in, true);

	opipe = get_pipe_info(out, true);



	if (ipipe && off_in)

	if (ipipe) {

		if (off_in)

			return -ESPIPE;

	if (opipe && off_out)

		pipe_clear_nowait(in);

	}

	if (opipe) {

		if (off_out)

			return -ESPIPE;

		pipe_clear_nowait(out);

	}



	if (off_out) {

		if (copy_from_user(&offset, off_out, sizeof(loff_t)))
@@ -1319,6 +1341,8 @@ static long vmsplice_to_user(struct file *file, struct iov_iter *iter, 
	if (!pipe)

		return -EBADF;



	pipe_clear_nowait(file);



	if (sd.total_len) {

		pipe_lock(pipe);

		ret = __splice_from_pipe(pipe, &sd, pipe_to_user);
@@ -1347,6 +1371,8 @@ static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter, 
	if (!pipe)

		return -EBADF;



	pipe_clear_nowait(file);



	pipe_lock(pipe);

	ret = wait_for_space(pipe, flags);

	if (!ret)