Commit 5d329e12 authored by Jens Axboe's avatar Jens Axboe
Browse files

io_uring: allow retry for O_NONBLOCK if async is supported 



A common complaint is that using O_NONBLOCK files with io_uring can be a
bit of a pain. Be a bit nicer and allow normal retry IFF the file does
support async behavior. This makes it possible to use io_uring more
reliably with O_NONBLOCK files, for use cases where it either isn't
possible or feasible to modify the file flags.

Cc: stable@vger.kernel.org
Reported-and-tested-by: default avatarDan Melnic <dmm@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 9c7b0ba8

fs/io_uring.c

+11 −5
Original line number Diff line number Diff line
@@ -2843,7 +2843,8 @@ static bool io_file_supports_nowait(struct io_kiocb *req, int rw) 
	return __io_file_supports_nowait(req->file, rw);

}



static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe)

static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe,

		      int rw)

{

	struct io_ring_ctx *ctx = req->ctx;

	struct kiocb *kiocb = &req->rw.kiocb;
@@ -2865,8 +2866,13 @@ static int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe) 
	if (unlikely(ret))

		return ret;



	/* don't allow async punt for O_NONBLOCK or RWF_NOWAIT */

	if ((kiocb->ki_flags & IOCB_NOWAIT) || (file->f_flags & O_NONBLOCK))

	/*

	 * If the file is marked O_NONBLOCK, still allow retry for it if it

	 * supports async. Otherwise it's impossible to use O_NONBLOCK files

	 * reliably. If not, or it IOCB_NOWAIT is set, don't retry.

	 */

	if ((kiocb->ki_flags & IOCB_NOWAIT) ||

	    ((file->f_flags & O_NONBLOCK) && !io_file_supports_nowait(req, rw)))

		req->flags |= REQ_F_NOWAIT;



	ioprio = READ_ONCE(sqe->ioprio);
@@ -3349,7 +3355,7 @@ static int io_read_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) 
{

	if (unlikely(!(req->file->f_mode & FMODE_READ)))

		return -EBADF;

	return io_prep_rw(req, sqe);

	return io_prep_rw(req, sqe, READ);

}



/*
@@ -3542,7 +3548,7 @@ static int io_write_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) 
{

	if (unlikely(!(req->file->f_mode & FMODE_WRITE)))

		return -EBADF;

	return io_prep_rw(req, sqe);

	return io_prep_rw(req, sqe, WRITE);

}



static int io_write(struct io_kiocb *req, unsigned int issue_flags)