From: Jens Axboe axboe@kernel.dk
commit 5d329e1286b0a040264e239b80257c937f6e685f upstream.
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: Dan Melnic dmm@fb.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/io_uring.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-)
--- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -2683,7 +2683,8 @@ static bool io_file_supports_async(struc return __io_file_supports_async(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; @@ -2705,8 +2706,13 @@ static int io_prep_rw(struct io_kiocb *r 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_async(req, rw))) req->flags |= REQ_F_NOWAIT;
ioprio = READ_ONCE(sqe->ioprio); @@ -3193,7 +3199,7 @@ static int io_read_prep(struct io_kiocb { if (unlikely(!(req->file->f_mode & FMODE_READ))) return -EBADF; - return io_prep_rw(req, sqe); + return io_prep_rw(req, sqe, READ); }
/* @@ -3382,7 +3388,7 @@ static int io_write_prep(struct io_kiocb { 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)