On Wed, Jul 15, 2020 at 10:54:21PM +0300, Pavel Begunkov wrote:
> On 15/07/2020 00:08, Josh Triplett wrote:
> > +static int io_openat2_fixed_file(struct io_kiocb *req, bool force_nonblock)
> > +{
>
> How about having it in io_openat2()? There are almost identical, that would be
> just a couple of if's.
It's a little more complex than that. It would require making three
pieces of io_openat2 conditional, and the control flow would be
intertwined with whether the file descriptor (from get_unused_fd_flags)
has been initialized. It's absolutely *doable*, but the resulting
complexity didn't seem worth it.
> > + struct io_open *open = &req->open;
> > + struct open_flags op;
> > + struct file *file;
> > + int ret;
> > +
> > + if (force_nonblock) {
> > + /* only need file table for an actual valid fd */
> > + if (open->dfd == -1 || open->dfd == AT_FDCWD)
> > + req->flags |= REQ_F_NO_FILE_TABLE;
> > + return -EAGAIN;
> > + }
> > +
> > + ret = build_open_flags(&open->how, &op);
> > + if (ret)
> > + goto err;
> > +
> > + file = do_filp_open(open->dfd, open->filename, &op);
> > + if (IS_ERR(file)) {
> > + ret = PTR_ERR(file);
> > + } else {
> > + fsnotify_open(file);
> > + ret = io_sqe_files_add_new(req->ctx, open->open_fixed_idx, file);
> > + if (ret)
> > + fput(file);
> > + }
> > +err:
> > + putname(open->filename);
> > + req->flags &= ~REQ_F_NEED_CLEANUP;
> > + if (ret < 0)
> > + req_set_fail_links(req);
> > + io_cqring_add_event(req, ret);
> > + io_put_req(req);
>
> These 2 lines are better to be replace with (since 5.9):
>
> io_req_complete(req, ret);
This was directly copied from the same code in io_openat2.
> > + return 0;
> > +}
> > +
> > static int io_openat2(struct io_kiocb *req, bool force_nonblock)
> > {
> > struct open_flags op;
> > @@ -5048,6 +5094,7 @@ static int io_req_defer_prep(struct io_kiocb *req,
> > ret = io_madvise_prep(req, sqe);
> > break;
> > case IORING_OP_OPENAT2:
> > + case IORING_OP_OPENAT2_FIXED_FILE:
> > ret = io_openat2_prep(req, sqe);
> > break;
> > case IORING_OP_EPOLL_CTL:
> > @@ -5135,6 +5182,7 @@ static void io_cleanup_req(struct io_kiocb *req)
> > break;
> > case IORING_OP_OPENAT:
> > case IORING_OP_OPENAT2:
> > + case IORING_OP_OPENAT2_FIXED_FILE:
>
> These OPENAT cases weren't doing anything, so were killed,
> as should be this line.
Makes sense.
> > break;
> > case IORING_OP_SPLICE:
> > case IORING_OP_TEE:
> > @@ -5329,12 +5377,17 @@ static int io_issue_sqe(struct io_kiocb *req, const struct io_uring_sqe *sqe,
> > ret = io_madvise(req, force_nonblock);
> > break;
> > case IORING_OP_OPENAT2:
> > + case IORING_OP_OPENAT2_FIXED_FILE:
> > if (sqe) {
> > ret = io_openat2_prep(req, sqe);
> > if (ret)
> > break;
> > }
> > - ret = io_openat2(req, force_nonblock);
> > + if (req->opcode == IORING_OP_OPENAT2) {
> > + ret = io_openat2(req, force_nonblock);
> > + } else {
> > + ret = io_openat2_fixed_file(req, force_nonblock);
> > + }
>
> We don't need all these brackets for one liners
Habit; most codebases I work on *always* include the braces.
> > --- a/include/uapi/linux/io_uring.h
> > +++ b/include/uapi/linux/io_uring.h
> > @@ -54,7 +54,10 @@ struct io_uring_sqe {
> > } __attribute__((packed));
> > /* personality to use, if used */
> > __u16 personality;
> > - __s32 splice_fd_in;
> > + union {
> > + __s32 splice_fd_in;
> > + __s32 open_fixed_idx;
> > + };
> > };
> > __u64 __pad2[3];
> > };
> > @@ -130,6 +133,7 @@ enum {
> > IORING_OP_PROVIDE_BUFFERS,
> > IORING_OP_REMOVE_BUFFERS,
> > IORING_OP_TEE,
> > + IORING_OP_OPENAT2_FIXED_FILE,
>
> I think, it's better to reuse IORING_OP_OPENAT2.
> E.g. fixed version if "open_fixed_idx != 0" or something similar.
As far as I can tell, nothing in today's handling of IORING_OP_OPENAT2
will give an EINVAL for splice_fd_in!=0. It might be possible to arrange
for it to be the same op via a new flag or something else that the
current IORING_OP_OPENAT2 wil reject (and if it's a flag or similar, all
other operations that don't involve opening a file would also need to
reject it).
