| Message ID | 20230911204021.1479172-4-axboe@kernel.dk (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add support for multishot reads | expand |
Jens Axboe <axboe@kernel.dk> writes: > This behaves like IORING_OP_READ, except: > > 1) It only supports pollable files (eg pipes, sockets, etc). Note that > for sockets, you probably want to use recv/recvmsg with multishot > instead. > > 2) It supports multishot mode, meaning it will repeatedly trigger a > read and fill a buffer when data is available. This allows similar > use to recv/recvmsg but on non-sockets, where a single request will > repeatedly post a CQE whenever data is read from it. > > 3) Because of #2, it must be used with provided buffers. This is > uniformly true across any request type that supports multishot and > transfers data, with the reason being that it's obviously not > possible to pass in a single buffer for the data, as multiple reads > may very well trigger before an application has a chance to process > previous CQEs and the data passed from them. > > Signed-off-by: Jens Axboe <axboe@kernel.dk> This is a really cool feature. Just two comments inline. > +/* > + * Multishot read is prepared just like a normal read/write request, only > + * difference is that we set the MULTISHOT flag. > + */ > +int io_read_mshot_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) > +{ > + int ret; > + > + ret = io_prep_rw(req, sqe); > + if (unlikely(ret)) > + return ret; > + > + req->flags |= REQ_F_APOLL_MULTISHOT; > + return 0; > +} > + > void io_readv_writev_cleanup(struct io_kiocb *req) > { > struct io_async_rw *io = req->async_data; > @@ -869,6 +885,56 @@ int io_read(struct io_kiocb *req, unsigned int issue_flags) > return kiocb_done(req, ret, issue_flags); > } > > +int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags) > +{ > + unsigned int cflags = 0; > + int ret; > + > + /* > + * Multishot MUST be used on a pollable file > + */ > + if (!file_can_poll(req->file)) > + return -EBADFD; io_uring is pollable, so I think you want to also reject when req->file->f_ops == io_uring_fops to avoid the loop where a ring monitoring itself will cause a recursive completion? Maybe this can't happen here for some reason I miss? > + > + ret = __io_read(req, issue_flags); > + > + /* > + * If we get -EAGAIN, recycle our buffer and just let normal poll > + * handling arm it. > + */ > + if (ret == -EAGAIN) { > + io_kbuf_recycle(req, issue_flags); > + return -EAGAIN; > + } > + > + /* > + * Any error will terminate a multishot request > + */ > + if (ret <= 0) { > +finish: > + io_req_set_res(req, ret, cflags); > + if (issue_flags & IO_URING_F_MULTISHOT) > + return IOU_STOP_MULTISHOT; > + return IOU_OK; Just a style detail, but I'd prefer to unfold this on the end of the function instead of jumping backwards here.. > + } > + > + /* > + * Put our buffer and post a CQE. If we fail to post a CQE, then > + * jump to the termination path. This request is then done. > + */ > + cflags = io_put_kbuf(req, issue_flags); > + > + if (io_fill_cqe_req_aux(req, issue_flags & IO_URING_F_COMPLETE_DEFER, > + ret, cflags | IORING_CQE_F_MORE)) { > + if (issue_flags & IO_URING_F_MULTISHOT) > + return IOU_ISSUE_SKIP_COMPLETE; > + else > + return -EAGAIN; > + } > + > + goto finish; > +} > + > int io_write(struct io_kiocb *req, unsigned int issue_flags) > { > struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw); > diff --git a/io_uring/rw.h b/io_uring/rw.h > index 4b89f9659366..c5aed03d42a4 100644 > --- a/io_uring/rw.h > +++ b/io_uring/rw.h > @@ -23,3 +23,5 @@ int io_writev_prep_async(struct io_kiocb *req); > void io_readv_writev_cleanup(struct io_kiocb *req); > void io_rw_fail(struct io_kiocb *req); > void io_req_rw_complete(struct io_kiocb *req, struct io_tw_state *ts); > +int io_read_mshot_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe); > +int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags);
Jens Axboe <axboe@kernel.dk> writes: > This behaves like IORING_OP_READ, except: > > 1) It only supports pollable files (eg pipes, sockets, etc). Note that > for sockets, you probably want to use recv/recvmsg with multishot > instead. > > 2) It supports multishot mode, meaning it will repeatedly trigger a > read and fill a buffer when data is available. This allows similar > use to recv/recvmsg but on non-sockets, where a single request will > repeatedly post a CQE whenever data is read from it. > > 3) Because of #2, it must be used with provided buffers. This is > uniformly true across any request type that supports multishot and > transfers data, with the reason being that it's obviously not > possible to pass in a single buffer for the data, as multiple reads > may very well trigger before an application has a chance to process > previous CQEs and the data passed from them. > > Signed-off-by: Jens Axboe <axboe@kernel.dk> > --- > include/uapi/linux/io_uring.h | 1 + > io_uring/opdef.c | 13 +++++++ > io_uring/rw.c | 66 +++++++++++++++++++++++++++++++++++ > io_uring/rw.h | 2 ++ > 4 files changed, 82 insertions(+) > > diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h > index daa363d1a502..c35438af679a 100644 > --- a/include/uapi/linux/io_uring.h > +++ b/include/uapi/linux/io_uring.h > @@ -246,6 +246,7 @@ enum io_uring_op { > IORING_OP_FUTEX_WAIT, > IORING_OP_FUTEX_WAKE, > IORING_OP_FUTEX_WAITV, > + IORING_OP_READ_MULTISHOT, > > /* this goes last, obviously */ > IORING_OP_LAST, > diff --git a/io_uring/opdef.c b/io_uring/opdef.c > index bfb7c53389c0..03e1a6f26fa5 100644 > --- a/io_uring/opdef.c > +++ b/io_uring/opdef.c > @@ -460,6 +460,16 @@ const struct io_issue_def io_issue_defs[] = { > .prep = io_eopnotsupp_prep, > #endif > }, > + [IORING_OP_READ_MULTISHOT] = { > + .needs_file = 1, > + .unbound_nonreg_file = 1, > + .pollin = 1, > + .buffer_select = 1, > + .audit_skip = 1, > + .ioprio = 1, > + .prep = io_read_mshot_prep, > + .issue = io_read_mshot, > + }, > }; > > const struct io_cold_def io_cold_defs[] = { > @@ -692,6 +702,9 @@ const struct io_cold_def io_cold_defs[] = { > [IORING_OP_FUTEX_WAITV] = { > .name = "FUTEX_WAITV", > }, > + [IORING_OP_READ_MULTISHOT] = { > + .name = "READ_MULTISHOT", > + }, > }; > > const char *io_uring_get_opcode(u8 opcode) > diff --git a/io_uring/rw.c b/io_uring/rw.c > index c3bf38419230..7305792fbbbf 100644 > --- a/io_uring/rw.c > +++ b/io_uring/rw.c > @@ -123,6 +123,22 @@ int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe) > return 0; > } > > +/* > + * Multishot read is prepared just like a normal read/write request, only > + * difference is that we set the MULTISHOT flag. > + */ > +int io_read_mshot_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) > +{ > + int ret; > + > + ret = io_prep_rw(req, sqe); > + if (unlikely(ret)) > + return ret; > + > + req->flags |= REQ_F_APOLL_MULTISHOT; > + return 0; > +} > + > void io_readv_writev_cleanup(struct io_kiocb *req) > { > struct io_async_rw *io = req->async_data; > @@ -869,6 +885,56 @@ int io_read(struct io_kiocb *req, unsigned int issue_flags) > return kiocb_done(req, ret, issue_flags); > } > > +int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags) > +{ > + unsigned int cflags = 0; > + int ret; > + > + /* > + * Multishot MUST be used on a pollable file > + */ > + if (!file_can_poll(req->file)) > + return -EBADFD; > + Please disregard my previous comment about checking for io_uring_fops. It is not necessary because this kind of file can't be read in the first place, so it would never get here. (Also, things seems to be misbehaving on my MUA archive and Lore didn't get my own message yet, so I'm not replying directly to it)
On 9/11/23 5:57 PM, Gabriel Krisman Bertazi wrote: >> +int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags) >> +{ >> + unsigned int cflags = 0; >> + int ret; >> + >> + /* >> + * Multishot MUST be used on a pollable file >> + */ >> + if (!file_can_poll(req->file)) >> + return -EBADFD; > > io_uring is pollable, so I think you want to also reject when > req->file->f_ops == io_uring_fops to avoid the loop where a ring > monitoring itself will cause a recursive completion? Maybe this can't > happen here for some reason I miss? I saw your followup, but we do actually handle that case - if this fd is an io_uring context, then we track the inflight state of it so we can appropriately cancel to break that loop. But yeah, doesn't matter for this case, as you cannot read or write to an io_uring fd in the first place. >> + ret = __io_read(req, issue_flags); >> + >> + /* >> + * If we get -EAGAIN, recycle our buffer and just let normal poll >> + * handling arm it. >> + */ >> + if (ret == -EAGAIN) { >> + io_kbuf_recycle(req, issue_flags); >> + return -EAGAIN; >> + } >> + >> + /* >> + * Any error will terminate a multishot request >> + */ >> + if (ret <= 0) { >> +finish: >> + io_req_set_res(req, ret, cflags); >> + if (issue_flags & IO_URING_F_MULTISHOT) >> + return IOU_STOP_MULTISHOT; >> + return IOU_OK; > > Just a style detail, but I'd prefer to unfold this on the end of the function > instead of jumping backwards here.. Sure, that might look better. I'll make the edit.
On 9/11/23 6:38 PM, Gabriel Krisman Bertazi wrote: > (Also, things seems to be misbehaving on my MUA archive and Lore didn't > get my own message yet, so I'm not replying directly to it) I'm having all sorts of delays too, both last week and this week... Pretty unfortunate for probably the most core of kernel development infrastructure.
On 9/11/23 6:46 PM, Jens Axboe wrote: >>> + ret = __io_read(req, issue_flags); >>> + >>> + /* >>> + * If we get -EAGAIN, recycle our buffer and just let normal poll >>> + * handling arm it. >>> + */ >>> + if (ret == -EAGAIN) { >>> + io_kbuf_recycle(req, issue_flags); >>> + return -EAGAIN; >>> + } >>> + >>> + /* >>> + * Any error will terminate a multishot request >>> + */ >>> + if (ret <= 0) { >>> +finish: >>> + io_req_set_res(req, ret, cflags); >>> + if (issue_flags & IO_URING_F_MULTISHOT) >>> + return IOU_STOP_MULTISHOT; >>> + return IOU_OK; >> >> Just a style detail, but I'd prefer to unfold this on the end of the >> function instead of jumping backwards here.. > > Sure, that might look better. I'll make the edit. Actually we can just indent the next case and get rid of the goto completely: int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags) { unsigned int cflags = 0; int ret; /* * Multishot MUST be used on a pollable file */ if (!file_can_poll(req->file)) return -EBADFD; ret = __io_read(req, issue_flags); /* * If we get -EAGAIN, recycle our buffer and just let normal poll * handling arm it. */ if (ret == -EAGAIN) { io_kbuf_recycle(req, issue_flags); return -EAGAIN; } /* * Any successful return value will keep the multishot read armed. */ if (ret > 0) { /* * Put our buffer and post a CQE. If we fail to post a CQE, then * jump to the termination path. This request is then done. */ cflags = io_put_kbuf(req, issue_flags); if (io_fill_cqe_req_aux(req, issue_flags & IO_URING_F_COMPLETE_DEFER, ret, cflags | IORING_CQE_F_MORE)) { if (issue_flags & IO_URING_F_MULTISHOT) return IOU_ISSUE_SKIP_COMPLETE; return -EAGAIN; } } /* * Either an error, or we've hit overflow posting the CQE. For any * multishot request, hitting overflow will terminate it. */ io_req_set_res(req, ret, cflags); if (issue_flags & IO_URING_F_MULTISHOT) return IOU_STOP_MULTISHOT; return IOU_OK; }
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index daa363d1a502..c35438af679a 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -246,6 +246,7 @@ enum io_uring_op { IORING_OP_FUTEX_WAIT, IORING_OP_FUTEX_WAKE, IORING_OP_FUTEX_WAITV, + IORING_OP_READ_MULTISHOT, /* this goes last, obviously */ IORING_OP_LAST, diff --git a/io_uring/opdef.c b/io_uring/opdef.c index bfb7c53389c0..03e1a6f26fa5 100644 --- a/io_uring/opdef.c +++ b/io_uring/opdef.c @@ -460,6 +460,16 @@ const struct io_issue_def io_issue_defs[] = { .prep = io_eopnotsupp_prep, #endif }, + [IORING_OP_READ_MULTISHOT] = { + .needs_file = 1, + .unbound_nonreg_file = 1, + .pollin = 1, + .buffer_select = 1, + .audit_skip = 1, + .ioprio = 1, + .prep = io_read_mshot_prep, + .issue = io_read_mshot, + }, }; const struct io_cold_def io_cold_defs[] = { @@ -692,6 +702,9 @@ const struct io_cold_def io_cold_defs[] = { [IORING_OP_FUTEX_WAITV] = { .name = "FUTEX_WAITV", }, + [IORING_OP_READ_MULTISHOT] = { + .name = "READ_MULTISHOT", + }, }; const char *io_uring_get_opcode(u8 opcode) diff --git a/io_uring/rw.c b/io_uring/rw.c index c3bf38419230..7305792fbbbf 100644 --- a/io_uring/rw.c +++ b/io_uring/rw.c @@ -123,6 +123,22 @@ int io_prep_rw(struct io_kiocb *req, const struct io_uring_sqe *sqe) return 0; } +/* + * Multishot read is prepared just like a normal read/write request, only + * difference is that we set the MULTISHOT flag. + */ +int io_read_mshot_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) +{ + int ret; + + ret = io_prep_rw(req, sqe); + if (unlikely(ret)) + return ret; + + req->flags |= REQ_F_APOLL_MULTISHOT; + return 0; +} + void io_readv_writev_cleanup(struct io_kiocb *req) { struct io_async_rw *io = req->async_data; @@ -869,6 +885,56 @@ int io_read(struct io_kiocb *req, unsigned int issue_flags) return kiocb_done(req, ret, issue_flags); } +int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags) +{ + unsigned int cflags = 0; + int ret; + + /* + * Multishot MUST be used on a pollable file + */ + if (!file_can_poll(req->file)) + return -EBADFD; + + ret = __io_read(req, issue_flags); + + /* + * If we get -EAGAIN, recycle our buffer and just let normal poll + * handling arm it. + */ + if (ret == -EAGAIN) { + io_kbuf_recycle(req, issue_flags); + return -EAGAIN; + } + + /* + * Any error will terminate a multishot request + */ + if (ret <= 0) { +finish: + io_req_set_res(req, ret, cflags); + if (issue_flags & IO_URING_F_MULTISHOT) + return IOU_STOP_MULTISHOT; + return IOU_OK; + } + + /* + * Put our buffer and post a CQE. If we fail to post a CQE, then + * jump to the termination path. This request is then done. + */ + cflags = io_put_kbuf(req, issue_flags); + + if (io_fill_cqe_req_aux(req, issue_flags & IO_URING_F_COMPLETE_DEFER, + ret, cflags | IORING_CQE_F_MORE)) { + if (issue_flags & IO_URING_F_MULTISHOT) + return IOU_ISSUE_SKIP_COMPLETE; + else + return -EAGAIN; + } + + goto finish; +} + int io_write(struct io_kiocb *req, unsigned int issue_flags) { struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw); diff --git a/io_uring/rw.h b/io_uring/rw.h index 4b89f9659366..c5aed03d42a4 100644 --- a/io_uring/rw.h +++ b/io_uring/rw.h @@ -23,3 +23,5 @@ int io_writev_prep_async(struct io_kiocb *req); void io_readv_writev_cleanup(struct io_kiocb *req); void io_rw_fail(struct io_kiocb *req); void io_req_rw_complete(struct io_kiocb *req, struct io_tw_state *ts); +int io_read_mshot_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe); +int io_read_mshot(struct io_kiocb *req, unsigned int issue_flags);
This behaves like IORING_OP_READ, except: 1) It only supports pollable files (eg pipes, sockets, etc). Note that for sockets, you probably want to use recv/recvmsg with multishot instead. 2) It supports multishot mode, meaning it will repeatedly trigger a read and fill a buffer when data is available. This allows similar use to recv/recvmsg but on non-sockets, where a single request will repeatedly post a CQE whenever data is read from it. 3) Because of #2, it must be used with provided buffers. This is uniformly true across any request type that supports multishot and transfers data, with the reason being that it's obviously not possible to pass in a single buffer for the data, as multiple reads may very well trigger before an application has a chance to process previous CQEs and the data passed from them. Signed-off-by: Jens Axboe <axboe@kernel.dk> --- include/uapi/linux/io_uring.h | 1 + io_uring/opdef.c | 13 +++++++ io_uring/rw.c | 66 +++++++++++++++++++++++++++++++++++ io_uring/rw.h | 2 ++ 4 files changed, 82 insertions(+)