On Tue, Sep 08, 2020 at 07:57:08AM -0600, Jens Axboe wrote: > On 9/8/20 7:44 AM, Stefano Garzarella wrote: > > Hi Jens, > > > > On Thu, Aug 27, 2020 at 04:58:31PM +0200, Stefano Garzarella wrote: > >> This patch adds a new IORING_SETUP_R_DISABLED flag to start the > >> rings disabled, allowing the user to register restrictions, > >> buffers, files, before to start processing SQEs. > >> > >> When IORING_SETUP_R_DISABLED is set, SQE are not processed and > >> SQPOLL kthread is not started. > >> > >> The restrictions registration are allowed only when the rings > >> are disable to prevent concurrency issue while processing SQEs. > >> > >> The rings can be enabled using IORING_REGISTER_ENABLE_RINGS > >> opcode with io_uring_register(2). > >> > >> Suggested-by: Jens Axboe <[email protected]> > >> Reviewed-by: Kees Cook <[email protected]> > >> Signed-off-by: Stefano Garzarella <[email protected]> > >> --- > >> v4: > >> - fixed io_uring_enter() exit path when ring is disabled > >> > >> v3: > >> - enabled restrictions only when the rings start > >> > >> RFC v2: > >> - removed return value of io_sq_offload_start() > >> --- > >> fs/io_uring.c | 52 ++++++++++++++++++++++++++++++----- > >> include/uapi/linux/io_uring.h | 2 ++ > >> 2 files changed, 47 insertions(+), 7 deletions(-) > >> > >> diff --git a/fs/io_uring.c b/fs/io_uring.c > >> index 5f62997c147b..b036f3373fbe 100644 > >> --- a/fs/io_uring.c > >> +++ b/fs/io_uring.c > >> @@ -226,6 +226,7 @@ struct io_restriction { > >> DECLARE_BITMAP(sqe_op, IORING_OP_LAST); > >> u8 sqe_flags_allowed; > >> u8 sqe_flags_required; > >> + bool registered; > >> }; > >> > >> struct io_ring_ctx { > >> @@ -7497,8 +7498,8 @@ static int io_init_wq_offload(struct io_ring_ctx > >> *ctx, > >> return ret; > >> } > >> > >> -static int io_sq_offload_start(struct io_ring_ctx *ctx, > >> - struct io_uring_params *p) > >> +static int io_sq_offload_create(struct io_ring_ctx *ctx, > >> + struct io_uring_params *p) > >> { > >> int ret; > >> > >> @@ -7532,7 +7533,6 @@ static int io_sq_offload_start(struct io_ring_ctx > >> *ctx, > >> ctx->sqo_thread = NULL; > >> goto err; > >> } > >> - wake_up_process(ctx->sqo_thread); > >> } else if (p->flags & IORING_SETUP_SQ_AFF) { > >> /* Can't have SQ_AFF without SQPOLL */ > >> ret = -EINVAL; > >> @@ -7549,6 +7549,12 @@ static int io_sq_offload_start(struct io_ring_ctx > >> *ctx, > >> return ret; > >> } > >> > >> +static void io_sq_offload_start(struct io_ring_ctx *ctx) > >> +{ > >> + if ((ctx->flags & IORING_SETUP_SQPOLL) && ctx->sqo_thread) > >> + wake_up_process(ctx->sqo_thread); > >> +} > >> + > >> static inline void __io_unaccount_mem(struct user_struct *user, > >> unsigned long nr_pages) > >> { > >> @@ -8295,6 +8301,9 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, > >> u32, to_submit, > >> if (!percpu_ref_tryget(&ctx->refs)) > >> goto out_fput; > >> > >> + if (ctx->flags & IORING_SETUP_R_DISABLED) > >> + goto out_fput; > >> + > > > > While writing the man page paragraph, I discovered that if the rings are > > disabled I returned ENXIO error in io_uring_enter(), coming from the > > previous > > check. > > > > I'm not sure it is the best one, maybe I can return EBADFD or another > > error. > > > > What do you suggest? > > EBADFD seems indeed the most appropriate - the fd is valid, but not in the > right state to do this.
Yeah, the same interpretation as mine! Also, in io_uring_register() I'm returning EINVAL if the rings are not disabled and the user wants to register restrictions. Maybe also in this case I can return EBADFD. I'll send a patch with the fixes. Thanks, Stefano
