The io_uring cancelation API is async, like any other API that we expose there. For the case of finding a request to cancel, or not finding one, it is fully sync in that when submission returns, the CQE for both the cancelation request and the targeted request have been posted to the CQ ring. However, if the targeted work is being executed by io-wq, the API can only start the act of canceling it. This makes it difficult to use in some circumstances, as the caller then has to wait for the CQEs to come in and match on the same cancelation data there. Provide a IORING_REGISTER_SYNC_CANCEL command for io_uring_register() that does sync cancelations, always. For the io-wq case, it'll wait for the cancelation to come in before returning. The only expected returns from this API is: 0 Request found and canceled fine. > 0 Requests found and canceled. Only happens if asked to cancel multiple requests, and if the work wasn't in progress. -ENOENT Request not found. -ETIME A timeout on the operation was requested, but the timeout expired before we could cancel. and we won't get -EALREADY via this API. If the timeout value passed in is -1 (tv_sec and tv_nsec), then that means that no timeout is requested. Otherwise, the timespec passed in is the amount of time the sync cancel will wait for a successful cancelation. Link: https://github.com/axboe/liburing/discussions/608 Signed-off-by: Jens Axboe <axboe@xxxxxxxxx> --- include/uapi/linux/io_uring.h | 15 +++++ io_uring/cancel.c | 107 ++++++++++++++++++++++++++++++++++ io_uring/cancel.h | 2 + io_uring/io_uring.c | 6 ++ 4 files changed, 130 insertions(+) diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index d69dac9bb02c..09e7c3b13d2d 100644 --- a/include/uapi/linux/io_uring.h +++ b/include/uapi/linux/io_uring.h @@ -10,6 +10,7 @@ #include <linux/fs.h> #include <linux/types.h> +#include <linux/time_types.h> /* * IO submission data structure (Submission Queue Entry) @@ -425,6 +426,9 @@ enum { IORING_REGISTER_PBUF_RING = 22, IORING_UNREGISTER_PBUF_RING = 23, + /* sync cancelation API */ + IORING_REGISTER_SYNC_CANCEL = 24, + /* this goes last */ IORING_REGISTER_LAST }; @@ -560,4 +564,15 @@ struct io_uring_getevents_arg { __u64 ts; }; +/* + * Argument for IORING_REGISTER_SYNC_CANCEL + */ +struct io_uring_sync_cancel_reg { + __u64 addr; + __s32 fd; + __u32 flags; + struct __kernel_timespec timeout; + __u64 pad[4]; +}; + #endif diff --git a/io_uring/cancel.c b/io_uring/cancel.c index da486de07029..78b5a3088ab3 100644 --- a/io_uring/cancel.c +++ b/io_uring/cancel.c @@ -6,6 +6,7 @@ #include <linux/mm.h> #include <linux/slab.h> #include <linux/namei.h> +#include <linux/nospec.h> #include <linux/io_uring.h> #include <uapi/linux/io_uring.h> @@ -206,3 +207,109 @@ void init_hash_table(struct io_hash_table *table, unsigned size) INIT_HLIST_HEAD(&table->hbs[i].list); } } + +static int __io_sync_cancel(struct io_uring_task *tctx, + struct io_cancel_data *cd, int fd) +{ + struct io_ring_ctx *ctx = cd->ctx; + + /* fixed must be grabbed every time since we drop the uring_lock */ + if ((cd->flags & IORING_ASYNC_CANCEL_FD) && + (cd->flags & IORING_ASYNC_CANCEL_FD_FIXED)) { + unsigned long file_ptr; + + if (unlikely(fd > ctx->nr_user_files)) + return -EBADF; + fd = array_index_nospec(fd, ctx->nr_user_files); + file_ptr = io_fixed_file_slot(&ctx->file_table, fd)->file_ptr; + cd->file = (struct file *) (file_ptr & FFS_MASK); + if (!cd->file) + return -EBADF; + } + + return __io_async_cancel(cd, tctx, 0); +} + +int io_sync_cancel(struct io_ring_ctx *ctx, void __user *arg) + __must_hold(&ctx->uring_lock) +{ + struct io_cancel_data cd = { + .ctx = ctx, + .seq = atomic_inc_return(&ctx->cancel_seq), + }; + ktime_t timeout = KTIME_MAX; + struct io_uring_sync_cancel_reg sc; + struct fd f = { }; + DEFINE_WAIT(wait); + int ret; + + if (copy_from_user(&sc, arg, sizeof(sc))) + return -EFAULT; + if (sc.flags & ~CANCEL_FLAGS) + return -EINVAL; + if (sc.pad[0] || sc.pad[1] || sc.pad[2] || sc.pad[3]) + return -EINVAL; + + cd.data = sc.addr; + cd.flags = sc.flags; + + /* we can grab a normal file descriptor upfront */ + if ((cd.flags & IORING_ASYNC_CANCEL_FD) && + !(cd.flags & IORING_ASYNC_CANCEL_FD_FIXED)) { + f = fdget(sc.fd); + if (!f.file) + return -EBADF; + cd.file = f.file; + } + + ret = __io_sync_cancel(current->io_uring, &cd, sc.fd); + + /* found something, done! */ + if (ret != -EALREADY) + goto out; + + if (sc.timeout.tv_sec != -1UL || sc.timeout.tv_nsec != -1UL) { + struct timespec64 ts = { + .tv_sec = sc.timeout.tv_sec, + .tv_nsec = sc.timeout.tv_nsec + }; + + timeout = ktime_add_ns(timespec64_to_ktime(ts), ktime_get_ns()); + } + + /* + * Keep looking until we get -ENOENT. we'll get woken everytime + * every time a request completes and will retry the cancelation. + */ + do { + cd.seq = atomic_inc_return(&ctx->cancel_seq), + + prepare_to_wait(&ctx->cq_wait, &wait, TASK_INTERRUPTIBLE); + + ret = __io_sync_cancel(current->io_uring, &cd, sc.fd); + + if (ret != -EALREADY) + break; + + mutex_unlock(&ctx->uring_lock); + ret = io_run_task_work_sig(); + if (ret < 0) { + mutex_lock(&ctx->uring_lock); + break; + } + ret = schedule_hrtimeout(&timeout, HRTIMER_MODE_ABS); + mutex_lock(&ctx->uring_lock); + if (!ret) { + ret = -ETIME; + break; + } + } while (1); + + finish_wait(&ctx->cq_wait, &wait); + + if (ret == -ENOENT || ret > 0) + ret = 0; +out: + fdput(f); + return ret; +} diff --git a/io_uring/cancel.h b/io_uring/cancel.h index 1bc7e917ce94..6a59ee484d0c 100644 --- a/io_uring/cancel.h +++ b/io_uring/cancel.h @@ -19,3 +19,5 @@ int io_async_cancel(struct io_kiocb *req, unsigned int issue_flags); int io_try_cancel(struct io_uring_task *tctx, struct io_cancel_data *cd, unsigned int issue_flags); void init_hash_table(struct io_hash_table *table, unsigned size); + +int io_sync_cancel(struct io_ring_ctx *ctx, void __user *arg); diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 430e65494989..8abb841e424d 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -3911,6 +3911,12 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode, break; ret = io_unregister_pbuf_ring(ctx, arg); break; + case IORING_REGISTER_SYNC_CANCEL: + ret = -EINVAL; + if (!arg || nr_args != 1) + break; + ret = io_sync_cancel(ctx, arg); + break; default: ret = -EINVAL; break; -- 2.35.1
