// SPDX-License-Identifier: MIT // Copyright (c) 2015-2020 Zig Contributors // This file is part of [zig](https://ziglang.org/), which is MIT licensed. // The MIT license requires this copyright notice to be included in all copies // and substantial portions of the software. const std = @import("../../std.zig"); const assert = std.debug.assert; const builtin = std.builtin; const mem = std.mem; const net = std.net; const os = std.os; const linux = os.linux; const testing = std.testing; const io_uring_params = linux.io_uring_params; const io_uring_sqe = linux.io_uring_sqe; const io_uring_cqe = linux.io_uring_cqe; pub const IO_Uring = struct { fd: os.fd_t = -1, sq: SubmissionQueue, cq: CompletionQueue, flags: u32, features: u32, /// A friendly way to setup an io_uring, with default io_uring_params. /// `entries` must be a power of two between 1 and 4096, although the kernel will make the final /// call on how many entries the submission and completion queues will ultimately have, /// see https://github.com/torvalds/linux/blob/v5.8/fs/io_uring.c#L8027-L8050. /// Matches the interface of io_uring_queue_init() in liburing. pub fn init(entries: u12, flags: u32) !IO_Uring { var params = mem.zeroInit(io_uring_params, .{ .flags = flags, .sq_thread_idle = 1000 }); return try IO_Uring.init_params(entries, ¶ms); } /// A powerful way to setup an io_uring, if you want to tweak io_uring_params such as submission /// queue thread cpu affinity or thread idle timeout (the kernel and our default is 1 second). /// `params` is passed by reference because the kernel needs to modify the parameters. /// You may only set the `flags`, `sq_thread_cpu` and `sq_thread_idle` parameters. /// Every other parameter belongs to the kernel and must be zeroed. /// Matches the interface of io_uring_queue_init_params() in liburing. pub fn init_params(entries: u12, p: *io_uring_params) !IO_Uring { if (entries == 0) return error.EntriesZero; if (!std.math.isPowerOfTwo(entries)) return error.EntriesNotPowerOfTwo; assert(p.sq_entries == 0); assert(p.cq_entries == 0); assert(p.features == 0); assert(p.wq_fd == 0); assert(p.resv[0] == 0); assert(p.resv[1] == 0); assert(p.resv[2] == 0); const res = linux.io_uring_setup(entries, p); switch (linux.getErrno(res)) { 0 => {}, linux.EFAULT => return error.ParamsOutsideAccessibleAddressSpace, // The resv array contains non-zero data, p.flags contains an unsupported flag, // entries out of bounds, IORING_SETUP_SQ_AFF was specified without IORING_SETUP_SQPOLL, // or IORING_SETUP_CQSIZE was specified but io_uring_params.cq_entries was invalid: linux.EINVAL => return error.ArgumentsInvalid, linux.EMFILE => return error.ProcessFdQuotaExceeded, linux.ENFILE => return error.SystemFdQuotaExceeded, linux.ENOMEM => return error.SystemResources, // IORING_SETUP_SQPOLL was specified but effective user ID lacks sufficient privileges, // or a container seccomp policy prohibits io_uring syscalls: linux.EPERM => return error.PermissionDenied, linux.ENOSYS => return error.SystemOutdated, else => |errno| return os.unexpectedErrno(errno) } const fd = @intCast(os.fd_t, res); assert(fd >= 0); errdefer os.close(fd); // Kernel versions 5.4 and up use only one mmap() for the submission and completion queues. // This is not an optional feature for us... if the kernel does it, we have to do it. // The thinking on this by the kernel developers was that both the submission and the // completion queue rings have sizes just over a power of two, but the submission queue ring // is significantly smaller with u32 slots. By bundling both in a single mmap, the kernel // gets the submission queue ring for free. // See https://patchwork.kernel.org/patch/11115257 for the kernel patch. // We do not support the double mmap() done before 5.4, because we want to keep the // init/deinit mmap paths simple and because io_uring has had many bug fixes even since 5.4. if ((p.features & linux.IORING_FEAT_SINGLE_MMAP) == 0) { return error.SystemOutdated; } // Check that the kernel has actually set params and that "impossible is nothing". assert(p.sq_entries != 0); assert(p.cq_entries != 0); assert(p.cq_entries >= p.sq_entries); // From here on, we only need to read from params, so pass `p` by value as immutable. // The completion queue shares the mmap with the submission queue, so pass `sq` there too. var sq = try SubmissionQueue.init(fd, p.*); errdefer sq.deinit(); var cq = try CompletionQueue.init(fd, p.*, sq); errdefer cq.deinit(); // Check that our starting state is as we expect. assert(sq.head.* == 0); assert(sq.tail.* == 0); assert(sq.mask == p.sq_entries - 1); // Allow flags.* to be non-zero, since the kernel may set IORING_SQ_NEED_WAKEUP at any time. assert(sq.dropped.* == 0); assert(sq.array.len == p.sq_entries); assert(sq.sqes.len == p.sq_entries); assert(sq.sqe_head == 0); assert(sq.sqe_tail == 0); assert(cq.head.* == 0); assert(cq.tail.* == 0); assert(cq.mask == p.cq_entries - 1); assert(cq.overflow.* == 0); assert(cq.cqes.len == p.cq_entries); return IO_Uring { .fd = fd, .sq = sq, .cq = cq, .flags = p.flags, .features = p.features }; } pub fn deinit(self: *IO_Uring) void { assert(self.fd >= 0); // The mmaps depend on the fd, so the order of these calls is important: self.cq.deinit(); self.sq.deinit(); os.close(self.fd); self.fd = -1; } /// Returns a pointer to a vacant SQE, or an error if the submission queue is full. /// We follow the implementation (and atomics) of liburing's `io_uring_get_sqe()` exactly. /// However, instead of a null we return an error to force safe handling. /// Any situation where the submission queue is full tends more towards a control flow error, /// and the null return in liburing is more a C idiom than anything else, for lack of a better /// alternative. In Zig, we have first-class error handling... so let's use it. /// Matches the implementation of io_uring_get_sqe() in liburing. pub fn get_sqe(self: *IO_Uring) !*io_uring_sqe { const head = @atomicLoad(u32, self.sq.head, .Acquire); // Remember that these head and tail offsets wrap around every four billion operations. // We must therefore use wrapping addition and subtraction to avoid a runtime crash. const next = self.sq.sqe_tail +% 1; if (next -% head > self.sq.sqes.len) return error.SubmissionQueueFull; var sqe = &self.sq.sqes[self.sq.sqe_tail & self.sq.mask]; self.sq.sqe_tail = next; return sqe; } /// Submits the SQEs acquired via get_sqe() to the kernel. You can call this once after you have /// called get_sqe() multiple times to setup multiple I/O requests. /// Returns the number of SQEs submitted. /// Matches the implementation of io_uring_submit() in liburing. pub fn submit(self: *IO_Uring) !u32 { return self.submit_and_wait(0); } /// Like submit(), but allows waiting for events as well. /// Returns the number of SQEs submitted. /// Matches the implementation of io_uring_submit_and_wait() in liburing. pub fn submit_and_wait(self: *IO_Uring, wait_nr: u32) !u32 { var submitted = self.flush_sq(); var flags: u32 = 0; if (self.sq_ring_needs_enter(submitted, &flags) or wait_nr > 0) { if (wait_nr > 0 or (self.flags & linux.IORING_SETUP_IOPOLL) != 0) { flags |= linux.IORING_ENTER_GETEVENTS; } return try self.enter(submitted, wait_nr, flags); } return submitted; } /// Tell the kernel we have submitted SQEs and/or want to wait for CQEs. /// Returns the number of SQEs submitted. pub fn enter(self: *IO_Uring, to_submit: u32, min_complete: u32, flags: u32) !u32 { assert(self.fd >= 0); const res = linux.io_uring_enter(self.fd, to_submit, min_complete, flags, null); switch (linux.getErrno(res)) { 0 => {}, // The kernel was unable to allocate memory or ran out of resources for the request. // The application should wait for some completions and try again: linux.EAGAIN => return error.SystemResources, // The SQE `fd` is invalid, or IOSQE_FIXED_FILE was set but no files were registered: linux.EBADF => return error.FileDescriptorInvalid, // The file descriptor is valid, but the ring is not in the right state. // See io_uring_register(2) for how to enable the ring. linux.EBADFD => return error.FileDescriptorInBadState, // The application attempted to overcommit the number of requests it can have pending. // The application should wait for some completions and try again: linux.EBUSY => return error.CompletionQueueOvercommitted, // The SQE is invalid, or valid but the ring was setup with IORING_SETUP_IOPOLL: linux.EINVAL => return error.SubmissionQueueEntryInvalid, // The buffer is outside the process' accessible address space, or IORING_OP_READ_FIXED // or IORING_OP_WRITE_FIXED was specified but no buffers were registered, or the range // described by `addr` and `len` is not within the buffer registered at `buf_index`: linux.EFAULT => return error.BufferInvalid, linux.ENXIO => return error.RingShuttingDown, // The kernel believes our `self.fd` does not refer to an io_uring instance, // or the opcode is valid but not supported by this kernel (more likely): linux.EOPNOTSUPP => return error.OpcodeNotSupported, // The operation was interrupted by a delivery of a signal before it could complete. // This can happen while waiting for events with IORING_ENTER_GETEVENTS: linux.EINTR => return error.SignalInterrupt, else => |errno| return os.unexpectedErrno(errno) } return @intCast(u32, res); } /// Sync internal state with kernel ring state on the SQ side. /// Returns the number of all pending events in the SQ ring, for the shared ring. /// This return value includes previously flushed SQEs, as per liburing. /// The rationale is to suggest that an io_uring_enter() call is needed rather than not. /// Matches the implementation of __io_uring_flush_sq() in liburing. pub fn flush_sq(self: *IO_Uring) u32 { if (self.sq.sqe_head != self.sq.sqe_tail) { // Fill in SQEs that we have queued up, adding them to the kernel ring. const to_submit = self.sq.sqe_tail -% self.sq.sqe_head; var tail = self.sq.tail.*; var i: usize = 0; while (i < to_submit) : (i += 1) { self.sq.array[tail & self.sq.mask] = self.sq.sqe_head & self.sq.mask; tail +%= 1; self.sq.sqe_head +%= 1; } // Ensure that the kernel can actually see the SQE updates when it sees the tail update. @atomicStore(u32, self.sq.tail, tail, .Release); } return self.sq_ready(); } /// Returns true if we are not using an SQ thread (thus nobody submits but us), /// or if IORING_SQ_NEED_WAKEUP is set and the SQ thread must be explicitly awakened. /// For the latter case, we set the SQ thread wakeup flag. /// Matches the implementation of sq_ring_needs_enter() in liburing. pub fn sq_ring_needs_enter(self: *IO_Uring, submitted: u32, flags: *u32) bool { assert(flags.* == 0); if ((self.flags & linux.IORING_SETUP_SQPOLL) == 0 and submitted > 0) return true; if ((@atomicLoad(u32, self.sq.flags, .Unordered) & linux.IORING_SQ_NEED_WAKEUP) != 0) { flags.* |= linux.IORING_ENTER_SQ_WAKEUP; return true; } return false; } /// Returns the number of flushed and unflushed SQEs pending in the submission queue. /// In other words, this is the number of SQEs in the submission queue, i.e. its length. /// These are SQEs that the kernel is yet to consume. /// Matches the implementation of io_uring_sq_ready in liburing. pub fn sq_ready(self: *IO_Uring) u32 { // Always use the shared ring state (i.e. head and not sqe_head) to avoid going out of sync, // see https://github.com/axboe/liburing/issues/92. return self.sq.sqe_tail -% @atomicLoad(u32, self.sq.head, .Acquire); } /// Returns the number of CQEs in the completion queue, i.e. its length. /// These are CQEs that the application is yet to consume. /// Matches the implementation of io_uring_cq_ready in liburing. pub fn cq_ready(self: *IO_Uring) u32 { return @atomicLoad(u32, self.cq.tail, .Acquire) -% self.cq.head.*; } /// Copies as many CQEs as are ready, and that can fit into the destination `cqes` slice. /// If none are available, enters into the kernel to wait for at most `wait_nr` CQEs. /// Returns the number of CQEs copied, advancing the CQ ring. /// Provides all the wait/peek methods found in liburing, but with batching and a single method. /// The rationale for copying CQEs rather than copying pointers is that pointers are 8 bytes /// whereas CQEs are not much more at only 16 bytes, and this provides a safer faster interface. /// Safer, because you no longer need to call cqe_seen(), avoiding idempotency bugs. /// Faster, because we can now amortize the atomic store release to `cq.head` across the batch. /// See https://github.com/axboe/liburing/issues/103#issuecomment-686665007. /// Matches the implementation of io_uring_peek_batch_cqe() in liburing, but supports waiting. pub fn copy_cqes(self: *IO_Uring, cqes: []io_uring_cqe, wait_nr: u32) !u32 { const count = self.copy_cqes_ready(cqes, wait_nr); if (count > 0) return count; if (self.cq_ring_needs_flush() or wait_nr > 0) { _ = try self.enter(0, wait_nr, linux.IORING_ENTER_GETEVENTS); return self.copy_cqes_ready(cqes, wait_nr); } return 0; } fn copy_cqes_ready(self: *IO_Uring, cqes: []io_uring_cqe, wait_nr: u32) u32 { const ready = self.cq_ready(); const count = std.math.min(cqes.len, ready); var head = self.cq.head.*; var tail = head +% count; // TODO Optimize this by using 1 or 2 memcpy's (if the tail wraps) rather than a loop. var i: usize = 0; // Do not use "less-than" operator since head and tail may wrap: while (head != tail) { cqes[i] = self.cq.cqes[head & self.cq.mask]; // Copy struct by value. head +%= 1; i += 1; } self.cq_advance(count); return count; } /// Returns a copy of an I/O completion, waiting for it if necessary, and advancing the CQ ring. /// A convenience method for `copy_cqes()` for when you don't need to batch or peek. pub fn copy_cqe(ring: *IO_Uring) !io_uring_cqe { var cqes: [1]io_uring_cqe = undefined; const count = try ring.copy_cqes(&cqes, 1); assert(count == 1); return cqes[0]; } /// Matches the implementation of cq_ring_needs_flush() in liburing. pub fn cq_ring_needs_flush(self: *IO_Uring) bool { return (@atomicLoad(u32, self.sq.flags, .Unordered) & linux.IORING_SQ_CQ_OVERFLOW) != 0; } /// For advanced use cases only that implement custom completion queue methods. /// If you use copy_cqes() or copy_cqe() you must not call cqe_seen() or cq_advance(). /// Must be called exactly once after a zero-copy CQE has been processed by your application. /// Not idempotent, calling more than once will result in other CQEs being lost. /// Matches the implementation of cqe_seen() in liburing. pub fn cqe_seen(self: *IO_Uring, cqe: *io_uring_cqe) void { self.cq_advance(1); } /// For advanced use cases only that implement custom completion queue methods. /// Matches the implementation of cq_advance() in liburing. pub fn cq_advance(self: *IO_Uring, count: u32) void { if (count > 0) { // Ensure the kernel only sees the new head value after the CQEs have been read. @atomicStore(u32, self.cq.head, self.cq.head.* +% count, .Release); } } /// Queues (but does not submit) an SQE to perform an `fsync(2)`. /// Returns a pointer to the SQE so that you can further modify the SQE for advanced use cases. /// For example, for `fdatasync()` you can set `IORING_FSYNC_DATASYNC` in the SQE's `rw_flags`. /// N.B. While SQEs are initiated in the order in which they appear in the submission queue, /// operations execute in parallel and completions are unordered. Therefore, an application that /// submits a write followed by an fsync in the submission queue cannot expect the fsync to /// apply to the write, since the fsync may complete before the write is issued to the disk. /// You should preferably use `link_with_next_sqe()` on a write's SQE to link it with an fsync, /// or else insert a full write barrier using `drain_previous_sqes()` when queueing an fsync. pub fn fsync(self: *IO_Uring, user_data: u64, fd: os.fd_t, flags: u32) !*io_uring_sqe { const sqe = try self.get_sqe(); io_uring_prep_fsync(sqe, fd, flags); sqe.user_data = user_data; return sqe; } /// Queues (but does not submit) an SQE to perform a no-op. /// Returns a pointer to the SQE so that you can further modify the SQE for advanced use cases. /// A no-op is more useful than may appear at first glance. /// For example, you could call `drain_previous_sqes()` on the returned SQE, to use the no-op to /// know when the ring is idle before acting on a kill signal. pub fn nop(self: *IO_Uring, user_data: u64) !*io_uring_sqe { const sqe = try self.get_sqe(); io_uring_prep_nop(sqe); sqe.user_data = user_data; return sqe; } /// Queues (but does not submit) an SQE to perform a `read(2)`. /// Returns a pointer to the SQE. pub fn read( self: *IO_Uring, user_data: u64, fd: os.fd_t, buffer: []u8, offset: u64 ) !*io_uring_sqe { const sqe = try self.get_sqe(); io_uring_prep_read(sqe, fd, buffer, offset); sqe.user_data = user_data; return sqe; } /// Queues (but does not submit) an SQE to perform a `write(2)`. /// Returns a pointer to the SQE. pub fn write( self: *IO_Uring, user_data: u64, fd: os.fd_t, buffer: []const u8, offset: u64 ) !*io_uring_sqe { const sqe = try self.get_sqe(); io_uring_prep_write(sqe, fd, buffer, offset); sqe.user_data = user_data; return sqe; } /// Queues (but does not submit) an SQE to perform a `preadv()`. /// Returns a pointer to the SQE so that you can further modify the SQE for advanced use cases. /// For example, if you want to do a `preadv2()` then set `rw_flags` on the returned SQE. /// See https://linux.die.net/man/2/preadv. pub fn readv( self: *IO_Uring, user_data: u64, fd: os.fd_t, iovecs: []const os.iovec, offset: u64 ) !*io_uring_sqe { const sqe = try self.get_sqe(); io_uring_prep_readv(sqe, fd, iovecs, offset); sqe.user_data = user_data; return sqe; } /// Queues (but does not submit) an SQE to perform a `pwritev()`. /// Returns a pointer to the SQE so that you can further modify the SQE for advanced use cases. /// For example, if you want to do a `pwritev2()` then set `rw_flags` on the returned SQE. /// See https://linux.die.net/man/2/pwritev. pub fn writev( self: *IO_Uring, user_data: u64, fd: os.fd_t, iovecs: []const os.iovec_const, offset: u64 ) !*io_uring_sqe { const sqe = try self.get_sqe(); io_uring_prep_writev(sqe, fd, iovecs, offset); sqe.user_data = user_data; return sqe; } /// Queues (but does not submit) an SQE to perform an `accept4(2)` on a socket. /// Returns a pointer to the SQE. pub fn accept( self: *IO_Uring, user_data: u64, fd: os.fd_t, addr: *os.sockaddr, addrlen: *os.socklen_t, flags: u32 ) !*io_uring_sqe { const sqe = try self.get_sqe(); io_uring_prep_accept(sqe, fd, addr, addrlen, flags); sqe.user_data = user_data; return sqe; } /// Queue (but does not submit) an SQE to perform a `connect(2)` on a socket. /// Returns a pointer to the SQE. pub fn connect( self: *IO_Uring, user_data: u64, fd: os.fd_t, addr: *const os.sockaddr, addrlen: os.socklen_t ) !*io_uring_sqe { const sqe = try self.get_sqe(); io_uring_prep_connect(sqe, fd, addr, addrlen); sqe.user_data = user_data; return sqe; } /// Queues (but does not submit) an SQE to perform a `recv(2)`. /// Returns a pointer to the SQE. pub fn recv( self: *IO_Uring, user_data: u64, fd: os.fd_t, buffer: []u8, flags: u32 ) !*io_uring_sqe { const sqe = try self.get_sqe(); io_uring_prep_recv(sqe, fd, buffer, flags); sqe.user_data = user_data; return sqe; } /// Queues (but does not submit) an SQE to perform a `send(2)`. /// Returns a pointer to the SQE. pub fn send( self: *IO_Uring, user_data: u64, fd: os.fd_t, buffer: []const u8, flags: u32 ) !*io_uring_sqe { const sqe = try self.get_sqe(); io_uring_prep_send(sqe, fd, buffer, flags); sqe.user_data = user_data; return sqe; } /// Queues (but does not submit) an SQE to perform an `openat(2)`. /// Returns a pointer to the SQE. pub fn openat( self: *IO_Uring, user_data: u64, fd: os.fd_t, path: [*:0]const u8, flags: u32, mode: os.mode_t ) !*io_uring_sqe { const sqe = try self.get_sqe(); io_uring_prep_openat(sqe, fd, path, flags, mode); sqe.user_data = user_data; return sqe; } /// Queues (but does not submit) an SQE to perform a `close(2)`. /// Returns a pointer to the SQE. pub fn close(self: *IO_Uring, user_data: u64, fd: os.fd_t) !*io_uring_sqe { const sqe = try self.get_sqe(); io_uring_prep_close(sqe, fd); sqe.user_data = user_data; return sqe; } /// Registers an array of file descriptors. /// Every time a file descriptor is put in an SQE and submitted to the kernel, the kernel must /// retrieve a reference to the file, and once I/O has completed the file reference must be /// dropped. The atomic nature of this file reference can be a slowdown for high IOPS workloads. /// This slowdown can be avoided by pre-registering file descriptors. /// To refer to a registered file descriptor, IOSQE_FIXED_FILE must be set in the SQE's flags, /// and the SQE's fd must be set to the index of the file descriptor in the registered array. /// Registering file descriptors will wait for the ring to idle. /// Files are automatically unregistered by the kernel when the ring is torn down. /// An application need unregister only if it wants to register a new array of file descriptors. pub fn register_files(self: *IO_Uring, fds: []const os.fd_t) !void { assert(self.fd >= 0); comptime assert(@sizeOf(os.fd_t) == @sizeOf(c_int)); const res = linux.io_uring_register( self.fd, .REGISTER_FILES, @ptrCast(*const c_void, fds.ptr), @intCast(u32, fds.len) ); switch (linux.getErrno(res)) { 0 => {}, // One or more fds in the array are invalid, or the kernel does not support sparse sets: linux.EBADF => return error.FileDescriptorInvalid, linux.EBUSY => return error.FilesAlreadyRegistered, linux.EINVAL => return error.FilesEmpty, // Adding `nr_args` file references would exceed the maximum allowed number of files the // user is allowed to have according to the per-user RLIMIT_NOFILE resource limit and // the CAP_SYS_RESOURCE capability is not set, or `nr_args` exceeds the maximum allowed // for a fixed file set (older kernels have a limit of 1024 files vs 64K files): linux.EMFILE => return error.UserFdQuotaExceeded, // Insufficient kernel resources, or the caller had a non-zero RLIMIT_MEMLOCK soft // resource limit but tried to lock more memory than the limit permitted (not enforced // when the process is privileged with CAP_IPC_LOCK): linux.ENOMEM => return error.SystemResources, // Attempt to register files on a ring already registering files or being torn down: linux.ENXIO => return error.RingShuttingDownOrAlreadyRegisteringFiles, else => |errno| return os.unexpectedErrno(errno) } } /// Unregisters all registered file descriptors previously associated with the ring. pub fn unregister_files(self: *IO_Uring) !void { assert(self.fd >= 0); const res = linux.io_uring_register(self.fd, .UNREGISTER_FILES, null, 0); switch (linux.getErrno(res)) { 0 => {}, linux.ENXIO => return error.FilesNotRegistered, else => |errno| return os.unexpectedErrno(errno) } } }; pub const SubmissionQueue = struct { head: *u32, tail: *u32, mask: u32, flags: *u32, dropped: *u32, array: []u32, sqes: []io_uring_sqe, mmap: []align(mem.page_size) u8, mmap_sqes: []align(mem.page_size) u8, // We use `sqe_head` and `sqe_tail` in the same way as liburing: // We increment `sqe_tail` (but not `tail`) for each call to `get_sqe()`. // We then set `tail` to `sqe_tail` once, only when these events are actually submitted. // This allows us to amortize the cost of the @atomicStore to `tail` across multiple SQEs. sqe_head: u32 = 0, sqe_tail: u32 = 0, pub fn init(fd: os.fd_t, p: io_uring_params) !SubmissionQueue { assert(fd >= 0); assert((p.features & linux.IORING_FEAT_SINGLE_MMAP) != 0); const size = std.math.max( p.sq_off.array + p.sq_entries * @sizeOf(u32), p.cq_off.cqes + p.cq_entries * @sizeOf(io_uring_cqe) ); const mmap = try os.mmap( null, size, os.PROT_READ | os.PROT_WRITE, os.MAP_SHARED | os.MAP_POPULATE, fd, linux.IORING_OFF_SQ_RING, ); errdefer os.munmap(mmap); assert(mmap.len == size); // The motivation for the `sqes` and `array` indirection is to make it possible for the // application to preallocate static io_uring_sqe entries and then replay them when needed. const size_sqes = p.sq_entries * @sizeOf(io_uring_sqe); const mmap_sqes = try os.mmap( null, size_sqes, os.PROT_READ | os.PROT_WRITE, os.MAP_SHARED | os.MAP_POPULATE, fd, linux.IORING_OFF_SQES, ); errdefer os.munmap(mmap_sqes); assert(mmap_sqes.len == size_sqes); const array = @ptrCast([*]u32, @alignCast(@alignOf(u32), &mmap[p.sq_off.array])); const sqes = @ptrCast([*]io_uring_sqe, @alignCast(@alignOf(io_uring_sqe), &mmap_sqes[0])); // We expect the kernel copies p.sq_entries to the u32 pointed to by p.sq_off.ring_entries, // see https://github.com/torvalds/linux/blob/v5.8/fs/io_uring.c#L7843-L7844. assert( p.sq_entries == @ptrCast(*u32, @alignCast(@alignOf(u32), &mmap[p.sq_off.ring_entries])).* ); return SubmissionQueue { .head = @ptrCast(*u32, @alignCast(@alignOf(u32), &mmap[p.sq_off.head])), .tail = @ptrCast(*u32, @alignCast(@alignOf(u32), &mmap[p.sq_off.tail])), .mask = @ptrCast(*u32, @alignCast(@alignOf(u32), &mmap[p.sq_off.ring_mask])).*, .flags = @ptrCast(*u32, @alignCast(@alignOf(u32), &mmap[p.sq_off.flags])), .dropped = @ptrCast(*u32, @alignCast(@alignOf(u32), &mmap[p.sq_off.dropped])), .array = array[0..p.sq_entries], .sqes = sqes[0..p.sq_entries], .mmap = mmap, .mmap_sqes = mmap_sqes }; } pub fn deinit(self: *SubmissionQueue) void { os.munmap(self.mmap_sqes); os.munmap(self.mmap); } }; pub const CompletionQueue = struct { head: *u32, tail: *u32, mask: u32, overflow: *u32, cqes: []io_uring_cqe, pub fn init(fd: os.fd_t, p: io_uring_params, sq: SubmissionQueue) !CompletionQueue { assert(fd >= 0); assert((p.features & linux.IORING_FEAT_SINGLE_MMAP) != 0); const mmap = sq.mmap; const cqes = @ptrCast( [*]io_uring_cqe, @alignCast(@alignOf(io_uring_cqe), &mmap[p.cq_off.cqes]) ); assert( p.cq_entries == @ptrCast(*u32, @alignCast(@alignOf(u32), &mmap[p.cq_off.ring_entries])).* ); return CompletionQueue { .head = @ptrCast(*u32, @alignCast(@alignOf(u32), &mmap[p.cq_off.head])), .tail = @ptrCast(*u32, @alignCast(@alignOf(u32), &mmap[p.cq_off.tail])), .mask = @ptrCast(*u32, @alignCast(@alignOf(u32), &mmap[p.cq_off.ring_mask])).*, .overflow = @ptrCast(*u32, @alignCast(@alignOf(u32), &mmap[p.cq_off.overflow])), .cqes = cqes[0..p.cq_entries] }; } pub fn deinit(self: *CompletionQueue) void { // A no-op since we now share the mmap with the submission queue. // Here for symmetry with the submission queue, and for any future feature support. } }; pub fn io_uring_prep_nop(sqe: *io_uring_sqe) void { sqe.* = .{ .opcode = .NOP, .flags = 0, .ioprio = 0, .fd = 0, .off = 0, .addr = 0, .len = 0, .rw_flags = 0, .user_data = 0, .buf_index = 0, .personality = 0, .splice_fd_in = 0, .__pad2 = [2]u64{ 0, 0 } }; } pub fn io_uring_prep_fsync(sqe: *io_uring_sqe, fd: os.fd_t, flags: u32) void { sqe.* = .{ .opcode = .FSYNC, .flags = 0, .ioprio = 0, .fd = fd, .off = 0, .addr = 0, .len = 0, .rw_flags = flags, .user_data = 0, .buf_index = 0, .personality = 0, .splice_fd_in = 0, .__pad2 = [2]u64{ 0, 0 } }; } pub fn io_uring_prep_rw( op: linux.IORING_OP, sqe: *io_uring_sqe, fd: os.fd_t, addr: anytype, len: usize, offset: u64 ) void { sqe.* = .{ .opcode = op, .flags = 0, .ioprio = 0, .fd = fd, .off = offset, .addr = @ptrToInt(addr), .len = @intCast(u32, len), .rw_flags = 0, .user_data = 0, .buf_index = 0, .personality = 0, .splice_fd_in = 0, .__pad2 = [2]u64{ 0, 0 } }; } pub fn io_uring_prep_read(sqe: *io_uring_sqe, fd: os.fd_t, buffer: []u8, offset: u64) void { io_uring_prep_rw(.READ, sqe, fd, buffer.ptr, buffer.len, offset); } pub fn io_uring_prep_write(sqe: *io_uring_sqe, fd: os.fd_t, buffer: []const u8, offset: u64) void { io_uring_prep_rw(.WRITE, sqe, fd, buffer.ptr, buffer.len, offset); } pub fn io_uring_prep_readv( sqe: *io_uring_sqe, fd: os.fd_t, iovecs: []const os.iovec, offset: u64 ) void { io_uring_prep_rw(.READV, sqe, fd, iovecs.ptr, iovecs.len, offset); } pub fn io_uring_prep_writev( sqe: *io_uring_sqe, fd: os.fd_t, iovecs: []const os.iovec_const, offset: u64 ) void { io_uring_prep_rw(.WRITEV, sqe, fd, iovecs.ptr, iovecs.len, offset); } pub fn io_uring_prep_accept( sqe: *io_uring_sqe, fd: os.fd_t, addr: *os.sockaddr, addrlen: *os.socklen_t, flags: u32 ) void { // `addr` holds a pointer to `sockaddr`, and `addr2` holds a pointer to socklen_t`. // `addr2` maps to `sqe.off` (u64) instead of `sqe.len` (which is only a u32). io_uring_prep_rw(.ACCEPT, sqe, fd, addr, 0, @ptrToInt(addrlen)); sqe.rw_flags = flags; } pub fn io_uring_prep_connect( sqe: *io_uring_sqe, fd: os.fd_t, addr: *const os.sockaddr, addrlen: os.socklen_t ) void { // `addrlen` maps to `sqe.off` (u64) instead of `sqe.len` (which is only a u32). io_uring_prep_rw(.CONNECT, sqe, fd, addr, 0, addrlen); } pub fn io_uring_prep_recv(sqe: *io_uring_sqe, fd: os.fd_t, buffer: []u8, flags: u32) void { io_uring_prep_rw(.RECV, sqe, fd, buffer.ptr, buffer.len, 0); sqe.rw_flags = flags; } pub fn io_uring_prep_send(sqe: *io_uring_sqe, fd: os.fd_t, buffer: []const u8, flags: u32) void { io_uring_prep_rw(.SEND, sqe, fd, buffer.ptr, buffer.len, 0); sqe.rw_flags = flags; } pub fn io_uring_prep_openat( sqe: *io_uring_sqe, fd: os.fd_t, path: [*:0]const u8, flags: u32, mode: os.mode_t ) void { io_uring_prep_rw(.OPENAT, sqe, fd, path, mode, 0); sqe.rw_flags = flags; } pub fn io_uring_prep_close(sqe: *io_uring_sqe, fd: os.fd_t) void { sqe.* = .{ .opcode = .CLOSE, .flags = 0, .ioprio = 0, .fd = fd, .off = 0, .addr = 0, .len = 0, .rw_flags = 0, .user_data = 0, .buf_index = 0, .personality = 0, .splice_fd_in = 0, .__pad2 = [2]u64{ 0, 0 } }; } test "structs/offsets/entries" { if (builtin.os.tag != .linux) return error.SkipZigTest; testing.expectEqual(@as(usize, 120), @sizeOf(io_uring_params)); testing.expectEqual(@as(usize, 64), @sizeOf(io_uring_sqe)); testing.expectEqual(@as(usize, 16), @sizeOf(io_uring_cqe)); testing.expectEqual(0, linux.IORING_OFF_SQ_RING); testing.expectEqual(0x8000000, linux.IORING_OFF_CQ_RING); testing.expectEqual(0x10000000, linux.IORING_OFF_SQES); testing.expectError(error.EntriesZero, IO_Uring.init(0, 0)); testing.expectError(error.EntriesNotPowerOfTwo, IO_Uring.init(3, 0)); } test "nop" { if (builtin.os.tag != .linux) return error.SkipZigTest; var ring = IO_Uring.init(1, 0) catch |err| switch (err) { error.SystemOutdated => return error.SkipZigTest, error.PermissionDenied => return error.SkipZigTest, else => return err }; defer { ring.deinit(); testing.expectEqual(@as(os.fd_t, -1), ring.fd); } const sqe = try ring.nop(0xaaaaaaaa); testing.expectEqual(io_uring_sqe { .opcode = .NOP, .flags = 0, .ioprio = 0, .fd = 0, .off = 0, .addr = 0, .len = 0, .rw_flags = 0, .user_data = 0xaaaaaaaa, .buf_index = 0, .personality = 0, .splice_fd_in = 0, .__pad2 = [2]u64{ 0, 0 } }, sqe.*); testing.expectEqual(@as(u32, 0), ring.sq.sqe_head); testing.expectEqual(@as(u32, 1), ring.sq.sqe_tail); testing.expectEqual(@as(u32, 0), ring.sq.tail.*); testing.expectEqual(@as(u32, 0), ring.cq.head.*); testing.expectEqual(@as(u32, 1), ring.sq_ready()); testing.expectEqual(@as(u32, 0), ring.cq_ready()); testing.expectEqual(@as(u32, 1), try ring.submit()); testing.expectEqual(@as(u32, 1), ring.sq.sqe_head); testing.expectEqual(@as(u32, 1), ring.sq.sqe_tail); testing.expectEqual(@as(u32, 1), ring.sq.tail.*); testing.expectEqual(@as(u32, 0), ring.cq.head.*); testing.expectEqual(@as(u32, 0), ring.sq_ready()); testing.expectEqual(io_uring_cqe { .user_data = 0xaaaaaaaa, .res = 0, .flags = 0 }, try ring.copy_cqe()); testing.expectEqual(@as(u32, 1), ring.cq.head.*); testing.expectEqual(@as(u32, 0), ring.cq_ready()); const sqe_barrier = try ring.nop(0xbbbbbbbb); sqe_barrier.flags |= linux.IOSQE_IO_DRAIN; testing.expectEqual(@as(u32, 1), try ring.submit()); testing.expectEqual(io_uring_cqe { .user_data = 0xbbbbbbbb, .res = 0, .flags = 0 }, try ring.copy_cqe()); testing.expectEqual(@as(u32, 2), ring.sq.sqe_head); testing.expectEqual(@as(u32, 2), ring.sq.sqe_tail); testing.expectEqual(@as(u32, 2), ring.sq.tail.*); testing.expectEqual(@as(u32, 2), ring.cq.head.*); } test "readv" { if (builtin.os.tag != .linux) return error.SkipZigTest; var ring = IO_Uring.init(1, 0) catch |err| switch (err) { error.SystemOutdated => return error.SkipZigTest, error.PermissionDenied => return error.SkipZigTest, else => return err }; defer ring.deinit(); const fd = try os.openZ("/dev/zero", os.O_RDONLY | os.O_CLOEXEC, 0); defer os.close(fd); // Linux Kernel 5.4 supports IORING_REGISTER_FILES but not sparse fd sets (i.e. an fd of -1). // Linux Kernel 5.5 adds support for sparse fd sets. // Compare: // https://github.com/torvalds/linux/blob/v5.4/fs/io_uring.c#L3119-L3124 vs // https://github.com/torvalds/linux/blob/v5.8/fs/io_uring.c#L6687-L6691 // We therefore avoid stressing sparse fd sets here: var registered_fds = [_]os.fd_t{0} ** 1; const fd_index = 0; registered_fds[fd_index] = fd; try ring.register_files(registered_fds[0..]); var buffer = [_]u8{42} ** 128; var iovecs = [_]os.iovec{ os.iovec { .iov_base = &buffer, .iov_len = buffer.len } }; const sqe = try ring.readv(0xcccccccc, fd_index, iovecs[0..], 0); testing.expectEqual(linux.IORING_OP.READV, sqe.opcode); sqe.flags |= linux.IOSQE_FIXED_FILE; testing.expectError(error.SubmissionQueueFull, ring.nop(0)); testing.expectEqual(@as(u32, 1), try ring.submit()); testing.expectEqual(linux.io_uring_cqe { .user_data = 0xcccccccc, .res = buffer.len, .flags = 0, }, try ring.copy_cqe()); testing.expectEqualSlices(u8, &([_]u8{0} ** buffer.len), buffer[0..]); try ring.unregister_files(); } test "writev/fsync/readv" { if (builtin.os.tag != .linux) return error.SkipZigTest; var ring = IO_Uring.init(4, 0) catch |err| switch (err) { error.SystemOutdated => return error.SkipZigTest, error.PermissionDenied => return error.SkipZigTest, else => return err }; defer ring.deinit(); const path = "test_io_uring_writev_fsync_readv"; const file = try std.fs.cwd().createFile(path, .{ .read = true, .truncate = true }); defer file.close(); defer std.fs.cwd().deleteFile(path) catch {}; const fd = file.handle; const buffer_write = [_]u8{42} ** 128; const iovecs_write = [_]os.iovec_const { os.iovec_const { .iov_base = &buffer_write, .iov_len = buffer_write.len } }; var buffer_read = [_]u8{0} ** 128; var iovecs_read = [_]os.iovec { os.iovec { .iov_base = &buffer_read, .iov_len = buffer_read.len } }; const sqe_writev = try ring.writev(0xdddddddd, fd, iovecs_write[0..], 17); testing.expectEqual(linux.IORING_OP.WRITEV, sqe_writev.opcode); testing.expectEqual(@as(u64, 17), sqe_writev.off); sqe_writev.flags |= linux.IOSQE_IO_LINK; const sqe_fsync = try ring.fsync(0xeeeeeeee, fd, 0); testing.expectEqual(linux.IORING_OP.FSYNC, sqe_fsync.opcode); testing.expectEqual(fd, sqe_fsync.fd); sqe_fsync.flags |= linux.IOSQE_IO_LINK; const sqe_readv = try ring.readv(0xffffffff, fd, iovecs_read[0..], 17); testing.expectEqual(linux.IORING_OP.READV, sqe_readv.opcode); testing.expectEqual(@as(u64, 17), sqe_readv.off); testing.expectEqual(@as(u32, 3), ring.sq_ready()); testing.expectEqual(@as(u32, 3), try ring.submit_and_wait(3)); testing.expectEqual(@as(u32, 0), ring.sq_ready()); testing.expectEqual(@as(u32, 3), ring.cq_ready()); testing.expectEqual(linux.io_uring_cqe { .user_data = 0xdddddddd, .res = buffer_write.len, .flags = 0, }, try ring.copy_cqe()); testing.expectEqual(@as(u32, 2), ring.cq_ready()); testing.expectEqual(linux.io_uring_cqe { .user_data = 0xeeeeeeee, .res = 0, .flags = 0, }, try ring.copy_cqe()); testing.expectEqual(@as(u32, 1), ring.cq_ready()); testing.expectEqual(linux.io_uring_cqe { .user_data = 0xffffffff, .res = buffer_read.len, .flags = 0, }, try ring.copy_cqe()); testing.expectEqual(@as(u32, 0), ring.cq_ready()); testing.expectEqualSlices(u8, buffer_write[0..], buffer_read[0..]); } test "write/read" { if (builtin.os.tag != .linux) return error.SkipZigTest; var ring = IO_Uring.init(2, 0) catch |err| switch (err) { error.SystemOutdated => return error.SkipZigTest, error.PermissionDenied => return error.SkipZigTest, else => return err }; defer ring.deinit(); const path = "test_io_uring_write_read"; const file = try std.fs.cwd().createFile(path, .{ .read = true, .truncate = true }); defer file.close(); defer std.fs.cwd().deleteFile(path) catch {}; const fd = file.handle; const buffer_write = [_]u8{97} ** 20; var buffer_read = [_]u8{98} ** 20; const sqe_write = try ring.write(0x11111111, fd, buffer_write[0..], 10); testing.expectEqual(linux.IORING_OP.WRITE, sqe_write.opcode); testing.expectEqual(@as(u64, 10), sqe_write.off); sqe_write.flags |= linux.IOSQE_IO_LINK; const sqe_read = try ring.read(0x22222222, fd, buffer_read[0..], 10); testing.expectEqual(linux.IORING_OP.READ, sqe_read.opcode); testing.expectEqual(@as(u64, 10), sqe_read.off); testing.expectEqual(@as(u32, 2), try ring.submit()); const cqe_write = try ring.copy_cqe(); const cqe_read = try ring.copy_cqe(); // Prior to Linux Kernel 5.6 this is the only way to test for read/write support: // https://lwn.net/Articles/809820/ if (cqe_write.res == -linux.EINVAL) return error.SkipZigTest; if (cqe_read.res == -linux.EINVAL) return error.SkipZigTest; testing.expectEqual(linux.io_uring_cqe { .user_data = 0x11111111, .res = buffer_write.len, .flags = 0, }, cqe_write); testing.expectEqual(linux.io_uring_cqe { .user_data = 0x22222222, .res = buffer_read.len, .flags = 0, }, cqe_read); testing.expectEqualSlices(u8, buffer_write[0..], buffer_read[0..]); } test "openat" { if (builtin.os.tag != .linux) return error.SkipZigTest; var ring = IO_Uring.init(1, 0) catch |err| switch (err) { error.SystemOutdated => return error.SkipZigTest, error.PermissionDenied => return error.SkipZigTest, else => return err }; defer ring.deinit(); const path = "test_io_uring_openat"; defer std.fs.cwd().deleteFile(path) catch {}; const flags: u32 = os.O_CLOEXEC | os.O_RDWR | os.O_CREAT; const mode: os.mode_t = 0o666; const sqe_openat = try ring.openat(0x33333333, linux.AT_FDCWD, path, flags, mode); testing.expectEqual(io_uring_sqe { .opcode = .OPENAT, .flags = 0, .ioprio = 0, .fd = linux.AT_FDCWD, .off = 0, .addr = @ptrToInt(path), .len = mode, .rw_flags = flags, .user_data = 0x33333333, .buf_index = 0, .personality = 0, .splice_fd_in = 0, .__pad2 = [2]u64{ 0, 0 } }, sqe_openat.*); testing.expectEqual(@as(u32, 1), try ring.submit()); const cqe_openat = try ring.copy_cqe(); testing.expectEqual(@as(u64, 0x33333333), cqe_openat.user_data); if (cqe_openat.res == -linux.EINVAL) return error.SkipZigTest; // AT_FDCWD is not fully supported before kernel 5.6: // See https://lore.kernel.org/io-uring/20200207155039.12819-1-axboe@kernel.dk/T/ // We use IORING_FEAT_RW_CUR_POS to know if we are pre-5.6 since that feature was added in 5.6. if (cqe_openat.res == -linux.EBADF and (ring.features & linux.IORING_FEAT_RW_CUR_POS) == 0) { return error.SkipZigTest; } if (cqe_openat.res <= 0) std.debug.print("\ncqe_openat.res={}\n", .{ cqe_openat.res }); testing.expect(cqe_openat.res > 0); testing.expectEqual(@as(u32, 0), cqe_openat.flags); os.close(cqe_openat.res); } test "close" { if (builtin.os.tag != .linux) return error.SkipZigTest; var ring = IO_Uring.init(1, 0) catch |err| switch (err) { error.SystemOutdated => return error.SkipZigTest, error.PermissionDenied => return error.SkipZigTest, else => return err }; defer ring.deinit(); const path = "test_io_uring_close"; const file = try std.fs.cwd().createFile(path, .{}); errdefer file.close(); defer std.fs.cwd().deleteFile(path) catch {}; const sqe_close = try ring.close(0x44444444, file.handle); testing.expectEqual(linux.IORING_OP.CLOSE, sqe_close.opcode); testing.expectEqual(file.handle, sqe_close.fd); testing.expectEqual(@as(u32, 1), try ring.submit()); const cqe_close = try ring.copy_cqe(); if (cqe_close.res == -linux.EINVAL) return error.SkipZigTest; testing.expectEqual(linux.io_uring_cqe { .user_data = 0x44444444, .res = 0, .flags = 0, }, cqe_close); } test "accept/connect/send/recv" { if (builtin.os.tag != .linux) return error.SkipZigTest; var ring = IO_Uring.init(16, 0) catch |err| switch (err) { error.SystemOutdated => return error.SkipZigTest, error.PermissionDenied => return error.SkipZigTest, else => return err }; defer ring.deinit(); const address = try net.Address.parseIp4("127.0.0.1", 3131); const kernel_backlog = 1; const server = try os.socket(address.any.family, os.SOCK_STREAM | os.SOCK_CLOEXEC, 0); defer os.close(server); try os.setsockopt(server, os.SOL_SOCKET, os.SO_REUSEADDR, &mem.toBytes(@as(c_int, 1))); try os.bind(server, &address.any, address.getOsSockLen()); try os.listen(server, kernel_backlog); const buffer_send = [_]u8{ 1,0,1,0,1,0,1,0,1,0 }; var buffer_recv = [_]u8{ 0,1,0,1,0 }; var accept_addr: os.sockaddr = undefined; var accept_addr_len: os.socklen_t = @sizeOf(@TypeOf(accept_addr)); const accept = try ring.accept(0xaaaaaaaa, server, &accept_addr, &accept_addr_len, 0); testing.expectEqual(@as(u32, 1), try ring.submit()); const client = try os.socket(address.any.family, os.SOCK_STREAM | os.SOCK_CLOEXEC, 0); defer os.close(client); const connect = try ring.connect(0xcccccccc, client, &address.any, address.getOsSockLen()); testing.expectEqual(@as(u32, 1), try ring.submit()); var cqe_accept = try ring.copy_cqe(); if (cqe_accept.res == -linux.EINVAL) return error.SkipZigTest; var cqe_connect = try ring.copy_cqe(); if (cqe_connect.res == -linux.EINVAL) return error.SkipZigTest; // The accept/connect CQEs may arrive in any order, the connect CQE will sometimes come first: if (cqe_accept.user_data == 0xcccccccc and cqe_connect.user_data == 0xaaaaaaaa) { const a = cqe_accept; const b = cqe_connect; cqe_accept = b; cqe_connect = a; } testing.expectEqual(@as(u64, 0xaaaaaaaa), cqe_accept.user_data); if (cqe_accept.res <= 0) std.debug.print("\ncqe_accept.res={}\n", .{ cqe_accept.res }); testing.expect(cqe_accept.res > 0); testing.expectEqual(@as(u32, 0), cqe_accept.flags); testing.expectEqual(linux.io_uring_cqe { .user_data = 0xcccccccc, .res = 0, .flags = 0, }, cqe_connect); const send = try ring.send(0xeeeeeeee, client, buffer_send[0..], 0); send.flags |= linux.IOSQE_IO_LINK; const recv = try ring.recv(0xffffffff, cqe_accept.res, buffer_recv[0..], 0); testing.expectEqual(@as(u32, 2), try ring.submit()); const cqe_send = try ring.copy_cqe(); if (cqe_send.res == -linux.EINVAL) return error.SkipZigTest; testing.expectEqual(linux.io_uring_cqe { .user_data = 0xeeeeeeee, .res = buffer_send.len, .flags = 0, }, cqe_send); const cqe_recv = try ring.copy_cqe(); if (cqe_recv.res == -linux.EINVAL) return error.SkipZigTest; testing.expectEqual(linux.io_uring_cqe { .user_data = 0xffffffff, .res = buffer_recv.len, .flags = 0, }, cqe_recv); testing.expectEqualSlices(u8, buffer_send[0..buffer_recv.len], buffer_recv[0..]); }