Fix IORing build for older Linux kernels

.github/workflows/pull_request.yml

@@ -9,7 +9,10 @@ jobs:
     name: Test
     uses: swiftlang/github-workflows/.github/workflows/swift_package_test.yml@main
     with:
-      linux_exclude_swift_versions: '[{"swift_version": "5.8"}]'
+      linux_os_versions: '["jammy", "focal"]'
+      enable_macos_checks: false
+      macos_xcode_versions: '["16.3"]'
+
   soundness:
     name: Soundness
     uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main

Sources/CSystem/include/io_uring.h

@@ -3,12 +3,112 @@
 #include <sys/uio.h>
 #include <signal.h>
 
+#define __SWIFT_IORING_SQE_FALLBACK_STRUCT { \
+    __u8    opcode; \
+    __u8    flags; \
+    __u16   ioprio; \
+    __s32   fd; \
+    union { \
+        __u64   off; \
+        __u64   addr2; \
+        struct { \
+            __u32   cmd_op; \
+            __u32   __pad1; \
+        }; \
+    }; \
+    union { \
+        __u64   addr; \
+        __u64   splice_off_in; \
+        struct { \
+            __u32   level; \
+            __u32   optname; \
+        }; \
+    }; \
+    __u32   len; \
+    union { \
+        __kernel_rwf_t  rw_flags; \
+        __u32           fsync_flags; \
+        __u16           poll_events; \
+        __u32           poll32_events; \
+        __u32           sync_range_flags; \
+        __u32           msg_flags; \
+        __u32           timeout_flags; \
+        __u32           accept_flags; \
+        __u32           cancel_flags; \
+        __u32           open_flags; \
+        __u32           statx_flags; \
+        __u32           fadvise_advice; \
+        __u32           splice_flags; \
+        __u32           rename_flags; \
+        __u32           unlink_flags; \
+        __u32           hardlink_flags; \
+        __u32           xattr_flags; \
+        __u32           msg_ring_flags; \
+        __u32           uring_cmd_flags; \
+        __u32           waitid_flags; \
+        __u32           futex_flags; \
+        __u32           install_fd_flags; \
+        __u32           nop_flags; \
+    }; \
+    __u64   user_data; \
+    union { \
+        __u16   buf_index; \
+        __u16   buf_group; \
+    } __attribute__((packed)); \
+    __u16   personality; \
+    union { \
+        __s32   splice_fd_in; \
+        __u32   file_index; \
+        __u32   optlen; \
+        struct { \
+            __u16   addr_len; \
+            __u16   __pad3[1]; \
+        }; \
+    }; \
+    union { \
+        struct { \
+            __u64   addr3; \
+            __u64   __pad2[1]; \
+        }; \
+        __u64   optval; \
+        __u8    cmd[0]; \
+    }; \
+}
+
 #if __has_include(<linux/io_uring.h>)
 #include <linux/io_uring.h>
+
+#ifdef IORING_TIMEOUT_BOOTTIME
+// Kernel version >= 5.15, io_uring_sqe has file_index
+// and all current Swift operations are supported.
+#define __SWIFT_IORING_SUPPORTED true
+typedef struct io_uring_sqe swift_io_uring_sqe;
+#else
+// io_uring_sqe is missing properties that IORequest expects.
+// This configuration is not supported for now.
+//
+// Define a fallback struct to avoid build errors, but IORing
+// will throw ENOTSUP on initialization.
+#define __SWIFT_IORING_SUPPORTED false
+typedef struct __SWIFT_IORING_SQE_FALLBACK_STRUCT swift_io_uring_sqe;
+#endif
+
+// We can define more specific availability later
+
+#ifdef IORING_FEAT_RW_CUR_POS
+// Kernel version >= 5.6, io_uring_sqe has open_flags
+#endif
+
+#ifdef IORING_FEAT_NODROP
+// Kernel version >= 5.5, io_uring_sqe has cancel_flags
+#endif
+
 #else
 // Minimal fallback definitions when linux/io_uring.h is not available (e.g. static SDK)
 #include <stdint.h>
 
+#define __SWIFT_IORING_SUPPORTED false
+
 #define IORING_OFF_SQ_RING      0ULL
 #define IORING_OFF_CQ_RING      0x8000000ULL
 #define IORING_OFF_SQES         0x10000000ULL
@@ -44,77 +144,7 @@ typedef int32_t  __s32;
 typedef int __kernel_rwf_t;
 #endif
 
-struct io_uring_sqe {
-    __u8    opcode;
-    __u8    flags;
-    __u16   ioprio;
-    __s32   fd;
-    union {
-        __u64   off;
-        __u64   addr2;
-        struct {
-            __u32   cmd_op;
-            __u32   __pad1;
-        };
-    };
-    union {
-        __u64   addr;
-        __u64   splice_off_in;
-        struct {
-            __u32   level;
-            __u32   optname;
-        };
-    };
-    __u32   len;
-    union {
-        __kernel_rwf_t  rw_flags;
-        __u32           fsync_flags;
-        __u16           poll_events;
-        __u32           poll32_events;
-        __u32           sync_range_flags;
-        __u32           msg_flags;
-        __u32           timeout_flags;
-        __u32           accept_flags;
-        __u32           cancel_flags;
-        __u32           open_flags;
-        __u32           statx_flags;
-        __u32           fadvise_advice;
-        __u32           splice_flags;
-        __u32           rename_flags;
-        __u32           unlink_flags;
-        __u32           hardlink_flags;
-        __u32           xattr_flags;
-        __u32           msg_ring_flags;
-        __u32           uring_cmd_flags;
-        __u32           waitid_flags;
-        __u32           futex_flags;
-        __u32           install_fd_flags;
-        __u32           nop_flags;
-    };
-    __u64   user_data;
-    union {
-        __u16   buf_index;
-        __u16   buf_group;
-    } __attribute__((packed));
-    __u16   personality;
-    union {
-        __s32   splice_fd_in;
-        __u32   file_index;
-        __u32   optlen;
-        struct {
-            __u16   addr_len;
-            __u16   __pad3[1];
-        };
-    };
-    union {
-        struct {
-            __u64   addr3;
-            __u64   __pad2[1];
-        };
-        __u64   optval;
-        __u8    cmd[0];
-    };
-};
+typedef struct __SWIFT_IORING_SQE_FALLBACK_STRUCT swift_io_uring_sqe;
 
 struct io_uring_cqe {
     __u64   user_data;

Sources/System/IORing/IORing.swift

@@ -10,6 +10,10 @@ import Musl
 #endif
 import Synchronization
 
+private var ioringSupported: Bool {
+    __SWIFT_IORING_SUPPORTED != 0
+}
+
 //This was #defines in older headers, so we redeclare it to get a consistent import
 internal enum RegistrationOps: UInt32 {
 	case registerBuffers		= 0
@@ -72,7 +76,7 @@ extension UnsafeMutableRawBufferPointer {
 @inline(__always) @inlinable
 internal func _tryWriteRequest(
     _ request: __owned RawIORequest, ring: inout SQRing,
-    submissionQueueEntries: UnsafeMutableBufferPointer<io_uring_sqe>
+    submissionQueueEntries: UnsafeMutableBufferPointer<swift_io_uring_sqe>
 )
     -> Bool
 {
@@ -151,9 +155,9 @@ internal func _flushQueue(ring: borrowing SQRing) -> UInt32 {
 
 @inlinable
 internal func _getSubmissionEntry(
-    ring: inout SQRing, submissionQueueEntries: UnsafeMutableBufferPointer<io_uring_sqe>
+    ring: inout SQRing, submissionQueueEntries: UnsafeMutableBufferPointer<swift_io_uring_sqe>
 ) -> UnsafeMutablePointer<
-    io_uring_sqe
+    swift_io_uring_sqe
 >? {
     let next = ring.userTail &+ 1  //this is expected to wrap
 
@@ -196,7 +200,7 @@ private func setUpRing(
         throw err
     }
 
-    if params.features & IORING_FEAT_NODROP == 0
+    if params.features & IORing.Features.nonDroppingCompletions.rawValue == 0
     {
         close(ringDescriptor)
         throw Errno.invalidArgument
@@ -266,7 +270,7 @@ private func setUpRing(
     // map the submission queue
     let sqes = mmap(
         /* addr: */ nil,
-        /* len: */ Int(params.sq_entries) * MemoryLayout<io_uring_sqe>.size,
+        /* len: */ Int(params.sq_entries) * MemoryLayout<swift_io_uring_sqe>.size,
         /* prot: */ PROT_READ | PROT_WRITE,
         /* flags: */ MAP_SHARED | MAP_POPULATE,
         /* fd: */ ringDescriptor,
@@ -307,7 +311,7 @@ public struct IORing: ~Copyable {
 
     @usableFromInline let completionRing: CQRing
 
-    @usableFromInline let submissionQueueEntries: UnsafeMutableBufferPointer<io_uring_sqe>
+    @usableFromInline let submissionQueueEntries: UnsafeMutableBufferPointer<swift_io_uring_sqe>
 
     // kept around for unmap / cleanup. TODO: we can save a few words of memory by figuring out how to handle cleanup for non-IORING_FEAT_SINGLE_MMAP better
     let ringSize: Int
@@ -366,6 +370,10 @@ public struct IORing: ~Copyable {
 
     /// Initializes an IORing with enough space for `queueDepth` prepared requests and completed operations
     public init(queueDepth: UInt32, flags: SetupFlags = []) throws(Errno) {
+        guard ioringSupported else {
+            throw Errno.notSupported
+        }
+
         let (params, tmpRingDescriptor, tmpRingPtr, tmpRingSize, tmpSQPtr, tmpSQSize, tmpCQPtr, tmpCQSize, sqes) = try setUpRing(queueDepth: queueDepth, flags: flags)
         // All throws need to be before initializing ivars here to avoid 
         // "error: conditional initialization or destruction of noncopyable types is not supported; 
@@ -421,7 +429,7 @@ public struct IORing: ~Copyable {
         )
 
         let submissionQueueEntries = UnsafeMutableBufferPointer(
-            start: sqes.assumingMemoryBound(to: io_uring_sqe.self),
+            start: sqes.assumingMemoryBound(to: swift_io_uring_sqe.self),
             count: Int(params.sq_entries)
         )
 
@@ -868,7 +876,7 @@ public struct IORing: ~Copyable {
         }
         munmap(
             UnsafeMutableRawPointer(submissionQueueEntries.baseAddress!),
-            submissionQueueEntries.count * MemoryLayout<io_uring_sqe>.size
+            submissionQueueEntries.count * MemoryLayout<swift_io_uring_sqe>.size
         )
         close(ringDescriptor)
     }

Sources/System/IORing/RawIORequest.swift

@@ -5,11 +5,13 @@ import CSystem
 
 @usableFromInline
 internal struct RawIORequest: ~Copyable {
-    @usableFromInline var rawValue: io_uring_sqe
+    // swift_io_uring_sqe is a typedef of io_uring_sqe on platforms where
+    // IORing is supported (currently requires kernel version >= 5.15).
+    @usableFromInline var rawValue: swift_io_uring_sqe
     @usableFromInline var path: FilePath? //buffer owner for the path pointer that the sqe may have
 
     @inlinable public init() {
-        self.rawValue = io_uring_sqe()
+        self.rawValue = swift_io_uring_sqe()
     }
 }
 
@@ -176,8 +178,8 @@ extension RawIORequest {
 
     @inlinable
     static func withTimeoutRequest<R>(
-        linkedTo opEntry: UnsafeMutablePointer<io_uring_sqe>,
-        in timeoutEntry: UnsafeMutablePointer<io_uring_sqe>,
+        linkedTo opEntry: UnsafeMutablePointer<swift_io_uring_sqe>,
+        in timeoutEntry: UnsafeMutablePointer<swift_io_uring_sqe>,
         duration: Duration, 
         flags: TimeOutFlags, 
         work: () throws -> R) rethrows -> R {