Tests/Kernel: Add a very simple test for posix_fallocate()

Tests/Kernel/CMakeLists.txt

@@ -40,6 +40,7 @@ set(LIBTEST_BASED_SOURCES
     TestEmptySharedInodeVMObject.cpp
     TestInvalidUIDSet.cpp
     TestSharedInodeVMObject.cpp
+    TestPosixFallocate.cpp
     TestPrivateInodeVMObject.cpp
     TestKernelAlarm.cpp
     TestKernelFilePermissions.cpp

Tests/Kernel/TestPosixFallocate.cpp

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2022, Andreas Kling <kling@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibCore/System.h>
+#include <LibTest/TestCase.h>
+
+TEST_CASE(posix_fallocate_basics)
+{
+    char pattern[] = "/tmp/posix_fallocate.XXXXXX";
+    auto fd = MUST(Core::System::mkstemp(pattern));
+    VERIFY(fd >= 0);
+
+    {
+        // Valid use, grows file to new size.
+        auto result = Core::System::posix_fallocate(fd, 0, 1024);
+        EXPECT_EQ(result.is_error(), false);
+
+        auto stat = MUST(Core::System::fstat(fd));
+        EXPECT_EQ(stat.st_size, 1024);
+    }
+
+    {
+        // Invalid fd (-1)
+        auto result = Core::System::posix_fallocate(-1, 0, 1024);
+        EXPECT_EQ(result.is_error(), true);
+        EXPECT_EQ(result.error().code(), EBADF);
+    }
+
+    {
+        // Invalid length (-1)
+        auto result = Core::System::posix_fallocate(fd, 0, -1);
+        EXPECT_EQ(result.is_error(), true);
+        EXPECT_EQ(result.error().code(), EINVAL);
+    }
+
+    {
+        // Invalid length (0)
+        auto result = Core::System::posix_fallocate(fd, 0, 0);
+        EXPECT_EQ(result.is_error(), true);
+        EXPECT_EQ(result.error().code(), EINVAL);
+    }
+
+    {
+        // Invalid offset (-1)
+        auto result = Core::System::posix_fallocate(fd, -1, 1024);
+        EXPECT_EQ(result.is_error(), true);
+        EXPECT_EQ(result.error().code(), EINVAL);
+    }
+
+    MUST(Core::System::close(fd));
+}
+
+TEST_CASE(posix_fallocate_on_device_file)
+{
+    auto fd = MUST(Core::System::open("/dev/zero"sv, O_RDWR));
+    VERIFY(fd >= 0);
+    auto result = Core::System::posix_fallocate(fd, 0, 100);
+    EXPECT_EQ(result.is_error(), true);
+    EXPECT_EQ(result.error().code(), ENODEV);
+    MUST(Core::System::close(fd));
+}
+
+TEST_CASE(posix_fallocate_on_pipe)
+{
+    auto pipefds = MUST(Core::System::pipe2(0));
+    auto result = Core::System::posix_fallocate(pipefds[1], 0, 100);
+    EXPECT_EQ(result.is_error(), true);
+    EXPECT_EQ(result.error().code(), ESPIPE);
+    MUST(Core::System::close(pipefds[0]));
+    MUST(Core::System::close(pipefds[1]));
+}