build: try to enable io_uring if it is not specified

* configure.py: do not specify an option if "value_when_none" is None
* configure.py: make IO_URING an nullable option, so we don't specify
  this option in the cmake command line option if user does not
  explicity specify it in the configure.py command line.
* cmake: add a function `set_option_if_package_is_found()` to set
  an option if its value is not explicitly specified, while the
  package required for building it is found. this function can be
  reused to set other nullable option which requires a corresponding
  package for enabling it.
* cmake: add the `Seastar_IO_URING` option only if it is specified,
  and try to enable it if it is not specified.
* cmake: mark "LibUring" REQUIRED only when "Seastar_IO_URING" is
  specified and is ON or yes or TRUE, etc.

Signed-off-by: Kefu Chai <[email protected]>

Author: tchaikov

CMakeLists.txt

@@ -188,6 +188,17 @@ set (Seastar_ALLOC_PAGE_SIZE
   STRING
   "Override the Seastar allocator page size, in bytes.")
 
+function (set_option_if_package_is_found option_name package_name)
+  # if the package is found, set the option on behalf of user unless it is
+  # explicitly specified,
+  if (DEFINED ${option_name})
+    return ()
+  endif ()
+  if (${package_name}_FOUND)
+    set (${option_name} ON CACHE BOOL "")
+  endif ()
+endfunction ()
+
 option (Seastar_APPS
   "Enable application targets."
   ON)
@@ -230,9 +241,11 @@ option (Seastar_HWLOC
   "Enable hwloc support."
   ON)
 
-option (Seastar_IO_URING
-  "Enable io_uring support."
-  ON)
+if (DEFINED Seastar_IO_URING)
+  option (Seastar_IO_URING
+    "Enable io_uring support."
+    ON)
+endif ()
 
 set (Seastar_JENKINS
   ""
@@ -925,11 +938,8 @@ if (Seastar_HWLOC)
     PRIVATE hwloc::hwloc)
 endif ()
 
+set_option_if_package_is_found(Seastar_IO_URING LibUring)
 if (Seastar_IO_URING)
-  if (NOT LibUring_FOUND)
-    message (FATAL_ERROR "`io_uring` supported is enabled but liburing is not available!")
-  endif ()
-
   list (APPEND Seastar_PRIVATE_COMPILE_DEFINITIONS SEASTAR_HAVE_URING)
   target_link_libraries (seastar
     PRIVATE URING::uring)

cmake/SeastarDependencies.cmake

@@ -97,6 +97,9 @@ macro (seastar_find_dependencies)
   set (_seastar_dep_args_lz4 1.7.3 REQUIRED)
   set (_seastar_dep_args_GnuTLS 3.3.26 REQUIRED)
   set (_seastar_dep_args_LibUring 2.0)
+  if (Seastar_IO_URING)
+    list (APPEND _seastar_dep_args_LibUring REQUIRED)
+  endif ()
   set (_seastar_dep_args_StdAtomic REQUIRED)
   set (_seastar_dep_args_hwloc 1.11.2)
   set (_seastar_dep_args_lksctp-tools REQUIRED)

configure.py

@@ -201,7 +201,7 @@ def configure_mode(mode):
         tr(args.dpdk, 'DPDK'),
         tr(infer_dpdk_machine(args.user_cflags), 'DPDK_MACHINE'),
         tr(args.hwloc, 'HWLOC', value_when_none='yes'),
-        tr(args.io_uring, 'IO_URING', value_when_none='yes'),
+        tr(args.io_uring, 'IO_URING', value_when_none=None),
         tr(args.alloc_failure_injection, 'ALLOC_FAILURE_INJECTION', value_when_none='DEFAULT'),
         tr(args.task_backtrace, 'TASK_BACKTRACE'),
         tr(args.alloc_page_size, 'ALLOC_PAGE_SIZE'),
@@ -233,7 +233,9 @@ def configure_mode(mode):
         # everything.
         ARGS = ['cmake', '-G', 'Ninja', '../..']
         dir = BUILD_PATH
-    ARGS += TRANSLATED_ARGS
+    # filter out empty args, their values are actually "guess",
+    # CMake should be able to figure it out.
+    ARGS += filter(lambda arg: arg, TRANSLATED_ARGS)
     if args.verbose:
         print("Running CMake in '{}' ...".format(dir))
         print(" \\\n  ".join(ARGS))

seastar_cmake.py

@@ -46,4 +46,7 @@ def translate_arg(arg, new_name, value_when_none='no'):
     else:
         value = arg
 
-    return '-DSeastar_{}={}'.format(new_name, value)
+    if value is None:
+        return ''
+    else:
+        return '-DSeastar_{}={}'.format(new_name, value)