[PATCH 1/2] NFSD: Add instructions on how to deal with xdrgen files

[PATCH 1/2] NFSD: Add instructions on how to deal with xdrgen files

[Chuck Lever]

From: Chuck Lever <chuck.lever@oracle.com>

xdrgen requires a number of Python packages on the build system. We
don't want to add these to the kernel build dependency list, which
is long enough already.

The generated files are generated manually using

  $ cd fs/nfsd && make xdrgen

whenever the .x files are modified, then they are checked into the
kernel repo so others do not need to rebuild them.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/Makefile | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/nfsd/Makefile b/fs/nfsd/Makefile
index 55744bb786c9..f0da4d69dc74 100644
--- a/fs/nfsd/Makefile
+++ b/fs/nfsd/Makefile
@@ -26,7 +26,15 @@ nfsd-$(CONFIG_NFSD_FLEXFILELAYOUT) += flexfilelayout.o flexfilelayoutxdr.o
 nfsd-$(CONFIG_NFS_LOCALIO) += localio.o
 nfsd-$(CONFIG_DEBUG_FS) += debugfs.o
 
-
+#
+# XDR code generation (requires Python and additional packages)
+#
+# The generated *xdr_gen.{h,c} files are checked into git. Normal kernel
+# builds do not require the xdrgen tool or its Python dependencies.
+#
+# Developers modifying .x files in Documentation/sunrpc/xdr/ should run
+# "make xdrgen" to regenerate the affected files.
+#
 .PHONY: xdrgen
 
 xdrgen: ../../include/linux/sunrpc/xdrgen/nfs4_1.h nfs4xdr_gen.h nfs4xdr_gen.c
-- 
2.51.0

[PATCH 2/2] xdrgen: Generate "if" instead of "switch" for boolean union enumerators

[Chuck Lever]

From: Chuck Lever <chuck.lever@oracle.com>

Eliminate this warning in code generated by xdrgen:

fs/nfsd/nfs3xdr_gen.c:220:2: warning: switch condition has boolean value [-Wswitch-bool]
  220 |         switch (ptr->attributes_follow) {
      |         ^       ~~~~~~~~~~~~~~~~~~~~~~

No more -Wswitch-bool warnings when compiling with W=1.

The generated code is functionally equivalent but somewhat more
idiomatic.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202511172336.Y75zj4v6-lkp@intel.com/
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 tools/net/sunrpc/xdrgen/generators/union.py   | 115 +++++++++++++++---
 .../templates/C/union/decoder/bool_spec.j2    |   7 ++
 .../templates/C/union/encoder/bool_spec.j2    |   7 ++
 3 files changed, 109 insertions(+), 20 deletions(-)
 create mode 100644 tools/net/sunrpc/xdrgen/templates/C/union/decoder/bool_spec.j2
 create mode 100644 tools/net/sunrpc/xdrgen/templates/C/union/encoder/bool_spec.j2

diff --git a/tools/net/sunrpc/xdrgen/generators/union.py b/tools/net/sunrpc/xdrgen/generators/union.py
index ad1f214ef22a..d15837dae651 100644
--- a/tools/net/sunrpc/xdrgen/generators/union.py
+++ b/tools/net/sunrpc/xdrgen/generators/union.py
@@ -84,6 +84,31 @@ def emit_union_switch_spec_decoder(
     print(template.render(name=node.name, type=node.spec.type_name))
 
 
+def emit_union_arm_decoder(
+    environment: Environment, node: _XdrCaseSpec
+) -> None:
+    """Emit decoder for an XDR union's arm (data only, no case/break)"""
+
+    if isinstance(node.arm, _XdrVoid):
+        return
+    if isinstance(node.arm, _XdrString):
+        type_name = "char *"
+        classifier = ""
+    else:
+        type_name = node.arm.spec.type_name
+        classifier = node.arm.spec.c_classifier
+
+    assert isinstance(node.arm, (_XdrBasic, _XdrString))
+    template = get_jinja2_template(environment, "decoder", node.arm.template)
+    print(
+        template.render(
+            name=node.arm.name,
+            type=type_name,
+            classifier=classifier,
+        )
+    )
+
+
 def emit_union_case_spec_decoder(
     environment: Environment, node: _XdrCaseSpec, big_endian_discriminant: bool
 ) -> None:
@@ -151,19 +176,33 @@ def emit_union_decoder(environment: Environment, node: _XdrUnion) -> None:
     template = get_jinja2_template(environment, "decoder", "open")
     print(template.render(name=node.name))
 
-    emit_union_switch_spec_decoder(environment, node.discriminant)
+    # For boolean discriminants, use if statement instead of switch
+    if node.discriminant.spec.type_name == "bool":
+        template = get_jinja2_template(environment, "decoder", "bool_spec")
+        print(template.render(name=node.discriminant.name, type=node.discriminant.spec.type_name))
 
-    for case in node.cases:
-        emit_union_case_spec_decoder(
-            environment,
-            case,
-            node.discriminant.spec.type_name in big_endian,
-        )
+        # Find and emit the TRUE case
+        for case in node.cases:
+            if case.values and case.values[0] == "TRUE":
+                emit_union_arm_decoder(environment, case)
+                break
 
-    emit_union_default_spec_decoder(environment, node)
+        template = get_jinja2_template(environment, "decoder", "close")
+        print(template.render())
+    else:
+        emit_union_switch_spec_decoder(environment, node.discriminant)
 
-    template = get_jinja2_template(environment, "decoder", "close")
-    print(template.render())
+        for case in node.cases:
+            emit_union_case_spec_decoder(
+                environment,
+                case,
+                node.discriminant.spec.type_name in big_endian,
+            )
+
+        emit_union_default_spec_decoder(environment, node)
+
+        template = get_jinja2_template(environment, "decoder", "close")
+        print(template.render())
 
 
 def emit_union_switch_spec_encoder(
@@ -175,6 +214,28 @@ def emit_union_switch_spec_encoder(
     print(template.render(name=node.name, type=node.spec.type_name))
 
 
+def emit_union_arm_encoder(
+    environment: Environment, node: _XdrCaseSpec
+) -> None:
+    """Emit encoder for an XDR union's arm (data only, no case/break)"""
+
+    if isinstance(node.arm, _XdrVoid):
+        return
+    if isinstance(node.arm, _XdrString):
+        type_name = "char *"
+    else:
+        type_name = node.arm.spec.type_name
+
+    assert isinstance(node.arm, (_XdrBasic, _XdrString))
+    template = get_jinja2_template(environment, "encoder", node.arm.template)
+    print(
+        template.render(
+            name=node.arm.name,
+            type=type_name,
+        )
+    )
+
+
 def emit_union_case_spec_encoder(
     environment: Environment, node: _XdrCaseSpec, big_endian_discriminant: bool
 ) -> None:
@@ -235,19 +296,33 @@ def emit_union_encoder(environment, node: _XdrUnion) -> None:
     template = get_jinja2_template(environment, "encoder", "open")
     print(template.render(name=node.name))
 
-    emit_union_switch_spec_encoder(environment, node.discriminant)
+    # For boolean discriminants, use if statement instead of switch
+    if node.discriminant.spec.type_name == "bool":
+        template = get_jinja2_template(environment, "encoder", "bool_spec")
+        print(template.render(name=node.discriminant.name, type=node.discriminant.spec.type_name))
 
-    for case in node.cases:
-        emit_union_case_spec_encoder(
-            environment,
-            case,
-            node.discriminant.spec.type_name in big_endian,
-        )
+        # Find and emit the TRUE case
+        for case in node.cases:
+            if case.values and case.values[0] == "TRUE":
+                emit_union_arm_encoder(environment, case)
+                break
 
-    emit_union_default_spec_encoder(environment, node)
+        template = get_jinja2_template(environment, "encoder", "close")
+        print(template.render())
+    else:
+        emit_union_switch_spec_encoder(environment, node.discriminant)
 
-    template = get_jinja2_template(environment, "encoder", "close")
-    print(template.render())
+        for case in node.cases:
+            emit_union_case_spec_encoder(
+                environment,
+                case,
+                node.discriminant.spec.type_name in big_endian,
+            )
+
+        emit_union_default_spec_encoder(environment, node)
+
+        template = get_jinja2_template(environment, "encoder", "close")
+        print(template.render())
 
 
 def emit_union_maxsize(environment: Environment, node: _XdrUnion) -> None:
diff --git a/tools/net/sunrpc/xdrgen/templates/C/union/decoder/bool_spec.j2 b/tools/net/sunrpc/xdrgen/templates/C/union/decoder/bool_spec.j2
new file mode 100644
index 000000000000..05ad491f74af
--- /dev/null
+++ b/tools/net/sunrpc/xdrgen/templates/C/union/decoder/bool_spec.j2
@@ -0,0 +1,7 @@
+{# SPDX-License-Identifier: GPL-2.0 #}
+{% if annotate %}
+	/* discriminant {{ name }} */
+{% endif %}
+	if (!xdrgen_decode_{{ type }}(xdr, &ptr->{{ name }}))
+		return false;
+	if (ptr->{{ name }}) {
diff --git a/tools/net/sunrpc/xdrgen/templates/C/union/encoder/bool_spec.j2 b/tools/net/sunrpc/xdrgen/templates/C/union/encoder/bool_spec.j2
new file mode 100644
index 000000000000..e5135ed6471c
--- /dev/null
+++ b/tools/net/sunrpc/xdrgen/templates/C/union/encoder/bool_spec.j2
@@ -0,0 +1,7 @@
+{# SPDX-License-Identifier: GPL-2.0 #}
+{% if annotate %}
+	/* discriminant {{ name }} */
+{% endif %}
+	if (!xdrgen_encode_{{ type }}(xdr, ptr->{{ name }}))
+		return false;
+	if (ptr->{{ name }}) {
-- 
2.51.0