Require sparse, and filter kernel sparse output

Fail the build if we don't check with sparse in both the kernel and
userspace utils.  Add a filtering wrapper to the kernel build so that we
have a place to filter out uninteresting errors from kernel sources that
we're building against.

Signed-off-by: Zach Brown <zab@versity.com>

kmod/Makefile

@@ -5,13 +5,6 @@ ifeq ($(SK_KSRC),)
 SK_KSRC := $(shell echo /lib/modules/`uname -r`/build)
 endif
 
-# fail if sparse fails if we find it
-ifeq ($(shell sparse && echo found),found)
-SP =
-else
-SP = @:
-endif
-
 SCOUTFS_GIT_DESCRIBE ?= \
 	$(shell git describe --all --abbrev=6 --long 2>/dev/null || \
 		echo no-git)
@@ -36,9 +29,7 @@ TARFILE = scoutfs-kmod-$(RPM_VERSION).tar
 all: module
 
 module:
-	$(MAKE) $(SCOUTFS_ARGS)
-	$(SP) $(MAKE) C=2 CF="-D__CHECK_ENDIAN__" $(SCOUTFS_ARGS)
-
+	$(MAKE) CHECK=$(CURDIR)/src/sparse-filtered.sh C=1 CF="-D__CHECK_ENDIAN__" $(SCOUTFS_ARGS)
 
 modules_install:
 	$(MAKE) $(SCOUTFS_ARGS) modules_install

kmod/src/sparse-filtered.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+
+#
+# Unfortunately, kernels can ship which contain sparse errors that are
+# unrelated to us.
+#
+# The exit status of this filtering wrapper will indicate an error if
+# sparse wasn't found or if there were any unfiltered output lines.  It
+# can hide error exit status from sparse or grep if they don't produce
+# output that makes it past the filters.
+#
+
+# must have sparse.  Fail with error message, mask success path.
+which sparse > /dev/null || exit 1
+
+# initial unmatchable, additional added as RE+="|..."
+RE="$^"
+
+sparse "$@" |& \
+	grep -E -v "($RE)" |& \
+	awk '{ print $0 } END { exit NR > 0 }'
+exit $?

utils/sparse.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 
-# can we find sparse?  If not, we're done.
-which sparse > /dev/null 2>&1 || exit 0
+# must have sparse.  Fail with error message, mask success path.
+which sparse > /dev/null || exit 1
 
 # 
 # one of the problems with using sparse in userspace is that it picks up