2 files changed, 22 insertions, 3 deletions

diff --git a/Makefile b/Makefile
index c839653..edf3402 100644
--- a/Makefile
+++ b/Makefile
@@ -89,12 +89,20 @@ endif
 
 # $(call test-build, snippet, ret) -> ret if snippet compiles
 #                                  -> empty otherwise
-test-build = $(if $(shell $(CC) -o /dev/null -c -x c - > /dev/null 2>&1 \
-                          <<<'$1' && echo y), $2)
+test-build = $(if $(shell sh -c 'echo "$(1)" | \
+        $(CC) -o /dev/null -c -x c - > /dev/null 2>&1 && echo y'), $2)
 
 # have udis86 disassembler library?
 udis86-flags := $(call test-build,\#include <udis86.h>,-DHAVE_UDIS86 -ludis86)
 
+define BLK_TC_FLUSH_SOURCE
+#include <linux/blktrace_api.h>
+int main(void) { return BLK_TC_FLUSH; }
+endef
+
+# have flush/fua block layer instead of barriers?
+blk-flags := $(call test-build,$(BLK_TC_FLUSH_SOURCE),-DHAVE_BLK_TC_FLUSH)
+
 ifeq ("$(origin O)", "command line")
   BUILD_OUTPUT := $(O)
 endif
@@ -223,7 +231,7 @@ endif
 
 # Append required CFLAGS
 override CFLAGS += $(CONFIG_FLAGS) $(INCLUDES) $(PLUGIN_DIR_SQ)
-override CFLAGS += $(udis86-flags)
+override CFLAGS += $(udis86-flags) $(blk-flags)
 
 ifeq ($(VERBOSE),1)
   Q =
diff --git a/plugin_blk.c b/plugin_blk.c
index 9327b17..c0ecef9 100644
--- a/plugin_blk.c
+++ b/plugin_blk.c
@@ -54,6 +54,11 @@ static void fill_rwbs(char *rwbs, int action, unsigned int bytes)
                 goto out;
         }
 
+#if defined(HAVE_BLK_TC_FLUSH)
+        if (tc & BLK_TC_FLUSH)
+                rwbs[i++] = 'F';
+#endif
+
         if (tc & BLK_TC_DISCARD)
                 rwbs[i++] = 'D';
         else if (tc & BLK_TC_WRITE)
@@ -63,10 +68,16 @@ static void fill_rwbs(char *rwbs, int action, unsigned int bytes)
         else
                 rwbs[i++] = 'N';
 
+#if defined(HAVE_BLK_TC_FLUSH)
+        if (tc & BLK_TC_FUA)
+                rwbs[i++] = 'F';
+#endif
         if (tc & BLK_TC_AHEAD)
                 rwbs[i++] = 'A';
+#if !defined(HAVE_BLK_TC_FLUSH)
         if (tc & BLK_TC_BARRIER)
                 rwbs[i++] = 'B';
+#endif
         if (tc & BLK_TC_SYNC)
                 rwbs[i++] = 'S';
         if (tc & BLK_TC_META)