blk plugin: replace BLK_TC_BARRIER with BLK_TC_FLUSH/BLK_TC_FUA

The BLK_TC_BARRIER flag was dropped in Linux commit c09c47caedc in
August 2011.  The blk plugin fails to build against recent kernel
headers.  Since no flag bits were left, the new BLK_TC_FLUSH flag reused
the BLK_TC_BARRIER bit.  The new BLK_TC_FUA flag was also added.

This patch updates fill_rwbs() to reflect the new
BLK_TC_FLUSH/BLK_TC_FUA flags.  This allows plugin_blk.c to build
successfully on recent kernels.  Most of the patch deals with detecting
old vs new kernel headers so we can build successfully on both.

(Namhyung Kim recommended using the makefile check used by perf and
 other tools)

Link: http://lkml.kernel.org/r/1326108639-13904-1-git-send-email-stefanha@linux.vnet.ibm.com

Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

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)