include blktrace_api.h in headers_install

This header file is of interest for user space programming, i.e.
for tools that process blktrace data.

We would like to use it for a tool on-top of blktrace which processes
data provided by blktrace. For this purpose, it would be helpful
if the blktrace API would make it to /usr/include/linux.

The git tree for the blktrace tools comes with its own copy of this header
file. I didn't manage to replace that copy with the file generated
by the patch below yet. A few more cleanups would be needed.
For example, the blktrace ioctl numbers, which are currently defined in
usr/include/fs.h, might need to be moved. Should be feasible, though.
Signed-off-by: Sven Schuetz <sven@linux.vnet.ibm.com>
Signed-off-by: Martin Peschke <mp3@de.ibm.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

include/linux/Kbuild

@@ -180,6 +180,7 @@ unifdef-y += audit.h
 unifdef-y += auto_fs.h
 unifdef-y += auxvec.h
 unifdef-y += binfmts.h
+unifdef-y += blktrace_api.h
 unifdef-y += capability.h
 unifdef-y += capi.h
 unifdef-y += cciss_ioctl.h

include/linux/blktrace_api.h

 #ifndef BLKTRACE_H
 #define BLKTRACE_H
 
+#ifdef __KERNEL__
 #include <linux/blkdev.h>
 #include <linux/relay.h>
+#endif
 
 /*
  * Trace categories
@@ -92,17 +94,17 @@ enum blktrace_notify {
  * The trace itself
  */
 struct blk_io_trace {
-	u32 magic;		/* MAGIC << 8 | version */
-	u32 sequence;		/* event number */
-	u64 time;		/* in microseconds */
-	u64 sector;		/* disk offset */
-	u32 bytes;		/* transfer length */
-	u32 action;		/* what happened */
-	u32 pid;		/* who did it */
-	u32 device;		/* device number */
-	u32 cpu;		/* on what cpu did it happen */
-	u16 error;		/* completion error */
-	u16 pdu_len;		/* length of data after this trace */
+	__u32 magic;		/* MAGIC << 8 | version */
+	__u32 sequence;		/* event number */
+	__u64 time;		/* in microseconds */
+	__u64 sector;		/* disk offset */
+	__u32 bytes;		/* transfer length */
+	__u32 action;		/* what happened */
+	__u32 pid;		/* who did it */
+	__u32 device;		/* device number */
+	__u32 cpu;		/* on what cpu did it happen */
+	__u16 error;		/* completion error */
+	__u16 pdu_len;		/* length of data after this trace */
 };
 
 /*
@@ -120,6 +122,25 @@ enum {
 	Blktrace_stopped,
 };
 
+/*
+ * User setup structure passed with BLKTRACESTART
+ */
+struct blk_user_trace_setup {
+#ifdef __KERNEL__
+	char name[BDEVNAME_SIZE];	/* output */
+#else
+	char name[32];			/* output */
+#endif
+	__u16 act_mask;			/* input */
+	__u32 buf_size;			/* input */
+	__u32 buf_nr;			/* input */
+	__u64 start_lba;
+	__u64 end_lba;
+	__u32 pid;
+};
+
+#ifdef __KERNEL__
+#if defined(CONFIG_BLK_DEV_IO_TRACE)
 struct blk_trace {
 	int trace_state;
 	struct rchan *rchan;
@@ -136,21 +157,6 @@ struct blk_trace {
 	atomic_t dropped;
 };
 
-/*
- * User setup structure passed with BLKTRACESTART
- */
-struct blk_user_trace_setup {
-	char name[BDEVNAME_SIZE];	/* output */
-	u16 act_mask;			/* input */
-	u32 buf_size;			/* input */
-	u32 buf_nr;			/* input */
-	u64 start_lba;
-	u64 end_lba;
-	u32 pid;
-};
-
-#ifdef __KERNEL__
-#if defined(CONFIG_BLK_DEV_IO_TRACE)
 extern int blk_trace_ioctl(struct block_device *, unsigned, char __user *);
 extern void blk_trace_shutdown(struct request_queue *);
 extern void __blk_add_trace(struct blk_trace *, sector_t, int, int, u32, int, int, void *);