[PATCH v4 11/20] blkiomon: read 'magic' first

Similar to blkparse, read the 'magic' portion of 'struct blk_io_trace'
first when reading the trace.

This is a preparation of supporting multiple trace protocol versions.

Reviewed-by: Damien Le Moal <[email protected]>
Reviewed-by: Martin K. Petersen <[email protected]>
Signed-off-by: Johannes Thumshirn <[email protected]>
---
 blkiomon.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/blkiomon.c b/blkiomon.c
index f8b0c9d..05f2d00 100644
--- a/blkiomon.c
+++ b/blkiomon.c
@@ -460,19 +460,28 @@ static int blkiomon_do_fifo(void)
 	bit = &t->bit;
 
 	while (up) {
+		__u32 magic;
+
+		if (fread(&magic, sizeof(magic), 1, ifp) != 1) {
+			if (!feof(ifp))
+				fprintf(stderr,
+					"blkiomon: could not read trace");
+			break;
+		}
 		if (fread(bit, sizeof(*bit), 1, ifp) != 1) {
 			if (!feof(ifp))
 				fprintf(stderr,
 					"blkiomon: could not read trace");
 			break;
 		}
+		bit->magic = magic;
 		if (ferror(ifp)) {
 			clearerr(ifp);
 			fprintf(stderr, "blkiomon: error while reading trace");
 			break;
 		}
 
-		if (data_is_native == -1 && check_data_endianness(bit->magic)) {
+		if (data_is_native == -1 && check_data_endianness(magic)) {
 			fprintf(stderr, "blkiomon: endianess problem\n");
 			break;
 		}
-- 
2.51.1