Factor out reading a single blk_io_trace event. This de-duplicates code
and also prepares for expansion with new trace protocol versions.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
 blkparse.c | 78 ++++++++++++++++++++++++------------------------------
 1 file changed, 34 insertions(+), 44 deletions(-)

diff --git a/blkparse.c b/blkparse.c
index 8381e20..5d5cd48 100644
--- a/blkparse.c
+++ b/blkparse.c
@@ -2428,6 +2428,34 @@ static inline __u32 get_magic(__u32 magic)
 	return __bswap_32(magic);
 }
 
+static int read_one_bit(int fd, struct blk_io_trace *bit, int block,
+			int *fdblock)
+{
+	int ret;
+	int pdu_len;
+	void *p = (void *) ((u8 *)bit + sizeof(__u32));
+
+	ret = read_data(fd, p, sizeof(*bit) - sizeof(__u32), block, fdblock);
+	if (ret)
+		return ret;
+
+	pdu_len = get_pdulen(bit);
+	if (pdu_len) {
+		void *ptr = realloc(bit, sizeof(*bit) + pdu_len);
+
+		ret = read_data(fd, ptr + sizeof(*bit), pdu_len, 1, fdblock);
+		if (ret) {
+			free(ptr);
+			return ret;
+		}
+		bit = ptr;
+	}
+
+	trace_to_cpu(bit);
+
+	return 0;
+}
+
 static int read_events(int fd, int always_block, int *fdblock)
 {
 	struct per_dev_info *pdi = NULL;
@@ -2436,9 +2464,8 @@ static int read_events(int fd, int always_block, int *fdblock)
 	while (!is_done() && events < rb_batch) {
 		struct blk_io_trace *bit;
 		struct trace *t;
-		int pdu_len, should_block, ret;
+		int should_block, ret;
 		__u32 magic;
-		void *p;
 
 		should_block = !events || always_block;
 
@@ -2465,33 +2492,14 @@ static int read_events(int fd, int always_block, int *fdblock)
 
 		bit = bit_alloc();
 		bit->magic = magic;
-		p = (void *) ((u8 *)bit + sizeof(magic));
 
-		ret = read_data(fd, p, sizeof(*bit) - sizeof(magic),
-				should_block, fdblock);
-		if (ret) {
-			bit_free(bit);
-			if (!events && ret < 0)
-				events = ret;
+		ret = read_one_bit(fd, bit, 1, fdblock);
+		if (ret)
 			break;
-		}
-
-		pdu_len = get_pdulen(bit);
-		if (pdu_len) {
-			void *ptr = realloc(bit, sizeof(*bit) + pdu_len);
-
-			if (read_data(fd, ptr + sizeof(*bit), pdu_len, 1, fdblock)) {
-				bit_free(ptr);
-				break;
-			}
-
-			bit = ptr;
-		}
-
-		trace_to_cpu(bit);
 
 		if (verify_trace(bit)) {
 			bit_free(bit);
+			bit = NULL;
 			continue;
 		}
 
@@ -2605,10 +2613,9 @@ static int ms_prime(struct ms_stream *msp)
 	struct per_dev_info *pdi = msp->pdi;
 	struct per_cpu_info *pci = get_cpu_info(pdi, msp->cpu);
 	struct blk_io_trace *bit = NULL;
-	int ret, pdu_len, ndone = 0;
+	int ret, ndone = 0;
 
 	for (i = 0; !is_done() && pci->fd >= 0 && i < rb_batch; i++) {
-		void *p;
 
 		ret = read_data(pci->fd, &magic, sizeof(magic), 1,
 				&pci->fdblock);
@@ -2626,28 +2633,11 @@ static int ms_prime(struct ms_stream *msp)
 		}
 		bit = bit_alloc();
 		bit->magic = magic;
-		p = (void *) ((u8 *)bit + sizeof(magic));
 
-		ret = read_data(pci->fd, p, sizeof(*bit) - sizeof(magic), 1,
-				&pci->fdblock);
+		ret = read_one_bit(pci->fd, bit, 1, &pci->fdblock);
 		if (ret)
 			goto err;
 
-		pdu_len = get_pdulen(bit);
-		if (pdu_len) {
-			void *ptr = realloc(bit, sizeof(*bit) + pdu_len);
-			ret = read_data(pci->fd, ptr + sizeof(*bit), pdu_len,
-							     1, &pci->fdblock);
-			if (ret) {
-				free(ptr);
-				bit = NULL;
-				goto err;
-			}
-
-			bit = ptr;
-		}
-
-		trace_to_cpu(bit);
 		if (verify_trace(bit))
 			goto err;
 
-- 
2.51.0