Fix read/write mix and different levels of randomness

Stephen reports:

When using fio configuration below:

[global]
ioengine=libaio
direct=1
runtime=600
bs=32k
iodepth=8
rw=randrw
rwmixread=80
percentage_random=100,0

[drive1]
filename=/dev/sda

I am expecting to see 80% reads, 20% writes where all reads are random
and all writes are sequential. I captured a bus trace of traffic to the
disk and the bus trace reflected as much with one issue. The write
commands are essentially random. Each write begins at a new random LBA.
If 2 or more writes occur in a row, the LBA's are sequential based on
the block size BUT I feel the heart of this feature would be to emulate
a large file write during random access. With that in mind would it be
possible for sequential reads or writes within mixed sequential/random
workload to remember the last LBA accessed? In this scenario the writes
would still only take up 20% of the workload but when a write did occur
it should be the next sequential step from the last write.

-----

This is due to the fact that fio tracks last start/end on a unified
basis, not per read/write/trim direction. Fix that.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/file.h b/file.h
index add7773..bb30310 100644
--- a/file.h
+++ b/file.h
@@ -88,8 +88,11 @@
 	uint64_t file_offset;
 	uint64_t io_size;
 
-	uint64_t last_pos;
-	uint64_t last_start;
+	/*
+	 * Track last end and last start of IO for a given data direction
+	 */
+	uint64_t last_pos[DDIR_RWDIR_CNT];
+	uint64_t last_start[DDIR_RWDIR_CNT];
 
 	uint64_t first_write;
 	uint64_t last_write;
diff --git a/filesetup.c b/filesetup.c
index cc6d440..a918234 100644
--- a/filesetup.c
+++ b/filesetup.c
@@ -1536,8 +1536,13 @@
 
 void fio_file_reset(struct thread_data *td, struct fio_file *f)
 {
-	f->last_pos = f->file_offset;
-	f->last_start = -1ULL;
+	int i;
+
+	for (i = 0; i < DDIR_RWDIR_CNT; i++) {
+		f->last_pos[i] = f->file_offset;
+		f->last_start[i] = -1ULL;
+	}
+
 	if (f->io_axmap)
 		axmap_reset(f->io_axmap);
 	if (td->o.random_generator == FIO_RAND_GEN_LFSR)
diff --git a/io_u.c b/io_u.c
index f135908..efbcea9 100644
--- a/io_u.c
+++ b/io_u.c
@@ -249,7 +249,7 @@
 	}
 
 	dprint(FD_IO, "%s: rand offset failed, last=%llu, size=%llu\n",
-			f->file_name, (unsigned long long) f->last_pos,
+			f->file_name, (unsigned long long) f->last_pos[ddir],
 			(unsigned long long) f->real_file_size);
 	return 1;
 }
@@ -261,17 +261,17 @@
 
 	assert(ddir_rw(ddir));
 
-	if (f->last_pos >= f->io_size + get_start_offset(td, f) &&
+	if (f->last_pos[ddir] >= f->io_size + get_start_offset(td, f) &&
 	    o->time_based)
-		f->last_pos = f->last_pos - f->io_size;
+		f->last_pos[ddir] = f->last_pos[ddir] - f->io_size;
 
-	if (f->last_pos < f->real_file_size) {
+	if (f->last_pos[ddir] < f->real_file_size) {
 		uint64_t pos;
 
-		if (f->last_pos == f->file_offset && o->ddir_seq_add < 0)
-			f->last_pos = f->real_file_size;
+		if (f->last_pos[ddir] == f->file_offset && o->ddir_seq_add < 0)
+			f->last_pos[ddir] = f->real_file_size;
 
-		pos = f->last_pos - f->file_offset;
+		pos = f->last_pos[ddir] - f->file_offset;
 		if (pos && o->ddir_seq_add) {
 			pos += o->ddir_seq_add;
 
@@ -330,8 +330,8 @@
 				*is_random = 0;
 			}
 		} else if (td->o.rw_seq == RW_SEQ_IDENT) {
-			if (f->last_start != -1ULL)
-				offset = f->last_start - f->file_offset;
+			if (f->last_start[ddir] != -1ULL)
+				offset = f->last_start[ddir] - f->file_offset;
 			else
 				offset = 0;
 			ret = 0;
@@ -743,7 +743,7 @@
 		 */
 		if (f->file_offset >= f->real_file_size)
 			f->file_offset = f->real_file_size - f->file_offset;
-		f->last_pos = f->file_offset;
+		f->last_pos[io_u->ddir] = f->file_offset;
 		td->io_skip_bytes += td->o.zone_skip;
 	}
 
@@ -1471,8 +1471,8 @@
 			goto err_put;
 		}
 
-		f->last_start = io_u->offset;
-		f->last_pos = io_u->offset + io_u->buflen;
+		f->last_start[io_u->ddir] = io_u->offset;
+		f->last_pos[io_u->ddir] = io_u->offset + io_u->buflen;
 
 		if (io_u->ddir == DDIR_WRITE) {
 			if (td->flags & TD_F_REFILL_BUFFERS) {