diff --git a/fio-log.c b/fio-log.c
new file mode 100644
index 0000000..42aedf2
--- /dev/null
+++ b/fio-log.c
@@ -0,0 +1,162 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "list.h"
+#include "fio.h"
+
+void write_iolog_put(struct thread_data *td, struct io_u *io_u)
+{
+	fprintf(td->iolog_f, "%d,%llu,%u\n", io_u->ddir, io_u->offset, io_u->buflen);
+}
+
+int read_iolog_get(struct thread_data *td, struct io_u *io_u)
+{
+	struct io_piece *ipo;
+
+	if (!list_empty(&td->io_log_list)) {
+		ipo = list_entry(td->io_log_list.next, struct io_piece, list);
+		list_del(&ipo->list);
+		io_u->offset = ipo->offset;
+		io_u->buflen = ipo->len;
+		io_u->ddir = ipo->ddir;
+		free(ipo);
+		return 0;
+	}
+
+	return 1;
+}
+
+void prune_io_piece_log(struct thread_data *td)
+{
+	struct io_piece *ipo;
+
+	while (!list_empty(&td->io_hist_list)) {
+		ipo = list_entry(td->io_hist_list.next, struct io_piece, list);
+
+		list_del(&ipo->list);
+		free(ipo);
+	}
+}
+
+/*
+ * log a succesful write, so we can unwind the log for verify
+ */
+void log_io_piece(struct thread_data *td, struct io_u *io_u)
+{
+	struct io_piece *ipo = malloc(sizeof(struct io_piece));
+	struct list_head *entry;
+
+	INIT_LIST_HEAD(&ipo->list);
+	ipo->offset = io_u->offset;
+	ipo->len = io_u->buflen;
+
+	/*
+	 * for random io where the writes extend the file, it will typically
+	 * be laid out with the block scattered as written. it's faster to
+	 * read them in in that order again, so don't sort
+	 */
+	if (td->sequential || !td->overwrite) {
+		list_add_tail(&ipo->list, &td->io_hist_list);
+		return;
+	}
+
+	/*
+	 * for random io, sort the list so verify will run faster
+	 */
+	entry = &td->io_hist_list;
+	while ((entry = entry->prev) != &td->io_hist_list) {
+		struct io_piece *__ipo = list_entry(entry, struct io_piece, list);
+
+		if (__ipo->offset < ipo->offset)
+			break;
+	}
+
+	list_add(&ipo->list, entry);
+}
+
+void write_iolog_close(struct thread_data *td)
+{
+	fflush(td->iolog_f);
+	fclose(td->iolog_f);
+	free(td->iolog_buf);
+}
+
+int init_iolog(struct thread_data *td)
+{
+	unsigned long long offset;
+	unsigned int bytes;
+	char *str, *p;
+	FILE *f;
+	int rw, i, reads, writes;
+
+	if (!td->read_iolog && !td->write_iolog)
+		return 0;
+
+	if (td->read_iolog)
+		f = fopen(td->iolog_file, "r");
+	else
+		f = fopen(td->iolog_file, "w");
+
+	if (!f) {
+		perror("fopen iolog");
+		printf("file %s, %d/%d\n", td->iolog_file, td->read_iolog, td->write_iolog);
+		return 1;
+	}
+
+	/*
+	 * That's it for writing, setup a log buffer and we're done.
+	  */
+	if (td->write_iolog) {
+		td->iolog_f = f;
+		td->iolog_buf = malloc(8192);
+		setvbuf(f, td->iolog_buf, _IOFBF, 8192);
+		return 0;
+	}
+
+	/*
+	 * Read in the read iolog and store it, reuse the infrastructure
+	 * for doing verifications.
+	 */
+	str = malloc(4096);
+	reads = writes = i = 0;
+	while ((p = fgets(str, 4096, f)) != NULL) {
+		struct io_piece *ipo;
+
+		if (sscanf(p, "%d,%llu,%u", &rw, &offset, &bytes) != 3) {
+			fprintf(stderr, "bad iolog: %s\n", p);
+			continue;
+		}
+		if (rw == DDIR_READ)
+			reads++;
+		else if (rw == DDIR_WRITE)
+			writes++;
+		else {
+			fprintf(stderr, "bad ddir: %d\n", rw);
+			continue;
+		}
+
+		ipo = malloc(sizeof(*ipo));
+		INIT_LIST_HEAD(&ipo->list);
+		ipo->offset = offset;
+		ipo->len = bytes;
+		if (bytes > td->max_bs)
+			td->max_bs = bytes;
+		ipo->ddir = rw;
+		list_add_tail(&ipo->list, &td->io_log_list);
+		i++;
+	}
+
+	free(str);
+	fclose(f);
+
+	if (!i)
+		return 1;
+
+	if (reads && !writes)
+		td->ddir = DDIR_READ;
+	else if (!reads && writes)
+		td->ddir = DDIR_READ;
+	else
+		td->iomix = 1;
+
+	return 0;
+}