return 0;
}
+/*
+ * Fill offset and start time into the buffer content, to prevent too
+ * easy compressible data for simple de-dupe attempts. Do this for every
+ * 512b block in the range, since that should be the smallest block size
+ * we can expect from a device.
+ */
+static void small_content_scramble(struct io_u *io_u)
+{
+ unsigned int i, nr_blocks = io_u->buflen / 512;
+ unsigned int offset;
+ void *p, *end;
+
+ if (!nr_blocks)
+ return;
+
+ p = io_u->xfer_buf;
+ for (i = 0; i < nr_blocks; i++) {
+ /*
+ * Fill the byte offset into a "random" start offset of
+ * the buffer, given by the product of the usec time
+ * and the actual offset.
+ */
+ offset = (io_u->start_time.tv_usec * io_u->offset) & 511;
+ if (offset >= 512 - sizeof(unsigned long long))
+ offset -= sizeof(unsigned long long);
+ *((unsigned long long *) p + offset) = io_u->offset;
+
+ end = p + 512 - sizeof(io_u->start_time);
+ memcpy(end, &io_u->start_time, sizeof(io_u->start_time));
+ p += 512;
+ }
+}
+
/*
* Return an io_u to be processed. Gets a buflen and offset, sets direction,
* etc. The returned io_u is fully ready to be prepped and submitted.
{
struct fio_file *f;
struct io_u *io_u;
+ int do_scramble = 0;
io_u = __get_io_u(td);
if (!io_u) {
populate_verify_io_u(td, io_u);
else if (td->o.refill_buffers && io_u->ddir == DDIR_WRITE)
io_u_fill_buffer(td, io_u, io_u->xfer_buflen);
+ else if (io_u->ddir == DDIR_WRITE)
+ do_scramble = 1;
else if (io_u->ddir == DDIR_READ) {
/*
* Reset the buf_filled parameters so next time if the
if (!td_io_prep(td, io_u)) {
if (!td->o.disable_slat)
fio_gettime(&io_u->start_time, NULL);
+ if (do_scramble)
+ small_content_scramble(io_u);
return io_u;
}
err_put: