/*
* Fill offset and start time into the buffer content, to prevent too
- * easy compressible data for simple de-dupe attempts.
+ * 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)
{
- void *end;
+ unsigned int i, nr_blocks = io_u->buflen / 512;
+ unsigned long long boffset;
+ unsigned int offset;
+ void *p, *end;
- *((unsigned long long *) io_u->xfer_buf) = io_u->offset;
- end = io_u->xfer_buf + io_u->xfer_buflen - sizeof(io_u->start_time);
- memcpy(end, &io_u->start_time, sizeof(io_u->start_time));
+ if (!nr_blocks)
+ return;
+
+ p = io_u->xfer_buf;
+ boffset = io_u->offset;
+
+ 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 ^ boffset) & 511;
+ offset &= ~(sizeof(unsigned long long) - 1);
+ if (offset >= 512 - sizeof(unsigned long long))
+ offset -= sizeof(unsigned long long);
+ memcpy(p + offset, &boffset, sizeof(boffset));
+
+ end = p + 512 - sizeof(io_u->start_time);
+ memcpy(end, &io_u->start_time, sizeof(io_u->start_time));
+ p += 512;
+ boffset += 512;
+ }
}
/*
f->last_start = io_u->offset;
f->last_pos = io_u->offset + io_u->buflen;
- if (td->o.verify != VERIFY_NONE && io_u->ddir == DDIR_WRITE)
- 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) {
+ if (io_u->ddir == DDIR_WRITE) {
+ if (td->o.verify != VERIFY_NONE)
+ populate_verify_io_u(td, io_u);
+ else if (td->o.refill_buffers)
+ io_u_fill_buffer(td, io_u, io_u->xfer_buflen);
+ else if (td->o.scramble_buffers)
+ do_scramble = 1;
+ } else if (io_u->ddir == DDIR_READ) {
/*
* Reset the buf_filled parameters so next time if the
* buffer is used for writes it is refilled.