Scramble on a 512b boundary

[fio.git] / io_u.c

diff --git a/io_u.c b/io_u.c
index 16c98b1f454869c43e4862b91c57b1278898de28..f4c4aa2ca432532d894d61c9559940c7b1ee43b4 100644 (file)
--- a/io_u.c
+++ b/io_u.c
@@ -1120,6 +1120,39 @@ static int check_get_verify(struct thread_data *td, struct io_u *io_u)
        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.
@@ -1128,6 +1161,7 @@ struct io_u *get_io_u(struct thread_data *td)
 {
        struct fio_file *f;
        struct io_u *io_u;
+       int do_scramble = 0;
 
        io_u = __get_io_u(td);
        if (!io_u) {
@@ -1173,6 +1207,8 @@ struct io_u *get_io_u(struct thread_data *td)
                        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
@@ -1193,6 +1229,8 @@ out:
        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:
@@ -1450,7 +1488,7 @@ void io_u_fill_buffer(struct thread_data *td, struct io_u *io_u,
        io_u->buf_filled_len = 0;
 
        if (!td->o.zero_buffers)
-               fill_random_buf(io_u->buf, max_bs);
+               fill_random_buf(&td->buf_state, io_u->buf, max_bs);
        else
                memset(io_u->buf, 0, max_bs);
 }