X-Git-Url: https://git.kernel.dk/?p=fio.git;a=blobdiff_plain;f=io_u.c;h=77069c55277f8aeb0cd93d99754b12913cdfbaee;hp=16c98b1f454869c43e4862b91c57b1278898de28;hb=b1d1b239d2a3299a4d7b7b3de185923c655d0a48;hpb=a66da7a2354aac16757c75a824ad7cbba678535c

diff --git a/io_u.c b/io_u.c
index 16c98b1f..77069c55 100644
--- a/io_u.c
+++ b/io_u.c
@@ -1120,6 +1120,44 @@ 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 long long boffset;
+	unsigned int offset;
+	void *p, *end;
+
+	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;
+	}
+}
+
 /*
  * 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 +1166,7 @@ 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) {
@@ -1169,11 +1208,14 @@ struct io_u *get_io_u(struct thread_data *td)
 		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_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.
@@ -1193,6 +1235,8 @@ 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 +1494,7 @@ 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);
 }