discard systemtap

1 files changed, 54 insertions, 0 deletions

diff --git a/systemtap/discard/test.stap b/systemtap/discard/test.stap
new file mode 100644
index 0000000..2202ba5
--- /dev/null
+++ b/systemtap/discard/test.stap
@@ -0,0 +1,54 @@
+
+function timestamp:string() {
+  printf("[%012ld]\t", jiffies());
+}
+
+// Filesystem level (ext4)
+probe module("ext4").function("ext4_issue_discard") {
+  timestamp();
+  printf("ext4_issue_discard dev=%s block_group=%u cluster=%d count=%d (=> *8 nr_sects=%d)\n", 
+	 bdevname($sb->s_bdev),
+	 $block_group, $cluster, $count, $count * 8);
+}
+
+// Block-Device level (disk-mapper)
+probe kernel.function("blkdev_issue_discard") {
+  timestamp();
+  printf("blkdev_issue_discard dev=%s sector=%u nr_sects=%u\n", 
+	 bdevname($bdev), $sector, $nr_sects);
+}
+
+// SCSI-Command
+probe scsi.iodispatching {
+  // drivers/scsi/sd.c:scsi_setup_discard_cmnd()
+  if ($cmd->cmd_len >= 16 
+      && $cmd->cmnd[0] == 0x93 /* WRITE_SAME_16 */
+      && $cmd->cmnd[1] == 0x08 /* UNMAP */) {
+
+    timestamp();
+    printf("SCSI [WRITE_SAME_16, UNMAP, sector, count] ");
+
+    sector = ( ($cmd->cmnd[2] << 56) +
+	       ($cmd->cmnd[3] << 48) +
+	       ($cmd->cmnd[4] << 40) +
+	       ($cmd->cmnd[5] << 32) +
+	       ($cmd->cmnd[6] << 24) +
+	       ($cmd->cmnd[7] << 16) +
+	       ($cmd->cmnd[8] << 8) +
+	       ($cmd->cmnd[9]) );	   
+
+    // Substract partition start position (fdisk: 22464512) + Crypto overhead (4096 sectors)
+    sector = sector - 22468608;
+
+    // Number of sectors (count)
+    nr_sects = ( ($cmd->cmnd[10] << 24) +
+		 ($cmd->cmnd[11] << 16) +
+		 ($cmd->cmnd[12] << 8) +
+		 ($cmd->cmnd[13]) );
+
+    printf("state=%s direction=%s dev=%u:%u:%u:%u sector=%u nr_sects=%u\n",
+	   device_state_str, data_direction_str, host_no, channel, lun, dev_id,
+	   sector, nr_sects);
+  }
+}
+