From: Ilya Dryomov <idryomov@gmail.com>
Date: Tue, 17 Sep 2019 16:55:18 +0000 (+0200)
Subject: qa: avoid page cache for krbd discard round off tests
X-Git-Tag: v15.1.0~1511^2
X-Git-Url: http://git.apps.os.sepia.ceph.com/?a=commitdiff_plain;h=a9ed8d32791463d4b52985f688dd856d7aba7c60;p=ceph-ci.git

qa: avoid page cache for krbd discard round off tests

rbd rounds off and ignores discards that are smaller than alloc_size,
but the page cache is invalidated according to the original offset and
length, before calling into the driver.  For a 512~4193792 discard, all
pages except for the first will be invalidated, but the first page may
remain cached after being partially zeroed out.  This results in an
inconsistency when alloc_size != 512.  E.g. for 64k:

                0       512     4k      64k             4M
                |       |       |       |               |
  page cache:   xxxxxxxx00000000xxxxxxxx0000000000000000
       RADOS:   xxxxxxxxxxxxxxxxxxxxxxxx0000000000000000

Given that these tests asserts on-disk state, we need to read directly
from disk.  krbd_discard_512b.t and krbd_zeroout.t are fine -- there is
no rounding there.

Fixes: https://tracker.ceph.com/issues/41753
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
---

diff --git a/qa/rbd/krbd_discard.t b/qa/rbd/krbd_discard.t
index a76f3bfcf20..99f7261f2ab 100644
--- a/qa/rbd/krbd_discard.t
+++ b/qa/rbd/krbd_discard.t
@@ -6,28 +6,28 @@ Zero, < 1 block:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 156672 -l 512 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131584 -l 64512 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131584 -l 65024 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131072 -l 65024 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
@@ -36,7 +36,7 @@ Zero, 1 block:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131072 -l 65536 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0020000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -47,7 +47,7 @@ Zero, 1 block:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131072 -l 66048 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0020000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -58,7 +58,7 @@ Zero, 1 block:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 130560 -l 66048 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0020000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -69,7 +69,7 @@ Zero, 1 block:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 130560 -l 66560 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0020000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -82,21 +82,21 @@ Zero, < 2 blocks:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 163840 -l 65536 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131584 -l 130048 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131584 -l 130560 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0030000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -107,7 +107,7 @@ Zero, < 2 blocks:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131072 -l 130560 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0020000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -120,7 +120,7 @@ Zero, 2 blocks:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131072 -l 131072 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0020000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -131,7 +131,7 @@ Zero, 2 blocks:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131072 -l 131584 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0020000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -142,7 +142,7 @@ Zero, 2 blocks:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 130560 -l 131584 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0020000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -153,7 +153,7 @@ Zero, 2 blocks:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 130560 -l 132096 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0020000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -166,7 +166,7 @@ Zero, 37 blocks:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 589824 -l 2424832 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0090000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -177,7 +177,7 @@ Zero, 37 blocks:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 589312 -l 2424832 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0090000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -188,7 +188,7 @@ Zero, 37 blocks:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 590336 -l 2424832 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   00a0000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -201,21 +201,21 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4193792 -l 512 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4129280 -l 65024 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4128768 -l 65536 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   03f0000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -224,7 +224,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4128256 -l 66048 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   03f0000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -233,7 +233,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4063744 -l 130560 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   03f0000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -242,7 +242,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4063232 -l 131072 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   03e0000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -251,7 +251,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4062720 -l 131584 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   03e0000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -260,7 +260,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 512 -l 4193792 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0010000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -271,7 +271,7 @@ Delete:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 0 -l 4194304 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 0000 0000 0000 0000 0000 0000 0000 0000
   *
   0400000
@@ -286,7 +286,7 @@ Empty clone:
   $ rbd clone img@snap cloneimg1
   $ DEV=$(sudo rbd map cloneimg1)
   $ blkdiscard -o 720896 -l 2719744 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 abab abab abab abab abab abab abab abab
   *
   0400000
@@ -295,7 +295,7 @@ Empty clone:
   $ rbd clone img@snap cloneimg2
   $ DEV=$(sudo rbd map cloneimg2)
   $ blkdiscard -o 1474560 -l 2719744 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 abab abab abab abab abab abab abab abab
   *
   0400000
@@ -304,7 +304,7 @@ Empty clone:
   $ rbd clone img@snap cloneimg3
   $ DEV=$(sudo rbd map cloneimg3)
   $ blkdiscard -o 0 -l 4194304 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 abab abab abab abab abab abab abab abab
   *
   0400000
@@ -317,7 +317,7 @@ Full clone:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 720896 -l 2719744 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   00b0000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -328,7 +328,7 @@ Full clone:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 1474560 -l 2719744 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0170000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -337,7 +337,7 @@ Full clone:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 0 -l 4194304 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 0000 0000 0000 0000 0000 0000 0000 0000
   *
   0400000
@@ -351,14 +351,14 @@ Multiple object requests:
 
   $ xfs_io -c 'pwrite -b 4M -w 0 50M' $DEV >/dev/null
   $ blkdiscard -o 0 -l 143360 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   3200000
 
   $ xfs_io -c 'pwrite -b 4M -w 0 50M' $DEV >/dev/null
   $ blkdiscard -o 0 -l 286720 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 0000 0000 0000 0000 0000 0000 0000 0000
   *
   0008000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
@@ -379,7 +379,7 @@ Multiple object requests:
 
   $ xfs_io -c 'pwrite -b 4M -w 0 50M' $DEV >/dev/null
   $ blkdiscard -o 0 -l 573440 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 0000 0000 0000 0000 0000 0000 0000 0000
   *
   0050000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
diff --git a/qa/rbd/krbd_discard_4M.t b/qa/rbd/krbd_discard_4M.t
index 395f0241d69..6c3d7cc74c1 100644
--- a/qa/rbd/krbd_discard_4M.t
+++ b/qa/rbd/krbd_discard_4M.t
@@ -6,28 +6,28 @@ Zero, < 1 block:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 156672 -l 512 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131584 -l 64512 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131584 -l 65024 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131072 -l 65024 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
@@ -36,28 +36,28 @@ Zero, 1 block:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131072 -l 65536 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131072 -l 66048 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 130560 -l 66048 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 130560 -l 66560 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
@@ -66,28 +66,28 @@ Zero, < 2 blocks:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 163840 -l 65536 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131584 -l 130048 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131584 -l 130560 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131072 -l 130560 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
@@ -96,28 +96,28 @@ Zero, 2 blocks:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131072 -l 131072 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 131072 -l 131584 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 130560 -l 131584 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 130560 -l 132096 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
@@ -126,21 +126,21 @@ Zero, 37 blocks:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 589824 -l 2424832 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 589312 -l 2424832 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 590336 -l 2424832 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
@@ -149,7 +149,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4193792 -l 512 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   03ffe00 0000 0000 0000 0000 0000 0000 0000 0000
@@ -158,7 +158,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4129280 -l 65024 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   03f0200 0000 0000 0000 0000 0000 0000 0000 0000
@@ -167,7 +167,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4128768 -l 65536 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   03f0000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -176,7 +176,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4128256 -l 66048 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   03efe00 0000 0000 0000 0000 0000 0000 0000 0000
@@ -185,7 +185,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4063744 -l 130560 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   03e0200 0000 0000 0000 0000 0000 0000 0000 0000
@@ -194,7 +194,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4063232 -l 131072 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   03e0000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -203,7 +203,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 4062720 -l 131584 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   03dfe00 0000 0000 0000 0000 0000 0000 0000 0000
@@ -212,7 +212,7 @@ Truncate:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 512 -l 4193792 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0000200 0000 0000 0000 0000 0000 0000 0000 0000
@@ -223,7 +223,7 @@ Delete:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 0 -l 4194304 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 0000 0000 0000 0000 0000 0000 0000 0000
   *
   0400000
@@ -238,7 +238,7 @@ Empty clone:
   $ rbd clone img@snap cloneimg1
   $ DEV=$(sudo rbd map -o alloc_size=4194304 cloneimg1)
   $ blkdiscard -o 720896 -l 2719744 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 abab abab abab abab abab abab abab abab
   *
   0400000
@@ -247,7 +247,7 @@ Empty clone:
   $ rbd clone img@snap cloneimg2
   $ DEV=$(sudo rbd map -o alloc_size=4194304 cloneimg2)
   $ blkdiscard -o 1474560 -l 2719744 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 abab abab abab abab abab abab abab abab
   *
   0400000
@@ -256,7 +256,7 @@ Empty clone:
   $ rbd clone img@snap cloneimg3
   $ DEV=$(sudo rbd map -o alloc_size=4194304 cloneimg3)
   $ blkdiscard -o 0 -l 4194304 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 abab abab abab abab abab abab abab abab
   *
   0400000
@@ -269,14 +269,14 @@ Full clone:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 720896 -l 2719744 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0400000
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 1474560 -l 2719744 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   0168000 0000 0000 0000 0000 0000 0000 0000 0000
@@ -285,7 +285,7 @@ Full clone:
 
   $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
   $ blkdiscard -o 0 -l 4194304 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 0000 0000 0000 0000 0000 0000 0000 0000
   *
   0400000
@@ -299,21 +299,21 @@ Multiple object requests:
 
   $ xfs_io -c 'pwrite -b 4M -w 0 50M' $DEV >/dev/null
   $ blkdiscard -o 0 -l 143360 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   3200000
 
   $ xfs_io -c 'pwrite -b 4M -w 0 50M' $DEV >/dev/null
   $ blkdiscard -o 0 -l 286720 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   3200000
 
   $ xfs_io -c 'pwrite -b 4M -w 0 50M' $DEV >/dev/null
   $ blkdiscard -o 0 -l 573440 $DEV
-  $ hexdump $DEV
+  $ dd if=$DEV iflag=direct bs=4M status=none | hexdump
   0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
   *
   3200000