From 031bbea739569721f767f9308ee73f5cf550167d Mon Sep 17 00:00:00 2001
From: Ilya Dryomov <idryomov@gmail.com>
Date: Thu, 31 Jan 2019 18:54:24 +0100
Subject: [PATCH] qa: krbd discard with alloc_size vs zeroout tests

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
---
 qa/rbd/krbd_discard.t                        | 398 +++++++++++++++++
 qa/rbd/krbd_discard_1b.t                     | 416 ++++++++++++++++++
 qa/rbd/krbd_discard_4M.t                     | 330 +++++++++++++++
 qa/rbd/krbd_zeroout.t                        | 422 +++++++++++++++++++
 qa/suites/krbd/basic/tasks/krbd_discard.yaml |   8 +
 5 files changed, 1574 insertions(+)
 create mode 100644 qa/rbd/krbd_discard.t
 create mode 100644 qa/rbd/krbd_discard_1b.t
 create mode 100644 qa/rbd/krbd_discard_4M.t
 create mode 100644 qa/rbd/krbd_zeroout.t
 create mode 100644 qa/suites/krbd/basic/tasks/krbd_discard.yaml

diff --git a/qa/rbd/krbd_discard.t b/qa/rbd/krbd_discard.t
new file mode 100644
index 0000000000000..a76f3bfcf2091
--- /dev/null
+++ b/qa/rbd/krbd_discard.t
@@ -0,0 +1,398 @@
+
+  $ rbd create --size 4M img
+  $ DEV=$(sudo rbd map img)
+
+Zero, < 1 block:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 156672 -l 512 $DEV
+  $ hexdump $DEV
+  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
+  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
+  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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, 1 block:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 131072 -l 65536 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, < 2 blocks:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 163840 -l 65536 $DEV
+  $ hexdump $DEV
+  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
+  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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0030000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, 2 blocks:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 131072 -l 131072 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, 37 blocks:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 589824 -l 2424832 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0090000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  02e0000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0090000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  02d0000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  00a0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  02e0000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Truncate:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4193792 -l 512 $DEV
+  $ hexdump $DEV
+  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
+  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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03f0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4128256 -l 66048 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03f0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4063744 -l 130560 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03f0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4063232 -l 131072 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03e0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4062720 -l 131584 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03e0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 512 -l 4193792 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0010000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+Delete:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 0 -l 4194304 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+Empty clone:
+
+  $ xfs_io -c 'pwrite -S 0xab -w 0 4M' $DEV >/dev/null
+  $ sudo rbd unmap $DEV
+  $ rbd snap create img@snap
+  $ rbd snap protect img@snap
+
+  $ rbd clone img@snap cloneimg1
+  $ DEV=$(sudo rbd map cloneimg1)
+  $ blkdiscard -o 720896 -l 2719744 $DEV
+  $ hexdump $DEV
+  0000000 abab abab abab abab abab abab abab abab
+  *
+  0400000
+  $ sudo rbd unmap $DEV
+
+  $ rbd clone img@snap cloneimg2
+  $ DEV=$(sudo rbd map cloneimg2)
+  $ blkdiscard -o 1474560 -l 2719744 $DEV
+  $ hexdump $DEV
+  0000000 abab abab abab abab abab abab abab abab
+  *
+  0400000
+  $ sudo rbd unmap $DEV
+
+  $ rbd clone img@snap cloneimg3
+  $ DEV=$(sudo rbd map cloneimg3)
+  $ blkdiscard -o 0 -l 4194304 $DEV
+  $ hexdump $DEV
+  0000000 abab abab abab abab abab abab abab abab
+  *
+  0400000
+  $ sudo rbd unmap $DEV
+
+Full clone:
+
+  $ rbd clone img@snap cloneimg4
+  $ DEV=$(sudo rbd map cloneimg4)
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 720896 -l 2719744 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  00b0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0340000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0170000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 0 -l 4194304 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ sudo rbd unmap $DEV
+
+Multiple object requests:
+
+  $ rbd create --size 50M --stripe-unit 16K --stripe-count 5 fancyimg
+  $ DEV=$(sudo rbd map fancyimg)
+
+  $ xfs_io -c 'pwrite -b 4M -w 0 50M' $DEV >/dev/null
+  $ blkdiscard -o 0 -l 143360 $DEV
+  $ hexdump $DEV
+  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
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0008000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0014000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  001c000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0028000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  003c000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0044000 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
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0050000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  3200000
+
+  $ sudo rbd unmap $DEV
+
+  $ rbd rm --no-progress fancyimg
+  $ rbd rm --no-progress cloneimg4
+  $ rbd rm --no-progress cloneimg3
+  $ rbd rm --no-progress cloneimg2
+  $ rbd rm --no-progress cloneimg1
+  $ rbd snap unprotect img@snap
+  $ rbd snap rm --no-progress img@snap
+  $ rbd rm --no-progress img
diff --git a/qa/rbd/krbd_discard_1b.t b/qa/rbd/krbd_discard_1b.t
new file mode 100644
index 0000000000000..5013e30fc2a7f
--- /dev/null
+++ b/qa/rbd/krbd_discard_1b.t
@@ -0,0 +1,416 @@
+
+  $ rbd create --size 4M img
+  $ DEV=$(sudo rbd map -o alloc_size=1 img)
+
+Zero, < 1 block:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 156672 -l 512 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0026400 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0026600 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  002fe00 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  002fe00 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, 1 block:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 131072 -l 65536 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030200 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  001fe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  001fe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030200 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, < 2 blocks:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 163840 -l 65536 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0028000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0038000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  003fe00 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  003fe00 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, 2 blocks:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 131072 -l 131072 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040200 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  001fe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  001fe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040200 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, 37 blocks:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 589824 -l 2424832 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0090000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  02e0000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  008fe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  02dfe00 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0090200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  02e0200 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Truncate:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4193792 -l 512 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03ffe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4129280 -l 65024 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03f0200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4128768 -l 65536 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03f0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4128256 -l 66048 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03efe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4063744 -l 130560 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03e0200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4063232 -l 131072 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03e0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4062720 -l 131584 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03dfe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 512 -l 4193792 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0000200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+Delete:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 0 -l 4194304 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+Empty clone:
+
+  $ xfs_io -c 'pwrite -S 0xab -w 0 4M' $DEV >/dev/null
+  $ sudo rbd unmap $DEV
+  $ rbd snap create img@snap
+  $ rbd snap protect img@snap
+
+  $ rbd clone img@snap cloneimg1
+  $ DEV=$(sudo rbd map -o alloc_size=1 cloneimg1)
+  $ blkdiscard -o 720896 -l 2719744 $DEV
+  $ hexdump $DEV
+  0000000 abab abab abab abab abab abab abab abab
+  *
+  0400000
+  $ sudo rbd unmap $DEV
+
+  $ rbd clone img@snap cloneimg2
+  $ DEV=$(sudo rbd map -o alloc_size=1 cloneimg2)
+  $ blkdiscard -o 1474560 -l 2719744 $DEV
+  $ hexdump $DEV
+  0000000 abab abab abab abab abab abab abab abab
+  *
+  0400000
+  $ sudo rbd unmap $DEV
+
+  $ rbd clone img@snap cloneimg3
+  $ DEV=$(sudo rbd map -o alloc_size=1 cloneimg3)
+  $ blkdiscard -o 0 -l 4194304 $DEV
+  $ hexdump $DEV
+  0000000 abab abab abab abab abab abab abab abab
+  *
+  0400000
+  $ sudo rbd unmap $DEV
+
+Full clone:
+
+  $ rbd clone img@snap cloneimg4
+  $ DEV=$(sudo rbd map -o alloc_size=1 cloneimg4)
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 720896 -l 2719744 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  00b0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0348000 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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0168000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 0 -l 4194304 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ sudo rbd unmap $DEV
+
+Multiple object requests:
+
+  $ rbd create --size 50M --stripe-unit 16K --stripe-count 5 fancyimg
+  $ DEV=$(sudo rbd map -o alloc_size=1 fancyimg)
+
+  $ xfs_io -c 'pwrite -b 4M -w 0 50M' $DEV >/dev/null
+  $ blkdiscard -o 0 -l 143360 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0023000 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
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0046000 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
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  008c000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  3200000
+
+  $ sudo rbd unmap $DEV
+
+  $ rbd rm --no-progress fancyimg
+  $ rbd rm --no-progress cloneimg4
+  $ rbd rm --no-progress cloneimg3
+  $ rbd rm --no-progress cloneimg2
+  $ rbd rm --no-progress cloneimg1
+  $ rbd snap unprotect img@snap
+  $ rbd snap rm --no-progress img@snap
+  $ rbd rm --no-progress img
diff --git a/qa/rbd/krbd_discard_4M.t b/qa/rbd/krbd_discard_4M.t
new file mode 100644
index 0000000000000..395f0241d699c
--- /dev/null
+++ b/qa/rbd/krbd_discard_4M.t
@@ -0,0 +1,330 @@
+
+  $ rbd create --size 4M img
+  $ DEV=$(sudo rbd map -o alloc_size=4194304 img)
+
+Zero, < 1 block:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 156672 -l 512 $DEV
+  $ hexdump $DEV
+  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
+  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
+  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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, 1 block:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 131072 -l 65536 $DEV
+  $ hexdump $DEV
+  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
+  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
+  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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, < 2 blocks:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 163840 -l 65536 $DEV
+  $ hexdump $DEV
+  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
+  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
+  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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, 2 blocks:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 131072 -l 131072 $DEV
+  $ hexdump $DEV
+  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
+  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
+  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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, 37 blocks:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 589824 -l 2424832 $DEV
+  $ hexdump $DEV
+  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
+  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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Truncate:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4193792 -l 512 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03ffe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4129280 -l 65024 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03f0200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4128768 -l 65536 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03f0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4128256 -l 66048 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03efe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4063744 -l 130560 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03e0200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4063232 -l 131072 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03e0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 4062720 -l 131584 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03dfe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 512 -l 4193792 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0000200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+Delete:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 0 -l 4194304 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+Empty clone:
+
+  $ xfs_io -c 'pwrite -S 0xab -w 0 4M' $DEV >/dev/null
+  $ sudo rbd unmap $DEV
+  $ rbd snap create img@snap
+  $ rbd snap protect img@snap
+
+  $ rbd clone img@snap cloneimg1
+  $ DEV=$(sudo rbd map -o alloc_size=4194304 cloneimg1)
+  $ blkdiscard -o 720896 -l 2719744 $DEV
+  $ hexdump $DEV
+  0000000 abab abab abab abab abab abab abab abab
+  *
+  0400000
+  $ sudo rbd unmap $DEV
+
+  $ rbd clone img@snap cloneimg2
+  $ DEV=$(sudo rbd map -o alloc_size=4194304 cloneimg2)
+  $ blkdiscard -o 1474560 -l 2719744 $DEV
+  $ hexdump $DEV
+  0000000 abab abab abab abab abab abab abab abab
+  *
+  0400000
+  $ sudo rbd unmap $DEV
+
+  $ rbd clone img@snap cloneimg3
+  $ DEV=$(sudo rbd map -o alloc_size=4194304 cloneimg3)
+  $ blkdiscard -o 0 -l 4194304 $DEV
+  $ hexdump $DEV
+  0000000 abab abab abab abab abab abab abab abab
+  *
+  0400000
+  $ sudo rbd unmap $DEV
+
+Full clone:
+
+  $ rbd clone img@snap cloneimg4
+  $ DEV=$(sudo rbd map -o alloc_size=4194304 cloneimg4)
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 720896 -l 2719744 $DEV
+  $ hexdump $DEV
+  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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0168000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ blkdiscard -o 0 -l 4194304 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ sudo rbd unmap $DEV
+
+Multiple object requests:
+
+  $ rbd create --size 50M --stripe-unit 16K --stripe-count 5 fancyimg
+  $ DEV=$(sudo rbd map -o alloc_size=4194304 fancyimg)
+
+  $ xfs_io -c 'pwrite -b 4M -w 0 50M' $DEV >/dev/null
+  $ blkdiscard -o 0 -l 143360 $DEV
+  $ hexdump $DEV
+  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
+  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
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  3200000
+
+  $ sudo rbd unmap $DEV
+
+  $ rbd rm --no-progress fancyimg
+  $ rbd rm --no-progress cloneimg4
+  $ rbd rm --no-progress cloneimg3
+  $ rbd rm --no-progress cloneimg2
+  $ rbd rm --no-progress cloneimg1
+  $ rbd snap unprotect img@snap
+  $ rbd snap rm --no-progress img@snap
+  $ rbd rm --no-progress img
diff --git a/qa/rbd/krbd_zeroout.t b/qa/rbd/krbd_zeroout.t
new file mode 100644
index 0000000000000..33c8e9d9e113a
--- /dev/null
+++ b/qa/rbd/krbd_zeroout.t
@@ -0,0 +1,422 @@
+
+  $ rbd create --size 4M img
+  $ DEV=$(sudo rbd map img)
+
+Zero, < 1 block:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 156672 -l 512 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0026400 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0026600 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 131584 -l 64512 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  002fe00 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 131584 -l 65024 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 131072 -l 65024 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  002fe00 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, 1 block:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 131072 -l 65536 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 131072 -l 66048 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030200 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 130560 -l 66048 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  001fe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 130560 -l 66560 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  001fe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0030200 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, < 2 blocks:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 163840 -l 65536 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0028000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0038000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 131584 -l 130048 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  003fe00 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 131584 -l 130560 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 131072 -l 130560 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  003fe00 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, 2 blocks:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 131072 -l 131072 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 131072 -l 131584 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0020000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040200 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 130560 -l 131584 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  001fe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 130560 -l 132096 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  001fe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0040200 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Zero, 37 blocks:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 589824 -l 2424832 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0090000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  02e0000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 589312 -l 2424832 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  008fe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  02dfe00 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 590336 -l 2424832 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0090200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  02e0200 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+Truncate:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 4193792 -l 512 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03ffe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 4129280 -l 65024 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03f0200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 4128768 -l 65536 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03f0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 4128256 -l 66048 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03efe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 4063744 -l 130560 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03e0200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 4063232 -l 131072 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03e0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 4062720 -l 131584 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  03dfe00 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 512 -l 4193792 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0000200 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+Delete:
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 0 -l 4194304 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+Empty clone:
+
+  $ xfs_io -c 'pwrite -S 0xab -w 0 4M' $DEV >/dev/null
+  $ sudo rbd unmap $DEV
+  $ rbd snap create img@snap
+  $ rbd snap protect img@snap
+
+  $ rbd clone img@snap cloneimg1
+  $ DEV=$(sudo rbd map cloneimg1)
+  $ fallocate -z -o 720896 -l 2719744 $DEV
+  $ hexdump $DEV
+  0000000 abab abab abab abab abab abab abab abab
+  *
+  00b0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0348000 abab abab abab abab abab abab abab abab
+  *
+  0400000
+  $ sudo rbd unmap $DEV
+
+  $ rbd clone img@snap cloneimg2
+  $ DEV=$(sudo rbd map cloneimg2)
+  $ fallocate -z -o 1474560 -l 2719744 $DEV
+  $ hexdump $DEV
+  0000000 abab abab abab abab abab abab abab abab
+  *
+  0168000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+  $ sudo rbd unmap $DEV
+
+  $ rbd clone img@snap cloneimg3
+  $ DEV=$(sudo rbd map cloneimg3)
+  $ fallocate -z -o 0 -l 4194304 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+  $ sudo rbd unmap $DEV
+
+Full clone:
+
+  $ rbd clone img@snap cloneimg4
+  $ DEV=$(sudo rbd map cloneimg4)
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 720896 -l 2719744 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  00b0000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0348000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 1474560 -l 2719744 $DEV
+  $ hexdump $DEV
+  0000000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  0168000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ xfs_io -c 'pwrite -w 0 4M' $DEV >/dev/null
+  $ fallocate -z -o 0 -l 4194304 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0400000
+
+  $ sudo rbd unmap $DEV
+
+Multiple object requests:
+
+  $ rbd create --size 50M --stripe-unit 16K --stripe-count 5 fancyimg
+  $ DEV=$(sudo rbd map fancyimg)
+
+  $ xfs_io -c 'pwrite -b 4M -w 0 50M' $DEV >/dev/null
+  $ fallocate -z -o 0 -l 143360 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0023000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  3200000
+
+  $ xfs_io -c 'pwrite -b 4M -w 0 50M' $DEV >/dev/null
+  $ fallocate -z -o 0 -l 286720 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  0046000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  3200000
+
+  $ xfs_io -c 'pwrite -b 4M -w 0 50M' $DEV >/dev/null
+  $ fallocate -z -o 0 -l 573440 $DEV
+  $ hexdump $DEV
+  0000000 0000 0000 0000 0000 0000 0000 0000 0000
+  *
+  008c000 cdcd cdcd cdcd cdcd cdcd cdcd cdcd cdcd
+  *
+  3200000
+
+  $ sudo rbd unmap $DEV
+
+  $ rbd rm --no-progress fancyimg
+  $ rbd rm --no-progress cloneimg4
+  $ rbd rm --no-progress cloneimg3
+  $ rbd rm --no-progress cloneimg2
+  $ rbd rm --no-progress cloneimg1
+  $ rbd snap unprotect img@snap
+  $ rbd snap rm --no-progress img@snap
+  $ rbd rm --no-progress img
diff --git a/qa/suites/krbd/basic/tasks/krbd_discard.yaml b/qa/suites/krbd/basic/tasks/krbd_discard.yaml
new file mode 100644
index 0000000000000..4132caeb23021
--- /dev/null
+++ b/qa/suites/krbd/basic/tasks/krbd_discard.yaml
@@ -0,0 +1,8 @@
+tasks:
+- cram:
+    clients:
+      client.0:
+      - qa/rbd/krbd_discard.t
+      - qa/rbd/krbd_discard_1b.t
+      - qa/rbd/krbd_discard_4M.t
+      - qa/rbd/krbd_zeroout.t
-- 
2.39.5