[PATCH v2 2/2] generic/470: Replace thin volume with blkdiscard -z

[Xiao Yang <yangx.jy@fujitsu.com>]

generic/470 was original designed to verify mmap(MAP_SYNC) which
is only valid to the DAX capable device(e.g. PMEM). Thin volume[1] was
introduced to fix the inconsistent filesystem issue[2] but it make
the test become not run because it doesn't support DAX. As Darrick
mentioned[3], zeroing the entire mapped range of scartch device
can fix the issue as well, so I try to use blkdiscard -z instead.

[1]: https://git.kernel.org/pub/scm/fs/xfs/xfstests-dev.git/commit/?id=fc5870da485aec0f9196a0f2bed32f73f6b2c664
[2]: https://lore.kernel.org/fstests/20190227061529.GF16436@dastard/
[3]: https://lore.kernel.org/linux-xfs/Y1NRNtToQTjs0Dbd@magnolia/T/#me0e77cb0ecd80bf4b5109e4433cb4863ae6e6727

Signed-off-by: Xiao Yang <yangx.jy@fujitsu.com>
---
 tests/generic/470 | 34 +++++++++++++++-------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/tests/generic/470 b/tests/generic/470
index f3407511..6da2ec22 100755
--- a/tests/generic/470
+++ b/tests/generic/470
@@ -15,38 +15,29 @@ _cleanup()
 {
 	cd /
 	_log_writes_cleanup
-	_dmthin_cleanup
 	rm -f $tmp.*
 }
 
 # Import common functions.
 . ./common/filter
-. ./common/dmthin
 . ./common/dmlogwrites
 
 # real QA test starts here
 _supported_fs generic
-_require_scratch_nocheck
+_require_scratch
 _require_no_logdev
 _require_log_writes_dax_mountopt "dax"
-_require_dm_target thin-pool
 _require_xfs_io_command "mmap" "-S"
 _require_xfs_io_command "log_writes"
+_require_command "$BLKDISCARD_PROG" blkdiscard
 
-devsize=$((1024*1024*200 / 512))        # 200m phys/virt size
-csize=$((1024*64 / 512))                # 64k cluster size
-lowspace=$((1024*1024 / 512))           # 1m low space threshold
-
-# Use a thin device to provide deterministic discard behavior. Discards are used
-# by the log replay tool for fast zeroing to prevent out-of-order replay issues.
-_dmthin_init $devsize $devsize $csize $lowspace
+MAPPED_LEN=$((512 * 1024 * 1024)) # 512 MiB
+LEN=$((1024 * 1024)) # 1 MiB
 
-_log_writes_init $DMTHIN_VOL_DEV
+_log_writes_init $SCRATCH_DEV $MAPPED_LEN
 _log_writes_mkfs >> $seqres.full 2>&1
 _log_writes_mount -o dax
 
-LEN=$((1024 * 1024)) # 1 MiB
-
 $XFS_IO_PROG -t -c "truncate $LEN" -c "mmap -S 0 $LEN" -c "mwrite 0 $LEN" \
 	-c "log_writes -d $LOGWRITES_NAME -m preunmap" \
 	-f $SCRATCH_MNT/test
@@ -54,14 +45,19 @@ $XFS_IO_PROG -t -c "truncate $LEN" -c "mmap -S 0 $LEN" -c "mwrite 0 $LEN" \
 # Unmount the scratch dir and tear down the log writes target
 _log_writes_unmount
 _log_writes_remove
-_dmthin_check_fs
+_check_scratch_fs
 
-# destroy previous filesystem so we can be sure our rebuild works
-_mkfs_dev $DMTHIN_VOL_DEV >> $seqres.full 2>&1
+# Forcibly zero the mapped range of scratch device and destroy
+# previous filesystem so we can be sure our rebuild works.
+# Note that blkdiscard -z will fall back to writing buffers of zeroes
+# if scratch device doesn't support write zeroes operation(i.e.
+# REQ_OP_WRITE_ZEROES).
+$BLKDISCARD_PROG -fzl $MAPPED_LEN $SCRATCH_DEV >> $seqres.full 2>&1
+_scratch_mkfs >> $seqres.full 2>&1
 
 # check pre-unmap state
-_log_writes_replay_log preunmap $DMTHIN_VOL_DEV
-_dmthin_mount
+_log_writes_replay_log preunmap $SCRATCH_DEV
+_scratch_mount
 
 # We should see $SCRATCH_MNT/test as having 1 MiB in block allocations
 du -sh $SCRATCH_MNT/test | _filter_scratch | _filter_spaces
-- 
2.34.1