[PATCH] generic: fallocate two bytes at block boundary

[Max Reitz <mreitz@redhat.com>]

Allocating two bytes at a block boundary with fallocate should allocate
both blocks involved.  Test this by writing both bytes with dd
afterwards and see whether the on-disk size increases (it should not).

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 tests/generic/568     | 63 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/568.out |  2 ++
 tests/generic/group   |  1 +
 3 files changed, 66 insertions(+)
 create mode 100755 tests/generic/568
 create mode 100644 tests/generic/568.out

diff --git a/tests/generic/568 b/tests/generic/568
new file mode 100755
index 00000000..8fbdcda0
--- /dev/null
+++ b/tests/generic/568
@@ -0,0 +1,63 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2019 Red Hat, Inc.  All Rights Reserved.
+#
+# FS QA Test No. generic/568
+#
+# Test that fallocating an unaligned range allocates all blocks
+# touched by that range
+#
+seq=$(basename $0)
+seqres="$RESULT_DIR/$seq"
+echo "QA output created by $seq"
+
+here=$PWD
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+	rm -f "$tmp".*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# real QA test starts here
+_supported_fs generic
+_supported_os Linux
+_require_scratch
+
+testfile="$SCRATCH_MNT/testfile"
+
+_scratch_mkfs > /dev/null 2>&1
+_scratch_mount
+
+# Fallocate 2 bytes across a block boundary
+block_size=$(stat -fc '%S' "$SCRATCH_MNT")
+fallocate -o $((block_size - 1)) -l 2 "$testfile"
+
+# Both the first blocks should be allocated now.  Check that by
+# inquiring whether the file grows when we write to the two bytes we
+# have just fallocated.
+
+allocated_size_before=$(($(stat -c '%b * %B' "$testfile")))
+
+dd if=/dev/zero of="$testfile" bs=1 conv=notrunc \
+    seek=$((block_size - 1)) count=2 \
+    2>&1 | _filter_dd
+
+allocated_size_after=$(($(stat -c '%b * %B' "$testfile")))
+
+if [ $allocated_size_after -gt $allocated_size_before ]; then
+	echo "ERROR: File grew from ${allocated_size_before} B to" \
+	     "${allocated_size_after} when writing to the fallocated range."
+else
+	echo "OK: File did not grow."
+fi
+
+status=0
+exit
diff --git a/tests/generic/568.out b/tests/generic/568.out
new file mode 100644
index 00000000..d8210882
--- /dev/null
+++ b/tests/generic/568.out
@@ -0,0 +1,2 @@
+QA output created by 568
+OK: File did not grow.
diff --git a/tests/generic/group b/tests/generic/group
index 7cf4f6c4..24ab29bc 100644
--- a/tests/generic/group
+++ b/tests/generic/group
@@ -570,3 +570,4 @@
 565 auto quick copy_range
 566 auto quick quota metadata
 567 auto quick rw punch
+568 auto quick rw
-- 
2.21.0