[PATCH] generic: test fiemap offsets and < 512 byte ranges

[Boris Burkov <boris@bur.io>]

btrfs trims fiemap extents to the inputted offset, which leads to
inconsistent results for most inputs, and downright bizarre outputs like
[7..6] when the trimmed extent is at the end of an extent and shorter
than 512 bytes.

This test covers a bunch of cases like that and ensures that file
systems always return the full extent without trimming it.

I also ran it under ext2, ext3, ext4, f2fs, and xfs successfully, but I
suppose it's no guarantee that every file system will store a 4k synced
write in a single extent. For that reason, this might be a bit fragile.

This test is fixed for btrfs by:
btrfs: return whole extents in fiemap
(https://lore.kernel.org/linux-btrfs/274e5bcebdb05a8969fc300b4802f33da2fbf218.1617746680.git.boris@bur.io/)

Signed-off-by: Boris Burkov <boris@bur.io>
---
 tests/generic/623     | 93 +++++++++++++++++++++++++++++++++++++++++++
 tests/generic/623.out |  2 +
 tests/generic/group   |  1 +
 3 files changed, 96 insertions(+)
 create mode 100755 tests/generic/623
 create mode 100644 tests/generic/623.out

diff --git a/tests/generic/623 b/tests/generic/623
new file mode 100755
index 00000000..d399c9f0
--- /dev/null
+++ b/tests/generic/623
@@ -0,0 +1,93 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2021 YOUR NAME HERE.  All Rights Reserved.
+#
+# FS QA Test 623
+#
+# what am I here for?
+#
+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
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs generic
+_require_test
+_require_scratch
+_require_xfs_io_command "fiemap"
+
+rm -f $seqres.full
+
+_do_fiemap() {
+	off=$1
+	len=$2
+	$XFS_IO_PROG -c "fiemap $off $len" $SCRATCH_MNT/foo
+}
+
+_check_fiemap() {
+	off=$1
+	len=$2
+	actual=$(_do_fiemap $off $len | tee -a $seqres.full)
+	[ "$actual" == "$expected" ] || _fail "unexpected fiemap on $off $len"
+}
+
+_scratch_mkfs >>$seqres.full 2>&1
+_scratch_mount
+
+# write a file with one extent
+$XFS_IO_PROG -f -s -c "pwrite -S 0xcf 0 4K" $SCRATCH_MNT/foo >/dev/null
+
+# since the exact extent location is unpredictable especially when
+# varying file systems, just test that they are all equal, which is
+# what we really expect.
+expected=$(_do_fiemap)
+
+# start to mid-extent
+_check_fiemap 0 2048
+# start to end
+_check_fiemap 0 4096
+# start to past-end
+_check_fiemap 0 4097
+# mid-extent to mid-extent
+_check_fiemap 1024 2048
+# mid-extent to end
+_check_fiemap 2048 4096
+# mid-extent to past-end
+_check_fiemap 2048 4097
+
+# to end; len < 512
+_check_fiemap 4091 5
+# to end; len == 512
+_check_fiemap 3584 512
+# past end; len < 512
+_check_fiemap 4091 500
+# past end; len == 512
+_check_fiemap 4091 512
+
+_scratch_unmount
+
+echo "Silence is golden"
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/623.out b/tests/generic/623.out
new file mode 100644
index 00000000..6f774f19
--- /dev/null
+++ b/tests/generic/623.out
@@ -0,0 +1,2 @@
+QA output created by 623
+Silence is golden
diff --git a/tests/generic/group b/tests/generic/group
index b10fdea4..39e02383 100644
--- a/tests/generic/group
+++ b/tests/generic/group
@@ -625,3 +625,4 @@
 620 auto mount quick
 621 auto quick encrypt
 622 auto shutdown metadata atime
+623 auto quick
-- 
2.30.2