[PATCH 4/4] generic: test corruption detection using T10 protection information

[Christoph Hellwig <hch@lst.de>]

Add a test that simulates bit flips in data and misdirected writes and
checks that file systems detect it when run on devices using protection
information.

This requires the new scsi_debug corruption injection.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 tests/generic/2302     | 143 +++++++++++++++++++++++++++++++++++++++++
 tests/generic/2302.out |  21 ++++++
 2 files changed, 164 insertions(+)
 create mode 100755 tests/generic/2302
 create mode 100644 tests/generic/2302.out

diff --git a/tests/generic/2302 b/tests/generic/2302
new file mode 100755
index 000000000000..5fff1f5e5015
--- /dev/null
+++ b/tests/generic/2302
@@ -0,0 +1,143 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2026 Christoph Hellwig
+#
+# FS QA Test No. 2302
+#
+# Test that T10 DIF detects bitflips and misplaced writes.
+#
+. ./common/preamble
+_begin_fstest auto rw
+
+_cleanup()
+{
+	cd /
+	rm -r -f $tmp.*
+	[ -d "$SCSI_DEBUG_MNT" ] && _unmount $SCSI_DEBUG_MNT 2>/dev/null
+	_put_scsi_debug_dev
+}
+
+. ./common/scsi_debug
+. ./common/filter
+
+_require_scsi_debug
+# If TEST_DEV is block device, make sure current fs is a localfs which can be
+# written on scsi_debug device
+_require_test
+_require_block_device $TEST_DEV
+
+# FIEMAP on Btrfs returns logical addresses within the filesystem's address
+# space, not physical device offsets. Writing to these offsets on $SCRATCH_DEV
+# would corrupt the filesystem in multi-device setups.
+_exclude_fs btrfs
+
+size=$(_small_fs_size_mb 256)
+
+# Get the physical block offset (in bytes) of the file's first block on device
+get_phys_blk()
+{
+	local file="$1"
+	local fiemap_output
+	local phys_blk
+
+	fiemap_output=$($XFS_IO_PROG -r -c "fiemap -v" "$file" 2>/dev/null)
+	phys_blk=$(echo "$fiemap_output" | _filter_xfs_io_fiemap | head -1 | awk '{print $3}')
+	if [ -z "$phys_blk" ]; then
+		echo ""
+		return
+	fi
+	echo $phys_blk
+}
+
+test_dif()
+{
+	local pi_type=$1
+	local last=$2
+	local bit_errors=$3
+	local reftag_adjust=$4
+
+	echo -n "Testing DIF type $pi_type "
+	if [ "$bit_errors" -gt "0" ]; then
+		echo -n "bit errors ($bit_errors) in "
+	fi
+	if [ "$reftag_adjust" -ne "0" ]; then
+		echo -n "reftag adjustment by $reftag_adjust in "
+	fi
+	if [ "$last" -eq 1 ]; then
+		echo "last sector"
+	else
+		echo "first sector"
+	fi
+
+	scsi_debug_pi_opts="write_same_length=0 dif=${pi_type} dix=1"
+	SCSI_DEBUG_DEV=`_get_scsi_debug_dev 512 512 0 $size $scsi_debug_pi_opts`
+
+	SCSI_DEBUG_MNT="$TEST_DIR/scsi_debug_$seq"
+	rm -rf $SCSI_DEBUG_MNT
+	mkdir $SCSI_DEBUG_MNT
+
+	_mkfs_dev $SCSI_DEBUG_DEV || \
+		_fail "Can't make $FSTYP on DIF-enabled scsi_debug device"
+	run_check _mount $SCSI_DEBUG_DEV $SCSI_DEBUG_MNT
+
+	local blksz=$(_get_block_size $SCSI_DEBUG_MNT)
+	local testfile="$SCSI_DEBUG_MNT/test"
+
+	$XFS_IO_PROG -d -f \
+		-c "pwrite -S 0x66 0 $((128 * blksz))" \
+		-c fsync \
+		$testfile >> $seqres.full 2>&1
+
+	local phys_blk=$(get_phys_blk $testfile)
+	if [ -z "$phys_blk" ]; then
+		_fail "$test_name: failed to get physical block offset via fiemap"
+	fi
+
+	local dev=$(_short_dev $SCSI_DEBUG_DEV)
+	local debugfs_dir=$(ls /sys/block/$dev/device/scsi_device/)
+	local debugfs_file="/sys/kernel/debug/scsi_debug/$debugfs_dir/corrupt"
+
+	if [ ! -f "$debugfs_file" ]; then
+		_notrun "scsi_debug corruption injection not supported"
+	fi
+
+	if [ "$last" -eq 1 ]; then
+		echo "adding to $phys_blk" >> $seqres.full
+		phys_blk=$((phys_blk + 127))
+	fi
+
+	echo "lba=$phys_blk,num=1,bit_errors=$bit_errors,reftag_adjust=$reftag_adjust" \
+		 > $debugfs_file
+
+	$XFS_IO_PROG -d -f \
+		-c "pread 0 $((128 * blksz))" \
+		$testfile
+
+	[ -d "$SCSI_DEBUG_MNT" ] && _unmount $SCSI_DEBUG_MNT 2>/dev/null
+	_put_scsi_debug_dev
+}
+
+# test data corruption in first block
+test_dif 1 0 2 0
+test_dif 2 0 2 0
+test_dif 3 0 2 0
+
+# test data corruption in last block
+test_dif 1 1 2 0
+test_dif 2 1 2 0
+test_dif 3 1 2 0
+
+
+# Note: Type 3 doesn't have a refrag, so don't test it
+
+# reftag mismatch in first block
+test_dif 1 0 0 8
+test_dif 2 0 0 8
+
+# reftag mismatch in last block
+test_dif 1 1 0 8
+test_dif 2 1 0 8
+
+# success, all done
+status=0
+exit
diff --git a/tests/generic/2302.out b/tests/generic/2302.out
new file mode 100644
index 000000000000..03b68d904943
--- /dev/null
+++ b/tests/generic/2302.out
@@ -0,0 +1,21 @@
+QA output created by 2302
+Testing DIF type 1 bit errors (2) in first sector
+pread: Invalid or incomplete multibyte or wide character
+Testing DIF type 2 bit errors (2) in first sector
+pread: Invalid or incomplete multibyte or wide character
+Testing DIF type 3 bit errors (2) in first sector
+pread: Invalid or incomplete multibyte or wide character
+Testing DIF type 1 bit errors (2) in last sector
+pread: Invalid or incomplete multibyte or wide character
+Testing DIF type 2 bit errors (2) in last sector
+pread: Invalid or incomplete multibyte or wide character
+Testing DIF type 3 bit errors (2) in last sector
+pread: Invalid or incomplete multibyte or wide character
+Testing DIF type 1 reftag adjustment by 8 in first sector
+pread: Invalid or incomplete multibyte or wide character
+Testing DIF type 2 reftag adjustment by 8 in first sector
+pread: Invalid or incomplete multibyte or wide character
+Testing DIF type 1 reftag adjustment by 8 in last sector
+pread: Invalid or incomplete multibyte or wide character
+Testing DIF type 2 reftag adjustment by 8 in last sector
+pread: Invalid or incomplete multibyte or wide character
-- 
2.53.0