xfs: Check for extent overflow when writing to unwritten extent

This test verifies that XFS does not cause inode fork's extent count to
overflow when writing to an unwritten extent.

Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>

tests/xfs/534

@@ -0,0 +1,84 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2021 Chandan Babu R.  All Rights Reserved.
+#
+# FS QA Test 534
+#
+# Verify that XFS does not cause inode fork's extent count to overflow when
+# writing to an unwritten extent.
+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
+. ./common/inject
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+_supported_fs xfs
+_require_scratch
+_require_xfs_debug
+_require_xfs_io_command "falloc"
+_require_xfs_io_error_injection "reduce_max_iextents"
+
+echo "Format and mount fs"
+_scratch_mkfs_sized $((1024 * 1024 * 1024)) >> $seqres.full
+_scratch_mount >> $seqres.full
+
+bsize=$(_get_file_block_size $SCRATCH_MNT)
+
+testfile=${SCRATCH_MNT}/testfile
+
+echo "Inject reduce_max_iextents error tag"
+_scratch_inject_error reduce_max_iextents 1
+
+nr_blks=15
+
+for io in Buffered Direct; do
+	echo "* $io write to unwritten extent"
+
+	echo "Fallocate $nr_blks blocks"
+	$XFS_IO_PROG -f -c "falloc 0 $((nr_blks * bsize))" $testfile >> $seqres.full
+
+	if [[ $io == "Buffered" ]]; then
+		xfs_io_flag=""
+	else
+		xfs_io_flag="-d"
+	fi
+
+	echo "$io write to every other block of fallocated space"
+	for i in $(seq 1 2 $((nr_blks - 1))); do
+		$XFS_IO_PROG -f -s $xfs_io_flag -c "pwrite $((i * bsize)) $bsize" \
+		       $testfile >> $seqres.full 2>&1
+		[[ $? != 0 ]] && break
+	done
+
+	echo "Verify \$testfile's extent count"
+	nextents=$(_xfs_get_fsxattr nextents $testfile)
+	if (( $nextents > 10 )); then
+		echo "Extent count overflow check failed: nextents = $nextents"
+		exit 1
+	fi
+
+	rm $testfile
+done
+
+# success, all done
+status=0
+exit

tests/xfs/534.out

@@ -0,0 +1,11 @@
+QA output created by 534
+Format and mount fs
+Inject reduce_max_iextents error tag
+* Buffered write to unwritten extent
+Fallocate 15 blocks
+Buffered write to every other block of fallocated space
+Verify $testfile's extent count
+* Direct write to unwritten extent
+Fallocate 15 blocks
+Direct write to every other block of fallocated space
+Verify $testfile's extent count

tests/xfs/group

@@ -510,3 +510,4 @@
 531 auto quick punch zero insert collapse
 532 auto quick attr
 533 auto quick dir hardlink symlink
+534 auto quick