xfs: Check for extent overflow when moving extent from cow to data fork

This test verifies that XFS does not cause inode fork's extent count to
overflow when writing to/funshare-ing a shared 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/535

@@ -0,0 +1,104 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2021 Chandan Babu R.  All Rights Reserved.
+#
+# FS QA Test 535
+#
+# Verify that XFS does not cause inode fork's extent count to overflow when
+# writing to a shared 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/reflink
+. ./common/inject
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+
+_supported_fs xfs
+_require_scratch
+_require_scratch_reflink
+_require_xfs_debug
+_require_xfs_io_command "reflink"
+_require_xfs_io_command "funshare"
+_require_xfs_io_error_injection "reduce_max_iextents"
+
+echo "Format and mount fs"
+_scratch_mkfs_sized $((512 * 1024 * 1024)) >> $seqres.full
+_scratch_mount >> $seqres.full
+
+bsize=$(_get_block_size $SCRATCH_MNT)
+
+nr_blks=15
+
+srcfile=${SCRATCH_MNT}/srcfile
+dstfile=${SCRATCH_MNT}/dstfile
+
+echo "Inject reduce_max_iextents error tag"
+_scratch_inject_error reduce_max_iextents 1
+
+echo "Create a \$srcfile having an extent of length $nr_blks blocks"
+$XFS_IO_PROG -f -c "pwrite -b $((nr_blks * bsize))  0 $((nr_blks * bsize))" \
+       -c fsync $srcfile  >> $seqres.full
+
+echo "* Write to shared extent"
+
+echo "Share the extent with \$dstfile"
+_reflink $srcfile $dstfile >> $seqres.full
+
+echo "Buffered write to every other block of \$dstfile's shared extent"
+for i in $(seq 1 2 $((nr_blks - 1))); do
+	$XFS_IO_PROG -f -s -c "pwrite $((i * bsize)) $bsize" $dstfile \
+	       >> $seqres.full 2>&1
+	[[ $? != 0 ]] && break
+done
+
+echo "Verify \$dstfile's extent count"
+nextents=$(_xfs_get_fsxattr nextents $dstfile)
+if (( $nextents > 10 )); then
+	echo "Extent count overflow check failed: nextents = $nextents"
+	exit 1
+fi
+
+rm $dstfile
+
+echo "* Funshare shared extent"
+
+echo "Share the extent with \$dstfile"
+_reflink $srcfile $dstfile >> $seqres.full
+
+echo "Funshare every other block of \$dstfile's shared extent"
+for i in $(seq 1 2 $((nr_blks - 1))); do
+	$XFS_IO_PROG -f -s -c "funshare $((i * bsize)) $bsize" $dstfile \
+	       >> $seqres.full 2>&1
+	[[ $? != 0 ]] && break
+done
+
+echo "Verify \$dstfile's extent count"
+nextents=$(_xfs_get_fsxattr nextents $dstfile)
+if (( $nextents > 10 )); then
+	echo "Extent count overflow check failed: nextents = $nextents"
+	exit 1
+fi
+
+# success, all done
+status=0
+exit
+ 

tests/xfs/535.out

@@ -0,0 +1,12 @@
+QA output created by 535
+Format and mount fs
+Inject reduce_max_iextents error tag
+Create a $srcfile having an extent of length 15 blocks
+* Write to shared extent
+Share the extent with $dstfile
+Buffered write to every other block of $dstfile's shared extent
+Verify $dstfile's extent count
+* Funshare shared extent
+Share the extent with $dstfile
+Funshare every other block of $dstfile's shared extent
+Verify $dstfile's extent count

tests/xfs/group

@@ -511,3 +511,4 @@
 532 auto quick attr
 533 auto quick dir hardlink symlink
 534 auto quick
+535 auto quick reflink