#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) 2017 Red Hat, Inc.  All Rights Reserved.
#
# FS QA Test 450
#
# Test read around EOF. If the file offset is at or past the end of file,
# no bytes are read, and read() returns zero. There was a bug, when DIO
# read offset is just past the EOF a little, but in the same block with
# EOF, read returns different negative values.
#
# The following two kernel commits fixed this bug:
# 74cedf9b6c60 direct-io: Fix negative return from dio read beyond eof
# 2d4594acbf6d fix the regression from "direct-io: Fix negative return
# from dio read beyond eof"
#
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.*
	rm -f $tfile
}

# get standard environment, filters and checks
. ./common/rc

# remove previous $seqres.full before test
rm -f $seqres.full

# real QA test starts here
_supported_fs generic
_supported_os Linux
_require_test
_require_odirect

tfile=$TEST_DIR/testfile_${seq}
ssize=`_min_dio_alignment $TEST_DEV`
bsize=`_get_block_size $TEST_DIR`

# let's focus on the specific bug that only happens when $ssize <= $bsize
if [ $ssize -gt $((bsize/4)) ]; then
	_notrun "Only test on sector size < half of block size"
fi

rm -f $tfile 2>/dev/null

# check xfs_io pread result, especially for
# Param1: expected pread offset
# Param2: expected pread count
# Param3: expected pread return
#
# If any of above values are not as expected, the output keeps
# using the real value
check_xfs_io_read()
{
	OFFSET=$1
	COUNT=$2
	RETURN=$3

	$AWK_PROG -v ret="$RETURN" -v cnt="$COUNT" -v off="$OFFSET" '
		/read/{
			split($2, bytes, "/")

			retval=bytes[1]
			count=bytes[2]
			offset=$NF

			if(retval != ret || count != cnt || offset != off)
				printf("expect [%s,%s,%s], got [%s,%s,%s]\n", \
					off, cnt, ret, offset, count, retval)

			next
		}
	'
}

# +-------------------------------------------------------+
# |           block           |           block           |
# +-------------------------------------------------------+
# | sect | sect | sect | sect | sect | sect | sect | sect |
#                                           |
#                                          EOF
# |<--------------- move EOF -------------->| xxxxxxxxxxx |
# [pread1]
#                             [           pread2          ]
#                                           [pread3]
#                                                  [pread4]  ...  [pread5]
#
# Run below steps with different $operation and $openflag
#
# 1) write 2 blocks (6 sectors) data to move EOF to the penultimate sector
# 2) read (pread1) the first sector within EOF
# 3) read (pread2) the second block contain EOF
# 4) read (pread3) a sector at (after) EOF
# 5) read (pread4) the last sector past EOF
# 6) read (pread5) at far away from EOF
#
asize=$((bsize * 2))
tsize=$((asize - ssize * 2))

read_test()
{
	local of="$1"
	local op="buffer read"

	if [ "$of" != "" ]; then
		op="direct read"
	fi

	echo "$op the first sector within EOF"
	$XFS_IO_PROG $of -c "pread 0 $ssize" $tfile | \
		check_xfs_io_read 0 "$ssize" "$ssize"

	echo "$op the second block contains EOF"
	$XFS_IO_PROG $of -c "pread $bsize $bsize" $tfile | \
		check_xfs_io_read "$bsize" "$bsize" "$((tsize - bsize))"

	echo "$op a sector at (after) EOF"
	$XFS_IO_PROG $of -c "pread $tsize $ssize" $tfile | \
		check_xfs_io_read "$tsize" "$ssize" "0"

	echo "$op the last sector past EOF"
	$XFS_IO_PROG $of -c "pread $((tsize + ssize)) $ssize" $tfile | \
		check_xfs_io_read "$((tsize + ssize))" "$ssize" "0"

	echo "$op at far away from EOF"
	$XFS_IO_PROG $of -c "pread $((bsize * 100)) $ssize" $tfile | \
		check_xfs_io_read "$((bsize * 100))" "$ssize" "0"
}

# Test buffer/direct I/O read
$XFS_IO_PROG -ft -c "pwrite 0 ${tsize}" -c "fsync" $tfile >>$seqres.full
for oflag in "" "-d"; do
	read_test "$oflag"
done

# success, all done
status=0
exit