Commit d4866503 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

selftests/ublk: add hugetlbfs shmem_zc test for loop target 



Add test_shmem_zc_02.sh which tests the UBLK_IO_F_SHMEM_ZC zero-copy
path on the loop target using a hugetlbfs shared buffer. Both kublk and
fio mmap the same hugetlbfs file with MAP_SHARED, sharing physical
pages. The kernel's PFN matching enables zero-copy — the loop target
reads/writes directly from the shared buffer to the backing file.

Uses standard fio --mem=mmaphuge:<path> (supported since fio 1.10),
no patched fio required.

Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://patch.msgid.link/20260331153207.3635125-9-ming.lei@redhat.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 2f1e9468

tools/testing/selftests/ublk/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -53,6 +53,7 @@ TEST_PROGS += test_part_01.sh 
TEST_PROGS += test_part_02.sh



TEST_PROGS += test_shmemzc_01.sh

TEST_PROGS += test_shmemzc_02.sh



TEST_PROGS += test_stress_01.sh

TEST_PROGS += test_stress_02.sh

tools/testing/selftests/ublk/test_shmemzc_02.sh

0 → 100755
+68 −0
Original line number Diff line number Diff line 
#!/bin/bash

# SPDX-License-Identifier: GPL-2.0

# Test: shmem_zc with hugetlbfs buffer on loop target

#

# kublk and fio both mmap the same hugetlbfs file (MAP_SHARED),

# so they share physical pages.  The kernel PFN match enables

# zero-copy I/O without socket-based fd passing.



. "$(cd "$(dirname "$0")" && pwd)"/test_common.sh



ERR_CODE=0



_prep_test "shmem_zc" "loop target hugetlbfs shmem zero-copy test"



if ! _have_program fio; then

	echo "SKIP: fio not available"

	exit "$UBLK_SKIP_CODE"

fi



if ! grep -q hugetlbfs /proc/filesystems; then

	echo "SKIP: hugetlbfs not supported"

	exit "$UBLK_SKIP_CODE"

fi



# Allocate hugepages

OLD_NR_HP=$(cat /proc/sys/vm/nr_hugepages)

echo 10 > /proc/sys/vm/nr_hugepages

NR_HP=$(cat /proc/sys/vm/nr_hugepages)

if [ "$NR_HP" -lt 2 ]; then

	echo "SKIP: cannot allocate hugepages"

	echo "$OLD_NR_HP" > /proc/sys/vm/nr_hugepages

	exit "$UBLK_SKIP_CODE"

fi



# Mount hugetlbfs

HTLB_MNT=$(mktemp -d "${UBLK_TEST_DIR}/htlb_mnt_XXXXXX")

if ! mount -t hugetlbfs none "$HTLB_MNT"; then

	echo "SKIP: cannot mount hugetlbfs"

	rmdir "$HTLB_MNT"

	echo "$OLD_NR_HP" > /proc/sys/vm/nr_hugepages

	exit "$UBLK_SKIP_CODE"

fi



HTLB_FILE="$HTLB_MNT/ublk_buf"

fallocate -l 4M "$HTLB_FILE"



_create_backfile 0 128M

BACKFILE="${UBLK_BACKFILES[0]}"



dev_id=$(_add_ublk_dev -t loop --shmem_zc --htlb "$HTLB_FILE" "$BACKFILE")

_check_add_dev $TID $?



_run_fio_verify_io --filename=/dev/ublkb"${dev_id}" \

	--size=128M \

	--mem=mmaphuge:"$HTLB_FILE"

ERR_CODE=$?



# Delete device first so daemon releases the htlb mmap

_ublk_del_dev "${dev_id}"



rm -f "$HTLB_FILE"

umount "$HTLB_MNT"

rmdir "$HTLB_MNT"

echo "$OLD_NR_HP" > /proc/sys/vm/nr_hugepages



_cleanup_test "shmem_zc"



_show_result $TID $ERR_CODE