From: Ming Lei Date: Tue, 31 Mar 2026 15:32:01 +0000 (+0800) Subject: selftests/ublk: add read-only buffer registration test X-Git-Url: http://git.ipfire.org/index.cgi?a=commitdiff_plain;h=affb5f67d73c1e0bd412e7807a55691502b5679e;p=thirdparty%2Fkernel%2Flinux.git selftests/ublk: add read-only buffer registration test Add --rdonly_shmem_buf option to kublk that registers shared memory buffers with UBLK_SHMEM_BUF_READ_ONLY (read-only pinning without FOLL_WRITE) and mmaps with PROT_READ only. Add test_shmemzc_04.sh which exercises the new flag with a null target, hugetlbfs buffer, and write workload. Write I/O works because the server only reads from the shared buffer — the data flows from client to kernel to the shared pages, and the server reads them out. Signed-off-by: Ming Lei Link: https://patch.msgid.link/20260331153207.3635125-11-ming.lei@redhat.com Signed-off-by: Jens Axboe --- diff --git a/tools/testing/selftests/ublk/Makefile b/tools/testing/selftests/ublk/Makefile index c453cd3690880..ec6a8ce83d381 100644 --- a/tools/testing/selftests/ublk/Makefile +++ b/tools/testing/selftests/ublk/Makefile @@ -55,6 +55,7 @@ TEST_PROGS += test_part_02.sh TEST_PROGS += test_shmemzc_01.sh TEST_PROGS += test_shmemzc_02.sh TEST_PROGS += test_shmemzc_03.sh +TEST_PROGS += test_shmemzc_04.sh TEST_PROGS += test_stress_01.sh TEST_PROGS += test_stress_02.sh diff --git a/tools/testing/selftests/ublk/kublk.c b/tools/testing/selftests/ublk/kublk.c index fce3f80c3ebac..fbd9b1e7342a3 100644 --- a/tools/testing/selftests/ublk/kublk.c +++ b/tools/testing/selftests/ublk/kublk.c @@ -1219,11 +1219,13 @@ static void ublk_shmem_unregister_all(void) shmem_count = 0; } -static int ublk_ctrl_reg_buf(struct ublk_dev *dev, void *addr, size_t size) +static int ublk_ctrl_reg_buf(struct ublk_dev *dev, void *addr, size_t size, + __u32 flags) { struct ublk_shmem_buf_reg buf_reg = { .addr = (unsigned long)addr, .len = size, + .flags = flags, }; struct ublk_ctrl_cmd_data data = { .cmd_op = UBLK_U_CMD_REG_BUF, @@ -1272,7 +1274,7 @@ static void ublk_shmem_handle_client(int sock_fd, struct ublk_dev *dev) } /* Register server's VA range with kernel for PFN matching */ - ret = ublk_ctrl_reg_buf(dev, base, size); + ret = ublk_ctrl_reg_buf(dev, base, size, 0); if (ret < 0) { ublk_dbg(UBLK_DBG_DEV, "shmem_zc: kernel reg failed %d\n", ret); @@ -1357,7 +1359,8 @@ static int ublk_shmem_htlb_setup(const struct dev_ctx *ctx, return -EINVAL; } - base = mmap(NULL, st.st_size, PROT_READ | PROT_WRITE, + base = mmap(NULL, st.st_size, + ctx->rdonly_shmem_buf ? PROT_READ : PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE, fd, 0); if (base == MAP_FAILED) { ublk_err("htlb: mmap failed\n"); @@ -1365,7 +1368,8 @@ static int ublk_shmem_htlb_setup(const struct dev_ctx *ctx, return -ENOMEM; } - ret = ublk_ctrl_reg_buf(dev, base, st.st_size); + ret = ublk_ctrl_reg_buf(dev, base, st.st_size, + ctx->rdonly_shmem_buf ? UBLK_SHMEM_BUF_READ_ONLY : 0); if (ret < 0) { ublk_err("htlb: reg_buf failed: %d\n", ret); munmap(base, st.st_size); @@ -2129,6 +2133,7 @@ int main(int argc, char *argv[]) { "no_auto_part_scan", 0, NULL, 0 }, { "shmem_zc", 0, NULL, 0 }, { "htlb", 1, NULL, 0 }, + { "rdonly_shmem_buf", 0, NULL, 0 }, { 0, 0, 0, 0 } }; const struct ublk_tgt_ops *ops = NULL; @@ -2248,6 +2253,8 @@ int main(int argc, char *argv[]) ctx.flags |= UBLK_F_SHMEM_ZC; if (!strcmp(longopts[option_idx].name, "htlb")) ctx.htlb_path = strdup(optarg); + if (!strcmp(longopts[option_idx].name, "rdonly_shmem_buf")) + ctx.rdonly_shmem_buf = 1; break; case '?': /* diff --git a/tools/testing/selftests/ublk/kublk.h b/tools/testing/selftests/ublk/kublk.h index 8ed2efc3ecb99..742c41d77df14 100644 --- a/tools/testing/selftests/ublk/kublk.h +++ b/tools/testing/selftests/ublk/kublk.h @@ -81,6 +81,7 @@ struct dev_ctx { unsigned int no_ublk_fixed_fd:1; unsigned int safe_stop:1; unsigned int no_auto_part_scan:1; + unsigned int rdonly_shmem_buf:1; __u32 integrity_flags; __u8 metadata_size; __u8 pi_offset; diff --git a/tools/testing/selftests/ublk/test_shmemzc_04.sh b/tools/testing/selftests/ublk/test_shmemzc_04.sh new file mode 100755 index 0000000000000..899de088ece4c --- /dev/null +++ b/tools/testing/selftests/ublk/test_shmemzc_04.sh @@ -0,0 +1,72 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# Test: shmem_zc with read-only buffer registration on null target +# +# Same as test_shmemzc_01 but with --rdonly_shmem_buf: pages are pinned +# without FOLL_WRITE (UBLK_BUF_F_READ). Write I/O works because +# the server only reads from the shared buffer. + +. "$(cd "$(dirname "$0")" && pwd)"/test_common.sh + +ERR_CODE=0 + +_prep_test "shmem_zc" "null target hugetlbfs shmem zero-copy rdonly_buf test" + +if ! _have_program fio; then + echo "SKIP: fio not available" + exit "$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" + +dev_id=$(_add_ublk_dev -t null --shmem_zc --htlb "$HTLB_FILE" --rdonly_shmem_buf) +_check_add_dev $TID $? + +fio --name=htlb_zc_rdonly \ + --filename=/dev/ublkb"${dev_id}" \ + --ioengine=io_uring \ + --rw=randwrite \ + --direct=1 \ + --bs=4k \ + --size=4M \ + --iodepth=32 \ + --mem=mmaphuge:"$HTLB_FILE" \ + > /dev/null 2>&1 +ERR_CODE=$? + +# 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