Implement a program to demonstrate mount listing using the new fsinfo() syscall. For example, to dump the tree from mount 21:
# ./test-mntinfo -m 21 MOUNT MOUNT ID CHANGE# AT P DEV TYPE -------------------------------- ---------- -------- -- - ----- -------- 21 21 0 e 4 0:14 sysfs \_ kernel/security 24 0 e 4 0:8 securityfs \_ fs/cgroup 28 4 2f 4 0:18 tmpfs | \_ unified 29 0 e 4 0:19 cgroup2 | \_ systemd 30 0 e 4 0:1a cgroup | \_ blkio 34 0 e 4 0:1e cgroup | \_ net_cls,net_prio 35 0 e 4 0:1f cgroup | \_ perf_event 36 0 e 4 0:20 cgroup | \_ freezer 37 0 e 4 0:21 cgroup | \_ devices 38 0 e 4 0:22 cgroup | \_ cpu,cpuacct 39 0 e 4 0:23 cgroup | \_ rdma 40 0 e 4 0:24 cgroup | \_ memory 41 0 e 4 0:25 cgroup | \_ cpuset 42 0 e 4 0:26 cgroup | \_ hugetlb 43 0 e 4 0:27 cgroup \_ fs/pstore 31 0 e 4 0:1b pstore \_ firmware/efi/efivars 32 0 e 4 0:1c efivarfs \_ fs/bpf 33 0 e 4 0:1d bpf \_ kernel/config 92 0 0 4 0:28 configfs \_ fs/selinux 44 0 0 4 0:11 selinuxfs \_ kernel/debug 45 1 0 4 0:7 debugfs Signed-off-by: David Howells <[email protected]> --- samples/vfs/Makefile | 6 + samples/vfs/test-mntinfo.c | 277 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 282 insertions(+), 1 deletion(-) create mode 100644 samples/vfs/test-mntinfo.c diff --git a/samples/vfs/Makefile b/samples/vfs/Makefile index d63af5106fc2..7bcdd7a2829e 100644 --- a/samples/vfs/Makefile +++ b/samples/vfs/Makefile @@ -1,5 +1,9 @@ # SPDX-License-Identifier: GPL-2.0-only -userprogs := test-fsinfo test-fsmount test-statx +userprogs := \ + test-fsinfo \ + test-fsmount \ + test-mntinfo \ + test-statx always-y := $(userprogs) userccflags += -I usr/include diff --git a/samples/vfs/test-mntinfo.c b/samples/vfs/test-mntinfo.c new file mode 100644 index 000000000000..a706b5e85997 --- /dev/null +++ b/samples/vfs/test-mntinfo.c @@ -0,0 +1,277 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Test the fsinfo() system call + * + * Copyright (C) 2020 Red Hat, Inc. All Rights Reserved. + * Written by David Howells ([email protected]) + */ + +#define _GNU_SOURCE +#define _ATFILE_SOURCE +#include <stdbool.h> +#include <stdio.h> +#include <stdlib.h> +#include <stdint.h> +#include <string.h> +#include <unistd.h> +#include <ctype.h> +#include <errno.h> +#include <time.h> +#include <math.h> +#include <sys/syscall.h> +#include <linux/fsinfo.h> +#include <linux/socket.h> +#include <linux/fcntl.h> +#include <sys/stat.h> +#include <arpa/inet.h> + +#ifndef __NR_fsinfo +#define __NR_fsinfo -1 +#endif + +static __attribute__((unused)) +ssize_t fsinfo(int dfd, const char *filename, + struct fsinfo_params *params, size_t params_size, + void *result_buffer, size_t result_buf_size) +{ + return syscall(__NR_fsinfo, dfd, filename, + params, params_size, + result_buffer, result_buf_size); +} + +static char tree_buf[4096]; +static char bar_buf[4096]; +static unsigned int children_list_interval; + +/* + * Get an fsinfo attribute in a statically allocated buffer. + */ +static void get_attr(unsigned int mnt_id, unsigned int attr, unsigned int Nth, + void *buf, size_t buf_size) +{ + struct fsinfo_params params = { + .flags = FSINFO_FLAGS_QUERY_MOUNT, + .request = attr, + .Nth = Nth, + }; + char file[32]; + long ret; + + sprintf(file, "%u", mnt_id); + + memset(buf, 0xbd, buf_size); + + ret = fsinfo(AT_FDCWD, file, ¶ms, sizeof(params), buf, buf_size); + if (ret == -1) { + fprintf(stderr, "mount-%s: %m\n", file); + exit(1); + } +} + +/* + * Get an fsinfo attribute in a dynamically allocated buffer. + */ +static void *get_attr_alloc(unsigned int mnt_id, unsigned int attr, + unsigned int Nth, size_t *_size) +{ + struct fsinfo_params params = { + .flags = FSINFO_FLAGS_QUERY_MOUNT, + .request = attr, + .Nth = Nth, + }; + size_t buf_size = 4096; + char file[32]; + void *r; + long ret; + + sprintf(file, "%u", mnt_id); + + for (;;) { + r = malloc(buf_size); + if (!r) { + perror("malloc"); + exit(1); + } + memset(r, 0xbd, buf_size); + + ret = fsinfo(AT_FDCWD, file, ¶ms, sizeof(params), r, buf_size); + if (ret == -1) { + fprintf(stderr, "mount-%s: %x,%x,%x %m\n", + file, params.request, params.Nth, params.Mth); + exit(1); + } + + if (ret <= buf_size) { + *_size = ret; + break; + } + buf_size = (ret + 4096 - 1) & ~(4096 - 1); + } + + return r; +} + +/* + * Display a mount and then recurse through its children. + */ +static void display_mount(unsigned int mnt_id, unsigned int depth, char *path) +{ + struct fsinfo_mount_topology top; + struct fsinfo_mount_child child; + struct fsinfo_mount_info info; + struct fsinfo_ids ids; + void *children; + unsigned int d; + size_t ch_size, p_size; + char dev[64]; + int i, n, s; + + get_attr(mnt_id, FSINFO_ATTR_MOUNT_TOPOLOGY, 0, &top, sizeof(top)); + get_attr(mnt_id, FSINFO_ATTR_MOUNT_INFO, 0, &info, sizeof(info)); + get_attr(mnt_id, FSINFO_ATTR_IDS, 0, &ids, sizeof(ids)); + if (depth > 0) + printf("%s", tree_buf); + + s = strlen(path); + printf("%s", !s ? "\"\"" : path); + if (!s) + s += 2; + s += depth; + if (s < 38) + s = 38 - s; + else + s = 1; + printf("%*.*s", s, s, ""); + + sprintf(dev, "%x:%x", ids.f_dev_major, ids.f_dev_minor); + printf("%10u %8llx %2x %x %5s %s", + info.mnt_id, + (info.mnt_attr_changes + + info.mnt_topology_changes + + info.mnt_subtree_notifications), + info.attr, top.propagation_type, + dev, ids.f_fs_name); + putchar('\n'); + + children = get_attr_alloc(mnt_id, FSINFO_ATTR_MOUNT_CHILDREN, 0, &ch_size); + n = ch_size / children_list_interval - 1; + + bar_buf[depth + 1] = '|'; + if (depth > 0) { + tree_buf[depth - 4 + 1] = bar_buf[depth - 4 + 1]; + tree_buf[depth - 4 + 2] = ' '; + } + + tree_buf[depth + 0] = ' '; + tree_buf[depth + 1] = '\\'; + tree_buf[depth + 2] = '_'; + tree_buf[depth + 3] = ' '; + tree_buf[depth + 4] = 0; + d = depth + 4; + + memset(&child, 0, sizeof(child)); + for (i = 0; i < n; i++) { + void *p = children + i * children_list_interval; + + if (sizeof(child) >= children_list_interval) + memcpy(&child, p, children_list_interval); + else + memcpy(&child, p, sizeof(child)); + + if (i == n - 1) + bar_buf[depth + 1] = ' '; + path = get_attr_alloc(child.mnt_id, FSINFO_ATTR_MOUNT_POINT, + 0, &p_size); + display_mount(child.mnt_id, d, path + 1); + free(path); + } + + free(children); + if (depth > 0) { + tree_buf[depth - 4 + 1] = '\\'; + tree_buf[depth - 4 + 2] = '_'; + } + tree_buf[depth] = 0; +} + +/* + * Find the ID of whatever is at the nominated path. + */ +static unsigned int lookup_mnt_by_path(const char *path) +{ + struct fsinfo_mount_info mnt; + struct fsinfo_params params = { + .flags = FSINFO_FLAGS_QUERY_PATH, + .request = FSINFO_ATTR_MOUNT_INFO, + }; + + if (fsinfo(AT_FDCWD, path, ¶ms, sizeof(params), &mnt, sizeof(mnt)) == -1) { + perror(path); + exit(1); + } + + return mnt.mnt_id; +} + +/* + * Determine the element size for the mount child list. + */ +static unsigned int query_list_element_size(int mnt_id, unsigned int attr) +{ + struct fsinfo_attribute_info attr_info; + + get_attr(mnt_id, FSINFO_ATTR_FSINFO_ATTRIBUTE_INFO, attr, + &attr_info, sizeof(attr_info)); + return attr_info.size; +} + +/* + * + */ +int main(int argc, char **argv) +{ + unsigned int mnt_id; + char *path; + bool use_mnt_id = false; + int opt; + + while ((opt = getopt(argc, argv, "m"))) { + switch (opt) { + case 'm': + use_mnt_id = true; + continue; + } + break; + } + + argc -= optind; + argv += optind; + + switch (argc) { + case 0: + mnt_id = lookup_mnt_by_path("/"); + path = "ROOT"; + break; + case 1: + path = argv[0]; + if (use_mnt_id) { + mnt_id = strtoul(argv[0], NULL, 0); + break; + } + + mnt_id = lookup_mnt_by_path(argv[0]); + break; + default: + printf("Format: test-mntinfo\n"); + printf("Format: test-mntinfo <path>\n"); + printf("Format: test-mntinfo -m <mnt_id>\n"); + exit(2); + } + + children_list_interval = + query_list_element_size(mnt_id, FSINFO_ATTR_MOUNT_CHILDREN); + + printf("MOUNT MOUNT ID CHANGE# AT P DEV TYPE\n"); + printf("------------------------------------- ---------- -------- -- - ----- --------\n"); + display_mount(mnt_id, 0, path); + return 0; +}
