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Message-ID: <9eeb6b39-c4a1-6e3d-246a-e1cf97d84b33@gmail.com>
Date: Wed, 5 Jun 2019 13:22:12 +0100
From: Alan Jenkins <alan.christopher.jenkins@...il.com>
To: David Howells <dhowells@...hat.com>, viro@...iv.linux.org.uk
Cc: raven@...maw.net, linux-api@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
mszeredi@...hat.com
Subject: Re: [PATCH 10/25] vfs: fsinfo sample: Mount listing program [ver #13]
On 28/05/2019 16:12, David Howells wrote:
> Implement a program to demonstrate mount listing using the new fsinfo()
> syscall,
Great. I understand this is only for demonstration, but IMO the output
would be clearer with a few tweaks:
> for example:
>
> # ./test-mntinfo
Can we have a header please? E.g.
MNT ID NOTIFS TYPE DEVICE
-------------------------------------- -------- -------- ---- ------
> ROOT 5d c ext4 8:12
> \_ sys 13 8 sysfs 0:13
> | \_ kernel/security 16 0 securityfs 0:7
I assume ID is the same ID which is shown in /proc/mounts. But it's
shown as decimal there. Can we match that?
And can we show NOTIFS in decimal as well? I find counters easier to
read in decimal :-).
I.e. change "%8x" to "%10d" in both cases.
major:minor is also more often seen formatted as "%d:%d": in
/proc/self/mountinfo, lsblk, and ls -l. I don't feel as strongly about
this one though.
Thanks
Alan
> | \_ fs/cgroup 1a 10 tmpfs 0:17
> | | \_ unified 1b 0 cgroup2 0:18
> | | \_ systemd 1c 0 cgroup 0:19
> | | \_ freezer 20 0 cgroup 0:1d
> | | \_ cpu,cpuacct 21 0 cgroup 0:1e
> | | \_ memory 22 0 cgroup 0:1f
> | | \_ cpuset 23 0 cgroup 0:20
> | | \_ hugetlb 24 0 cgroup 0:21
> | | \_ net_cls,net_prio 25 0 cgroup 0:22
> | | \_ blkio 26 0 cgroup 0:23
> | | \_ perf_event 27 0 cgroup 0:24
> | | \_ devices 28 0 cgroup 0:25
> | | \_ rdma 29 0 cgroup 0:26
> | \_ fs/pstore 1d 0 pstore 0:1a
> | \_ firmware/efi/efivars 1e 0 efivarfs 0:1b
> | \_ fs/bpf 1f 0 bpf 0:1c
> | \_ kernel/config 5a 0 configfs 0:10
> | \_ fs/selinux 2a 0 selinuxfs 0:12
> | \_ kernel/debug 2e 0 debugfs 0:8
> \_ dev 15 4 devtmpfs 0:6
> | \_ shm 17 0 tmpfs 0:14
> | \_ pts 18 0 devpts 0:15
> | \_ hugepages 2b 0 hugetlbfs 0:27
> | \_ mqueue 2c 0 mqueue 0:11
> \_ run 19 1 tmpfs 0:16
> | \_ user/0 1b4 0 tmpfs 0:2d
> \_ proc 14 1 proc 0:4
> | \_ sys/fs/binfmt_misc 2d 0 autofs 0:28
> \_ tmp 2f 7d0 tmpfs 0:29
> \_ var/cache/fscache 71 0 tmpfs 0:2a
> \_ boot 74 0 ext4 8:15
> \_ home 74 0 ext4 8:15
> \_ var/lib/nfs/rpc_pipefs bf 0 rpc_pipefs 0:2b
> \_ mnt 15b 5 tmpfs 0:2c
> | \_ foo 164 0 tmpfs 0:2e
> | \_ foo1 16d 0 tmpfs 0:2f
> | \_ foo2 176 0 tmpfs 0:30
> | \_ foo3 17f 0 tmpfs 0:31
> | \_ foo4 188 1 tmpfs 0:32
> | \_ "" 191 0 tmpfs 0:33
> \_ afs 19a 2 afs 0:34
> \_ procyon.org.uk 1a3 0 afs 0:35
> \_ grand.central.org 1ac 0 afs 0:36
>
> Signed-off-by: David Howells<dhowells@...hat.com>
> ---
>
> samples/vfs/Makefile | 3 +
> samples/vfs/test-mntinfo.c | 239 ++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 242 insertions(+)
> create mode 100644 samples/vfs/test-mntinfo.c
> diff --git a/samples/vfs/test-mntinfo.c b/samples/vfs/test-mntinfo.c
> new file mode 100644
> index 000000000000..00fbefae98fa
> --- /dev/null
> +++ b/samples/vfs/test-mntinfo.c
> +/*
> + * 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_child *children;
> + struct fsinfo_mount_info info;
> + struct fsinfo_ids ids;
> + unsigned int d;
> + size_t ch_size, p_size;
> + int i, n, s;
> +
> + get_attr(mnt_id, FSINFO_ATTR_MOUNT_INFO, &info, sizeof(info));
> + get_attr(mnt_id, FSINFO_ATTR_IDS, &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 < 40)
> + s = 40 - s;
> + else
> + s = 1;
> + printf("%*.*s", s, s, "");
> +
> + printf("%8x %8x %s %x:%x",
> + info.mnt_id, info.notify_counter,
> + ids.f_fs_name, ids.f_dev_major, ids.f_dev_minor);
> + putchar('\n');
> +
> + children = get_attr_alloc(mnt_id, FSINFO_ATTR_MOUNT_CHILDREN, 0, &ch_size);
> + n = ch_size / sizeof(children[0]) - 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;
> +
> + for (i = 0; i < n; i++) {
> + if (i == n - 1)
> + bar_buf[depth + 1] = ' ';
> + path = get_attr_alloc(mnt_id, FSINFO_ATTR_MOUNT_SUBMOUNT, i, &p_size);
> + display_mount(children[i].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 = {
> + .request = FSINFO_ATTR_MOUNT_INFO,
> + };
> +
> + if (fsinfo(AT_FDCWD, path, ¶ms, &mnt, sizeof(mnt)) == -1) {
> + perror(path);
> + exit(1);
> + }
> +
> + return mnt.mnt_id;
> +}
> +
> +/*
> + *
> + */
> +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);
> + }
> +
> + display_mount(mnt_id, 0, path);
> + return 0;
> +}
>
>
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