On Thu 07-11-24 16:00:07, Jeff Layton wrote:
> /proc/self/mountinfo displays the devicename for the mount, but
> statmount() doesn't yet have a way to return it. Add a new
> STATMOUNT_MNT_DEVNAME flag, claim the 32-bit __spare1 field to hold the
> offset into the str[] array. STATMOUNT_MNT_DEVNAME will only be set in
> the return mask if there is a device string.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
Looks good to me. Feel free to add:
Reviewed-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/namespace.c | 36 +++++++++++++++++++++++++++++++++++-
> include/uapi/linux/mount.h | 3 ++-
> 2 files changed, 37 insertions(+), 2 deletions(-)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index fc4f81891d544305caf863904c0a6e16562fab49..56750fcc890271e22b3b722dc0b4af445686bb86 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -5014,6 +5014,32 @@ static void statmount_fs_subtype(struct kstatmount *s, struct seq_file *seq)
> seq_puts(seq, sb->s_subtype);
> }
>
> +static int statmount_mnt_devname(struct kstatmount *s, struct seq_file *seq)
> +{
> + struct super_block *sb = s->mnt->mnt_sb;
> + struct mount *r = real_mount(s->mnt);
> +
> + if (sb->s_op->show_devname) {
> + size_t start = seq->count;
> + int ret;
> +
> + ret = sb->s_op->show_devname(seq, s->mnt->mnt_root);
> + if (ret)
> + return ret;
> +
> + if (unlikely(seq_has_overflowed(seq)))
> + return -EAGAIN;
> +
> + /* Unescape the result */
> + seq->buf[seq->count] = '\0';
> + seq->count = start;
> + seq_commit(seq, string_unescape_inplace(seq->buf + start, UNESCAPE_OCTAL));
> + } else if (r->mnt_devname) {
> + seq_puts(seq, r->mnt_devname);
> + }
> + return 0;
> +}
> +
> static void statmount_mnt_ns_id(struct kstatmount *s, struct mnt_namespace *ns)
> {
> s->sm.mask |= STATMOUNT_MNT_NS_ID;
> @@ -5077,6 +5103,10 @@ static int statmount_string(struct kstatmount *s, u64 flag)
> sm->fs_subtype = start;
> statmount_fs_subtype(s, seq);
> break;
> + case STATMOUNT_MNT_DEVNAME:
> + sm->mnt_devname = seq->count;
> + ret = statmount_mnt_devname(s, seq);
> + break;
> default:
> WARN_ON_ONCE(true);
> return -EINVAL;
> @@ -5225,6 +5255,9 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id,
> if (!err && s->mask & STATMOUNT_FS_SUBTYPE)
> err = statmount_string(s, STATMOUNT_FS_SUBTYPE);
>
> + if (!err && s->mask & STATMOUNT_MNT_DEVNAME)
> + err = statmount_string(s, STATMOUNT_MNT_DEVNAME);
> +
> if (!err && s->mask & STATMOUNT_MNT_NS_ID)
> statmount_mnt_ns_id(s, ns);
>
> @@ -5246,7 +5279,8 @@ static inline bool retry_statmount(const long ret, size_t *seq_size)
> }
>
> #define STATMOUNT_STRING_REQ (STATMOUNT_MNT_ROOT | STATMOUNT_MNT_POINT | \
> - STATMOUNT_FS_TYPE | STATMOUNT_MNT_OPTS | STATMOUNT_FS_SUBTYPE)
> + STATMOUNT_FS_TYPE | STATMOUNT_MNT_OPTS | \
> + STATMOUNT_FS_SUBTYPE | STATMOUNT_MNT_DEVNAME)
>
> static int prepare_kstatmount(struct kstatmount *ks, struct mnt_id_req *kreq,
> struct statmount __user *buf, size_t bufsize,
> diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
> index 2e939dddf9cbabe574dafdb6cff9ad4cf9298a74..3de1b0231b639fb8ed739d65b5b5406021f74196 100644
> --- a/include/uapi/linux/mount.h
> +++ b/include/uapi/linux/mount.h
> @@ -174,7 +174,7 @@ struct statmount {
> __u32 mnt_point; /* [str] Mountpoint relative to current root */
> __u64 mnt_ns_id; /* ID of the mount namespace */
> __u32 fs_subtype; /* [str] Subtype of fs_type (if any) */
> - __u32 __spare1[1];
> + __u32 mnt_devname; /* [str] Device string for the mount */
> __u64 __spare2[48];
> char str[]; /* Variable size part containing strings */
> };
> @@ -210,6 +210,7 @@ struct mnt_id_req {
> #define STATMOUNT_MNT_NS_ID 0x00000040U /* Want/got mnt_ns_id */
> #define STATMOUNT_MNT_OPTS 0x00000080U /* Want/got mnt_opts */
> #define STATMOUNT_FS_SUBTYPE 0x00000100U /* Want/got fs_subtype */
> +#define STATMOUNT_MNT_DEVNAME 0x00000200U /* Want/got mnt_devname */
>
> /*
> * Special @mnt_id values that can be passed to listmount
>
> --
> 2.47.0
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
