On Wed 06-11-24 08:29:19, Jeff Layton wrote:
> /proc/self/mountinfo prints out the sb->s_subtype after the type. In
> particular, FUSE makes use of this to display the fstype as
> fuse.<subtype>.
>
> Add STATMOUNT_FS_SUBTYPE and claim one of the __spare2 fields to point
> to the offset into the str[] array. The STATMOUNT_FS_SUBTYPE will only
> be set in the return mask if there is a subtype associated with the
> mount.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
Looks good to me. I'm just curious: Do you have any particular user that is
interested in getting subtype from statmount(2)?
Honza
> ---
> fs/namespace.c | 20 +++++++++++++++++++-
> include/uapi/linux/mount.h | 5 ++++-
> 2 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/fs/namespace.c b/fs/namespace.c
> index ba77ce1c6788dfe461814b5826fcbb3aab68fad4..5f2fb692449a9c0a15b60549fb9f7bedd10f1f3d 100644
> --- a/fs/namespace.c
> +++ b/fs/namespace.c
> @@ -5006,6 +5006,14 @@ static int statmount_fs_type(struct kstatmount *s, struct seq_file *seq)
> return 0;
> }
>
> +static int statmount_fs_subtype(struct kstatmount *s, struct seq_file *seq)
> +{
> + struct super_block *sb = s->mnt->mnt_sb;
> +
> + seq_puts(seq, sb->s_subtype);
> + return 0;
> +}
> +
> static void statmount_mnt_ns_id(struct kstatmount *s, struct mnt_namespace *ns)
> {
> s->sm.mask |= STATMOUNT_MNT_NS_ID;
> @@ -5064,6 +5072,13 @@ static int statmount_string(struct kstatmount *s, u64 flag)
> sm->mnt_opts = seq->count;
> ret = statmount_mnt_opts(s, seq);
> break;
> + case STATMOUNT_FS_SUBTYPE:
> + /* ignore if no s_subtype */
> + if (!s->mnt->mnt_sb->s_subtype)
> + return 0;
> + sm->fs_subtype = seq->count;
> + ret = statmount_fs_subtype(s, seq);
> + break;
> default:
> WARN_ON_ONCE(true);
> return -EINVAL;
> @@ -5203,6 +5218,9 @@ static int do_statmount(struct kstatmount *s, u64 mnt_id, u64 mnt_ns_id,
> if (!err && s->mask & STATMOUNT_MNT_OPTS)
> err = statmount_string(s, STATMOUNT_MNT_OPTS);
>
> + if (!err && s->mask & STATMOUNT_FS_SUBTYPE)
> + err = statmount_string(s, STATMOUNT_FS_SUBTYPE);
> +
> if (!err && s->mask & STATMOUNT_MNT_NS_ID)
> statmount_mnt_ns_id(s, ns);
>
> @@ -5224,7 +5242,7 @@ 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_TYPE | STATMOUNT_MNT_OPTS | STATMOUNT_FS_SUBTYPE)
>
> 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 225bc366ffcbf0319929e2f55f1fbea88e4d7b81..fa206fb56b3b25cf80f7d430e1b6bab19c3220e4 100644
> --- a/include/uapi/linux/mount.h
> +++ b/include/uapi/linux/mount.h
> @@ -173,7 +173,9 @@ struct statmount {
> __u32 mnt_root; /* [str] Root of mount relative to root of fs */
> __u32 mnt_point; /* [str] Mountpoint relative to current root */
> __u64 mnt_ns_id; /* ID of the mount namespace */
> - __u64 __spare2[49];
> + __u32 fs_subtype; /* [str] Subtype of fs_type (if any) */
> + __u32 __spare1[1];
> + __u64 __spare2[48];
> char str[]; /* Variable size part containing strings */
> };
>
> @@ -207,6 +209,7 @@ struct mnt_id_req {
> #define STATMOUNT_FS_TYPE 0x00000020U /* Want/got fs_type */
> #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 subtype */
>
> /*
> * Special @mnt_id values that can be passed to listmount
>
> ---
> base-commit: 26213e1a6caa5a7f508b919059b0122b451f4dfe
> change-id: 20241106-statmount-3f91a7ed75fa
>
> Best regards,
> --
> Jeff Layton <jlayton@xxxxxxxxxx>
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
