On Mon, Feb 05, 2024 at 03:05:15PM -0500, Kent Overstreet wrote:
> Add a new ioctl for getting the sysfs name of a filesystem - the path
> under /sys/fs.
>
> This is going to let us standardize exporting data from sysfs across
> filesystems, e.g. time stats.
>
> The returned path will always be of the form "$FSTYP/$SYSFS_IDENTIFIER",
> where the sysfs identifier may be a UUID (for bcachefs) or a device name
> (xfs).
>
> Signed-off-by: Kent Overstreet <[email protected]>
> Cc: Christian Brauner <[email protected]>
> Cc: Jan Kara <[email protected]>
> Cc: Dave Chinner <[email protected]>
> Cc: "Darrick J. Wong" <[email protected]>
> Cc: Theodore Ts'o <[email protected]>
> Cc: Josef Bacik <[email protected]>
> ---
> fs/ioctl.c | 17 +++++++++++++++++
> include/linux/fs.h | 1 +
> include/uapi/linux/fs.h | 5 +++++
> 3 files changed, 23 insertions(+)
>
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index 858801060408..cb3690811d3d 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -776,6 +776,20 @@ static int ioctl_getfsuuid(struct file *file, void __user *argp)
> return copy_to_user(argp, &u, sizeof(u)) ? -EFAULT : 0;
> }
>
> +static int ioctl_getfssysfsname(struct file *file, void __user *argp)
ackpthspacesplease.
"ioctl_get_fs_sysfs_name"?
> +{
> + struct super_block *sb = file_inode(file)->i_sb;
> +
> + if (!strlen(sb->s_sysfs_name))
> + return -ENOIOCTLCMD;
> +
> + struct fssysfsname u = {};
> +
> + snprintf(u.name, sizeof(u.name), "%s/%s", sb->s_type->name, sb->s_sysfs_name);
Does this actually guarantee that there will be a trailing null in the
output? It's really stupid that GETFSLABEL can return an unterminated
string if the label is exactly the size of the char array.
> +
> + return copy_to_user(argp, &u, sizeof(u)) ? -EFAULT : 0;
> +}
> +
> /*
> * do_vfs_ioctl() is not for drivers and not intended to be EXPORT_SYMBOL()'d.
> * It's just a simple helper for sys_ioctl and compat_sys_ioctl.
> @@ -861,6 +875,9 @@ static int do_vfs_ioctl(struct file *filp, unsigned int fd,
> case FS_IOC_GETFSUUID:
> return ioctl_getfsuuid(filp, argp);
>
> + case FS_IOC_GETFSSYSFSNAME:
File System Ioctl Get File System System File System Name.
Yuck.
FS_IOC_GETSYSFSPATH?
Also, do we want to establish that this works for /sys/fs and
/sys/kernel/debug at the same time?
> + return ioctl_getfssysfsname(filp, argp);
> +
> default:
> if (S_ISREG(inode->i_mode))
> return file_ioctl(filp, cmd, argp);
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index ff41ea6c3a9c..7f23f593f17c 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1258,6 +1258,7 @@ struct super_block {
> char s_id[32]; /* Informational name */
> uuid_t s_uuid; /* UUID */
> u8 s_uuid_len; /* Default 16, possibly smaller for weird filesystems */
> + char s_sysfs_name[UUID_STRING_LEN + 1];
>
> unsigned int s_max_links;
>
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index 0389fea87db5..6dd14a453277 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -78,6 +78,10 @@ struct fsuuid2 {
> __u8 fsu_uuid[16];
> };
>
> +struct fssysfsname {
> + __u8 name[64];
> +};
> +
> /* extent-same (dedupe) ioctls; these MUST match the btrfs ioctl definitions */
> #define FILE_DEDUPE_RANGE_SAME 0
> #define FILE_DEDUPE_RANGE_DIFFERS 1
> @@ -231,6 +235,7 @@ struct fsxattr {
> #define FS_IOC_SETFSLABEL _IOW(0x94, 50, char[FSLABEL_MAX])
> #define FS_IOC_GETFSUUID _IOR(0x94, 51, struct fsuuid2)
> #define FS_IOC_SETFSUUID _IOW(0x94, 52, struct fsuuid2)
> +#define FS_IOC_GETFSSYSFSNAME _IOR(0x94, 53, struct fssysfsname)
0x94 is btrfs, don't add things to their "name" space.
--D
>
> /*
> * Inode flags (FS_IOC_GETFLAGS / FS_IOC_SETFLAGS)
> --
> 2.43.0
>
>