On Mon, Feb 05, 2024 at 03:05:13PM -0500, Kent Overstreet wrote:
> Add a new generic ioctls for querying the filesystem UUID.
>
> These are lifted versions of the ext4 ioctls, with one change: we're not
> using a flexible array member, because UUIDs will never be more than 16
> bytes.
>
> This patch adds a generic implementation of FS_IOC_GETFSUUID, which
> reads from super_block->s_uuid; FS_IOC_SETFSUUID is left for individual
> filesystems to implement.
>
> 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: [email protected]
> Signed-off-by: Kent Overstreet <[email protected]>
> ---
> fs/ioctl.c | 16 ++++++++++++++++
> include/uapi/linux/fs.h | 16 ++++++++++++++++
> 2 files changed, 32 insertions(+)
>
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index 76cf22ac97d7..858801060408 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -763,6 +763,19 @@ static int ioctl_fssetxattr(struct file *file, void __user *argp)
> return err;
> }
>
> +static int ioctl_getfsuuid(struct file *file, void __user *argp)
> +{
> + struct super_block *sb = file_inode(file)->i_sb;
> +
> + if (WARN_ON(sb->s_uuid_len > sizeof(sb->s_uuid)))
> + sb->s_uuid_len = sizeof(sb->s_uuid);
A "get"/read only ioctl should not be change superblock fields -
this is not the place for enforcing superblock filed constraints.
Make a helper function super_set_uuid(sb, uuid, uuid_len) for the
filesystems to call that does all the validity checking and then
sets the superblock fields appropriately.
> +
> + struct fsuuid2 u = { .fsu_len = sb->s_uuid_len, };
> + memcpy(&u.fsu_uuid[0], &sb->s_uuid, sb->s_uuid_len);
if (!u.fsu_len)
return -ENOENT;
memcpy(&u.fsu_uuid[0], &sb->s_uuid, u.fsu_len);
> +
> + 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.
> @@ -845,6 +858,9 @@ static int do_vfs_ioctl(struct file *filp, unsigned int fd,
> case FS_IOC_FSSETXATTR:
> return ioctl_fssetxattr(filp, argp);
>
> + case FS_IOC_GETFSUUID:
> + return ioctl_getfsuuid(filp, argp);
> +
> default:
> if (S_ISREG(inode->i_mode))
> return file_ioctl(filp, cmd, argp);
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index 48ad69f7722e..0389fea87db5 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -64,6 +64,20 @@ struct fstrim_range {
> __u64 minlen;
> };
>
> +/*
> + * We include a length field because some filesystems (vfat) have an identifier
> + * that we do want to expose as a UUID, but doesn't have the standard length.
> + *
> + * We use a fixed size buffer beacuse this interface will, by fiat, never
> + * support "UUIDs" longer than 16 bytes; we don't want to force all downstream
> + * users to have to deal with that.
> + */
> +struct fsuuid2 {
> + __u32 fsu_len;
> + __u32 fsu_flags;
> + __u8 fsu_uuid[16];
> +};
Nobody in userspace will care that this is "version 2" of the ext4
ioctl. I'd just name it "fs_uuid" as though the ext4 version didn't
ever exist.
> +
> /* extent-same (dedupe) ioctls; these MUST match the btrfs ioctl definitions */
> #define FILE_DEDUPE_RANGE_SAME 0
> #define FILE_DEDUPE_RANGE_DIFFERS 1
> @@ -215,6 +229,8 @@ struct fsxattr {
> #define FS_IOC_FSSETXATTR _IOW('X', 32, struct fsxattr)
> #define FS_IOC_GETFSLABEL _IOR(0x94, 49, char[FSLABEL_MAX])
> #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)
0x94 is the btrfs ioctl space, not the VFS space - why did you
choose that? That said, what is the VFS ioctl space identifier? 'v',
perhaps?
-Dave.
--
Dave Chinner
[email protected]
On Tue, Feb 06, 2024 at 09:17:58AM +1100, Dave Chinner wrote:
> On Mon, Feb 05, 2024 at 03:05:13PM -0500, Kent Overstreet wrote:
> > Add a new generic ioctls for querying the filesystem UUID.
> >
> > These are lifted versions of the ext4 ioctls, with one change: we're not
> > using a flexible array member, because UUIDs will never be more than 16
> > bytes.
> >
> > This patch adds a generic implementation of FS_IOC_GETFSUUID, which
> > reads from super_block->s_uuid; FS_IOC_SETFSUUID is left for individual
> > filesystems to implement.
> >
> > 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: [email protected]
> > Signed-off-by: Kent Overstreet <[email protected]>
> > ---
> > fs/ioctl.c | 16 ++++++++++++++++
> > include/uapi/linux/fs.h | 16 ++++++++++++++++
> > 2 files changed, 32 insertions(+)
> >
> > diff --git a/fs/ioctl.c b/fs/ioctl.c
> > index 76cf22ac97d7..858801060408 100644
> > --- a/fs/ioctl.c
> > +++ b/fs/ioctl.c
> > @@ -763,6 +763,19 @@ static int ioctl_fssetxattr(struct file *file, void __user *argp)
> > return err;
> > }
> >
> > +static int ioctl_getfsuuid(struct file *file, void __user *argp)
> > +{
> > + struct super_block *sb = file_inode(file)->i_sb;
> > +
> > + if (WARN_ON(sb->s_uuid_len > sizeof(sb->s_uuid)))
> > + sb->s_uuid_len = sizeof(sb->s_uuid);
>
> A "get"/read only ioctl should not be change superblock fields -
> this is not the place for enforcing superblock filed constraints.
> Make a helper function super_set_uuid(sb, uuid, uuid_len) for the
> filesystems to call that does all the validity checking and then
> sets the superblock fields appropriately.
*nod* good thought...
> > +struct fsuuid2 {
> > + __u32 fsu_len;
> > + __u32 fsu_flags;
> > + __u8 fsu_uuid[16];
> > +};
>
> Nobody in userspace will care that this is "version 2" of the ext4
> ioctl. I'd just name it "fs_uuid" as though the ext4 version didn't
> ever exist.
I considered that - but I decided I wanted the explicit versioning,
because too often we live with unfixed mistakes because versioning is
ugly, or something?
Doing a new revision of an API should be a normal, frequent thing, and I
want to start making it a convention.
>
> > +
> > /* extent-same (dedupe) ioctls; these MUST match the btrfs ioctl definitions */
> > #define FILE_DEDUPE_RANGE_SAME 0
> > #define FILE_DEDUPE_RANGE_DIFFERS 1
> > @@ -215,6 +229,8 @@ struct fsxattr {
> > #define FS_IOC_FSSETXATTR _IOW('X', 32, struct fsxattr)
> > #define FS_IOC_GETFSLABEL _IOR(0x94, 49, char[FSLABEL_MAX])
> > #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)
>
> 0x94 is the btrfs ioctl space, not the VFS space - why did you
> choose that? That said, what is the VFS ioctl space identifier? 'v',
> perhaps?
"Promoting ioctls from fs to vfs without revising and renaming
considered harmful"... this is a mess that could have been avoided if we
weren't taking the lazy route.
And 'v' doesn't look like it to me, I really have no idea what to use
here. Does anyone?
On Mon, Feb 05, 2024 at 05:49:30PM -0500, Kent Overstreet wrote:
> On Tue, Feb 06, 2024 at 09:17:58AM +1100, Dave Chinner wrote:
> > On Mon, Feb 05, 2024 at 03:05:13PM -0500, Kent Overstreet wrote:
> > > Add a new generic ioctls for querying the filesystem UUID.
> > >
> > > These are lifted versions of the ext4 ioctls, with one change: we're not
> > > using a flexible array member, because UUIDs will never be more than 16
> > > bytes.
> > >
> > > This patch adds a generic implementation of FS_IOC_GETFSUUID, which
> > > reads from super_block->s_uuid; FS_IOC_SETFSUUID is left for individual
> > > filesystems to implement.
> > >
> > > 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: [email protected]
> > > Signed-off-by: Kent Overstreet <[email protected]>
> > > ---
> > > fs/ioctl.c | 16 ++++++++++++++++
> > > include/uapi/linux/fs.h | 16 ++++++++++++++++
> > > 2 files changed, 32 insertions(+)
> > >
> > > diff --git a/fs/ioctl.c b/fs/ioctl.c
> > > index 76cf22ac97d7..858801060408 100644
> > > --- a/fs/ioctl.c
> > > +++ b/fs/ioctl.c
> > > @@ -763,6 +763,19 @@ static int ioctl_fssetxattr(struct file *file, void __user *argp)
> > > return err;
> > > }
> > >
> > > +static int ioctl_getfsuuid(struct file *file, void __user *argp)
> > > +{
> > > + struct super_block *sb = file_inode(file)->i_sb;
> > > +
> > > + if (WARN_ON(sb->s_uuid_len > sizeof(sb->s_uuid)))
> > > + sb->s_uuid_len = sizeof(sb->s_uuid);
> >
> > A "get"/read only ioctl should not be change superblock fields -
> > this is not the place for enforcing superblock filed constraints.
> > Make a helper function super_set_uuid(sb, uuid, uuid_len) for the
> > filesystems to call that does all the validity checking and then
> > sets the superblock fields appropriately.
>
> *nod* good thought...
>
> > > +struct fsuuid2 {
> > > + __u32 fsu_len;
> > > + __u32 fsu_flags;
> > > + __u8 fsu_uuid[16];
> > > +};
> >
> > Nobody in userspace will care that this is "version 2" of the ext4
> > ioctl. I'd just name it "fs_uuid" as though the ext4 version didn't
> > ever exist.
>
> I considered that - but I decided I wanted the explicit versioning,
> because too often we live with unfixed mistakes because versioning is
> ugly, or something?
>
> Doing a new revision of an API should be a normal, frequent thing, and I
> want to start making it a convention.
>
> >
> > > +
> > > /* extent-same (dedupe) ioctls; these MUST match the btrfs ioctl definitions */
> > > #define FILE_DEDUPE_RANGE_SAME 0
> > > #define FILE_DEDUPE_RANGE_DIFFERS 1
> > > @@ -215,6 +229,8 @@ struct fsxattr {
> > > #define FS_IOC_FSSETXATTR _IOW('X', 32, struct fsxattr)
> > > #define FS_IOC_GETFSLABEL _IOR(0x94, 49, char[FSLABEL_MAX])
> > > #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)
> >
> > 0x94 is the btrfs ioctl space, not the VFS space - why did you
> > choose that? That said, what is the VFS ioctl space identifier? 'v',
> > perhaps?
>
> "Promoting ioctls from fs to vfs without revising and renaming
> considered harmful"... this is a mess that could have been avoided if we
> weren't taking the lazy route.
>
> And 'v' doesn't look like it to me, I really have no idea what to use
> here. Does anyone?
I thought it was 'f' but apparently that's ext?
--D