On Wed, Feb 7, 2024 at 4:57 AM Kent Overstreet <kent.overstreet@xxxxxxxxx> 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. We're not lifting SETFSUUID from ext4 - > that can be done on offline filesystems by the people who need it, > trying to do it online is just asking for too much trouble. > > Cc: Christian Brauner <brauner@xxxxxxxxxx> > Cc: Jan Kara <jack@xxxxxxx> > Cc: Dave Chinner <dchinner@xxxxxxxxxx> > Cc: "Darrick J. Wong" <djwong@xxxxxxxxxx> > Cc: Theodore Ts'o <tytso@xxxxxxx> > Cc: linux-fsdevel@xxxxxxxxxxxxxx > Signed-off-by: Kent Overstreet <kent.overstreet@xxxxxxxxx> > --- > .../userspace-api/ioctl/ioctl-number.rst | 3 ++- > fs/ioctl.c | 16 ++++++++++++++++ > include/uapi/linux/fs.h | 16 ++++++++++++++++ > 3 files changed, 34 insertions(+), 1 deletion(-) > > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst b/Documentation/userspace-api/ioctl/ioctl-number.rst > index 457e16f06e04..3731ecf1e437 100644 > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst > @@ -82,8 +82,9 @@ Code Seq# Include File Comments > 0x10 00-0F drivers/char/s390/vmcp.h > 0x10 10-1F arch/s390/include/uapi/sclp_ctl.h > 0x10 20-2F arch/s390/include/uapi/asm/hypfs.h > -0x12 all linux/fs.h > +0x12 all linux/fs.h BLK* ioctls > linux/blkpg.h > +0x15 all linux/fs.h FS_IOC_* ioctls > 0x1b all InfiniBand Subsystem > <http://infiniband.sourceforge.net/> > 0x20 all drivers/cdrom/cm206.h > diff --git a/fs/ioctl.c b/fs/ioctl.c > index 76cf22ac97d7..74eab9549383 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; > + struct fsuuid2 u = { .len = sb->s_uuid_len, }; > + > + if (!sb->s_uuid_len) > + return -ENOIOCTLCMD; > + > + memcpy(&u.uuid[0], &sb->s_uuid, sb->s_uuid_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..d459f816cd50 100644 > --- a/include/uapi/linux/fs.h > +++ b/include/uapi/linux/fs.h > @@ -64,6 +64,19 @@ 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 { > + __u8 len; > + __u8 uuid[16]; > +}; > + > /* extent-same (dedupe) ioctls; these MUST match the btrfs ioctl definitions */ > #define FILE_DEDUPE_RANGE_SAME 0 > #define FILE_DEDUPE_RANGE_DIFFERS 1 > @@ -190,6 +203,9 @@ struct fsxattr { > * (see uapi/linux/blkzoned.h) > */ > > +/* Returns the external filesystem UUID, the same one blkid returns */ > +#define FS_IOC_GETFSUUID _IOR(0x15, 0, struct fsuuid2) Please move that to the end of FS_IOC_* ioctls block. The fact that it started a new vfs ioctl namespace does not justify starting a different list IMO. uapi readers don't care about the value of the ioctl. locality to FS_IOC_GETFSLABEL is more important IMO. Thanks, Amir. > + > #define BMAP_IOCTL 1 /* obsolete - kept for compatibility */ > #define FIBMAP _IO(0x00,1) /* bmap access */ > #define FIGETBSZ _IO(0x00,2) /* get the block size used for bmap */ > -- > 2.43.0 > >
