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)
+
#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
