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fs: FS_IOC_GETUUID

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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@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Link: https://lore.kernel.org/r/20240207025624.1019754-4-kent.overstreet@linux.dev
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Kent Overstreet 2024-02-06 21:56:17 -05:00 committed by Christian Brauner
parent dd9019604c
commit 41bcbe59c3
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GPG key ID: 91C61BC06578DCA2
3 changed files with 33 additions and 1 deletions
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3
Documentation/userspace-api/ioctl/ioctl-number.rst
View file

@ -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

16
fs/ioctl.c
View file

@ -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);

15
include/uapi/linux/fs.h
View file

@ -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
@ -215,6 +228,8 @@ 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])
/* Returns the external filesystem UUID, the same one blkid returns */
#define FS_IOC_GETFSUUID _IOR(0x15, 0, struct fsuuid2)
/*
* Inode flags (FS_IOC_GETFLAGS / FS_IOC_SETFLAGS)