linux-kernel - Re: [PATCH 4/6] fs: FS_IOC

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Date: Mon, 5 Feb 2024 23:33:11 -0500
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Randy Dunlap <rdunlap@...radead.org>
Cc: dsterba@...e.cz, "Darrick J. Wong" <djwong@...nel.org>, 
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-btrfs@...r.kernel.org, 
	linux-xfs@...r.kernel.org, linux-ext4@...r.kernel.org, 
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, Dave Chinner <dchinner@...hat.com>, 
	Theodore Ts'o <tytso@....edu>, Josef Bacik <josef@...icpanda.com>
Subject: Re: [PATCH 4/6] fs: FS_IOC_GETSYSFSNAME

On Mon, Feb 05, 2024 at 08:20:10PM -0800, Randy Dunlap wrote:
> 
> 
> On 2/5/24 17:39, David Sterba wrote:
> > On Mon, Feb 05, 2024 at 05:43:37PM -0500, Kent Overstreet wrote:
> >> On Mon, Feb 05, 2024 at 02:27:32PM -0800, Darrick J. Wong wrote:
> >>> On Mon, Feb 05, 2024 at 03:05:15PM -0500, Kent Overstreet wrote:
> >>>> @@ -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.
> >>
> >> Can we please document this somewhere!?
> >>
> >> What, dare I ask, is the "namespace" I should be using?
> > 
> > Grep for _IOCTL_MAGIC in include/uapi:
> > 
> > uapi/linux/aspeed-lpc-ctrl.h:#define __ASPEED_LPC_CTRL_IOCTL_MAGIC 0xb2
> > uapi/linux/aspeed-p2a-ctrl.h:#define __ASPEED_P2A_CTRL_IOCTL_MAGIC 0xb3
> > uapi/linux/bt-bmc.h:#define __BT_BMC_IOCTL_MAGIC        0xb1
> > uapi/linux/btrfs.h:#define BTRFS_IOCTL_MAGIC 0x94
> > uapi/linux/f2fs.h:#define F2FS_IOCTL_MAGIC              0xf5
> > uapi/linux/ipmi_bmc.h:#define __IPMI_BMC_IOCTL_MAGIC        0xB1
> > uapi/linux/pfrut.h:#define PFRUT_IOCTL_MAGIC 0xEE
> > uapi/rdma/rdma_user_ioctl.h:#define IB_IOCTL_MAGIC RDMA_IOCTL_MAGIC
> > uapi/rdma/rdma_user_ioctl_cmds.h:#define RDMA_IOCTL_MAGIC       0x1b
> > 
> > The label ioctls inherited the 0x94 namespace for backward
> > compatibility but as already said, it's the private namespace of btrfs.
> > 
> 
> or more generally, see Documentation/userspace-api/ioctl/ioctl-number.rst.
> 
> For 0x94, it says:
> 
> 0x94  all    fs/btrfs/ioctl.h                                        Btrfs filesystem
>              and linux/fs.h                                          some lifted to vfs/generic

You guys keep giving the same info over and over again, instead of
anything that would be actually helpful...

Does anyone know what the proper "namespace" is for new VFS level
ioctls?

..Anyone?