linux-kernel - Re: [PATCH v6 0/6] fs: introduce file_getattr and file

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Message-ID: <20250701-quittung-garnieren-ceaf58dcb762@brauner>
Date: Tue, 1 Jul 2025 14:29:42 +0200
From: Christian Brauner <brauner@...nel.org>
To: Andrey Albershteyn <aalbersh@...hat.com>
Cc: Amir Goldstein <amir73il@...il.com>, Arnd Bergmann <arnd@...db.de>, 
	Casey Schaufler <casey@...aufler-ca.com>, Jan Kara <jack@...e.cz>, 
	Pali Rohár <pali@...nel.org>, Paul Moore <paul@...l-moore.com>, linux-api@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org, 
	selinux@...r.kernel.org, Andrey Albershteyn <aalbersh@...nel.org>
Subject: Re: [PATCH v6 0/6] fs: introduce file_getattr and file_setattr
 syscalls

On Mon, Jun 30, 2025 at 06:20:10PM +0200, Andrey Albershteyn wrote:
> This patchset introduced two new syscalls file_getattr() and
> file_setattr(). These syscalls are similar to FS_IOC_FSSETXATTR ioctl()
> except they use *at() semantics. Therefore, there's no need to open the
> file to get a fd.
> 
> These syscalls allow userspace to set filesystem inode attributes on
> special files. One of the usage examples is XFS quota projects.
> 
> XFS has project quotas which could be attached to a directory. All
> new inodes in these directories inherit project ID set on parent
> directory.
> 
> The project is created from userspace by opening and calling
> FS_IOC_FSSETXATTR on each inode. This is not possible for special
> files such as FIFO, SOCK, BLK etc. Therefore, some inodes are left
> with empty project ID. Those inodes then are not shown in the quota
> accounting but still exist in the directory. This is not critical but in
> the case when special files are created in the directory with already
> existing project quota, these new inodes inherit extended attributes.
> This creates a mix of special files with and without attributes.
> Moreover, special files with attributes don't have a possibility to
> become clear or change the attributes. This, in turn, prevents userspace
> from re-creating quota project on these existing files.

Only small nits I'm going to comment on that I can fix myself.
Otherwise looks great.