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.
