On Sun, Mar 23, 2025 at 11:32 AM Pali Rohár <p...@kernel.org> wrote: > > On Sunday 23 March 2025 09:45:06 Amir Goldstein wrote: > > On Fri, Mar 21, 2025 at 8:50 PM Andrey Albershteyn <aalbe...@redhat.com> > > wrote: > > > > > > This patchset introduced two new syscalls getfsxattrat() and > > > setfsxattrat(). 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 an 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. > > > > > > Christian, if this get in some mergeable state, please don't merge it > > > yet. Amir suggested these syscalls better to use updated struct fsxattr > > > with masking from Pali Rohár patchset, so, let's see how it goes. > > > > Andrey, > > > > To be honest I don't think it would be fair to delay your syscalls more > > than needed. > > I agree. > > > If Pali can follow through and post patches on top of your syscalls for > > next merge window that would be great, but otherwise, I think the > > minimum requirement is that the syscalls return EINVAL if fsx_pad > > is not zero. we can take it from there later. > > IMHO SYS_getfsxattrat is fine in this form. > > For SYS_setfsxattrat I think there are needed some modifications > otherwise we would have problem again with backward compatibility as > is with ioctl if the syscall wants to be extended in future. > > I would suggest for following modifications for SYS_setfsxattrat: > > - return EINVAL if fsx_xflags contains some reserved or unsupported flag > > - add some flag to completely ignore fsx_extsize, fsx_projid, and > fsx_cowextsize fields, so SYS_setfsxattrat could be used just to > change fsx_xflags, and so could be used without the preceding > SYS_getfsxattrat call. > > What do you think about it?
I think all Andrey needs to do now is return -EINVAL if fsx_pad is not zero. You can use this later to extend for the semantics of flags/fields mask and we can have a long discussion later on what this semantics should be. Right? Amir.
