On Tue, Jul 01, 2025 at 08:54:57PM +0200, Pali Rohár wrote:
> On Tuesday 01 July 2025 11:43:17 Darrick J. Wong wrote:
> > On Mon, Jun 30, 2025 at 06:20:16PM +0200, Andrey Albershteyn wrote:
> > > diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> > > index 0098b0ce8ccb..0784f2033ba4 100644
> > > --- a/include/uapi/linux/fs.h
> > > +++ b/include/uapi/linux/fs.h
> > > @@ -148,6 +148,24 @@ struct fsxattr {
> > > unsigned char fsx_pad[8];
> > > };
> > >
> > > +/*
> > > + * Variable size structure for file_[sg]et_attr().
> > > + *
> > > + * Note. This is alternative to the structure 'struct fileattr'/'struct fsxattr'.
> > > + * As this structure is passed to/from userspace with its size, this can
> > > + * be versioned based on the size.
> > > + */
> > > +struct fsx_fileattr {
> > > + __u32 fsx_xflags; /* xflags field value (get/set) */
> >
> > Should this to be __u64 from the start? Seeing as (a) this struct is
> > not already a multiple of 8 bytes and (b) it's likely that we'll have to
> > add a u64 field at some point. That would also address brauner's
> > comment about padding.
>
> Hello!
>
> As I have already mentioned, after this syscall API/ABI is finished, I'm
> planning to prepare patches for changing just selected fields / flags by
> introducing a new mask field, and support for additional flags used by
> existing filesystems (like windows flags).
>
> My idea is extending this structure for a new "u32 fsx_xflags_mask"
> and new "u32 fsx_xflags2" + "u32 fsx_xflags2_mask". (field names are
> just examples).
>
> So in case you are extending the structure now, please consider if it
> makes sense to add all members, so we do not have to define 2 or 3
> structure versions in near feature.
>
> Your idea of __u64 for fsx_xflags means that it will already cover the
> "u32 fsx_xflags2" field.
Ah, ok, so that work *is* still coming. :)
Are you still planning to add masks for xflags bits that are clearable
and settable? i.e.
__u64 fa_xflags; /* state */
...
<end of V0 structure>
__u64 fa_xflags_mask; /* bits for setattr to examine */
__u64 fa_xflags_clearable; /* clearable bits */
__u64 fa_xflags_settable; /* settable bits */
I think it's easier just to define u64 in the V0 structure and then add
the three new fields in V1. What do you think?
--D
> > --D
> >
> > > + __u32 fsx_extsize; /* extsize field value (get/set)*/
> > > + __u32 fsx_nextents; /* nextents field value (get) */
> > > + __u32 fsx_projid; /* project identifier (get/set) */
> > > + __u32 fsx_cowextsize; /* CoW extsize field value (get/set) */
> > > +};
> > > +
> > > +#define FSX_FILEATTR_SIZE_VER0 20
> > > +#define FSX_FILEATTR_SIZE_LATEST FSX_FILEATTR_SIZE_VER0
> > > +
> > > /*
> > > * Flags for the fsx_xflags field
> > > */
> > > diff --git a/scripts/syscall.tbl b/scripts/syscall.tbl
> > > index 580b4e246aec..d1ae5e92c615 100644
> > > --- a/scripts/syscall.tbl
> > > +++ b/scripts/syscall.tbl
> > > @@ -408,3 +408,5 @@
> > > 465 common listxattrat sys_listxattrat
> > > 466 common removexattrat sys_removexattrat
> > > 467 common open_tree_attr sys_open_tree_attr
> > > +468 common file_getattr sys_file_getattr
> > > +469 common file_setattr sys_file_setattr
> > >
> > > --
> > > 2.47.2
> > >
> > >
>
