On May 13, 2025 2:53:23 AM PDT, Arnd Bergmann [off-list ref] wrote:

On Tue, May 13, 2025, at 11:17, Andrey Albershteyn wrote:

quoted

	long syscall(SYS_file_getattr, int dirfd, const char *pathname,
		struct fsxattr *fsx, size_t size, unsigned int at_flags);
	long syscall(SYS_file_setattr, int dirfd, const char *pathname,
		struct fsxattr *fsx, size_t size, unsigned int at_flags);

I don't think we can have both the "struct fsxattr" from the uapi
headers, and a variable size as an additional argument. I would
still prefer not having the extensible structure at all and just
use fsxattr, but if you want to make it extensible in this way,
it should use a different structure (name). Otherwise adding
fields after fsx_pad[] would break the ioctl interface.

I also find the bit confusing where the argument contains both
"ignored but assumed zero" flags, and "required to be zero"
flags depending on whether it's in the fsx_pad[] field or
after it. This would be fine if it was better documented.

quoted

		fsx.fsx_xflags |= FS_XFLAG_NODUMP;
		error = syscall(468, dfd, "./foo", &fsx, 0);

The example still uses the calling conventions from a previous
version.

      Arnd

Well, ioctls carry the structure size in the ioctl number, so changing the structure size would change the ioctl number with it.