Re: [RFC PATCH v2 1/7] statx: add I/O alignment information

Christoph Hellwig
2022-06-15T13:12:10Z

On Mon, Jun 13, 2022 at 10:25:12PM -0700, Eric Biggers wrote:
> While working on the man-pages update, I'm having second thoughts about the
> stx_offset_align_optimal field. Does any filesystem other than XFS actually
> want stx_offset_align_optimal, when st[x]_blksize already exists? Many network
> filesystems, as well as tmpfs when hugepages are enabled, already report large
> (megabytes) sizes in st[x]_blksize. And all documentation I looked at (man
> pages for Linux, POSIX, FreeBSD, NetBSD, macOS) documents st_blksize as
> something like "the preferred blocksize for efficient I/O". It's never
> documented as being limited to PAGE_SIZE, which makes sense because it's not.

Yes. While st_blksize is utterly misnamed, it has always aways been
the optimal I/O size.

> Perhaps for now we should just add STATX_DIOALIGN instead of STATX_IOALIGN,
> leaving out the stx_offset_align_optimal field? What do people think?

Yes, this sounds like a good plan.