On Thu, Jun 20, 2024 at 04:15:23PM +0100, Matthew Wilcox wrote:

quoted

and have O_DIRECT with a 32-bit memory alignment work just fine, where
before it would EINVAL. The sector size memory alignment thing has
always been odd and never rooted in anything other than "oh let's just
require the whole combination of size/disk offset/alignment to be sector
based".

Oh, cool!  https://man7.org/linux/man-pages/man2/open.2.html
doesn't know about this yet; is anyone working on updating it?

Just remember that there are two kinds of alignments:

 - the memory alignment, which Jens is talking about
 - the offset/size alignment, which is set by the LBA size

statx (optionally) exposes both in the stx_dio_mem_align and
stx_dio_offset_align fields, which are documented in the statx(2)
man page.  For network file systems like nfs there might be no
alignment requirements at all.