On Wed, Jun 23, 2021 at 11:15 PM Omar Sandoval [off-list ref] wrote:

On Thu, Jun 24, 2021 at 03:00:39AM +0100, Matthew Wilcox wrote:

quoted

Does that work for O_DIRECT and the required 512-byte alignment?

I suppose the kernel could pad the encoded_iov structure with zeroes to
the next sector boundary, since zeroes are effectively noops for
encoded_iov.

Ugh.

I really think the whole "embed the control structure in the stream"
is wrong. The alignment issue is just another sign of that.

Separating it out is the right thing to do. At least the "first iov
entry" thing did separate the control structure from the actual data.
I detest the whole "embed the two together".

            Linus