Re: [PATCH 02/21] block: Limit atomic writes according to bio and queue limits

Ming Lei
2023-12-04T03:56:11Z

On Mon, Dec 04, 2023 at 11:19:20AM +0800, Ming Lei wrote:
> On Fri, Sep 29, 2023 at 10:27:07AM +0000, John Garry wrote:
> > We rely the block layer always being able to send a bio of size
> > atomic_write_unit_max without being required to split it due to request
> > queue or other bio limits.
> >
> > A bio may contain min(BIO_MAX_VECS, limits->max_segments) vectors,
> > and each vector is at worst case the device logical block size from
> > direct IO alignment requirement.
>
> Both unit_max and unit_min are applied to FS bio, which is built over
> single userspace buffer, so only the 1st and last vector can include

Actually it isn't true for pwritev, and sorry for the noise.

Thanks,
Ming