Re: [PATCH 2/5] mm/zswap: change dstmem size to one page

[Yosry Ahmed]

On Tue, Dec 12, 2023 at 8:18 PM Chengming Zhou
<zhouchengming@xxxxxxxxxxxxx> wrote:
>
> Change the dstmem size from 2 * PAGE_SIZE to only one page since
> we only need at most one page when compress, and the "dlen" is also
> PAGE_SIZE in acomp_request_set_params(). If the output size > PAGE_SIZE
> we don't wanna store the output in zswap anyway.
>
> So change it to one page, and delete the stale comment.

I couldn't find the history of why we needed 2 * PAGE_SIZE, it would
be nice if someone has the context, perhaps one of the maintainers.

One potential reason is that we used to store a zswap header
containing the swap entry in the compressed page for writeback
purposes, but we don't do that anymore. Maybe we wanted to be able to
handle the case where an incompressible page would exceed PAGE_SIZE
because of that?