Re: [PATCH] memcg: set page->private before calling swap_readpage

[Johannes Weiner]

On Thu, Mar 18, 2021 at 03:01:25PM +0100, Michal Hocko wrote:
> On Wed 17-03-21 18:59:59, Shakeel Butt wrote:
> > The function swap_readpage() (and other functions it call) extracts swap
> > entry from page->private. However for SWP_SYNCHRONOUS_IO, the kernel
> > skips the swapcache and thus we need to manually set the page->private
> > with the swap entry before calling swap_readpage().
> 
> One thing that is not really clear to me is whether/why this is only
> needed with your patch. Can you expand a bit on that please? Maybe I am
> just missing something obvious but I just do not see any connection.

It was always needed, his original patch erroneously removed it.