linux-kernel - Re: [PATCH v7 2/2] mm: support large folios swap-in for sync io devices

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Message-Id: <20240903130757.f584c73f356c03617a2c8804@linux-foundation.org>
Date: Tue, 3 Sep 2024 13:07:57 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Yosry Ahmed <yosryahmed@...gle.com>
Cc: Kairui Song <ryncsn@...il.com>, hanchuanhua@...o.com, Usama Arif
 <usamaarif642@...il.com>, linux-mm@...ck.org,
 baolin.wang@...ux.alibaba.com, chrisl@...nel.org, david@...hat.com,
 hannes@...xchg.org, hughd@...gle.com, kaleshsingh@...gle.com,
 linux-kernel@...r.kernel.org, mhocko@...e.com, minchan@...nel.org,
 nphamcs@...il.com, ryan.roberts@....com, senozhatsky@...omium.org,
 shakeel.butt@...ux.dev, shy828301@...il.com, surenb@...gle.com,
 v-songbaohua@...o.com, willy@...radead.org, xiang@...nel.org,
 ying.huang@...el.com, hch@...radead.org
Subject: Re: [PATCH v7 2/2] mm: support large folios swap-in for sync io
 devices

On Tue, 3 Sep 2024 11:38:37 -0700 Yosry Ahmed <yosryahmed@...gle.com> wrote:

> > [   39.157954] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000007
> > [   39.158288] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
> > [   39.158634] R13: 0000000000002b9a R14: 0000000000000000 R15: 00007ffd619d5518
> > [   39.158998]  </TASK>
> > [   39.159226] ---[ end trace 0000000000000000 ]---
> >
> > After reverting this or Usama's "mm: store zero pages to be swapped
> > out in a bitmap", the problem is gone. I think these two patches may
> > have some conflict that needs to be resolved.
> 
> Yup. I saw this conflict coming and specifically asked for this
> warning to be added in Usama's patch to catch it [1]. It served its
> purpose.
> 
> Usama's patch does not handle large folio swapin, because at the time
> it was written we didn't have it. We expected Usama's series to land
> sooner than this one, so the warning was to make sure that this series
> handles large folio swapin in the zeromap code. Now that they are both
> in mm-unstable, we are gonna have to figure this out.
> 
> I suspect Usama's patches are closer to land so it's better to handle
> this in this series, but I will leave it up to Usama and
> Chuanhua/Barry to figure this out :)
> 
> [1]https://lore.kernel.org/lkml/CAJD7tkbpXjg00CRSrXU_pbaHwEaW1b3k8AQgu8y2PAh7EkTOug@mail.gmail.com/

Thanks.  To unbreak -next I'll drop the two-patch series "mm: Ignite
large folios swap-in support" for now.

btw, next time can we please call it "enable large folios swap-in
support"?  "ignite" doesn't make much sense here.