linux-kernel - Re: [PATCH] fs: buffer: check huge page size instead of single page for invalidatepage

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Date:   Thu, 21 Oct 2021 00:49:51 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Yang Shi <shy828301@...il.com>
Cc:     Hugh Dickins <hughd@...gle.com>, Song Liu <song@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Hao Sun <sunhao.th@...il.com>, Linux MM <linux-mm@...ck.org>,
        Linux FS-devel Mailing List <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Song Liu <songliubraving@...com>
Subject: Re: [PATCH] fs: buffer: check huge page size instead of single page
 for invalidatepage

On Wed, Oct 20, 2021 at 04:38:49PM -0700, Yang Shi wrote:
> > However, it still doesn't make too much sense to have thp_size passed
> > to do_invalidatepage(), then have PAGE_SIZE hardcoded in a BUG
> > assertion IMHO. So it seems this patch is still useful because
> > block_invalidatepage() is called by a few filesystems as well, for
> > example, ext4. Or I'm wondering whether we should call
> > do_invalidatepage() for each subpage of THP in truncate_cleanup_page()
> > since private is for each subpage IIUC.
> 
> Seems no interest?

No.  I have changes in this area as part of the folio patchset (where
we end up converting this to invalidate_folio).  I'm not really
interested in doing anything before that, since this shouldn't be
reachable today.

> Anyway the more I was staring at the code the more I thought calling
> do_invalidatepage() for each subpage made more sense. So, something
> like the below makes sense?

Definitely not.  We want to invalidate the entire folio at once.