linux-kernel - Re: [PATCH] fs/vboxsf: Replace kmap() with kmap_local

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Date:   Thu, 29 Jun 2023 04:08:11 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Ira Weiny <ira.weiny@...el.com>
Cc:     Sumitra Sharma <sumitraartsy@...il.com>,
        Hans de Goede <hdegoede@...hat.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Fabio <fmdefrancesco@...il.com>, Deepak R Varma <drv@...lo.com>
Subject: Re: [PATCH] fs/vboxsf: Replace kmap() with kmap_local_{page, folio}()

On Wed, Jun 28, 2023 at 07:23:54PM -0700, Ira Weiny wrote:
> Matthew Wilcox wrote:
> > Here's a more comprehensive read_folio patch.  It's not at all
> > efficient, but then if we wanted an efficient vboxsf, we'd implement
> > vboxsf_readahead() and actually do an async call with deferred setting
> > of the uptodate flag.  I can consult with anyone who wants to do all
> > this work.
> > 
> > I haven't even compiled this, just trying to show the direction this
> > should take.
> 
> I'm a bit confused.  Is this progressing toward having the folio passed
> down to vboxsf_read() or just an expanded vboxsf_read_folio which can
> handle larger folios as well as fix the kmap?

This just handles large folios & switches to kmap_local_folio().  Doing
this properly is a _lot_ of work, and needs someone who can commit to
actually testing it.