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

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Message-ID: <20230629043031.GA455425@sumitra.com>
Date:   Wed, 28 Jun 2023 21:30:31 -0700
From:   Sumitra Sharma <sumitraartsy@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Hans de Goede <hdegoede@...hat.com>, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ira Weiny <ira.weiny@...el.com>,
        Fabio <fmdefrancesco@...il.com>, Deepak R Varma <drv@...lo.com>,
        Sumitra Sharma <sumitraartsy@...il.com>
Subject: Re: [PATCH] fs/vboxsf: Replace kmap() with kmap_local_{page, folio}()

On Tue, Jun 27, 2023 at 06:48:20PM +0100, Matthew Wilcox wrote:
> On Tue, Jun 27, 2023 at 06:51:15AM -0700, Sumitra Sharma wrote:
> > +++ b/fs/vboxsf/file.c
> > @@ -234,7 +234,7 @@ static int vboxsf_read_folio(struct file *file, struct folio *folio)
> >  	u8 *buf;
> >  	int err;
> >  
> > -	buf = kmap(page);
> > +	buf = kmap_local_folio(folio, off);
> 
> Did you test this?  'off' is the offset in the _file_.  Whereas
> kmap_local_folio() takes the offset within the _folio_.  They have
> different types (loff_t vs size_t) to warn you that they're different
> things.
>

Hi Matthew,

When creating this patch, I read and searched about the loff_t vs size_t.
By mistake, I implemented it in the wrong way.

Also, I did not test it and just compiled it. I apologise for doing so.

And for the other points you have put as feedback. I will take some time to understand
it. And would like to work on the changes you suggest.

Thanks & regards
Sumitra