linux-kernel - Re: [PATCH v2] xen: Convert kmap() to kmap_local

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Date:   Wed, 20 Apr 2022 08:03:05 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...ia.fr>
To:     Alaa Mohamed <eng.alaamohamedsoliman.am@...il.com>
cc:     outreachy@...ts.linux.dev, boris.ostrovsky@...cle.com,
        jgross@...e.com, sstabellini@...nel.org,
        xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org,
        ira.weiny@...el.com
Subject: Re: [PATCH v2] xen:  Convert kmap() to kmap_local_page()



On Wed, 20 Apr 2022, Alaa Mohamed wrote:

> kmap() is being deprecated and these usages are all local to the thread
> so there is no reason kmap_local_page() can't be used.
>
> Replace kmap() calls with kmap_local_page().

OK, so from a Coccinelle point of view, could we do

@@
expression e1,e2,x,f;
@@

e1 =
- kmap
+ kmap_local_page
    (e2)
... when != x = e1 // not stored in any location and not passed to another function
    when != f(...,e1,...)
    when != x = e2
    when != f(...,e2,...)
-kunmap(e2)
+kunmap_local(e1)

julia

>
> Signed-off-by: Alaa Mohamed <eng.alaamohamedsoliman.am@...il.com>
> ---
> changes in V2:
> 	-edit commit subject
> 	-edit commit message
> ---
>  drivers/xen/gntalloc.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/xen/gntalloc.c b/drivers/xen/gntalloc.c
> index 4849f94372a4..55acb32842a3 100644
> --- a/drivers/xen/gntalloc.c
> +++ b/drivers/xen/gntalloc.c
> @@ -178,9 +178,9 @@ static void __del_gref(struct gntalloc_gref *gref)
>  	unsigned long addr;
>
>  	if (gref->notify.flags & UNMAP_NOTIFY_CLEAR_BYTE) {
> -		uint8_t *tmp = kmap(gref->page);
> +		uint8_t *tmp = kmap_local_page(gref->page);
>  		tmp[gref->notify.pgoff] = 0;
> -		kunmap(gref->page);
> +		kunmap_local(tmp);
>  	}
>  	if (gref->notify.flags & UNMAP_NOTIFY_SEND_EVENT) {
>  		notify_remote_via_evtchn(gref->notify.event);
> --
> 2.35.2
>
>
>