linux-kernel - Re: [PATCH v3 1/6] gfs2: Replace kmap_atomic() by kmap_local_page() in stuffed

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Message-ID: <1804362.TLkxdtWsSY@suse>
Date:   Sat, 01 Jul 2023 13:02:55 +0200
From:   "Fabio M. De Francesco" <fmdefrancesco@...il.com>
To:     Bob Peterson <rpeterso@...hat.com>,
        Andreas Gruenbacher <agruenba@...hat.com>,
        cluster-devel@...hat.com, linux-kernel@...r.kernel.org,
        Deepak R Varma <drv@...lo.com>
Cc:     Ira Weiny <ira.weiny@...el.com>,
        Sumitra Sharma <sumitraartsy@...il.com>,
        Deepak R Varma <drv@...lo.com>
Subject: Re: [PATCH v3 1/6] gfs2: Replace kmap_atomic() by kmap_local_page() in
 stuffed_readpage

On giovedì 29 giugno 2023 23:49:29 CEST Deepak R Varma wrote:
> kmap_atomic() is deprecated in favor of kmap_local_{folio,page}().
> 
> Therefore, replace kmap_atomic() with kmap_local_page() in
> stuffed_readpage().
> 
> kmap_atomic() disables page-faults and preemption (the latter only for
> !PREEMPT_RT kernels), However, the code within the mapping/un-mapping in
> stuffed_readpage() does not depend on the above-mentioned side effects.
> 
> Therefore, a mere replacement of the old API with the new one is all that
> is required (i.e., there is no need to explicitly add any calls to
> pagefault_disable() and/or preempt_disable()).
> 
> Suggested-by: Fabio M. De Francesco <fmdefrancesco@...il.com>

It LGTM, therefore, it is...

Reviewed-by: Fabio M. De Francesco <fmdefrancesco@...il.com>

> Signed-off-by: Deepak R Varma <drv@...lo.com>
> ---
> Changes in v3:
>    - split into 2 patches

NIT: I can't understand why you think the previous single patch needed to be 
split. Despite I can't understand why, I have nothing against it :-)

Thanks,

Fabio

P.S.: Next time please take note somewhere (maybe after the three dashes?) 
that you are re-using my commit message word by word. I'd appreciate it :-) 
However, it doesn't really matter much so please _don't_ send a newer patch 
only for this little request.

>    - included in the patch set. Was sent as standalone patch previously
> 
> Changes in v2:
>    - Update patch description to correct the replacement function name from
>      kmap_local_page to kmap_local_folio
> 
> 
>  fs/gfs2/aops.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
> index 3b41542d6697..3eac4f2f5c27 100644
> --- a/fs/gfs2/aops.c
> +++ b/fs/gfs2/aops.c
> @@ -432,10 +432,10 @@ static int stuffed_readpage(struct gfs2_inode *ip,
> struct page *page) if (error)
>  		return error;
> 
> -	kaddr = kmap_atomic(page);
> +	kaddr = kmap_local_page(page);
>  	memcpy(kaddr, dibh->b_data + sizeof(struct gfs2_dinode), dsize);
>  	memset(kaddr + dsize, 0, PAGE_SIZE - dsize);
> -	kunmap_atomic(kaddr);
> +	kunmap_local(kaddr);
>  	flush_dcache_page(page);
>  	brelse(dibh);
>  	SetPageUptodate(page);
> --
> 2.34.1