linux-kernel - Re: [PATCH v2] gfs2: Replace deprecated kmap_atomic() by kmap_local

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Date:   Tue, 27 Jun 2023 15:45:20 +0200
From:   Andreas Gruenbacher <agruenba@...hat.com>
To:     Deepak R Varma <drv@...lo.com>
Cc:     Bob Peterson <rpeterso@...hat.com>, cluster-devel@...hat.com,
        linux-kernel@...r.kernel.org, Ira Weiny <ira.weiny@...el.com>,
        "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        Sumitra Sharma <sumitraartsy@...il.com>
Subject: Re: [PATCH v2] gfs2: Replace deprecated kmap_atomic() by kmap_local_page()

On Mon, Jun 26, 2023 at 8:51 AM Deepak R Varma <drv@...lo.com> wrote:
> kmap_atomic() is deprecated in favor of kmap_local_{folio,page}().

I'll apply this, convert the remaining instances of kmap_atomic(), and
switch to memcpy_{from,to}_page() where appropriate.

Thanks,
Andreas

> Therefore, replace kmap_atomic() with kmap_local_page() in
> gfs2_internal_read() and 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
> gfs2_internal_read() and 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()).
>
> Signed-off-by: Deepak R Varma <drv@...lo.com>
> ---
> Note: The Patch is build tested only. I will be happy to run recommended testing
> with some guidance if required.
>
> Changes in v2:
>    - Update patch description to correct the replacement function name from
>      kmap_local_folio to kmap_local _page
>
>
>  fs/gfs2/aops.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
> index 3b41542d6697..7bd92054d353 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);
> @@ -498,12 +498,12 @@ int gfs2_internal_read(struct gfs2_inode *ip, char *buf, loff_t *pos,
>                                 continue;
>                         return PTR_ERR(page);
>                 }
> -               p = kmap_atomic(page);
> +               p = kmap_local_page(page);
>                 amt = size - copied;
>                 if (offset + size > PAGE_SIZE)
>                         amt = PAGE_SIZE - offset;
>                 memcpy(buf + copied, p + offset, amt);
> -               kunmap_atomic(p);
> +               kunmap_local(p);
>                 put_page(page);
>                 copied += amt;
>                 index++;
> --
> 2.34.1
>
>
>