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

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Message-ID: <ZJspAwi5NycJopQf@bu2204.myguest.virtualbox.org>
Date:   Tue, 27 Jun 2023 23:52:59 +0530
From:   Deepak R Varma <drv@...lo.com>
To:     Andreas Gruenbacher <agruenba@...hat.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 Tue, Jun 27, 2023 at 03:45:20PM +0200, Andreas Gruenbacher wrote:
> 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.

Hello Andreas,
Thank you for your review. I am working on the other conversion opportunities
for this module and will send those in shortly.

Regards,
Deepak.

> 
> 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
> >
> >
> >
>