All of lore.kernel.org
 help / color / mirror / Atom feed
From: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>,
	akpm@linux-foundation.org, mike.kravetz@oracle.com,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	linux-sparse@vger.kernel.org
Subject: Re: [PATCH] include/linux/hugetlb.h: Convert to use vm_fault_t
Date: Tue, 19 Mar 2019 18:51:08 +0100	[thread overview]
Message-ID: <20190319175107.oxwjf72hpcqqmo3l@ltop.local> (raw)
In-Reply-To: <20190319032022.GR19508@bombadil.infradead.org>

On Mon, Mar 18, 2019 at 08:20:22PM -0700, Matthew Wilcox wrote:
> On Mon, Mar 18, 2019 at 09:56:05PM +0530, Souptick Joarder wrote:
> > >> mm/memory.c:3968:21: sparse: incorrect type in assignment (different
> > >> base types) @@    expected restricted vm_fault_t [usertype] ret @@
> > >> got e] ret @@
> >    mm/memory.c:3968:21:    expected restricted vm_fault_t [usertype] ret
> >    mm/memory.c:3968:21:    got int
> 
> I think this may be a sparse bug.
> 
> Compare:
> 
> +++ b/mm/memory.c
> @@ -3964,6 +3964,9 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
>         if (flags & FAULT_FLAG_USER)
>                 mem_cgroup_enter_user_fault();
>  
> +       ret = 0;
> +       ret = ({ BUG(); 0; });
> +       ret = 1;
>         if (unlikely(is_vm_hugetlb_page(vma)))
>                 ret = hugetlb_fault(vma->vm_mm, vma, address, flags);
>         else
> 
> ../mm/memory.c:3968:13: sparse: warning: incorrect type in assignment (different base types)
> ../mm/memory.c:3968:13: sparse:    expected restricted vm_fault_t [assigned] [usertype] ret
> ../mm/memory.c:3968:13: sparse:    got int
> ../mm/memory.c:3969:13: sparse: warning: incorrect type in assignment (different base types)
> ../mm/memory.c:3969:13: sparse:    expected restricted vm_fault_t [assigned] [usertype] ret
> ../mm/memory.c:3969:13: sparse:    got int
> 
> vm_fault_t is __bitwise:
> 
> include/linux/mm_types.h:typedef __bitwise unsigned int vm_fault_t;
> 
> so simply assigning 0 to ret should work (and does on line 3967), but
> sparse doesn't seem to like it as part of a ({ .. }) expression.

This is the expected behaviour. The constant 0 is magic regarding
bitwise types but ({ ...; 0; }) is not, it is just an ordinary expression
of type 'int'.

So, IMHO, Souptick's patch is the right thing to do.


Best regards,
-- Luc Van Oostenryck

      reply	other threads:[~2019-03-19 17:51 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-18 16:26 Souptick Joarder
2019-03-19  0:17 ` Mike Kravetz
2019-03-19  2:34   ` Souptick Joarder
2019-03-19  2:34     ` Souptick Joarder
2019-03-19  3:20 ` Matthew Wilcox
2019-03-19 17:51   ` Luc Van Oostenryck [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190319175107.oxwjf72hpcqqmo3l@ltop.local \
    --to=luc.vanoostenryck@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=jrdr.linux@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-sparse@vger.kernel.org \
    --cc=mike.kravetz@oracle.com \
    --cc=willy@infradead.org \
    --subject='Re: [PATCH] include/linux/hugetlb.h: Convert to use vm_fault_t' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.