Re: [PATCH] mm: Release a semaphore in 'get_vaddr_frames()'

[Christophe JAILLET]

Le 10/12/2017 Ã 10:45, Michal Hocko a ÃcritÂ:
> On Sat 09-12-17 08:09:41, Christophe JAILLET wrote:
> > A semaphore is acquired before this check, so we must release it before
> > leaving.
> >
> > Fixes: b7f0554a56f2 ("mm: fail get_vaddr_frames() for filesystem-dax mappings")
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> > ---
> > -- Untested --
> >
> > The wording of the commit entry and log description could be improved
> > but I didn't find something better.
> The changelog is ok imo.
>
> > ---
> >   mm/frame_vector.c | 4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/frame_vector.c b/mm/frame_vector.c
> > index 297c7238f7d4..e0c5e659fa82 100644
> > --- a/mm/frame_vector.c
> > +++ b/mm/frame_vector.c
> > @@ -62,8 +62,10 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
> >   	 * get_user_pages_longterm() and disallow it for filesystem-dax
> >   	 * mappings.
> >   	 */
> > -	if (vma_is_fsdax(vma))
> > +	if (vma_is_fsdax(vma)) {
> > +		up_read(&mm->mmap_sem);
> >   		return -EOPNOTSUPP;
> > +	}
> Is there any reason to do a different error handling than other error
> paths? Namely not going without goto out?

You are right, I misread the code after out:.
I thought it would override the returned value, but I was wrong.
'goto out' is definitively better, IMHO. I'll propose a v2.

CJ