Re: [RFC PATCH 4/4] mm: madvise allow remove operation for hugetlbfs

[Mike Kravetz]

On 04/17/2015 10:11 AM, Mike Kravetz wrote:
> On 04/17/2015 12:10 AM, Hillf Danton wrote:
> > > Now that we have hole punching support for hugetlbfs, we can
> > > also support the MADV_REMOVE interface to it.
> > >
> > > Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
> > > Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> > > ---
> > >   mm/madvise.c | 2 +-
> > >   1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/mm/madvise.c b/mm/madvise.c
> > > index d551475..c4a1027 100644
> > > --- a/mm/madvise.c
> > > +++ b/mm/madvise.c
> > > @@ -299,7 +299,7 @@ static long madvise_remove(struct vm_area_struct
> > > *vma,
> > >
> > >       *prev = NULL;    /* tell sys_madvise we drop mmap_sem */
> > >
> > > -    if (vma->vm_flags & (VM_LOCKED | VM_HUGETLB))
> > > +    if (vma->vm_flags & VM_LOCKED)
> > >           return -EINVAL;
> > >
> > >       f = vma->vm_file;
> > > --
> > > 2.1.0
> >
> > After the above change offset is computed,
> >
> >     offset = (loff_t)(start - vma->vm_start)
> >         + ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
> >
> > and I wonder if it is correct for huge page mapping.
>
> I think it will be correct.
>
> The above will be a (base) page size aligned offset into the file.
> This offset will be huge page aligned in the fallocate hole punch
> code.
>
>      /*
>       * For hole punch round up the beginning offset of the hole and
>       * round down the end.
>       */
>      hole_start = (offset + hpage_size - 1) & ~huge_page_mask(h);
>      hole_end = (offset + len - (hpage_size - 1)) * ~huge_page_mask(h);
>
> Was the alignment your concern, or something else?

Well, that alignment code in fallocate hole punch obviously wrong. :(
Sorry about that.  I'll send out an updated RFC with working hole punch.

--
Mike Kravetz
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/