Messages in this thread | | | Date | Tue, 1 Dec 2015 16:17:05 +0000 | From | Will Deacon <> | Subject | Re: [PATCH] virtio: Do not drop __GFP_HIGH in alloc_indirect |
| |
On Tue, Dec 01, 2015 at 03:32:49PM +0100, Michal Hocko wrote: > From: Michal Hocko <mhocko@suse.com> > > b92b1b89a33c ("virtio: force vring descriptors to be allocated from > lowmem") tried to exclude highmem pages for descriptors so it cleared > __GFP_HIGHMEM from a given gfp mask. The patch also cleared __GFP_HIGH > which doesn't make much sense for this fix because __GFP_HIGH only > controls access to memory reserves and it doesn't have any influence > on the zone selection. Some of the call paths use GFP_ATOMIC and > dropping __GFP_HIGH will reduce their changes for success because the > lack of access to memory reserves. > > Signed-off-by: Michal Hocko <mhocko@suse.com> > --- > Hi, > I have stumbled over this code while looking at other issue [1]. I think > that using __GFP_HIGH simply got there because of its confusing name. It > doesn't have anything to do with the highmem zone. > > The patch is based on the current linux-next. > > I think that clearing __GFP_HIGHMEM is bogus in the current code because > all code paths either use GFP_KERNEL or GFP_ATOMIC and those do not fall > back to the highmem zone but I have kept it because clearing the flag > cannot be harmful. > > [1] http://lkml.kernel.org/r/87h9k4kzcv.fsf%40yhuang-dev.intel.com > > drivers/virtio/virtio_ring.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-)
Thanks for cleaning this up:
Acked-by: Will Deacon <will.deacon@arm.com>
Will
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index 14e7ce9b3e96..734de927c89d 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -110,7 +110,7 @@ static struct vring_desc *alloc_indirect(struct virtqueue *_vq, > * otherwise virt_to_phys will give us bogus addresses in the > * virtqueue. > */ > - gfp &= ~(__GFP_HIGHMEM | __GFP_HIGH); > + gfp &= ~__GFP_HIGHMEM; > > desc = kmalloc(total_sg * sizeof(struct vring_desc), gfp); > if (!desc) > -- > 2.6.2 >
| |