[PATCH 2/2] mm/hmm: Only set FAULT_FLAG_ALLOW_RETRY for non-blocking

[Kuehling, Felix]

On 2019-05-13 4:21 p.m., Deucher, Alexander wrote:
> [CAUTION: External Email]
> I reverted all the amdgpu HMM patches for 5.2 because they also 
> depended on this patch:
> https://cgit.freedesktop.org/~agd5f/linux/commit/?h=drm-next-5.2-wip&id=ce05ef71564f7cbe270cd4337c36ee720ea534db
> which did not have a clear line of sight for 5.2 either.

When was that? I saw "Use HMM for userptr" in Dave's 5.2-rc1 pull 
request to Linus.


Regards,
   Felix


>
> Alex
> ------------------------------------------------------------------------
> *From:* amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of 
> Kuehling, Felix <Felix.Kuehling at amd.com>
> *Sent:* Monday, May 13, 2019 3:36 PM
> *To:* Jerome Glisse
> *Cc:* linux-mm at kvack.org; airlied at gmail.com; 
> amd-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org; 
> alex.deucher at amd.com
> *Subject:* Re: [PATCH 2/2] mm/hmm: Only set FAULT_FLAG_ALLOW_RETRY for 
> non-blocking
> [CAUTION: External Email]
>
> Hi Jerome,
>
> Do you want me to push the patches to your branch? Or are you going to
> apply them yourself?
>
> Is your hmm-5.2-v3 branch going to make it into Linux 5.2? If so, do you
> know when? I'd like to coordinate with Dave Airlie so that we can also
> get that update into a drm-next branch soon.
>
> I see that Linus merged Dave's pull request for Linux 5.2, which
> includes the first changes in amdgpu using HMM. They're currently broken
> without these two patches.
>
> Thanks,
>    Felix
>
> On 2019-05-10 4:14 p.m., Jerome Glisse wrote:
> > [CAUTION: External Email]
> >
> > On Fri, May 10, 2019 at 07:53:24PM +0000, Kuehling, Felix wrote:
> >> Don't set this flag by default in hmm_vma_do_fault. It is set
> >> conditionally just a few lines below. Setting it unconditionally
> >> can lead to handle_mm_fault doing a non-blocking fault, returning
> >> -EBUSY and unlocking mmap_sem unexpectedly.
> >>
> >> Signed-off-by: Felix Kuehling <Felix.Kuehling at amd.com>
> > Reviewed-by: Jérôme Glisse <jglisse at redhat.com>
> >
> >> ---
> >>   mm/hmm.c | 2 +-
> >>   1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/mm/hmm.c b/mm/hmm.c
> >> index b65c27d5c119..3c4f1d62202f 100644
> >> --- a/mm/hmm.c
> >> +++ b/mm/hmm.c
> >> @@ -339,7 +339,7 @@ struct hmm_vma_walk {
> >>   static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
> >>                            bool write_fault, uint64_t *pfn)
> >>   {
> >> -     unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
> >> +     unsigned int flags = FAULT_FLAG_REMOTE;
> >>        struct hmm_vma_walk *hmm_vma_walk = walk->private;
> >>        struct hmm_range *range = hmm_vma_walk->range;
> >>        struct vm_area_struct *vma = walk->vma;
> >> --
> >> 2.17.1
> >>
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