From: Jason Gunthorpe <jgg@mellanox.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Jerome Glisse <jglisse@redhat.com>,
Ralph Campbell <rcampbell@nvidia.com>,
Felix.Kuehling@amd.com, linux-mm@kvack.org,
John Hubbard <jhubbard@nvidia.com>,
dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org,
Philip Yang <Philip.Yang@amd.com>
Subject: Re: [PATCH v2 hmm 4/9] mm/hmm: remove HMM_FAULT_SNAPSHOT
Date: Tue, 24 Mar 2020 16:31:16 -0300 [thread overview]
Message-ID: <20200324193116.GO13183@mellanox.com> (raw)
In-Reply-To: <20200324073339.GC23447@lst.de>
On Tue, Mar 24, 2020 at 08:33:39AM +0100, Christoph Hellwig wrote:
> >
> > +/*
> > + * If the valid flag is masked off, and default_flags doesn't set valid, then
> > + * hmm_pte_need_fault() always returns 0.
> > + */
> > +static bool hmm_can_fault(struct hmm_range *range)
> > +{
> > + return ((range->flags[HMM_PFN_VALID] & range->pfn_flags_mask) |
> > + range->default_flags) &
> > + range->flags[HMM_PFN_VALID];
> > +}
>
> So my idea behind the helper was to turn this into something readable :)
Well, it does help to give the expression a name :)
> E.g.
>
> /*
> * We only need to fault if either the default mask requires to fault all
> * pages, or at least the mask allows for individual pages to be faulted.
> */
> static bool hmm_can_fault(struct hmm_range *range)
> {
> return ((range->default_flags | range->pfn_flags_mask) &
> range->flags[HMM_PFN_VALID]);
> }
Okay, I find this as understandable and it is less cluttered. I think
the comment is good enough now.
Can we concur on this then:
static unsigned int
hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
const uint64_t *pfns, unsigned long npages,
uint64_t cpu_flags)
{
+ struct hmm_range *range = hmm_vma_walk->range;
unsigned int required_fault = 0;
unsigned long i;
- if (hmm_vma_walk->flags & HMM_FAULT_SNAPSHOT)
+ /*
+ * If the default flags do not request to fault pages, and the mask does
+ * not allow for individual pages to be faulted, then
+ * hmm_pte_need_fault() will always return 0.
+ */
+ if (!((range->default_flags | range->pfn_flags_mask) &
+ range->flags[HMM_PFN_VALID]))
return 0;
I think everything else is sorted now, so if yes I'll send this as v3.
Thanks,
Jason
next prev parent reply other threads:[~2020-03-24 19:31 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-24 1:14 [PATCH v2 hmm 0/9] Small hmm_range_fault() cleanups Jason Gunthorpe
2020-03-24 1:14 ` [PATCH v2 hmm 1/9] mm/hmm: remove pgmap checking for devmap pages Jason Gunthorpe
2020-03-24 1:14 ` [PATCH v2 hmm 2/9] mm/hmm: return the fault type from hmm_pte_need_fault() Jason Gunthorpe
2020-03-24 7:27 ` Christoph Hellwig
2020-03-24 18:58 ` Jason Gunthorpe
2020-03-24 1:14 ` [PATCH v2 hmm 3/9] mm/hmm: remove unused code and tidy comments Jason Gunthorpe
2020-03-24 7:27 ` Christoph Hellwig
2020-03-24 1:14 ` [PATCH v2 hmm 4/9] mm/hmm: remove HMM_FAULT_SNAPSHOT Jason Gunthorpe
2020-03-24 7:33 ` Christoph Hellwig
2020-03-24 19:31 ` Jason Gunthorpe [this message]
2020-03-24 1:14 ` [PATCH v2 hmm 5/9] mm/hmm: remove the CONFIG_TRANSPARENT_HUGEPAGE #ifdef Jason Gunthorpe
2020-03-24 7:33 ` Christoph Hellwig
2020-03-24 1:14 ` [PATCH v2 hmm 6/9] mm/hmm: use device_private_entry_to_pfn() Jason Gunthorpe
2020-03-24 7:34 ` Christoph Hellwig
2020-03-24 1:14 ` [PATCH v2 hmm 7/9] mm/hmm: do not unconditionally set pfns when returning EBUSY Jason Gunthorpe
2020-03-24 7:37 ` Christoph Hellwig
2020-03-24 15:47 ` Jason Gunthorpe
2020-03-24 1:14 ` [PATCH v2 hmm 8/9] mm/hmm: do not set pfns when returning an error code Jason Gunthorpe
2020-03-24 7:38 ` Christoph Hellwig
2020-03-24 1:14 ` [PATCH v2 hmm 9/9] mm/hmm: return error for non-vma snapshots Jason Gunthorpe
2020-03-24 7:45 ` Christoph Hellwig
2020-03-26 21:21 ` [PATCH v2 hmm 0/9] Small hmm_range_fault() cleanups Ralph Campbell
2020-03-27 20:00 [PATCH v3 " Jason Gunthorpe
2020-03-27 20:00 ` [PATCH v2 hmm 4/9] mm/hmm: remove HMM_FAULT_SNAPSHOT Jason Gunthorpe
2020-03-28 8:11 ` Christoph Hellwig
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