From: Jason Gunthorpe <jgg@mellanox.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Philip Yang <Philip.Yang@amd.com>,
Ralph Campbell <rcampbell@nvidia.com>,
John Hubbard <jhubbard@nvidia.com>,
Felix.Kuehling@amd.com, dri-devel@lists.freedesktop.org,
linux-mm@kvack.org, Jerome Glisse <jglisse@redhat.com>,
amd-gfx@lists.freedesktop.org
Subject: Re: [PATCH hmm 2/6] mm/hmm: return the fault type from hmm_pte_need_fault()
Date: Mon, 23 Mar 2020 17:14:06 -0300 [thread overview]
Message-ID: <20200323201406.GD13183@mellanox.com> (raw)
In-Reply-To: <20200321083726.GB28695@lst.de>
On Sat, Mar 21, 2020 at 09:37:26AM +0100, Christoph Hellwig wrote:
> On Fri, Mar 20, 2020 at 01:49:01PM -0300, Jason Gunthorpe wrote:
> > +enum {
> > + NEED_FAULT = 1 << 0,
> > + NEED_WRITE_FAULT = 1 << 1,
> > +};
>
> Maybe add a HMM_ prefix?
Yes, OK, the existing names are pretty generic
> > for (i = 0; i < npages; ++i) {
> > + required_fault |=
> > + hmm_pte_need_fault(hmm_vma_walk, pfns[i], cpu_flags);
> > + if (required_fault == (NEED_FAULT | NEED_WRITE_FAULT))
> > + return required_fault;
>
> No need for the inner braces.
Techincally yes, but gcc demands them:
mm/hmm.c:146:22: warning: suggest parentheses around comparison in operand of '|' [-Wparentheses]
if (required_fault == NEED_FAULT | NEED_WRITE_FAULT)
~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
Probably because | vs || is a common confusion?
Actually this whole NEED_FAULT | WRITE_FAULT thing is silly, I'm going
to define NEED_WRITE_FAULT == NEED_FAULT | (1<<1) and add a
NEED_ALL_BITS to make this clear what this test is for (early loop
exit once there is no possible change to required_fault).
> > @@ -532,17 +515,15 @@ static int hmm_vma_walk_test(unsigned long start, unsigned long end,
> > */
> > if ((vma->vm_flags & (VM_IO | VM_PFNMAP | VM_MIXEDMAP)) ||
> > !(vma->vm_flags & VM_READ)) {
> > - bool fault, write_fault;
> > -
>
> No that there is no need for local variables I'd invert the test and
> return early:
This is more readable, I reworked the comment too
Jason
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next prev parent reply other threads:[~2020-03-24 8:10 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-20 16:48 [PATCH hmm 0/6] Small hmm_range_fault() cleanups Jason Gunthorpe
2020-03-20 16:49 ` [PATCH hmm 1/6] mm/hmm: remove pgmap checking for devmap pages Jason Gunthorpe
2020-03-20 16:49 ` [PATCH hmm 2/6] mm/hmm: return the fault type from hmm_pte_need_fault() Jason Gunthorpe
[not found] ` <20200321083726.GB28695@lst.de>
2020-03-23 20:14 ` Jason Gunthorpe [this message]
2020-03-20 16:49 ` [PATCH hmm 3/6] mm/hmm: remove unused code and tidy comments Jason Gunthorpe
2020-03-20 21:46 ` Ralph Campbell
2020-03-23 17:24 ` Jason Gunthorpe
[not found] ` <20200321083902.GC28695@lst.de>
2020-03-23 17:24 ` Jason Gunthorpe
2020-03-20 16:49 ` [PATCH hmm 4/6] mm/hmm: remove HMM_FAULT_SNAPSHOT Jason Gunthorpe
2020-03-20 16:49 ` [PATCH hmm 5/6] mm/hmm: remove the CONFIG_TRANSPARENT_HUGEPAGE #ifdef Jason Gunthorpe
[not found] ` <20200321084317.GE28695@lst.de>
2020-03-23 17:33 ` Jason Gunthorpe
2020-03-20 16:49 ` [PATCH hmm 6/6] mm/hmm: use device_private_entry_to_pfn() Jason Gunthorpe
[not found] ` <20200321084347.GF28695@lst.de>
2020-03-23 17:44 ` Jason Gunthorpe
2020-03-20 18:51 ` [PATCH hmm 0/6] Small hmm_range_fault() cleanups Ralph Campbell
2020-03-20 18:55 ` Jason Gunthorpe
2020-03-20 21:47 ` Ralph Campbell
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