From: Jason Gunthorpe <jgg@ziepe.ca>
To: David Hildenbrand <david@redhat.com>
Cc: Qi Zheng <zhengqi.arch@bytedance.com>,
akpm@linux-foundation.org, tglx@linutronix.de,
hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com,
kirill.shutemov@linux.intel.com, mika.penttila@nextfour.com,
linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, songmuchun@bytedance.com
Subject: Re: [PATCH v2 0/9] Free user PTE page table pages
Date: Wed, 1 Sep 2021 13:07:42 -0300 [thread overview]
Message-ID: <20210901160742.GR1200268@ziepe.ca> (raw)
In-Reply-To: <5b9348fc-95fe-5be2-e9df-7c906e0c9b81@redhat.com>
On Wed, Sep 01, 2021 at 02:32:08PM +0200, David Hildenbrand wrote:
> b) pmd_trans_unstable_or_pte_try_get() and friends are really ugly.
I suspect the good API here is really more like:
ptep = pte_try_map(pmdp, &pmd_value)
if (!ptep) {
// pmd_value is guarenteed to not be a PTE table pointer.
if (pmd_XXX(pmd_value))
}
Ie the core code will do whatever stuff, including the THP data race
avoidance, to either return the next level page table or the value of
a pmd that is not a enxt level page table. Callers are much clearer in
this way.
Eg this is a fairly representative sample user:
static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
struct mm_walk *walk)
{
if (pmd_trans_unstable(pmd))
goto out;
pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
And it is obviously pretty easy to integrate any refcount into
pte_try_map and pte_unmap as in my other email.
Jason
next prev parent reply other threads:[~2021-09-01 16:07 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-19 3:18 [PATCH v2 0/9] Free user PTE page table pages Qi Zheng
2021-08-19 3:18 ` [PATCH v2 1/9] mm: introduce pmd_install() helper Qi Zheng
2021-08-24 16:26 ` David Hildenbrand
2021-08-25 16:20 ` Qi Zheng
2021-08-25 16:32 ` David Hildenbrand
2021-08-26 3:04 ` Qi Zheng
2021-08-19 3:18 ` [PATCH v2 2/9] mm: remove redundant smp_wmb() Qi Zheng
2021-08-19 3:18 ` [PATCH v2 3/9] mm: rework the parameter of lock_page_or_retry() Qi Zheng
2021-08-19 3:18 ` [PATCH v2 4/9] mm: move pte_alloc{,_map,_map_lock}() to a separate file Qi Zheng
2021-08-19 3:18 ` [PATCH v2 5/9] mm: pte_refcount infrastructure Qi Zheng
2021-08-19 3:18 ` [PATCH v2 6/9] mm: free user PTE page table pages Qi Zheng
2021-08-19 7:01 ` David Hildenbrand
2021-08-19 10:18 ` [External] " Qi Zheng
2021-09-01 13:53 ` Jason Gunthorpe
2021-09-01 13:57 ` David Hildenbrand
2021-09-01 15:32 ` Jason Gunthorpe
2021-09-01 16:13 ` David Hildenbrand
2021-09-01 16:16 ` Jason Gunthorpe
2021-09-01 16:19 ` David Hildenbrand
2021-09-01 17:10 ` Jason Gunthorpe
2021-09-01 17:49 ` David Hildenbrand
2021-09-01 17:55 ` Jason Gunthorpe
2021-09-01 17:58 ` David Hildenbrand
2021-09-01 18:09 ` Jason Gunthorpe
2021-09-01 18:10 ` David Hildenbrand
2021-09-02 7:04 ` Qi Zheng
2021-09-02 6:53 ` Qi Zheng
2021-08-19 3:18 ` [PATCH v2 7/9] mm: add THP support for pte_ref Qi Zheng
2021-08-19 3:18 ` [PATCH v2 8/9] mm: free PTE page table by using rcu mechanism Qi Zheng
2021-08-19 3:18 ` [PATCH v2 9/9] mm: use mmu_gather to free PTE page table Qi Zheng
2021-09-01 12:32 ` [PATCH v2 0/9] Free user PTE page table pages David Hildenbrand
2021-09-01 16:07 ` Jason Gunthorpe [this message]
2021-09-01 16:10 ` David Hildenbrand
2021-09-02 3:37 ` Qi Zheng
2021-09-15 14:52 ` Qi Zheng
2021-09-15 14:59 ` Jason Gunthorpe
2021-09-16 5:32 ` Qi Zheng
2021-09-16 8:30 ` David Hildenbrand
2021-09-16 8:41 ` Qi Zheng
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