From: Gavin Shan <gshan@redhat.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>, linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org, catalin.marinas@arm.com,
will@kernel.org, akpm@linux-foundation.org, chuhu@redhat.com,
shan.gavin@gmail.com
Subject: Re: [PATCH v3 07/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PTE modifying tests
Date: Fri, 23 Jul 2021 14:23:24 +1000 [thread overview]
Message-ID: <2666f07b-7a84-89a4-a738-ffb21f76ca8a@redhat.com> (raw)
In-Reply-To: <492c96ea-5f60-2720-7da8-1fc18a1f95d3@arm.com>
Hi Anshuman,
On 7/23/21 12:39 PM, Anshuman Khandual wrote:
> On 7/22/21 12:07 PM, Gavin Shan wrote:
>>
>>>> pgdp = pgd_offset(mm, vaddr);
>>>> p4dp = p4d_alloc(mm, pgdp, vaddr);
>>>> @@ -1272,11 +1275,11 @@ static int __init debug_vm_pgtable(void)
>>>> * Page table modifying tests. They need to hold
>>>> * proper page table lock.
>>>> */
>>>> -
>>>> - ptep = pte_offset_map_lock(mm, pmdp, vaddr, &ptl);
>>>> - pte_clear_tests(mm, ptep, pte_aligned, vaddr, prot);
>>>> - pte_advanced_tests(mm, vma, ptep, pte_aligned, vaddr, prot);
>>>> - pte_unmap_unlock(ptep, ptl);
>>>> + ptl = pte_lockptr(args.mm, args.pmdp);
>>>> + spin_lock(ptl);
>>>> + pte_clear_tests(&args);
>>>> + pte_advanced_tests(&args);
>>>> + spin_unlock(ptl);
>>>
>>> Why pte_offset_map_lock()/pte_unmap_unlock() has been dropped and
>>> spin_lock()/spin_unlock() sequence has been added ? Please dont
>>> change the tests in these patches.
>>>
>>
>> The semantics of pte_offset_map_lock() is to grab and take the lock
>> and return the PTE entry, which is mapped if needed. We already had
>> the PTE entry tracked by args->ptep in init_args(). So some of the
>> operations covered by pte_offset_map_lock() isn't needed any more
>
> To keep the patch on purpose, please avoid this change here. But if
> required, you could send a follow up patch later.
>
In order to use pte_offset_map_lock() and pte_unmap_unlock(), we need
a temporary variable @ptep to store the return value from pte_offset_map_lock().
The temporary variable @ptep is passed to pte_unmap_unlock(). It means
we just need the temporary variable to keep the original implementation
in this regard. I will keep pte_offset_map_lock() and pte_unmap_unlock()
in v4.
If we really want to remove the temporary variable (@ptep), we can do it
after this series gets merged.
Thanks,
Gavin
next prev parent reply other threads:[~2021-07-23 4:23 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-19 13:06 [PATCH v3 00/12] mm/debug_vm_pgtable: Enhancements Gavin Shan
2021-07-19 13:06 ` [PATCH v3 01/12] mm/debug_vm_pgtable: Introduce struct pgtable_debug_args Gavin Shan
2021-07-21 5:44 ` Anshuman Khandual
2021-07-21 10:20 ` Gavin Shan
2021-07-21 10:39 ` Anshuman Khandual
2021-07-21 10:59 ` Anshuman Khandual
2021-07-21 11:59 ` Gavin Shan
2021-07-22 4:41 ` Anshuman Khandual
2021-07-22 6:23 ` Gavin Shan
2021-07-22 7:08 ` Anshuman Khandual
2021-07-23 0:43 ` Gavin Shan
2021-07-19 13:06 ` [PATCH v3 02/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in basic tests Gavin Shan
2021-07-21 5:57 ` Anshuman Khandual
2021-07-21 11:57 ` Gavin Shan
2021-07-19 13:06 ` [PATCH v3 03/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in leaf and savewrite tests Gavin Shan
2021-07-19 13:06 ` [PATCH v3 04/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in protnone and devmap tests Gavin Shan
2021-07-19 13:06 ` [PATCH v3 05/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in soft_dirty and swap tests Gavin Shan
2021-07-19 13:06 ` [PATCH v3 06/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in migration and thp tests Gavin Shan
2021-07-19 13:06 ` [PATCH v3 07/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PTE modifying tests Gavin Shan
2021-07-22 5:56 ` Anshuman Khandual
2021-07-22 6:37 ` Gavin Shan
2021-07-23 2:39 ` Anshuman Khandual
2021-07-23 4:23 ` Gavin Shan [this message]
2021-07-19 13:06 ` [PATCH v3 08/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PMD " Gavin Shan
2021-07-22 5:45 ` Anshuman Khandual
2021-07-22 6:41 ` Gavin Shan
2021-07-22 7:11 ` Anshuman Khandual
2021-07-23 1:00 ` Gavin Shan
2021-07-23 2:33 ` Anshuman Khandual
2021-07-19 13:06 ` [PATCH v3 09/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PUD " Gavin Shan
2021-07-22 5:39 ` Anshuman Khandual
2021-07-22 6:47 ` Gavin Shan
2021-07-19 13:06 ` [PATCH v3 10/12] mm/debug_vm_pgtable: Use struct pgtable_debug_args in PGD and P4D " Gavin Shan
2021-07-22 5:09 ` Anshuman Khandual
2021-07-22 6:50 ` Gavin Shan
2021-07-19 13:06 ` [PATCH v3 11/12] mm/debug_vm_pgtable: Remove unused code Gavin Shan
2021-07-22 4:51 ` Anshuman Khandual
2021-07-22 6:53 ` Gavin Shan
2021-07-19 13:06 ` [PATCH v3 12/12] mm/debug_vm_pgtable: Fix corrupted page flag Gavin Shan
2021-07-21 10:18 ` Anshuman Khandual
2021-07-21 12:03 ` Gavin Shan
2021-07-22 3:51 ` Anshuman Khandual
2021-07-22 6:54 ` Gavin Shan
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