From: Laurent Dufour <ldufour@linux.vnet.ibm.com>
To: vinayak menon <vinayakm.list@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
kirill@shutemov.name, ak@linux.intel.com, dave@stgolabs.net,
jack@suse.cz, Matthew Wilcox <willy@infradead.org>,
benh@kernel.crashing.org, mpe@ellerman.id.au, paulus@samba.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
hpa@zytor.com, Will Deacon <will.deacon@arm.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Alexei Starovoitov <alexei.starovoitov@gmail.com>,
kemi.wang@intel.com, sergey.senozhatsky.work@gmail.com,
Daniel Jordan <daniel.m.jordan@oracle.com>,
David Rientjes <rientjes@google.com>,
Jerome Glisse <jglisse@redhat.com>,
Ganesh Mahendran <opensource.ganesh@gmail.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
haren@linux.vnet.ibm.com, khandual@linux.vnet.ibm.com,
npiggin@gmail.com, bsingharora@gmail.com,
Paul McKenney <paulmck@linux.vnet.ibm.com>,
Tim Chen <tim.c.chen@linux.intel.com>,
linuxppc-dev@lists.ozlabs.org, x86@kernel.org,
Vinayak Menon <vinmenon@codeaurora.org>
Subject: Re: [PATCH v10 06/25] mm: make pte_unmap_same compatible with SPF
Date: Mon, 14 May 2018 17:09:48 +0200 [thread overview]
Message-ID: <e543c7a9-5aff-3f87-4ccf-e7da345f5bb1@linux.vnet.ibm.com> (raw)
In-Reply-To: <CAOaiJ-n6P-hjBEkiR4+MyFYunocPgzAYkG1wALDcmi7ROe4-ag@mail.gmail.com>
On 10/05/2018 18:15, vinayak menon wrote:
> On Tue, Apr 17, 2018 at 8:03 PM, Laurent Dufour
> <ldufour@linux.vnet.ibm.com> wrote:
>> pte_unmap_same() is making the assumption that the page table are still
>> around because the mmap_sem is held.
>> This is no more the case when running a speculative page fault and
>> additional check must be made to ensure that the final page table are still
>> there.
>>
>> This is now done by calling pte_spinlock() to check for the VMA's
>> consistency while locking for the page tables.
>>
>> This is requiring passing a vm_fault structure to pte_unmap_same() which is
>> containing all the needed parameters.
>>
>> As pte_spinlock() may fail in the case of a speculative page fault, if the
>> VMA has been touched in our back, pte_unmap_same() should now return 3
>> cases :
>> 1. pte are the same (0)
>> 2. pte are different (VM_FAULT_PTNOTSAME)
>> 3. a VMA's changes has been detected (VM_FAULT_RETRY)
>>
>> The case 2 is handled by the introduction of a new VM_FAULT flag named
>> VM_FAULT_PTNOTSAME which is then trapped in cow_user_page().
>> If VM_FAULT_RETRY is returned, it is passed up to the callers to retry the
>> page fault while holding the mmap_sem.
>>
>> Acked-by: David Rientjes <rientjes@google.com>
>> Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com>
>> ---
>> include/linux/mm.h | 1 +
>> mm/memory.c | 39 ++++++++++++++++++++++++++++-----------
>> 2 files changed, 29 insertions(+), 11 deletions(-)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 4d1aff80669c..714da99d77a3 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -1208,6 +1208,7 @@ static inline void clear_page_pfmemalloc(struct page *page)
>> #define VM_FAULT_NEEDDSYNC 0x2000 /* ->fault did not modify page tables
>> * and needs fsync() to complete (for
>> * synchronous page faults in DAX) */
>> +#define VM_FAULT_PTNOTSAME 0x4000 /* Page table entries have changed */
>
>
> This has to be added to VM_FAULT_RESULT_TRACE ?
Indeed there is no chance that the macro VM_FAULT_RESULT_TRACE would have to
translate that code to a string since VM_FAULT_PTNOTSAME is currently only
returned by pte_unmap_same() and then converted by its only caller
do_swap_page() to return 0. So VM_FAULT_PTNOTSAME is not expected to be seen
outside of these services which are never using VM_FAULT_RESULT_TRACE().
This being said, this may be a good idea to add it in the case of future
potential usage.
next prev parent reply other threads:[~2018-05-14 15:10 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-17 14:33 [PATCH v10 00/25] Speculative page faults Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 01/25] mm: introduce CONFIG_SPECULATIVE_PAGE_FAULT Laurent Dufour
2018-04-23 5:58 ` Minchan Kim
2018-04-23 15:10 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 02/25] x86/mm: define ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT Laurent Dufour
2018-05-08 11:04 ` Punit Agrawal
2018-05-14 14:47 ` Laurent Dufour
2018-05-14 15:05 ` Punit Agrawal
2018-04-17 14:33 ` [PATCH v10 03/25] powerpc/mm: set ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 04/25] mm: prepare for FAULT_FLAG_SPECULATIVE Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 05/25] mm: introduce pte_spinlock " Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 06/25] mm: make pte_unmap_same compatible with SPF Laurent Dufour
2018-04-23 6:31 ` Minchan Kim
2018-04-30 14:07 ` Laurent Dufour
2018-05-01 13:04 ` Minchan Kim
2018-05-10 16:15 ` vinayak menon
2018-05-14 15:09 ` Laurent Dufour [this message]
2018-04-17 14:33 ` [PATCH v10 07/25] mm: introduce INIT_VMA() Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 08/25] mm: VMA sequence count Laurent Dufour
2018-04-23 6:42 ` Minchan Kim
2018-04-30 15:14 ` Laurent Dufour
2018-05-01 13:16 ` Minchan Kim
2018-05-03 14:45 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 09/25] mm: protect VMA modifications using " Laurent Dufour
2018-04-23 7:19 ` Minchan Kim
2018-05-14 15:25 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 10/25] mm: protect mremap() against SPF hanlder Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 11/25] mm: protect SPF handler against anon_vma changes Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 12/25] mm: cache some VMA fields in the vm_fault structure Laurent Dufour
2018-04-23 7:42 ` Minchan Kim
2018-05-03 12:25 ` Laurent Dufour
2018-05-03 15:42 ` Minchan Kim
2018-05-04 9:10 ` Laurent Dufour
2018-05-08 10:56 ` Minchan Kim
2018-04-17 14:33 ` [PATCH v10 13/25] mm/migrate: Pass vm_fault pointer to migrate_misplaced_page() Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 14/25] mm: introduce __lru_cache_add_active_or_unevictable Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 15/25] mm: introduce __vm_normal_page() Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 16/25] mm: introduce __page_add_new_anon_rmap() Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 17/25] mm: protect mm_rb tree with a rwlock Laurent Dufour
2018-04-30 18:47 ` Punit Agrawal
2018-05-02 6:37 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 18/25] mm: provide speculative fault infrastructure Laurent Dufour
2018-05-15 13:09 ` vinayak menon
2018-05-15 14:07 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 19/25] mm: adding speculative page fault failure trace events Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 20/25] perf: add a speculative page fault sw event Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 21/25] perf tools: add support for the SPF perf event Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 22/25] mm: speculative page fault handler return VMA Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 23/25] mm: add speculative page fault vmstats Laurent Dufour
2018-05-16 2:50 ` Ganesh Mahendran
2018-05-16 6:42 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 24/25] x86/mm: add speculative pagefault handling Laurent Dufour
2018-04-30 18:43 ` Punit Agrawal
2018-05-03 14:59 ` Laurent Dufour
2018-04-17 14:33 ` [PATCH v10 25/25] powerpc/mm: add speculative page fault Laurent Dufour
2018-05-02 14:17 ` [PATCH v10 00/25] Speculative page faults Punit Agrawal
2018-05-02 14:45 ` Laurent Dufour
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