From: Anshuman Khandual <khandual@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>,
Laurent Dufour <ldufour@linux.vnet.ibm.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
paulmck@linux.vnet.ibm.com, akpm@linux-foundation.org,
ak@linux.intel.com, mhocko@kernel.org, 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>,
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,
Tim Chen <tim.c.chen@linux.intel.com>,
linuxppc-dev@lists.ozlabs.org, x86@kernel.org
Subject: Re: [PATCH v2 14/20] mm: Provide speculative fault infrastructure
Date: Wed, 30 Aug 2017 10:33:50 +0530 [thread overview]
Message-ID: <ab0634c4-274d-208f-fc4b-43991986bacf@linux.vnet.ibm.com> (raw)
In-Reply-To: <20170829134550.t7du5zdssvlzemtk@hirez.programming.kicks-ass.net>
On 08/29/2017 07:15 PM, Peter Zijlstra wrote:
> On Tue, Aug 29, 2017 at 03:18:25PM +0200, Laurent Dufour wrote:
>> On 29/08/2017 14:04, Peter Zijlstra wrote:
>>> On Tue, Aug 29, 2017 at 09:59:30AM +0200, Laurent Dufour wrote:
>>>> On 27/08/2017 02:18, Kirill A. Shutemov wrote:
>>>>>> +
>>>>>> + if (unlikely(!vma->anon_vma))
>>>>>> + goto unlock;
>>>>>
>>>>> It deserves a comment.
>>>>
>>>> You're right I'll add it in the next version.
>>>> For the record, the root cause is that __anon_vma_prepare() requires the
>>>> mmap_sem to be held because vm_next and vm_prev must be safe.
>>>
>>> But should that test not be:
>>>
>>> if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma))
>>> goto unlock;
>>>
>>> Because !anon vmas will never have ->anon_vma set and you don't want to
>>> exclude those.
>>
>> Yes in the case we later allow non anonymous vmas to be handled.
>> Currently only anonymous vmas are supported so the check is good enough,
>> isn't it ?
>
> That wasn't at all clear from reading the code. This makes it clear
> ->anon_vma is only ever looked at for anonymous.
>
> And like Kirill says, we _really_ should start allowing some (if not
> all) vm_ops. Large file based mappings aren't particularly rare.
>
> I'm not sure we want to introduce a white-list or just bite the bullet
> and audit all ->fault() implementations. But either works and isn't
> terribly difficult, auditing all is more work though.
filemap_fault() is used as vma-vm_ops->fault() for most of the file
systems. Changing it can enable speculative fault support for all of
them. It will still exclude other driver based vma-vm_ops->fault()
implementation. AFAICS, __lock_page_or_retry() function can drop
mm->mmap_sem if the page could not be locked right away. As suggested
by Peterz, making it understand FAULT_FLAG_SPECULATIVE should be good
enough. The patch is lightly tested for file mappings on top of this
series.
diff --git a/mm/filemap.c b/mm/filemap.c
index a497024..08f3042 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1181,6 +1181,18 @@ int __lock_page_killable(struct page *__page)
int __lock_page_or_retry(struct page *page, struct mm_struct *mm,
unsigned int flags)
{
+ if (flags & FAULT_FLAG_SPECULATIVE) {
+ if (flags & FAULT_FLAG_KILLABLE) {
+ int ret;
+
+ ret = __lock_page_killable(page);
+ if (ret)
+ return 0;
+ } else
+ __lock_page(page);
+ return 1;
+ }
+
if (flags & FAULT_FLAG_ALLOW_RETRY) {
/*
* CAUTION! In this case, mmap_sem is not released
diff --git a/mm/memory.c b/mm/memory.c
index 549d235..02347f3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3836,8 +3836,6 @@ static int handle_pte_fault(struct vm_fault *vmf)
if (!vmf->pte) {
if (vma_is_anonymous(vmf->vma))
return do_anonymous_page(vmf);
- else if (vmf->flags & FAULT_FLAG_SPECULATIVE)
- return VM_FAULT_RETRY;
else
return do_fault(vmf);
}
@@ -4012,17 +4010,7 @@ int handle_speculative_fault(struct mm_struct *mm, unsigned long address,
goto unlock;
}
- /*
- * Can't call vm_ops service has we don't know what they would do
- * with the VMA.
- * This include huge page from hugetlbfs.
- */
- if (vma->vm_ops) {
- trace_spf_vma_notsup(_RET_IP_, vma, address);
- goto unlock;
- }
-
- if (unlikely(!vma->anon_vma)) {
+ if (unlikely(vma_is_anonymous(vma) && !vma->anon_vma)) {
trace_spf_vma_notsup(_RET_IP_, vma, address);
goto unlock;
}
next prev parent reply other threads:[~2017-08-30 5:04 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-17 22:04 [PATCH v2 00/20] Speculative page faults Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 01/20] mm: Dont assume page-table invariance during faults Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 02/20] mm: Prepare for FAULT_FLAG_SPECULATIVE Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 03/20] mm: Introduce pte_spinlock " Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 04/20] mm: VMA sequence count Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 05/20] mm: Protect VMA modifications using " Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 06/20] mm: RCU free VMAs Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 07/20] mm: Cache some VMA fields in the vm_fault structure Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 08/20] mm: Protect SPF handler against anon_vma changes Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 09/20] mm/migrate: Pass vm_fault pointer to migrate_misplaced_page() Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 10/20] mm: Introduce __lru_cache_add_active_or_unevictable Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 11/20] mm: Introduce __maybe_mkwrite() Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 12/20] mm: Introduce __vm_normal_page() Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 13/20] mm: Introduce __page_add_new_anon_rmap() Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 14/20] mm: Provide speculative fault infrastructure Laurent Dufour
2017-08-20 12:11 ` Sergey Senozhatsky
2017-08-25 8:52 ` Laurent Dufour
2017-08-27 0:18 ` Kirill A. Shutemov
2017-08-28 9:37 ` Peter Zijlstra
2017-08-28 21:14 ` Benjamin Herrenschmidt
2017-08-28 22:35 ` Andi Kleen
2017-08-29 8:15 ` Peter Zijlstra
2017-08-29 8:33 ` Peter Zijlstra
2017-08-29 11:27 ` Peter Zijlstra
2017-08-29 21:19 ` Benjamin Herrenschmidt
2017-08-30 6:13 ` Peter Zijlstra
2017-08-29 7:59 ` Laurent Dufour
2017-08-29 12:04 ` Peter Zijlstra
2017-08-29 13:18 ` Laurent Dufour
2017-08-29 13:45 ` Peter Zijlstra
2017-08-30 5:03 ` Anshuman Khandual [this message]
2017-08-30 5:58 ` Peter Zijlstra
2017-08-30 9:32 ` Laurent Dufour
2017-08-31 6:55 ` Anshuman Khandual
2017-08-31 7:31 ` Peter Zijlstra
2017-08-30 9:53 ` Laurent Dufour
2017-08-30 3:48 ` Anshuman Khandual
2017-08-30 5:25 ` Anshuman Khandual
2017-08-30 8:56 ` Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 15/20] mm: Try spin lock in speculative path Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 16/20] mm: Adding speculative page fault failure trace events Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 17/20] perf: Add a speculative page fault sw event Laurent Dufour
2017-08-21 8:55 ` Anshuman Khandual
2017-08-22 1:46 ` Michael Ellerman
2017-08-17 22:05 ` [PATCH v2 18/20] perf tools: Add support for the SPF perf event Laurent Dufour
2017-08-21 8:48 ` Anshuman Khandual
2017-08-25 8:53 ` Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 19/20] x86/mm: Add speculative pagefault handling Laurent Dufour
2017-08-21 7:29 ` Anshuman Khandual
2017-08-29 14:50 ` Laurent Dufour
2017-08-29 14:58 ` Laurent Dufour
2017-08-17 22:05 ` [PATCH v2 20/20] powerpc/mm: Add speculative page fault Laurent Dufour
2017-08-21 6:58 ` Anshuman Khandual
2017-08-29 15:13 ` Laurent Dufour
2017-08-21 2:26 ` [PATCH v2 00/20] Speculative page faults Sergey Senozhatsky
2017-09-08 9:24 ` Laurent Dufour
2017-09-11 0:45 ` Sergey Senozhatsky
2017-09-11 6:28 ` Laurent Dufour
2017-08-21 6:28 ` Anshuman Khandual
2017-08-22 0:41 ` Paul E. McKenney
2017-08-25 9:41 ` Laurent Dufour
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