From: Suren Baghdasaryan <surenb@google.com>
To: Laurent Dufour <ldufour@linux.ibm.com>
Cc: akpm@linux-foundation.org, michel@lespinasse.org,
jglisse@google.com, mhocko@suse.com, vbabka@suse.cz,
hannes@cmpxchg.org, mgorman@suse.de, dave@stgolabs.net,
willy@infradead.org, liam.howlett@oracle.com,
peterz@infradead.org, laurent.dufour@fr.ibm.com,
paulmck@kernel.org, luto@kernel.org, songliubraving@fb.com,
peterx@redhat.com, david@redhat.com, dhowells@redhat.com,
hughd@google.com, bigeasy@linutronix.de,
kent.overstreet@linux.dev, rientjes@google.com,
axelrasmussen@google.com, joelaf@google.com, minchan@google.com,
kernel-team@android.com, linux-mm@kvack.org,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, x86@kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH RESEND 21/28] mm: introduce find_and_lock_anon_vma to be used from arch-specific code
Date: Fri, 9 Sep 2022 09:10:08 -0700 [thread overview]
Message-ID: <CAJuCfpFtsP6s+pgus4RjFdwasg69hQ-LOSOL8XV4zUMey0zS9g@mail.gmail.com> (raw)
In-Reply-To: <630714df-dec1-4a41-6af3-380181d11669@linux.ibm.com>
On Fri, Sep 9, 2022 at 7:38 AM Laurent Dufour <ldufour@linux.ibm.com> wrote:
>
> Le 01/09/2022 à 19:35, Suren Baghdasaryan a écrit :
> > Introduce find_and_lock_anon_vma function to lookup and lock an anonymous
> > VMA during page fault handling. When VMA is not found, can't be locked
> > or changes after being locked, the function returns NULL. The lookup is
> > performed under RCU protection to prevent the found VMA from being
> > destroyed before the VMA lock is acquired. VMA lock statistics are
> > updated according to the results.
> >
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> > ---
> > include/linux/mm.h | 3 +++
> > mm/memory.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 48 insertions(+)
> >
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 7c3190eaabd7..a3cbaa7b9119 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -684,6 +684,9 @@ static inline void vma_assert_no_reader(struct vm_area_struct *vma)
> > vma);
> > }
> >
> > +struct vm_area_struct *find_and_lock_anon_vma(struct mm_struct *mm,
> > + unsigned long address);
> > +
> > #else /* CONFIG_PER_VMA_LOCK */
> >
> > static inline void vma_init_lock(struct vm_area_struct *vma) {}
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 29d2f49f922a..bf557f7056de 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -5183,6 +5183,51 @@ vm_fault_t handle_mm_fault(struct vm_area_struct *vma, unsigned long address,
> > }
> > EXPORT_SYMBOL_GPL(handle_mm_fault);
> >
> > +#ifdef CONFIG_PER_VMA_LOCK
> > +static inline struct vm_area_struct *find_vma_under_rcu(struct mm_struct *mm,
> > + unsigned long address)
> > +{
> > + struct vm_area_struct *vma = __find_vma(mm, address);
> > +
> > + if (!vma || vma->vm_start > address)
> > + return NULL;
> > +
> > + if (!vma_is_anonymous(vma))
> > + return NULL;
> > +
>
> It looks to me more natural to first check that the VMA is part of the RB
> tree before try read locking it.
I think we want to check that the VMA is still part of the mm _after_
we locked it. Otherwise we might pass the check, then some other
thread does (lock->isolate->unlock) and then we lock the VMA. We would
end up with a VMA that is not part of mm anymore but we assume it is.
>
> > + if (!vma_read_trylock(vma)) {
> > + count_vm_vma_lock_event(VMA_LOCK_ABORT);
> > + return NULL;
> > + }
> > +
> > + /* Check if the VMA got isolated after we found it */
> > + if (RB_EMPTY_NODE(&vma->vm_rb)) {
> > + vma_read_unlock(vma);
> > + count_vm_vma_lock_event(VMA_LOCK_MISS);
> > + return NULL;
> > + }
> > +
> > + return vma;
> > +}
> > +
> > +/*
> > + * Lookup and lock and anonymous VMA. Returned VMA is guaranteed to be stable
> > + * and not isolated. If the VMA is not found of is being modified the function
> > + * returns NULL.
> > + */
> > +struct vm_area_struct *find_and_lock_anon_vma(struct mm_struct *mm,
> > + unsigned long address)
> > +{
> > + struct vm_area_struct *vma;
> > +
> > + rcu_read_lock();
> > + vma = find_vma_under_rcu(mm, address);
> > + rcu_read_unlock();
> > +
> > + return vma;
> > +}
> > +#endif /* CONFIG_PER_VMA_LOCK */
> > +
> > #ifndef __PAGETABLE_P4D_FOLDED
> > /*
> > * Allocate p4d page table.
>
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next prev parent reply other threads:[~2022-09-09 16:11 UTC|newest]
Thread overview: 91+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-01 17:34 [RFC PATCH RESEND 00/28] per-VMA locks proposal Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 01/28] mm: introduce CONFIG_PER_VMA_LOCK Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 02/28] mm: rcu safe VMA freeing Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 03/28] mm: introduce __find_vma to be used without mmap_lock protection Suren Baghdasaryan
2022-09-01 20:22 ` Kent Overstreet
2022-09-01 23:18 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 04/28] mm: move mmap_lock assert function definitions Suren Baghdasaryan
2022-09-01 20:24 ` Kent Overstreet
2022-09-01 20:51 ` Liam Howlett
2022-09-01 23:21 ` Suren Baghdasaryan
2022-09-02 6:23 ` Sebastian Andrzej Siewior
2022-09-02 17:46 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 05/28] mm: add per-VMA lock and helper functions to control it Suren Baghdasaryan
2022-09-06 13:46 ` Laurent Dufour
2022-09-06 17:24 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 06/28] mm: mark VMA as locked whenever vma->vm_flags are modified Suren Baghdasaryan
2022-09-06 14:26 ` Laurent Dufour
2022-09-06 19:00 ` Suren Baghdasaryan
2022-09-06 20:00 ` Liam Howlett
2022-09-06 20:13 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 07/28] kernel/fork: mark VMAs as locked before copying pages during fork Suren Baghdasaryan
2022-09-06 14:37 ` Laurent Dufour
2022-09-08 23:57 ` Suren Baghdasaryan
2022-09-09 13:27 ` Laurent Dufour
2022-09-09 16:29 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 08/28] mm/khugepaged: mark VMA as locked while collapsing a hugepage Suren Baghdasaryan
2022-09-06 14:43 ` Laurent Dufour
2022-09-09 0:15 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 09/28] mm/mempolicy: mark VMA as locked when changing protection policy Suren Baghdasaryan
2022-09-06 14:47 ` Laurent Dufour
2022-09-09 0:27 ` Suren Baghdasaryan
2022-09-01 17:34 ` [RFC PATCH RESEND 10/28] mm/mmap: mark VMAs as locked in vma_adjust Suren Baghdasaryan
2022-09-06 15:35 ` Laurent Dufour
2022-09-09 0:51 ` Suren Baghdasaryan
2022-09-09 15:52 ` Laurent Dufour
2022-09-01 17:34 ` [RFC PATCH RESEND 11/28] mm/mmap: mark VMAs as locked before merging or splitting them Suren Baghdasaryan
2022-09-06 15:44 ` Laurent Dufour
2022-09-01 17:35 ` [RFC PATCH RESEND 12/28] mm/mremap: mark VMA as locked while remapping it to a new address range Suren Baghdasaryan
2022-09-06 16:09 ` Laurent Dufour
2022-09-01 17:35 ` [RFC PATCH RESEND 13/28] mm: conditionally mark VMA as locked in free_pgtables and unmap_page_range Suren Baghdasaryan
2022-09-09 10:33 ` Laurent Dufour
2022-09-09 16:43 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 14/28] mm: mark VMAs as locked before isolating them Suren Baghdasaryan
2022-09-09 13:35 ` Laurent Dufour
2022-09-09 16:28 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 15/28] mm/mmap: mark adjacent VMAs as locked if they can grow into unmapped area Suren Baghdasaryan
2022-09-09 13:43 ` Laurent Dufour
2022-09-09 16:25 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 16/28] kernel/fork: assert no VMA readers during its destruction Suren Baghdasaryan
2022-09-09 13:56 ` Laurent Dufour
2022-09-09 16:19 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 17/28] mm/mmap: prevent pagefault handler from racing with mmu_notifier registration Suren Baghdasaryan
2022-09-09 14:20 ` Laurent Dufour
2022-09-09 16:12 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 18/28] mm: add FAULT_FLAG_VMA_LOCK flag Suren Baghdasaryan
2022-09-09 14:26 ` Laurent Dufour
2022-09-01 17:35 ` [RFC PATCH RESEND 19/28] mm: disallow do_swap_page to handle page faults under VMA lock Suren Baghdasaryan
2022-09-06 19:39 ` Peter Xu
2022-09-06 20:08 ` Suren Baghdasaryan
2022-09-06 20:22 ` Peter Xu
2022-09-07 0:58 ` Suren Baghdasaryan
2022-09-09 14:26 ` Laurent Dufour
2022-09-01 17:35 ` [RFC PATCH RESEND 20/28] mm: introduce per-VMA lock statistics Suren Baghdasaryan
2022-09-09 14:28 ` Laurent Dufour
2022-09-09 16:11 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 21/28] mm: introduce find_and_lock_anon_vma to be used from arch-specific code Suren Baghdasaryan
2022-09-09 14:38 ` Laurent Dufour
2022-09-09 16:10 ` Suren Baghdasaryan [this message]
2022-09-01 17:35 ` [RFC PATCH RESEND 22/28] x86/mm: try VMA lock-based page fault handling first Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 23/28] x86/mm: define ARCH_SUPPORTS_PER_VMA_LOCK Suren Baghdasaryan
2022-09-01 20:20 ` Kent Overstreet
2022-09-01 23:17 ` Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 24/28] arm64/mm: try VMA lock-based page fault handling first Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 25/28] arm64/mm: define ARCH_SUPPORTS_PER_VMA_LOCK Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 26/28] powerc/mm: try VMA lock-based page fault handling first Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 27/28] powerpc/mm: define ARCH_SUPPORTS_PER_VMA_LOCK Suren Baghdasaryan
2022-09-01 17:35 ` [RFC PATCH RESEND 28/28] kernel/fork: throttle call_rcu() calls in vm_area_free Suren Baghdasaryan
2022-09-09 15:19 ` Laurent Dufour
2022-09-09 16:02 ` Suren Baghdasaryan
2022-09-09 16:14 ` Laurent Dufour
2022-09-01 20:58 ` [RFC PATCH RESEND 00/28] per-VMA locks proposal Kent Overstreet
2022-09-01 23:26 ` Suren Baghdasaryan
2022-09-11 9:35 ` Vlastimil Babka
2022-09-28 2:28 ` Suren Baghdasaryan
2022-09-29 11:18 ` Vlastimil Babka
2022-09-02 7:42 ` Peter Zijlstra
2022-09-02 14:45 ` Suren Baghdasaryan
2022-09-05 12:32 ` Michal Hocko
2022-09-05 18:32 ` Suren Baghdasaryan
2022-09-05 20:35 ` Kent Overstreet
2022-09-06 15:46 ` Suren Baghdasaryan
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