From: Suren Baghdasaryan <surenb@google.com>
To: Michal Hocko <mhocko@suse.com>
Cc: akpm@linux-foundation.org, michel@lespinasse.org,
jglisse@google.com, vbabka@suse.cz, hannes@cmpxchg.org,
mgorman@techsingularity.net, dave@stgolabs.net,
willy@infradead.org, liam.howlett@oracle.com,
peterz@infradead.org, ldufour@linux.ibm.com,
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, punit.agrawal@bytedance.com,
lstoakes@gmail.com, peterjung1337@gmail.com, rientjes@google.com,
axelrasmussen@google.com, joelaf@google.com, minchan@google.com,
jannh@google.com, shakeelb@google.com, tatashin@google.com,
edumazet@google.com, gthelen@google.com, gurua@google.com,
arjunroy@google.com, soheil@google.com, hughlynch@google.com,
leewalsh@google.com, posk@google.com, linux-mm@kvack.org,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, x86@kernel.org,
linux-kernel@vger.kernel.org, kernel-team@android.com
Subject: Re: [PATCH 28/41] mm: introduce lock_vma_under_rcu to be used from arch-specific code
Date: Tue, 17 Jan 2023 17:06:57 -0800 [thread overview]
Message-ID: <CAJuCfpHRRsUMNHp2H3UiB4EZbe9CXTVcAC+oOR1dscENjp1Jbw@mail.gmail.com> (raw)
In-Reply-To: <Y8bDAVC/aiL9tCyz@dhcp22.suse.cz>
On Tue, Jan 17, 2023 at 7:47 AM Michal Hocko <mhocko@suse.com> wrote:
>
> On Mon 09-01-23 12:53:23, Suren Baghdasaryan wrote:
> > Introduce lock_vma_under_rcu function to lookup and lock a 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.
> > For now only anonymous VMAs can be searched this way. In other cases the
> > function returns NULL.
>
> Could you describe why only anonymous vmas are handled at this stage and
> what (roughly) has to be done to support other vmas? lock_vma_under_rcu
> doesn't seem to have any anonymous vma specific requirements AFAICS.
TBH I haven't spent too much time looking into file-backed page faults
yet but a couple of tasks I can think of are:
- Ensure that all vma->vm_ops->fault() handlers do not rely on
mmap_lock being read-locked;
- vma->vm_file freeing like VMA freeing will need to be done after RCU
grace period since page fault handlers use it. This will require some
caution because simply adding it into __vm_area_free() called via
call_rcu() will cause corresponding fops->release() to be called
asynchronously. I had to solve this issue with out-of-tree SPF
implementation when asynchronously called snd_pcm_release() was
problematic.
I'm sure I'm missing more potential issues and maybe Matthew and
Michel can pinpoint more things to resolve here?
>
> Also isn't lock_vma_under_rcu effectively find_read_lock_vma? Not that
> the naming is really the most important part but the rcu locking is
> internal to the function so why should we spread this implementation
> detail to the world...
I wanted the name to indicate that the lookup is done with no locks
held. But I'm open to suggestions.
>
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> > ---
> > include/linux/mm.h | 3 +++
> > mm/memory.c | 51 ++++++++++++++++++++++++++++++++++++++++++++++
> > 2 files changed, 54 insertions(+)
> >
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index c464fc8a514c..d0fddf6a1de9 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -687,6 +687,9 @@ static inline void vma_assert_no_reader(struct vm_area_struct *vma)
> > vma);
> > }
> >
> > +struct vm_area_struct *lock_vma_under_rcu(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 9ece18548db1..a658e26d965d 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -5242,6 +5242,57 @@ 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
> > +/*
> > + * Lookup and lock a VMA under RCU protection. Returned VMA is guaranteed to be
> > + * stable and not isolated. If the VMA is not found or is being modified the
> > + * function returns NULL.
> > + */
> > +struct vm_area_struct *lock_vma_under_rcu(struct mm_struct *mm,
> > + unsigned long address)
> > +{
> > + MA_STATE(mas, &mm->mm_mt, address, address);
> > + struct vm_area_struct *vma, *validate;
> > +
> > + rcu_read_lock();
> > + vma = mas_walk(&mas);
> > +retry:
> > + if (!vma)
> > + goto inval;
> > +
> > + /* Only anonymous vmas are supported for now */
> > + if (!vma_is_anonymous(vma))
> > + goto inval;
> > +
> > + if (!vma_read_trylock(vma))
> > + goto inval;
> > +
> > + /* Check since vm_start/vm_end might change before we lock the VMA */
> > + if (unlikely(address < vma->vm_start || address >= vma->vm_end)) {
> > + vma_read_unlock(vma);
> > + goto inval;
> > + }
> > +
> > + /* Check if the VMA got isolated after we found it */
> > + mas.index = address;
> > + validate = mas_walk(&mas);
> > + if (validate != vma) {
> > + vma_read_unlock(vma);
> > + count_vm_vma_lock_event(VMA_LOCK_MISS);
> > + /* The area was replaced with another one. */
> > + vma = validate;
> > + goto retry;
> > + }
> > +
> > + rcu_read_unlock();
> > + return vma;
> > +inval:
> > + rcu_read_unlock();
> > + count_vm_vma_lock_event(VMA_LOCK_ABORT);
> > + return NULL;
> > +}
> > +#endif /* CONFIG_PER_VMA_LOCK */
> > +
> > #ifndef __PAGETABLE_P4D_FOLDED
> > /*
> > * Allocate p4d page table.
> > --
> > 2.39.0
>
> --
> Michal Hocko
> SUSE Labs
next prev parent reply other threads:[~2023-01-18 1:13 UTC|newest]
Thread overview: 186+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-09 20:52 [PATCH 00/41] Per-VMA locks Suren Baghdasaryan
2023-01-09 20:52 ` [PATCH 01/41] maple_tree: Be more cautious about dead nodes Suren Baghdasaryan
2023-01-09 20:52 ` [PATCH 02/41] maple_tree: Detect dead nodes in mas_start() Suren Baghdasaryan
2023-01-09 20:52 ` [PATCH 03/41] maple_tree: Fix freeing of nodes in rcu mode Suren Baghdasaryan
2023-01-09 20:52 ` [PATCH 04/41] maple_tree: remove extra smp_wmb() from mas_dead_leaves() Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 05/41] maple_tree: Fix write memory barrier of nodes once dead for RCU mode Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 06/41] maple_tree: Add smp_rmb() to dead node detection Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 07/41] mm: Enable maple tree RCU mode by default Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 08/41] mm: introduce CONFIG_PER_VMA_LOCK Suren Baghdasaryan
2023-01-11 0:13 ` Davidlohr Bueso
2023-01-11 0:44 ` Suren Baghdasaryan
2023-01-11 8:23 ` Michal Hocko
2023-01-11 9:54 ` Ingo Molnar
[not found] ` <6be809f5554a4faaa22c287ba4224bd0@AcuMS.aculab.com>
2023-01-11 16:28 ` Suren Baghdasaryan
2023-01-11 16:44 ` Michal Hocko
2023-01-11 17:04 ` Suren Baghdasaryan
2023-01-11 17:37 ` Michal Hocko
2023-01-11 17:49 ` Suren Baghdasaryan
2023-01-11 18:02 ` Michal Hocko
2023-01-11 18:09 ` Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 09/41] mm: rcu safe VMA freeing Suren Baghdasaryan
2023-01-17 14:25 ` Michal Hocko
2023-01-18 2:16 ` Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 10/41] mm: move mmap_lock assert function definitions Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 11/41] mm: export dump_mm() Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 12/41] mm: add per-VMA lock and helper functions to control it Suren Baghdasaryan
2023-01-17 15:04 ` Michal Hocko
2023-01-17 15:12 ` Michal Hocko
2023-01-17 21:21 ` Suren Baghdasaryan
2023-01-17 21:54 ` Matthew Wilcox
2023-01-17 22:33 ` Suren Baghdasaryan
2023-01-18 9:18 ` Michal Hocko
2023-01-17 21:08 ` Suren Baghdasaryan
2023-01-17 15:07 ` Michal Hocko
2023-01-17 21:09 ` Suren Baghdasaryan
2023-01-17 18:02 ` Jann Horn
2023-01-17 21:28 ` Suren Baghdasaryan
2023-01-17 21:45 ` Jann Horn
2023-01-17 22:36 ` Suren Baghdasaryan
2023-01-17 23:15 ` Matthew Wilcox
2023-11-22 14:04 ` Alexander Gordeev
2023-01-18 12:28 ` Michal Hocko
2023-01-18 13:23 ` Jann Horn
2023-01-18 15:11 ` Michal Hocko
2023-01-18 17:36 ` Suren Baghdasaryan
2023-01-18 21:28 ` Michal Hocko
2023-01-18 21:45 ` Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 13/41] mm: introduce vma->vm_flags modifier functions Suren Baghdasaryan
2023-01-11 15:47 ` Davidlohr Bueso
2023-01-11 17:36 ` Suren Baghdasaryan
2023-01-11 19:52 ` Davidlohr Bueso
2023-01-11 21:23 ` Suren Baghdasaryan
2023-01-17 15:09 ` Michal Hocko
2023-01-17 15:15 ` Michal Hocko
2023-01-18 2:07 ` Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 14/41] mm: replace VM_LOCKED_CLEAR_MASK with VM_LOCKED_MASK Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 15/41] mm: replace vma->vm_flags direct modifications with modifier calls Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 16/41] mm: replace vma->vm_flags indirect modification in ksm_madvise Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 17/41] mm/mmap: move VMA locking before anon_vma_lock_write call Suren Baghdasaryan
2023-01-17 15:16 ` Michal Hocko
2023-01-18 2:01 ` Suren Baghdasaryan
2023-01-18 9:23 ` Michal Hocko
2023-01-18 18:09 ` Suren Baghdasaryan
2023-01-18 21:33 ` Michal Hocko
2023-01-18 21:48 ` Suren Baghdasaryan
2023-01-19 9:31 ` Michal Hocko
2023-01-19 18:53 ` Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 18/41] mm/khugepaged: write-lock VMA while collapsing a huge page Suren Baghdasaryan
2023-01-17 15:25 ` Michal Hocko
2023-01-17 20:28 ` Jann Horn
2023-01-17 21:05 ` Suren Baghdasaryan
2023-01-18 9:40 ` Michal Hocko
2023-01-18 12:38 ` Jann Horn
2023-01-18 17:41 ` Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 19/41] mm/mmap: write-lock VMAs before merging, splitting or expanding them Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 20/41] mm/mmap: write-lock VMAs in vma_adjust Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 21/41] mm/mmap: write-lock VMAs affected by VMA expansion Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 22/41] mm/mremap: write-lock VMA while remapping it to a new address range Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 23/41] mm: write-lock VMAs before removing them from VMA tree Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 24/41] mm: conditionally write-lock VMA in free_pgtables Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 25/41] mm/mmap: write-lock adjacent VMAs if they can grow into unmapped area Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 26/41] kernel/fork: assert no VMA readers during its destruction Suren Baghdasaryan
2023-01-17 15:42 ` Michal Hocko
2023-01-18 1:53 ` Suren Baghdasaryan
2023-01-18 9:43 ` Michal Hocko
2023-01-18 18:06 ` Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 27/41] mm/mmap: prevent pagefault handler from racing with mmu_notifier registration Suren Baghdasaryan
2023-01-18 12:50 ` Jann Horn
2023-01-18 17:40 ` Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 28/41] mm: introduce lock_vma_under_rcu to be used from arch-specific code Suren Baghdasaryan
2023-01-17 15:47 ` Michal Hocko
2023-01-18 1:06 ` Suren Baghdasaryan [this message]
2023-01-18 2:44 ` Matthew Wilcox
2023-01-18 21:33 ` Suren Baghdasaryan
2023-01-17 21:03 ` Jann Horn
2023-01-17 23:18 ` Liam Howlett
2023-01-09 20:53 ` [PATCH 29/41] mm: fall back to mmap_lock if vma->anon_vma is not yet set Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 30/41] mm: add FAULT_FLAG_VMA_LOCK flag Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 31/41] mm: prevent do_swap_page from handling page faults under VMA lock Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 32/41] mm: prevent userfaults to be handled under per-vma lock Suren Baghdasaryan
2023-01-17 19:51 ` Jann Horn
2023-01-17 20:36 ` Jann Horn
2023-01-17 20:57 ` Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 33/41] mm: introduce per-VMA lock statistics Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 34/41] x86/mm: try VMA lock-based page fault handling first Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 35/41] arm64/mm: " Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 36/41] powerc/mm: " Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 37/41] mm: introduce mod_vm_flags_nolock Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 38/41] mm: avoid assertion in untrack_pfn Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 39/41] kernel/fork: throttle call_rcu() calls in vm_area_free Suren Baghdasaryan
2023-01-17 15:57 ` Michal Hocko
2023-01-18 1:19 ` Suren Baghdasaryan
2023-01-18 9:49 ` Michal Hocko
2023-01-18 18:04 ` Suren Baghdasaryan
2023-01-18 18:34 ` Paul E. McKenney
2023-01-18 19:01 ` Suren Baghdasaryan
2023-01-18 20:20 ` Paul E. McKenney
2023-01-19 12:52 ` Michal Hocko
2023-01-19 19:17 ` Paul E. McKenney
2023-01-20 8:57 ` Michal Hocko
2023-01-20 16:08 ` Paul E. McKenney
2023-01-19 12:59 ` Michal Hocko
2023-01-19 18:52 ` Suren Baghdasaryan
2023-01-19 19:20 ` Paul E. McKenney
2023-01-19 19:47 ` Suren Baghdasaryan
2023-01-19 19:55 ` Paul E. McKenney
2023-01-20 8:52 ` Michal Hocko
2023-01-20 16:20 ` Suren Baghdasaryan
2023-01-20 16:45 ` Suren Baghdasaryan
2023-01-20 16:49 ` Matthew Wilcox
2023-01-20 17:08 ` Liam R. Howlett
2023-01-20 17:17 ` Suren Baghdasaryan
2023-01-20 17:32 ` Matthew Wilcox
2023-01-20 17:50 ` Suren Baghdasaryan
2023-01-20 19:23 ` Liam R. Howlett
2023-01-23 9:56 ` Michal Hocko
2023-01-23 16:22 ` Suren Baghdasaryan
2023-01-23 16:55 ` Michal Hocko
2023-01-23 17:07 ` Suren Baghdasaryan
2023-01-23 17:16 ` Michal Hocko
2023-01-23 17:46 ` Suren Baghdasaryan
2023-01-23 18:23 ` Matthew Wilcox
2023-01-23 18:47 ` Suren Baghdasaryan
2023-01-23 19:18 ` Michal Hocko
2023-01-23 19:30 ` Matthew Wilcox
2023-01-23 19:57 ` Suren Baghdasaryan
2023-01-23 20:00 ` Michal Hocko
2023-01-23 20:08 ` Suren Baghdasaryan
2023-01-23 20:38 ` Liam R. Howlett
2023-01-20 17:21 ` Paul E. McKenney
2023-01-20 18:42 ` Suren Baghdasaryan
2023-01-23 9:59 ` Michal Hocko
2023-01-23 17:43 ` Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 40/41] mm: separate vma->lock from vm_area_struct Suren Baghdasaryan
2023-01-17 18:33 ` Jann Horn
2023-01-17 19:01 ` Suren Baghdasaryan
2023-01-09 20:53 ` [PATCH 41/41] mm: replace rw_semaphore with atomic_t in vma_lock Suren Baghdasaryan
2023-01-10 8:04 ` Vlastimil Babka
2023-01-10 17:05 ` Suren Baghdasaryan
2023-01-16 11:14 ` Hyeonggon Yoo
2023-01-16 22:36 ` Suren Baghdasaryan
2023-01-17 4:14 ` Matthew Wilcox
2023-01-17 4:34 ` Suren Baghdasaryan
2023-01-17 5:46 ` Matthew Wilcox
2023-01-17 5:58 ` Suren Baghdasaryan
2023-01-17 18:23 ` Matthew Wilcox
2023-01-17 18:28 ` Suren Baghdasaryan
2023-01-17 20:31 ` Michal Hocko
2023-01-17 21:00 ` Suren Baghdasaryan
[not found] ` <20230116140649.2012-1-hdanton@sina.com>
2023-01-16 23:08 ` Suren Baghdasaryan
2023-01-16 23:11 ` Suren Baghdasaryan
[not found] ` <20230117031632.2321-1-hdanton@sina.com>
2023-01-17 4:52 ` Suren Baghdasaryan
[not found] ` <20230117083355.2374-1-hdanton@sina.com>
2023-01-17 18:21 ` Suren Baghdasaryan
2023-01-17 18:27 ` Matthew Wilcox
2023-01-17 18:31 ` Suren Baghdasaryan
[not found] ` <20230118062639.2839-1-hdanton@sina.com>
2023-01-18 18:35 ` Matthew Wilcox
2023-01-17 18:11 ` Jann Horn
2023-01-17 18:26 ` Suren Baghdasaryan
2023-01-17 18:31 ` Matthew Wilcox
2023-01-17 18:36 ` Jann Horn
2023-01-17 18:49 ` Suren Baghdasaryan
2023-01-17 18:36 ` Suren Baghdasaryan
2023-01-17 18:48 ` Matthew Wilcox
2023-01-17 18:55 ` Suren Baghdasaryan
2023-01-17 18:59 ` Jann Horn
2023-01-17 19:06 ` Suren Baghdasaryan
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