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Message-Id: <20220128131006.67712-24-michel@lespinasse.org>
Date: Fri, 28 Jan 2022 05:09:54 -0800
From: Michel Lespinasse <michel@...pinasse.org>
To: Linux-MM <linux-mm@...ck.org>, linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>
Cc: kernel-team@...com, Laurent Dufour <ldufour@...ux.ibm.com>,
Jerome Glisse <jglisse@...gle.com>,
Peter Zijlstra <peterz@...radead.org>,
Michal Hocko <mhocko@...e.com>,
Vlastimil Babka <vbabka@...e.cz>,
Davidlohr Bueso <dave@...olabs.net>,
Matthew Wilcox <willy@...radead.org>,
Liam Howlett <liam.howlett@...cle.com>,
Rik van Riel <riel@...riel.com>,
Paul McKenney <paulmck@...nel.org>,
Song Liu <songliubraving@...com>,
Suren Baghdasaryan <surenb@...gle.com>,
Minchan Kim <minchan@...gle.com>,
Joel Fernandes <joelaf@...gle.com>,
David Rientjes <rientjes@...gle.com>,
Axel Rasmussen <axelrasmussen@...gle.com>,
Andy Lutomirski <luto@...nel.org>,
Michel Lespinasse <michel@...pinasse.org>
Subject: [PATCH v2 23/35] mm: add mmu_notifier_lock
Introduce mmu_notifier_lock as a per-mm percpu_rw_semaphore,
as well as the code to initialize and destroy it together with the mm.
This lock will be used to prevent races between mmu_notifier_register()
and speculative fault handlers that need to fire MMU notifications
without holding any of the mmap or rmap locks.
Signed-off-by: Michel Lespinasse <michel@...pinasse.org>
---
include/linux/mm_types.h | 6 +++++-
include/linux/mmu_notifier.h | 27 +++++++++++++++++++++++++--
kernel/fork.c | 3 ++-
3 files changed, 32 insertions(+), 4 deletions(-)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 305f05d2a4bc..f77e2dec038d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -462,6 +462,7 @@ struct vm_area_struct {
} __randomize_layout;
struct kioctx_table;
+struct percpu_rw_semaphore;
struct mm_struct {
struct {
struct vm_area_struct *mmap; /* list of VMAs */
@@ -608,7 +609,10 @@ struct mm_struct {
struct file __rcu *exe_file;
#ifdef CONFIG_MMU_NOTIFIER
struct mmu_notifier_subscriptions *notifier_subscriptions;
-#endif
+#ifdef CONFIG_SPECULATIVE_PAGE_FAULT
+ struct percpu_rw_semaphore *mmu_notifier_lock;
+#endif /* CONFIG_SPECULATIVE_PAGE_FAULT */
+#endif /* CONFIG_MMU_NOTIFIER */
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
pgtable_t pmd_huge_pte; /* protected by page_table_lock */
#endif
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 45fc2c81e370..ace76fe91c0c 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -6,6 +6,8 @@
#include <linux/spinlock.h>
#include <linux/mm_types.h>
#include <linux/mmap_lock.h>
+#include <linux/percpu-rwsem.h>
+#include <linux/slab.h>
#include <linux/srcu.h>
#include <linux/interval_tree.h>
@@ -499,15 +501,35 @@ static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
__mmu_notifier_invalidate_range(mm, start, end);
}
-static inline void mmu_notifier_subscriptions_init(struct mm_struct *mm)
+static inline bool mmu_notifier_subscriptions_init(struct mm_struct *mm)
{
+#ifdef CONFIG_SPECULATIVE_PAGE_FAULT
+ mm->mmu_notifier_lock = kzalloc(sizeof(struct percpu_rw_semaphore), GFP_KERNEL);
+ if (!mm->mmu_notifier_lock)
+ return false;
+ if (percpu_init_rwsem(mm->mmu_notifier_lock)) {
+ kfree(mm->mmu_notifier_lock);
+ return false;
+ }
+#endif
+
mm->notifier_subscriptions = NULL;
+ return true;
}
static inline void mmu_notifier_subscriptions_destroy(struct mm_struct *mm)
{
if (mm_has_notifiers(mm))
__mmu_notifier_subscriptions_destroy(mm);
+
+#ifdef CONFIG_SPECULATIVE_PAGE_FAULT
+ if (!in_atomic()) {
+ percpu_free_rwsem(mm->mmu_notifier_lock);
+ kfree(mm->mmu_notifier_lock);
+ } else {
+ percpu_rwsem_async_destroy(mm->mmu_notifier_lock);
+ }
+#endif
}
@@ -724,8 +746,9 @@ static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
{
}
-static inline void mmu_notifier_subscriptions_init(struct mm_struct *mm)
+static inline bool mmu_notifier_subscriptions_init(struct mm_struct *mm)
{
+ return true;
}
static inline void mmu_notifier_subscriptions_destroy(struct mm_struct *mm)
diff --git a/kernel/fork.c b/kernel/fork.c
index 2e5f2e8de31a..db92e42d0087 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1069,7 +1069,8 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p,
mm_init_owner(mm, p);
mm_init_pasid(mm);
RCU_INIT_POINTER(mm->exe_file, NULL);
- mmu_notifier_subscriptions_init(mm);
+ if (!mmu_notifier_subscriptions_init(mm))
+ goto fail_nopgd;
init_tlb_flush_pending(mm);
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS
mm->pmd_huge_pte = NULL;
--
2.20.1
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