linux-kernel - [PATCH v2 25/35] mm: add mmu_notifier_trylock() and mmu_notifier

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Message-Id: <20220128131006.67712-26-michel@lespinasse.org>
Date:   Fri, 28 Jan 2022 05:09:56 -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 25/35] mm: add mmu_notifier_trylock() and mmu_notifier_unlock()

These new functions are to be used when firing MMU notifications
without holding any of the mmap or rmap locks, as is the case with
speculative page fault handlers.

Signed-off-by: Michel Lespinasse <michel@...pinasse.org>
---
 include/linux/mmu_notifier.h | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index ace76fe91c0c..d0430410fdd8 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -772,4 +772,29 @@ static inline void mmu_notifier_synchronize(void)
 
 #endif /* CONFIG_MMU_NOTIFIER */
 
+#if defined(CONFIG_MMU_NOTIFIER) && defined(CONFIG_SPECULATIVE_PAGE_FAULT)
+
+static inline bool mmu_notifier_trylock(struct mm_struct *mm)
+{
+	return percpu_down_read_trylock(mm->mmu_notifier_lock);
+}
+
+static inline void mmu_notifier_unlock(struct mm_struct *mm)
+{
+	percpu_up_read(mm->mmu_notifier_lock);
+}
+
+#else
+
+static inline bool mmu_notifier_trylock(struct mm_struct *mm)
+{
+	return true;
+}
+
+static inline void mmu_notifier_unlock(struct mm_struct *mm)
+{
+}
+
+#endif
+
 #endif /* _LINUX_MMU_NOTIFIER_H */
-- 
2.20.1