From nobody Mon Apr 6 23:07:10 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2F6EECAAD1 for ; Thu, 1 Sep 2022 17:36:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234856AbiIARgh (ORCPT ); Thu, 1 Sep 2022 13:36:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44730 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233250AbiIARfj (ORCPT ); Thu, 1 Sep 2022 13:35:39 -0400 Received: from mail-yw1-x1149.google.com (mail-yw1-x1149.google.com [IPv6:2607:f8b0:4864:20::1149]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4851548C83 for ; Thu, 1 Sep 2022 10:35:35 -0700 (PDT) Received: by mail-yw1-x1149.google.com with SMTP id 00721157ae682-335ff2ef600so235531877b3.18 for ; Thu, 01 Sep 2022 10:35:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date; bh=eIMt0K4Dq/+E4lj9SQ/fnMIDQQYvNY/8MPu6+maRPr0=; b=OULzLK//lObTRMGAKryDz/AAItdyiK5yqhZqIIxu+sL1Dieokt2jidmnz3C7/IkvFZ m9XlR/LP/dWBo2UxnXyYn7qdVCzxgLbSFD2CG9EOYY1gruRvre30gd8M27oZrFHurKvO KqLi6QjNq7f2EcLrXhJZo+HJMeLkP9RVRxlBnBeo9kXpz7L5PtGPdJWGZy8ptDnDibsD BU++Zg9dqZVio0ctwQpkNxICzBLOlMkeBzfVJBfO5ajkBVunOWr6F+myD0p5P9YWiss6 hO75UDowCTjrDDdzDEi22CFFlp+R1gx4mTcBiehvp3OGDbyQbHz6/QfMRzJJk1Rc6B1v GPRQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date; bh=eIMt0K4Dq/+E4lj9SQ/fnMIDQQYvNY/8MPu6+maRPr0=; b=0zh6HWvC2VGSaNYS+u3GT4M/2kZGOpRSKuMSbgcUcD8L3uSNs4uNahp+lGZLR7xfYt BZHDJR8tdLoH8vqG0ZGUhcim/l9hCsy86OPa3WCBp/z1TUVdMN2Aq0Kk5uhm0ZwLERjd u8bfFg9mQDX2RnHFFTXWBFLSKXNdewiAbLhOiCcFmvZ8IdS5yOskyXbGDYHMYsY15nRt 1VnG4FR0j7+7cDD8N17T0eeqr3v3Z/kirrs88z6ZGYxOmF8zzY5JhL+EVl8N9eeh8jyM rxj8FPV0ToXokgr/R2B/mT7xQbvGEWa3iTTG6/WWkxnlRUK+RkSld+W4016Sb6uMptJ1 Ojeg== X-Gm-Message-State: ACgBeo1K1g8kGrvcd7DT3Q4oKlteb0vbiYXLpWYOq+XuRVkXzYd9Psnz 7nwOzo3aN7kPGKmPdeePRDfpmlydypOHeQHx2gK2rVoszIK6VRCsjt5vsYu1AkL4XJ2IlXG+qNg pz1ke6bdFRu31o0dDH/7Q X-Google-Smtp-Source: AA6agR57KkNIgUFHWPdFiQWyoY7oyjG1ZvVgnOFqYQ9kJCo94JBJEo43qz2wa5ev7XB45jgLE1aOSNe2TR4= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:200:1bfc:e7ee:6530:4449]) (user=surenb job=sendgmr) by 2002:a0d:ff86:0:b0:341:5844:5527 with SMTP id p128-20020a0dff86000000b0034158445527mr14770867ywf.504.1662053734514; Thu, 01 Sep 2022 10:35:34 -0700 (PDT) Date: Thu, 1 Sep 2022 10:34:53 -0700 In-Reply-To: <20220901173516.702122-1-surenb@google.com> Mime-Version: 1.0 References: <20220901173516.702122-1-surenb@google.com> X-Mailer: git-send-email 2.37.2.789.g6183377224-goog Message-ID: <20220901173516.702122-6-surenb@google.com> Subject: [RFC PATCH RESEND 05/28] mm: add per-VMA lock and helper functions to control it From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: 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, 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, rientjes@google.com, axelrasmussen@google.com, joelaf@google.com, minchan@google.com, surenb@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 X-ccpol: medium Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Introduce a per-VMA rw_semaphore to be used during page fault handling instead of mmap_lock. Because there are cases when multiple VMAs need to be exclusively locked during VMA tree modifications, instead of the usual lock/unlock patter we mark a VMA as locked by taking per-VMA lock exclusively and setting vma->lock_seq to the current mm->lock_seq. When mmap_write_lock holder is done with all modifications and drops mmap_lock, it will increment mm->lock_seq, effectively unlocking all VMAs marked as locked. Signed-off-by: Suren Baghdasaryan Reviewed-by: Laurent Dufour --- include/linux/mm.h | 78 +++++++++++++++++++++++++++++++++++++++ include/linux/mm_types.h | 7 ++++ include/linux/mmap_lock.h | 13 +++++++ kernel/fork.c | 4 ++ mm/init-mm.c | 3 ++ 5 files changed, 105 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 7d322a979455..476bf936c5f0 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -611,6 +611,83 @@ struct vm_operations_struct { unsigned long addr); }; =20 +#ifdef CONFIG_PER_VMA_LOCK +static inline void vma_init_lock(struct vm_area_struct *vma) +{ + init_rwsem(&vma->lock); + vma->vm_lock_seq =3D -1; +} + +static inline void vma_mark_locked(struct vm_area_struct *vma) +{ + int mm_lock_seq; + + mmap_assert_write_locked(vma->vm_mm); + + /* + * current task is holding mmap_write_lock, both vma->vm_lock_seq and + * mm->mm_lock_seq can't be concurrently modified. + */ + mm_lock_seq =3D READ_ONCE(vma->vm_mm->mm_lock_seq); + if (vma->vm_lock_seq =3D=3D mm_lock_seq) + return; + + down_write(&vma->lock); + vma->vm_lock_seq =3D mm_lock_seq; + up_write(&vma->lock); +} + +static inline bool vma_read_trylock(struct vm_area_struct *vma) +{ + if (unlikely(down_read_trylock(&vma->lock) =3D=3D 0)) + return false; + + /* + * Overflow might produce false locked result but it's not critical. + * False unlocked result is critical but is impossible because we + * modify and check vma->vm_lock_seq under vma->lock protection and + * mm->mm_lock_seq modification invalidates all existing locks. + */ + if (vma->vm_lock_seq =3D=3D READ_ONCE(vma->vm_mm->mm_lock_seq)) { + up_read(&vma->lock); + return false; + } + return true; +} + +static inline void vma_read_unlock(struct vm_area_struct *vma) +{ + up_read(&vma->lock); +} + +static inline void vma_assert_locked(struct vm_area_struct *vma) +{ + lockdep_assert_held(&vma->lock); + VM_BUG_ON_VMA(!rwsem_is_locked(&vma->lock), vma); +} + +static inline void vma_assert_write_locked(struct vm_area_struct *vma, int= pos) +{ + mmap_assert_write_locked(vma->vm_mm); + /* + * current task is holding mmap_write_lock, both vma->vm_lock_seq and + * mm->mm_lock_seq can't be concurrently modified. + */ + VM_BUG_ON_VMA(vma->vm_lock_seq !=3D READ_ONCE(vma->vm_mm->mm_lock_seq), v= ma); +} + +#else /* CONFIG_PER_VMA_LOCK */ + +static inline void vma_init_lock(struct vm_area_struct *vma) {} +static inline void vma_mark_locked(struct vm_area_struct *vma) {} +static inline bool vma_read_trylock(struct vm_area_struct *vma) + { return false; } +static inline void vma_read_unlock(struct vm_area_struct *vma) {} +static inline void vma_assert_locked(struct vm_area_struct *vma) {} +static inline void vma_assert_write_locked(struct vm_area_struct *vma, int= pos) {} + +#endif /* CONFIG_PER_VMA_LOCK */ + static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *= mm) { static const struct vm_operations_struct dummy_vm_ops =3D {}; @@ -619,6 +696,7 @@ static inline void vma_init(struct vm_area_struct *vma,= struct mm_struct *mm) vma->vm_mm =3D mm; vma->vm_ops =3D &dummy_vm_ops; INIT_LIST_HEAD(&vma->anon_vma_chain); + vma_init_lock(vma); } =20 static inline void vma_set_anonymous(struct vm_area_struct *vma) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index bed25ef7c994..6a03f59c1e78 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -486,6 +486,10 @@ struct vm_area_struct { struct mempolicy *vm_policy; /* NUMA policy for the VMA */ #endif struct vm_userfaultfd_ctx vm_userfaultfd_ctx; +#ifdef CONFIG_PER_VMA_LOCK + struct rw_semaphore lock; + int vm_lock_seq; +#endif } __randomize_layout; =20 struct kioctx_table; @@ -567,6 +571,9 @@ struct mm_struct { * init_mm.mmlist, and are protected * by mmlist_lock */ +#ifdef CONFIG_PER_VMA_LOCK + int mm_lock_seq; +#endif =20 =20 unsigned long hiwater_rss; /* High-watermark of RSS usage */ diff --git a/include/linux/mmap_lock.h b/include/linux/mmap_lock.h index e49ba91bb1f0..a391ae226564 100644 --- a/include/linux/mmap_lock.h +++ b/include/linux/mmap_lock.h @@ -72,6 +72,17 @@ static inline void mmap_assert_write_locked(struct mm_st= ruct *mm) VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm); } =20 +#ifdef CONFIG_PER_VMA_LOCK +static inline void vma_mark_unlocked_all(struct mm_struct *mm) +{ + mmap_assert_write_locked(mm); + /* No races during update due to exclusive mmap_lock being held */ + WRITE_ONCE(mm->mm_lock_seq, mm->mm_lock_seq + 1); +} +#else +static inline void vma_mark_unlocked_all(struct mm_struct *mm) {} +#endif + static inline void mmap_init_lock(struct mm_struct *mm) { init_rwsem(&mm->mmap_lock); @@ -114,12 +125,14 @@ static inline bool mmap_write_trylock(struct mm_struc= t *mm) static inline void mmap_write_unlock(struct mm_struct *mm) { __mmap_lock_trace_released(mm, true); + vma_mark_unlocked_all(mm); up_write(&mm->mmap_lock); } =20 static inline void mmap_write_downgrade(struct mm_struct *mm) { __mmap_lock_trace_acquire_returned(mm, false, true); + vma_mark_unlocked_all(mm); downgrade_write(&mm->mmap_lock); } =20 diff --git a/kernel/fork.c b/kernel/fork.c index 614872438393..bfab31ecd11e 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -475,6 +475,7 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struc= t *orig) */ *new =3D data_race(*orig); INIT_LIST_HEAD(&new->anon_vma_chain); + vma_init_lock(new); new->vm_next =3D new->vm_prev =3D NULL; dup_anon_vma_name(orig, new); } @@ -1130,6 +1131,9 @@ static struct mm_struct *mm_init(struct mm_struct *mm= , struct task_struct *p, seqcount_init(&mm->write_protect_seq); mmap_init_lock(mm); INIT_LIST_HEAD(&mm->mmlist); +#ifdef CONFIG_PER_VMA_LOCK + WRITE_ONCE(mm->mm_lock_seq, 0); +#endif mm_pgtables_bytes_init(mm); mm->map_count =3D 0; mm->locked_vm =3D 0; diff --git a/mm/init-mm.c b/mm/init-mm.c index fbe7844d0912..8399f90d631c 100644 --- a/mm/init-mm.c +++ b/mm/init-mm.c @@ -37,6 +37,9 @@ struct mm_struct init_mm =3D { .page_table_lock =3D __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock), .arg_lock =3D __SPIN_LOCK_UNLOCKED(init_mm.arg_lock), .mmlist =3D LIST_HEAD_INIT(init_mm.mmlist), +#ifdef CONFIG_PER_VMA_LOCK + .mm_lock_seq =3D 0, +#endif .user_ns =3D &init_user_ns, .cpu_bitmap =3D CPU_BITS_NONE, #ifdef CONFIG_IOMMU_SVA --=20 2.37.2.789.g6183377224-goog