From mboxrd@z Thu Jan 1 00:00:00 1970 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 7F04EC7618D for ; Thu, 6 Apr 2023 03:03:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235131AbjDFDDx (ORCPT ); Wed, 5 Apr 2023 23:03:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57424 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234983AbjDFDDi (ORCPT ); Wed, 5 Apr 2023 23:03:38 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E3C683E4 for ; Wed, 5 Apr 2023 20:03:36 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 94B8264125 for ; Thu, 6 Apr 2023 03:03:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED54BC433D2; Thu, 6 Apr 2023 03:03:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1680750215; bh=BwSt8vJpR2EWI8EGqWLQsok8fk2tAk8klz7sryj4Mj0=; h=Date:To:From:Subject:From; b=fPu+HEh8h4Ko0HpFMOrPqGjtjw59MOI+cBLkdvnd+oLX6CDmkQxB6cEo4q/u7JUaM D7ZdTAU/R73crZVYMI2rXibxnBs8U00d11Kj8MCfsH0MffzW3AqzaRPpDMSaEoHo7y KAXWjRSisSsNhbjzbaHM8f/oT+0Bh0VSORPk72JQ= Date: Wed, 05 Apr 2023 20:03:34 -0700 To: mm-commits@vger.kernel.org, surenb@google.com, akpm@linux-foundation.org From: Andrew Morton Subject: [merged mm-stable] mm-add-per-vma-lock-and-helper-functions-to-control-it.patch removed from -mm tree Message-Id: <20230406030334.ED54BC433D2@smtp.kernel.org> Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org The quilt patch titled Subject: mm: add per-VMA lock and helper functions to control it has been removed from the -mm tree. Its filename was mm-add-per-vma-lock-and-helper-functions-to-control-it.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: Suren Baghdasaryan Subject: mm: add per-VMA lock and helper functions to control it Date: Mon, 27 Feb 2023 09:36:11 -0800 Introduce per-VMA locking. The lock implementation relies on a per-vma and per-mm sequence counters to note exclusive locking: - read lock - (implemented by vma_start_read) requires the vma (vm_lock_seq) and mm (mm_lock_seq) sequence counters to differ. If they match then there must be a vma exclusive lock held somewhere. - read unlock - (implemented by vma_end_read) is a trivial vma->lock unlock. - write lock - (vma_start_write) requires the mmap_lock to be held exclusively and the current mm counter is assigned to the vma counter. This will allow multiple vmas to be locked under a single mmap_lock write lock (e.g. during vma merging). The vma counter is modified under exclusive vma lock. - write unlock - (vma_end_write_all) is a batch release of all vma locks held. It doesn't pair with a specific vma_start_write! It is done before exclusive mmap_lock is released by incrementing mm sequence counter (mm_lock_seq). - write downgrade - if the mmap_lock is downgraded to the read lock, all vma write locks are released as well (effectivelly same as write unlock). Link: https://lkml.kernel.org/r/20230227173632.3292573-13-surenb@google.com Signed-off-by: Suren Baghdasaryan Signed-off-by: Andrew Morton --- include/linux/mm.h | 82 ++++++++++++++++++++++++++++++++++++ include/linux/mm_types.h | 8 +++ include/linux/mmap_lock.h | 13 +++++ kernel/fork.c | 4 + mm/init-mm.c | 3 + 5 files changed, 110 insertions(+) --- a/include/linux/mmap_lock.h~mm-add-per-vma-lock-and-helper-functions-to-control-it +++ a/include/linux/mmap_lock.h @@ -72,6 +72,17 @@ static inline void mmap_assert_write_loc VM_BUG_ON_MM(!rwsem_is_locked(&mm->mmap_lock), mm); } +#ifdef CONFIG_PER_VMA_LOCK +static inline void vma_end_write_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_end_write_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(st static inline void mmap_write_unlock(struct mm_struct *mm) { __mmap_lock_trace_released(mm, true); + vma_end_write_all(mm); up_write(&mm->mmap_lock); } static inline void mmap_write_downgrade(struct mm_struct *mm) { __mmap_lock_trace_acquire_returned(mm, false, true); + vma_end_write_all(mm); downgrade_write(&mm->mmap_lock); } --- a/include/linux/mm.h~mm-add-per-vma-lock-and-helper-functions-to-control-it +++ a/include/linux/mm.h @@ -624,6 +624,87 @@ struct vm_operations_struct { unsigned long addr); }; +#ifdef CONFIG_PER_VMA_LOCK +static inline void vma_init_lock(struct vm_area_struct *vma) +{ + init_rwsem(&vma->lock); + vma->vm_lock_seq = -1; +} + +/* + * Try to read-lock a vma. The function is allowed to occasionally yield false + * locked result to avoid performance overhead, in which case we fall back to + * using mmap_lock. The function should never yield false unlocked result. + */ +static inline bool vma_start_read(struct vm_area_struct *vma) +{ + /* Check before locking. A race might cause false locked result. */ + if (vma->vm_lock_seq == READ_ONCE(vma->vm_mm->mm_lock_seq)) + return false; + + if (unlikely(down_read_trylock(&vma->lock) == 0)) + return false; + + /* + * Overflow might produce false locked result. + * False unlocked result 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 (unlikely(vma->vm_lock_seq == READ_ONCE(vma->vm_mm->mm_lock_seq))) { + up_read(&vma->lock); + return false; + } + return true; +} + +static inline void vma_end_read(struct vm_area_struct *vma) +{ + rcu_read_lock(); /* keeps vma alive till the end of up_read */ + up_read(&vma->lock); + rcu_read_unlock(); +} + +static inline void vma_start_write(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 = READ_ONCE(vma->vm_mm->mm_lock_seq); + if (vma->vm_lock_seq == mm_lock_seq) + return; + + down_write(&vma->lock); + vma->vm_lock_seq = mm_lock_seq; + up_write(&vma->lock); +} + +static inline void vma_assert_write_locked(struct vm_area_struct *vma) +{ + 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 != READ_ONCE(vma->vm_mm->mm_lock_seq), vma); +} + +#else /* CONFIG_PER_VMA_LOCK */ + +static inline void vma_init_lock(struct vm_area_struct *vma) {} +static inline bool vma_start_read(struct vm_area_struct *vma) + { return false; } +static inline void vma_end_read(struct vm_area_struct *vma) {} +static inline void vma_start_write(struct vm_area_struct *vma) {} +static inline void vma_assert_write_locked(struct vm_area_struct *vma) {} + +#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 = {}; @@ -632,6 +713,7 @@ static inline void vma_init(struct vm_ar vma->vm_mm = mm; vma->vm_ops = &dummy_vm_ops; INIT_LIST_HEAD(&vma->anon_vma_chain); + vma_init_lock(vma); } /* Use when VMA is not part of the VMA tree and needs no locking */ --- a/include/linux/mm_types.h~mm-add-per-vma-lock-and-helper-functions-to-control-it +++ a/include/linux/mm_types.h @@ -503,6 +503,11 @@ struct vm_area_struct { vm_flags_t __private __vm_flags; }; +#ifdef CONFIG_PER_VMA_LOCK + int vm_lock_seq; + struct rw_semaphore lock; +#endif + /* * For areas with an address space and backing store, * linkage into the address_space->i_mmap interval tree. @@ -639,6 +644,9 @@ struct mm_struct { * init_mm.mmlist, and are protected * by mmlist_lock */ +#ifdef CONFIG_PER_VMA_LOCK + int mm_lock_seq; +#endif unsigned long hiwater_rss; /* High-watermark of RSS usage */ --- a/kernel/fork.c~mm-add-per-vma-lock-and-helper-functions-to-control-it +++ a/kernel/fork.c @@ -474,6 +474,7 @@ struct vm_area_struct *vm_area_dup(struc */ data_race(memcpy(new, orig, sizeof(*new))); INIT_LIST_HEAD(&new->anon_vma_chain); + vma_init_lock(new); dup_anon_vma_name(orig, new); } return new; @@ -1208,6 +1209,9 @@ static struct mm_struct *mm_init(struct seqcount_init(&mm->write_protect_seq); mmap_init_lock(mm); INIT_LIST_HEAD(&mm->mmlist); +#ifdef CONFIG_PER_VMA_LOCK + mm->mm_lock_seq = 0; +#endif mm_pgtables_bytes_init(mm); mm->map_count = 0; mm->locked_vm = 0; --- a/mm/init-mm.c~mm-add-per-vma-lock-and-helper-functions-to-control-it +++ a/mm/init-mm.c @@ -37,6 +37,9 @@ struct mm_struct init_mm = { .page_table_lock = __SPIN_LOCK_UNLOCKED(init_mm.page_table_lock), .arg_lock = __SPIN_LOCK_UNLOCKED(init_mm.arg_lock), .mmlist = LIST_HEAD_INIT(init_mm.mmlist), +#ifdef CONFIG_PER_VMA_LOCK + .mm_lock_seq = 0, +#endif .user_ns = &init_user_ns, .cpu_bitmap = CPU_BITS_NONE, #ifdef CONFIG_IOMMU_SVA _ Patches currently in -mm which might be from surenb@google.com are