From patchwork Fri Apr 18 17:49:59 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Suren Baghdasaryan X-Patchwork-Id: 882451 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6BC8B22578A for ; Fri, 18 Apr 2025 17:50:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744998623; cv=none; b=o1m5vuAp/JO8j/QJg9IEgZ04cITJJyeoFxxS2oxz1FRNakIPPIfhhJOuM7v/tvlSFAuvTE9OqqGYNEOXY1NsJYqE86l7uavyKmZnkteUoBf1oIaELoMSJG3ukr0TcBjI1piK2/nO2BeoSODPUYrzC7N/VAxvHN6lIJ+oJ1Jf7Pk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744998623; c=relaxed/simple; bh=sKg7f329Zs3O82Sqp+e8qxPxOZ/t4mW6H6H8eA3C9lA=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=pALU2TB9p3znABAOAv04qbkkXIkA1f5/mwyHs3lRb10lbjFQLaO9iDfzchncirt7eNdF1qaAEwVv6XQtAR0YuAm48u3kSJkGZKEZPTPoteitYv1nlc20F2N++rHwkLU2w0zJwWYtUzfRT1KcnNTPLuutAK6LrtalZXfCx3IEiZA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=AZqb7kPy; arc=none smtp.client-ip=209.85.214.201 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--surenb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="AZqb7kPy" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-224191d9228so27164335ad.3 for ; Fri, 18 Apr 2025 10:50:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1744998621; x=1745603421; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=GDNsq3YX7eW5e3apKRRmkWWvDDDuWE0xbjvQjwBgCsE=; b=AZqb7kPy/oRHhVyW00nvGWJKO6OQN2L0ukhaFp7qXyDPXhS+GR+w5FMSEtkQa/zcZZ dw+GmEy1385+mbG1El3VlhBm2rn6nwWEwg8YHBz3fKKQPMecS+cJiz7tHTUDW0Qsqj9t mE4If8izxzVDtWRnhsr+DEHlGTFNgFTEwADD41JxWYc+VnaDBqUST4v0Yw1hdqY0f2gq ny+ySQxHj3mGDwHrK2kzMl83Vm/5IzHPJE3USmbUKHK2TjEwu1VvTdMl3yDgwrVlNqjC Px0Ezpd8E/c730HRLMwGA+zNHLeiZVxDYWjAAzwkMnWb5aVJ57Kr2hbR0jlJ1M/R+U2G qoSw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1744998621; x=1745603421; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=GDNsq3YX7eW5e3apKRRmkWWvDDDuWE0xbjvQjwBgCsE=; b=aANTK9WjNcvmpBzzk0z92g4jFeyoiFMqZm6d5dilmT8NlWLCHvx0BZirBJkr1hgsIL cU7fMyqFHgNFszeM8k39XCC0/Tl3pnRwH+Er4hrqVFcy5Mg7wVdzIit3h4DeGV2Mxhr1 md/rzxYfIa6+D51uNuA5X52t/bnbt4/pKkKL5uxewBbu/HqPmtq82yzDtA5rkoJCVoYn RemFmdyPMy04kJACuIZewK4pGrpeXE5L7MnevS6BZRiwDYlgBd5ORWWa0xuIxTw2kBiE TeMkagH5dthfzgr1/dP8+AB1tJ/IqQ/ZRN+gM7MiBMfTfO1lYWTOhsx4ijy/aHz3hu6j zHrg== X-Forwarded-Encrypted: i=1; AJvYcCXbp04jPRtl4OJOUljHTJC+37Gjt0DPbMn89sW+LeAtOzfh7OeyV/kecN9Bp2xsXyhAx8serBzGwbNWeF2Ykxc=@vger.kernel.org X-Gm-Message-State: AOJu0YyEWxBkX53D6viBDNDfQKfig+AZL98YH6jBDV0g9+kDUTowH8tr tnmmk1Tr3PyeEdQ0k4MKfFLlhEDELIpk1QmFCQPwFRxnBK0QPAflKdfNmMEe9BA2RNBArAMDKxx jFg== X-Google-Smtp-Source: AGHT+IH4SzFcgriEZeEyINeEOYHsKsBduZvh1a8UF65TGxe4ng4DHNhTgv3meBOCFXGKpW1iswhVW2S93bM= X-Received: from plrd9.prod.google.com ([2002:a17:902:aa89:b0:223:225b:3d83]) (user=surenb job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:19cc:b0:224:24d5:f20a with SMTP id d9443c01a7336-22c53620caamr57870345ad.48.1744998620802; Fri, 18 Apr 2025 10:50:20 -0700 (PDT) Date: Fri, 18 Apr 2025 10:49:59 -0700 In-Reply-To: <20250418174959.1431962-1-surenb@google.com> Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250418174959.1431962-1-surenb@google.com> X-Mailer: git-send-email 2.49.0.805.g082f7c87e0-goog Message-ID: <20250418174959.1431962-9-surenb@google.com> Subject: [PATCH v3 8/8] mm/maps: execute PROCMAP_QUERY ioctl under RCU From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, david@redhat.com, vbabka@suse.cz, peterx@redhat.com, jannh@google.com, hannes@cmpxchg.org, mhocko@kernel.org, paulmck@kernel.org, shuah@kernel.org, adobriyan@gmail.com, brauner@kernel.org, josef@toxicpanda.com, yebin10@huawei.com, linux@weissschuh.net, willy@infradead.org, osalvador@suse.de, andrii@kernel.org, ryan.roberts@arm.com, christophe.leroy@csgroup.eu, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, surenb@google.com Utilize speculative vma lookup to find and snapshot a vma without taking mmap_lock during PROCMAP_QUERY ioctl execution. Concurrent address space modifications are detected and the lookup is retried. While we take the mmap_lock for reading during such contention, we do that momentarily only to record new mm_wr_seq counter. This change is designed to reduce mmap_lock contention and prevent PROCMAP_QUERY ioctl calls (often a low priority task, such as monitoring/data collection services) from blocking address space updates. Signed-off-by: Suren Baghdasaryan --- fs/proc/task_mmu.c | 63 ++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 55 insertions(+), 8 deletions(-) diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index f9d50a61167c..28b975ddff26 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -525,9 +525,53 @@ static int pid_maps_open(struct inode *inode, struct file *file) PROCMAP_QUERY_VMA_FLAGS \ ) -static int query_vma_setup(struct mm_struct *mm) +#ifdef CONFIG_PER_VMA_LOCK + +static int query_vma_setup(struct proc_maps_private *priv) { - return mmap_read_lock_killable(mm); + if (!mmap_lock_speculate_try_begin(priv->mm, &priv->mm_wr_seq)) { + int ret = mmap_read_lock_killable(priv->mm); + + if (ret) + return ret; + + /* mmap_lock_speculate_try_begin() succeeds when holding mmap_read_lock */ + mmap_lock_speculate_try_begin(priv->mm, &priv->mm_wr_seq); + mmap_read_unlock(priv->mm); + } + + memset(&priv->vma_copy, 0, sizeof(priv->vma_copy)); + rcu_read_lock(); + + return 0; +} + +static void query_vma_teardown(struct mm_struct *mm, struct vm_area_struct *vma) +{ + rcu_read_unlock(); +} + +static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_private *priv, + unsigned long addr) +{ + struct vm_area_struct *vma; + + vma_iter_init(&priv->iter, priv->mm, addr); + vma = vma_next(&priv->iter); + if (!vma) + return NULL; + + vma = get_stable_vma(vma, priv, addr); + + /* The only possible error is EINTR, just pretend we found nothing */ + return IS_ERR(vma) ? NULL : vma; +} + +#else /* CONFIG_PER_VMA_LOCK */ + +static int query_vma_setup(struct proc_maps_private *priv) +{ + return mmap_read_lock_killable(priv->mm); } static void query_vma_teardown(struct mm_struct *mm, struct vm_area_struct *vma) @@ -535,18 +579,21 @@ static void query_vma_teardown(struct mm_struct *mm, struct vm_area_struct *vma) mmap_read_unlock(mm); } -static struct vm_area_struct *query_vma_find_by_addr(struct mm_struct *mm, unsigned long addr) +static struct vm_area_struct *query_vma_find_by_addr(struct proc_maps_private *priv, + unsigned long addr) { - return find_vma(mm, addr); + return find_vma(priv->mm, addr); } -static struct vm_area_struct *query_matching_vma(struct mm_struct *mm, +#endif /* CONFIG_PER_VMA_LOCK */ + +static struct vm_area_struct *query_matching_vma(struct proc_maps_private *priv, unsigned long addr, u32 flags) { struct vm_area_struct *vma; next_vma: - vma = query_vma_find_by_addr(mm, addr); + vma = query_vma_find_by_addr(priv, addr); if (!vma) goto no_vma; @@ -622,13 +669,13 @@ static int do_procmap_query(struct proc_maps_private *priv, void __user *uarg) if (!mm || !mmget_not_zero(mm)) return -ESRCH; - err = query_vma_setup(mm); + err = query_vma_setup(priv); if (err) { mmput(mm); return err; } - vma = query_matching_vma(mm, karg.query_addr, karg.query_flags); + vma = query_matching_vma(priv, karg.query_addr, karg.query_flags); if (IS_ERR(vma)) { err = PTR_ERR(vma); vma = NULL;