From patchwork Mon Jun 24 21:01:05 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jason Gunthorpe X-Patchwork-Id: 11014945 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1537D14BB for ; Tue, 25 Jun 2019 07:30:35 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0147C2853C for ; Tue, 25 Jun 2019 07:30:35 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id E9B3628723; Tue, 25 Jun 2019 07:30:34 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 5E5F5285CD for ; Tue, 25 Jun 2019 07:30:34 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id CDB486E07F; Tue, 25 Jun 2019 07:28:32 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail-wr1-x442.google.com (mail-wr1-x442.google.com [IPv6:2a00:1450:4864:20::442]) by gabe.freedesktop.org (Postfix) with ESMTPS id DB64189DE3 for ; Mon, 24 Jun 2019 21:02:08 +0000 (UTC) Received: by mail-wr1-x442.google.com with SMTP id f15so5491803wrp.2 for ; Mon, 24 Jun 2019 14:02:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=tsR/80TrTiUsWjQJpDlrT4mzZAmfUfoSI9FV/A0UaHU=; b=U22VvpY0pIivJR7F5EZoDM0n8mGLqLnqB+hQ/sHB+LbDIVycOioc2dNiBB7iHpdBda gd72GzQsGq/E052aWtOD3t1qewg0znOV9qd5rRmCk10cz5wy3t1yuMiQPQ65zdeWw+BC nPnkHJYTIGBD7Z5/8VfAu1F9FOxSWKVt8o2mTVSJU0+JHXSInb1Ynkw6K5wCrw81PSXr tMMzKwkJ/XWrECt+3+ru3x1+RuvD/i32rJXDEX708YWi5q+J1t9JYelfffE207o0/1NE tRxYqrVKja9/B5ozilp6CQr8ak8yNzZcYHOMTiQ75+wRs1fffu4A+Ztl9DOCAvGzHJLy fQCg== X-Gm-Message-State: APjAAAVj8RLENw5ItBCkLBPmCeVMK2sb1ZaG3XYPbbxP52Sh60MriCGb 3jEThw4xuuX8v6mPtmaXpnzchw== X-Google-Smtp-Source: APXvYqyzrTyoPhYHFWjo48jic83g1/CALuSvPyW3MCerg+RPA+Kf+K4POtxSR/W0sWmHBTVwQ3b5Mw== X-Received: by 2002:adf:a312:: with SMTP id c18mr18493691wrb.332.1561410127528; Mon, 24 Jun 2019 14:02:07 -0700 (PDT) Received: from ziepe.ca ([66.187.232.66]) by smtp.gmail.com with ESMTPSA id x11sm469692wmg.23.2019.06.24.14.02.02 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 24 Jun 2019 14:02:02 -0700 (PDT) Received: from jgg by jggl.ziepe.ca with local (Exim 4.90_1) (envelope-from ) id 1hfW6C-0001MW-VA; Mon, 24 Jun 2019 18:02:00 -0300 From: Jason Gunthorpe To: Jerome Glisse , Ralph Campbell , John Hubbard , Felix.Kuehling@amd.com Subject: [PATCH v4 hmm 07/12] mm/hmm: Hold on to the mmget for the lifetime of the range Date: Mon, 24 Jun 2019 18:01:05 -0300 Message-Id: <20190624210110.5098-8-jgg@ziepe.ca> X-Mailer: git-send-email 2.22.0 In-Reply-To: <20190624210110.5098-1-jgg@ziepe.ca> References: <20190624210110.5098-1-jgg@ziepe.ca> MIME-Version: 1.0 X-Mailman-Approved-At: Tue, 25 Jun 2019 07:27:07 +0000 X-Mailman-Original-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ziepe.ca; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=tsR/80TrTiUsWjQJpDlrT4mzZAmfUfoSI9FV/A0UaHU=; b=eEL2e+Rdsoiw+QWNMAoS5eOmfH9fxVT52iqVy3PrFcraDcKDNUukaiSHGjOkUDbkf4 8WHJYUyZdN7bf/y/Jstfu3A1fXcJitPxheR1/65Jv090zH+Eo5OQi1q+O4dWucKvZtrF Svhl2dcm8mOneehpNFXJVkZ7TYkrWa7CSn4DrBB60/QLpDJEVZeh45IqxTnVZkAWRCWG fnhCq6Ea5ODgJg75hQ/Xpeto43ZyjWXSU53z1FdntKD0LH/Otni2IWokQ2rJk9vV5gII L0dENrfxVOm9si6Xksz7dp0Ey4NfHgch3yvMfxoEZTAShU86NCM8h0UHtjz8kyN+4J6G MbOw== X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Andrea Arcangeli , Philip Yang , linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org, linux-mm@kvack.org, Jason Gunthorpe , dri-devel@lists.freedesktop.org, Ira Weiny , Christoph Hellwig , Ben Skeggs Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP From: Jason Gunthorpe Range functions like hmm_range_snapshot() and hmm_range_fault() call find_vma, which requires hodling the mmget() and the mmap_sem for the mm. Make this simpler for the callers by holding the mmget() inside the range for the lifetime of the range. Other functions that accept a range should only be called if the range is registered. This has the side effect of directly preventing hmm_release() from happening while a range is registered. That means range->dead cannot be false during the lifetime of the range, so remove dead and hmm_mirror_mm_is_alive() entirely. Signed-off-by: Jason Gunthorpe Reviewed-by: John Hubbard Reviewed-by: Ralph Campbell Reviewed-by: Christoph Hellwig Tested-by: Philip Yang --- v2: - Use Jerome's idea of just holding the mmget() for the range lifetime, rework the patch to use that as as simplification to remove dead in one step v3: - Use list_del_careful (Christoph) --- include/linux/hmm.h | 26 -------------------------- mm/hmm.c | 32 +++++++++++--------------------- 2 files changed, 11 insertions(+), 47 deletions(-) diff --git a/include/linux/hmm.h b/include/linux/hmm.h index 26e7c477490c4e..bf013e96525771 100644 --- a/include/linux/hmm.h +++ b/include/linux/hmm.h @@ -82,7 +82,6 @@ * @mirrors_sem: read/write semaphore protecting the mirrors list * @wq: wait queue for user waiting on a range invalidation * @notifiers: count of active mmu notifiers - * @dead: is the mm dead ? */ struct hmm { struct mm_struct *mm; @@ -95,7 +94,6 @@ struct hmm { wait_queue_head_t wq; struct rcu_head rcu; long notifiers; - bool dead; }; /* @@ -459,30 +457,6 @@ struct hmm_mirror { int hmm_mirror_register(struct hmm_mirror *mirror, struct mm_struct *mm); void hmm_mirror_unregister(struct hmm_mirror *mirror); -/* - * hmm_mirror_mm_is_alive() - test if mm is still alive - * @mirror: the HMM mm mirror for which we want to lock the mmap_sem - * Return: false if the mm is dead, true otherwise - * - * This is an optimization, it will not always accurately return false if the - * mm is dead; i.e., there can be false negatives (process is being killed but - * HMM is not yet informed of that). It is only intended to be used to optimize - * out cases where the driver is about to do something time consuming and it - * would be better to skip it if the mm is dead. - */ -static inline bool hmm_mirror_mm_is_alive(struct hmm_mirror *mirror) -{ - struct mm_struct *mm; - - if (!mirror || !mirror->hmm) - return false; - mm = READ_ONCE(mirror->hmm->mm); - if (mirror->hmm->dead || !mm) - return false; - - return true; -} - /* * Please see Documentation/vm/hmm.rst for how to use the range API. */ diff --git a/mm/hmm.c b/mm/hmm.c index 73c8af4827fe87..1eddda45cefae7 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -67,7 +67,6 @@ static struct hmm *hmm_get_or_create(struct mm_struct *mm) mutex_init(&hmm->lock); kref_init(&hmm->kref); hmm->notifiers = 0; - hmm->dead = false; hmm->mm = mm; hmm->mmu_notifier.ops = &hmm_mmu_notifier_ops; @@ -120,21 +119,16 @@ static void hmm_release(struct mmu_notifier *mn, struct mm_struct *mm) { struct hmm *hmm = container_of(mn, struct hmm, mmu_notifier); struct hmm_mirror *mirror; - struct hmm_range *range; /* Bail out if hmm is in the process of being freed */ if (!kref_get_unless_zero(&hmm->kref)) return; - /* Report this HMM as dying. */ - hmm->dead = true; - - /* Wake-up everyone waiting on any range. */ - mutex_lock(&hmm->lock); - list_for_each_entry(range, &hmm->ranges, list) - range->valid = false; - wake_up_all(&hmm->wq); - mutex_unlock(&hmm->lock); + /* + * Since hmm_range_register() holds the mmget() lock hmm_release() is + * prevented as long as a range exists. + */ + WARN_ON(!list_empty_careful(&hmm->ranges)); down_write(&hmm->mirrors_sem); mirror = list_first_entry_or_null(&hmm->mirrors, struct hmm_mirror, @@ -903,8 +897,8 @@ int hmm_range_register(struct hmm_range *range, range->start = start; range->end = end; - /* Check if hmm_mm_destroy() was call. */ - if (hmm->mm == NULL || hmm->dead) + /* Prevent hmm_release() from running while the range is valid */ + if (!mmget_not_zero(hmm->mm)) return -EFAULT; /* Initialize range to track CPU page table updates. */ @@ -942,11 +936,12 @@ void hmm_range_unregister(struct hmm_range *range) return; mutex_lock(&hmm->lock); - list_del(&range->list); + list_del_init(&range->list); mutex_unlock(&hmm->lock); /* Drop reference taken by hmm_range_register() */ range->valid = false; + mmput(hmm->mm); hmm_put(hmm); range->hmm = NULL; } @@ -974,10 +969,7 @@ long hmm_range_snapshot(struct hmm_range *range) struct vm_area_struct *vma; struct mm_walk mm_walk; - /* Check if hmm_mm_destroy() was call. */ - if (hmm->mm == NULL || hmm->dead) - return -EFAULT; - + lockdep_assert_held(&hmm->mm->mmap_sem); do { /* If range is no longer valid force retry. */ if (!range->valid) @@ -1072,9 +1064,7 @@ long hmm_range_fault(struct hmm_range *range, bool block) struct mm_walk mm_walk; int ret; - /* Check if hmm_mm_destroy() was call. */ - if (hmm->mm == NULL || hmm->dead) - return -EFAULT; + lockdep_assert_held(&hmm->mm->mmap_sem); do { /* If range is no longer valid force retry. */