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 CE9ADC77B7C for ; Mon, 1 May 2023 17:50:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232357AbjEARud (ORCPT ); Mon, 1 May 2023 13:50:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40374 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229871AbjEARuc (ORCPT ); Mon, 1 May 2023 13:50:32 -0400 Received: from mail-yw1-x114a.google.com (mail-yw1-x114a.google.com [IPv6:2607:f8b0:4864:20::114a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0737F10CC for ; Mon, 1 May 2023 10:50:31 -0700 (PDT) Received: by mail-yw1-x114a.google.com with SMTP id 00721157ae682-55a7d1f6914so11729617b3.1 for ; Mon, 01 May 2023 10:50:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1682963430; x=1685555430; h=cc:to:from:subject:message-id:mime-version:date:from:to:cc:subject :date:message-id:reply-to; bh=Vjmy9npoFS1ltTIQSU6SYKXLbdap9UrmwfWM+Y2ixPk=; b=dZCcwJncaHug3B8HkBJA8I4rogyge1EVTo4b3P8k7VcTSJVpEkICoBGsnhmO7W+EaQ BIxtz97RUXIfYWYlU1CJsKlwqGVGZ7x+vS+3P/rfb8ANuZUjR7SbifV/F6aSBN5z7ZRt /AMQ4KNfWlhXtFlPUDhe7iDHC11AWgJzvh0HYI/QSVDj28sAvGrMcNoB1jrqM2PiCRxV MKWY+ho9Y/9MhG5dJ5YP+l84eWwLxXehtDV3C+sB45yhtiKFovPsBc0ojtZnWpwnmUO1 OgbB8QClj+k71UJXHVn/U9WcLkhMORsNKUzA9GKVhmcWDmrnB5+OYkqWUJRZdkLT90UK DpmA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1682963430; x=1685555430; h=cc:to:from:subject:message-id:mime-version:date:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=Vjmy9npoFS1ltTIQSU6SYKXLbdap9UrmwfWM+Y2ixPk=; b=Opj3Ftwzsb9l1Bd2ZTaFEwuSLh/t2yo8+lIibBerZQnfxhlxitw92hahhFQTn28GKf dFnrCOUPe4kydwJ+AaLFZ8U0eD6apjcr2cjNJFUCKjJO6Rd5npP+xpwfssKND+6NZ3wZ Ru9Lw5MEh6H5vW6j8Ee5CmYs7wYnc5WnUse2b8xZdYqgXjkievh0TnFFXofzdH2FcQdo gfOCZ1PCwR37i0M7yxgvsFV/0ICBkmfjkjEzxcTQEAmZM4gcrJsISrs4Ab5/GiNMXnAD J75L1DKN1HTtGoQIUhKblTA42CCV49ZepJQ81kdvU1QEL20sP1cp+eva9yoa74VSHBTz TpHQ== X-Gm-Message-State: AC+VfDxi+5hFjWzLRBkgKV67MvUzxbfeIWHneW/MPkItTlDCnsB5lgM2 N2G9TNrVzCTzFHSWn4WRJ5Q3VCICmWM= X-Google-Smtp-Source: ACHHUZ64NZ3/9tsMewuAy2AdTfarKe08wL+z4DEH/85FRjs3ZEIBqL9XqLFWxrB85BCLpG0FPVBpKygFEUY= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:201:6d24:3efd:facc:7ac4]) (user=surenb job=sendgmr) by 2002:a81:9f09:0:b0:559:e830:60f1 with SMTP id s9-20020a819f09000000b00559e83060f1mr4687408ywn.8.1682963430249; Mon, 01 May 2023 10:50:30 -0700 (PDT) Date: Mon, 1 May 2023 10:50:23 -0700 Mime-Version: 1.0 X-Mailer: git-send-email 2.40.1.495.gc816e09b53d-goog Message-ID: <20230501175025.36233-1-surenb@google.com> Subject: [PATCH 1/3] mm: handle swap page faults under VMA lock if page is uncontended From: Suren Baghdasaryan To: akpm@linux-foundation.org Cc: willy@infradead.org, hannes@cmpxchg.org, mhocko@suse.com, josef@toxicpanda.com, jack@suse.cz, ldufour@linux.ibm.com, laurent.dufour@fr.ibm.com, michel@lespinasse.org, liam.howlett@oracle.com, jglisse@google.com, vbabka@suse.cz, minchan@google.com, dave@stgolabs.net, punit.agrawal@bytedance.com, lstoakes@gmail.com, hdanton@sina.com, apopple@nvidia.com, surenb@google.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org When page fault is handled under VMA lock protection, all swap page faults are retried with mmap_lock because folio_lock_or_retry implementation has to drop and reacquire mmap_lock if folio could not be immediately locked. Instead of retrying all swapped page faults, retry only when folio locking fails. Drivers implementing ops->migrate_to_ram might still rely on mmap_lock, therefore fall back to mmap_lock in this case. Signed-off-by: Suren Baghdasaryan --- mm/filemap.c | 6 ++++++ mm/memory.c | 14 +++++++++----- 2 files changed, 15 insertions(+), 5 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index a34abfe8c654..84f39114d4de 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1706,6 +1706,8 @@ static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait) * mmap_lock has been released (mmap_read_unlock(), unless flags had both * FAULT_FLAG_ALLOW_RETRY and FAULT_FLAG_RETRY_NOWAIT set, in * which case mmap_lock is still held. + * If flags had FAULT_FLAG_VMA_LOCK set, meaning the operation is performed + * with VMA lock only, the VMA lock is still held. * * If neither ALLOW_RETRY nor KILLABLE are set, will always return true * with the folio locked and the mmap_lock unperturbed. @@ -1713,6 +1715,10 @@ static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait) bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm, unsigned int flags) { + /* Can't do this if not holding mmap_lock */ + if (flags & FAULT_FLAG_VMA_LOCK) + return false; + if (fault_flag_allow_retry_first(flags)) { /* * CAUTION! In this case, mmap_lock is not released diff --git a/mm/memory.c b/mm/memory.c index f69fbc251198..41f45819a923 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3711,11 +3711,6 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) if (!pte_unmap_same(vmf)) goto out; - if (vmf->flags & FAULT_FLAG_VMA_LOCK) { - ret = VM_FAULT_RETRY; - goto out; - } - entry = pte_to_swp_entry(vmf->orig_pte); if (unlikely(non_swap_entry(entry))) { if (is_migration_entry(entry)) { @@ -3725,6 +3720,15 @@ vm_fault_t do_swap_page(struct vm_fault *vmf) vmf->page = pfn_swap_entry_to_page(entry); ret = remove_device_exclusive_entry(vmf); } else if (is_device_private_entry(entry)) { + if (vmf->flags & FAULT_FLAG_VMA_LOCK) { + /* + * migrate_to_ram is not yet ready to operate + * under VMA lock. + */ + ret |= VM_FAULT_RETRY; + goto out; + } + vmf->page = pfn_swap_entry_to_page(entry); vmf->pte = pte_offset_map_lock(vma->vm_mm, vmf->pmd, vmf->address, &vmf->ptl); -- 2.40.1.495.gc816e09b53d-goog