From patchwork Wed Jun 28 07:17:59 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Suren Baghdasaryan X-Patchwork-Id: 13295379 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 2D206EB64DA for ; Wed, 28 Jun 2023 08:38:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234252AbjF1Iiy (ORCPT ); Wed, 28 Jun 2023 04:38:54 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42954 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235160AbjF1IfV (ORCPT ); Wed, 28 Jun 2023 04:35:21 -0400 Received: from mail-qk1-x749.google.com (mail-qk1-x749.google.com [IPv6:2607:f8b0:4864:20::749]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5767049DF for ; Wed, 28 Jun 2023 01:26:53 -0700 (PDT) Received: by mail-qk1-x749.google.com with SMTP id af79cd13be357-765986c0521so312340485a.3 for ; Wed, 28 Jun 2023 01:26:53 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1687940812; x=1690532812; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=b7MqQHJHdH35CYJ6Jb1zpJ4/eRYK1pcerh43dShkH+M=; b=LA2E19xf7pdXj42A1ExmJSbdMIaIbsn7NWmS9urFjUy/mNI98IsTbKUKdeui0/yaYA hA8WhjLz+tlG2LQrbUqRv+bCNiqRBz3Ow/Ir38THLz/uOLDlktWQjDRYkOGrClthKIH8 88rADAgRwM4a7SvKH7Tc5/wsUsonQMNhX/qboDJQr3bvMfWE8nrJr/cN7CKEQZyQ/zl+ PKg1CZTu0m3nXicuafs4hHYj1qjQDcWTs5N+b4z1WGmFzatznKMugkaipKlHv8d6x/Mb 25StywCuDNj2wyw70TU82osLYLvglPWcSxaCp4h+fhOxWdoCf5jPI34AUXXQTcU+f1eF e3LA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1687940812; x=1690532812; 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=b7MqQHJHdH35CYJ6Jb1zpJ4/eRYK1pcerh43dShkH+M=; b=Ux1grZ/xCoNohR+4RKTXBA8glYyPNDWubQVCWR9vkPott8lQz+HqBJWNsk5Qls+0fF 0C1lq6lsxjuEFLtzKiDGyNLgDfAC031np4ftx0uz/ipDJI/s5QRgp2veEzkN+R2ase5y z/CJFX+O6djzq5AEE04R7MoSdJoxANxYqoTt2tsYzn6RtsLvRM6qnXA6q7bXgLNo+9r3 qwN2idwjDeO05rpTzsP2Wai2q8fTbHQEqtppE/Z7nChtH1XgOxT/YRteO1QHHJlodpQF Z36oZbiH/BfjdKyev8VaydJqFcQwNnNeWhLC5dhG6lPnkAcUhXf62wmIXA/g5IZSRKf8 lFlA== X-Gm-Message-State: AC+VfDz5dUhyWGuqyfJGiJLnBIEYluMieiQkBNoZiuePWtf3ADaSiYXD OU9Zq4cX9k2NNFt7roztOgO0LqdLrS4= X-Google-Smtp-Source: ACHHUZ5p7K5vwu3GLTcOloeUXHu3uFg6BFvaVURIKfx6u7AbyQoKOvh6cJprBsCrY0QmdnAunXGn4WazRWI= X-Received: from surenb-desktop.mtv.corp.google.com ([2620:15c:211:201:6664:8bd3:57fd:c83a]) (user=surenb job=sendgmr) by 2002:a81:af22:0:b0:559:c032:eb5e with SMTP id n34-20020a81af22000000b00559c032eb5emr14112427ywh.1.1687936696048; Wed, 28 Jun 2023 00:18:16 -0700 (PDT) Date: Wed, 28 Jun 2023 00:17:59 -0700 In-Reply-To: <20230628071800.544800-1-surenb@google.com> Mime-Version: 1.0 References: <20230628071800.544800-1-surenb@google.com> X-Mailer: git-send-email 2.41.0.162.gfafddb0af9-goog Message-ID: <20230628071800.544800-6-surenb@google.com> Subject: [PATCH v4 5/6] mm: handle swap page faults under per-VMA lock 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, peterx@redhat.com, ying.huang@intel.com, david@redhat.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, pasha.tatashin@soleen.com, surenb@google.com, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@android.com Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org When page fault is handled under per-VMA lock protection, all swap page faults are retried with mmap_lock because folio_lock_or_retry has to drop and reacquire mmap_lock if folio could not be immediately locked. Follow the same pattern as mmap_lock to drop per-VMA lock when waiting for folio and retrying once folio is available. With this obstacle removed, enable do_swap_page to operate under per-VMA lock protection. Drivers implementing ops->migrate_to_ram might still rely on mmap_lock, therefore we have to fall back to mmap_lock in that particular case. Note that the only time do_swap_page calls synchronous swap_readpage is when SWP_SYNCHRONOUS_IO is set, which is only set for QUEUE_FLAG_SYNCHRONOUS devices: brd, zram and nvdimms (both btt and pmem). Therefore we don't sleep in this path, and there's no need to drop the mmap or per-VMA lock. Signed-off-by: Suren Baghdasaryan Acked-by: Peter Xu --- mm/filemap.c | 25 ++++++++++++++++--------- mm/memory.c | 16 ++++++++++------ 2 files changed, 26 insertions(+), 15 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 52bcf12dcdbf..7ee078e1a0d2 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1699,31 +1699,38 @@ static int __folio_lock_async(struct folio *folio, struct wait_page_queue *wait) return ret; } +static void release_fault_lock(struct vm_fault *vmf) +{ + if (vmf->flags & FAULT_FLAG_VMA_LOCK) + vma_end_read(vmf->vma); + else + mmap_read_unlock(vmf->vma->vm_mm); +} + /* * Return values: * 0 - folio is locked. * VM_FAULT_RETRY - folio is not locked. - * 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. + * mmap_lock or per-VMA lock has been released (mmap_read_unlock() or + * vma_end_read()), unless flags had both FAULT_FLAG_ALLOW_RETRY and + * FAULT_FLAG_RETRY_NOWAIT set, in which case the lock is still held. * * If neither ALLOW_RETRY nor KILLABLE are set, will always return 0 - * with the folio locked and the mmap_lock unperturbed. + * with the folio locked and the mmap_lock/per-VMA lock is left unperturbed. */ vm_fault_t __folio_lock_or_retry(struct folio *folio, struct vm_fault *vmf) { - struct mm_struct *mm = vmf->vma->vm_mm; unsigned int flags = vmf->flags; if (fault_flag_allow_retry_first(flags)) { /* - * CAUTION! In this case, mmap_lock is not released - * even though return VM_FAULT_RETRY. + * CAUTION! In this case, mmap_lock/per-VMA lock is not + * released even though returning VM_FAULT_RETRY. */ if (flags & FAULT_FLAG_RETRY_NOWAIT) return VM_FAULT_RETRY; - mmap_read_unlock(mm); + release_fault_lock(vmf); if (flags & FAULT_FLAG_KILLABLE) folio_wait_locked_killable(folio); else @@ -1735,7 +1742,7 @@ vm_fault_t __folio_lock_or_retry(struct folio *folio, struct vm_fault *vmf) ret = __folio_lock_killable(folio); if (ret) { - mmap_read_unlock(mm); + release_fault_lock(vmf); return VM_FAULT_RETRY; } } else { diff --git a/mm/memory.c b/mm/memory.c index 345080052003..76c7907e7286 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3712,12 +3712,6 @@ 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; - vma_end_read(vma); - goto out; - } - entry = pte_to_swp_entry(vmf->orig_pte); if (unlikely(non_swap_entry(entry))) { if (is_migration_entry(entry)) { @@ -3727,6 +3721,16 @@ 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. + */ + vma_end_read(vma); + 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);