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 X-Spam-Level: X-Spam-Status: No, score=-13.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FDD4C433B4 for ; Fri, 23 Apr 2021 13:07:55 +0000 (UTC) Received: from ml01.01.org (ml01.01.org [198.145.21.10]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E38A8611AE for ; Fri, 23 Apr 2021 13:07:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E38A8611AE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvdimm-bounces@lists.01.org Received: from ml01.vlan13.01.org (localhost [IPv6:::1]) by ml01.01.org (Postfix) with ESMTP id 4FE40100EAAED; Fri, 23 Apr 2021 06:07:54 -0700 (PDT) Received-SPF: Pass (mailfrom) identity=mailfrom; client-ip=170.10.133.124; helo=us-smtp-delivery-124.mimecast.com; envelope-from=vgoyal@redhat.com; receiver= Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id 48DA9100EAB5E for ; Fri, 23 Apr 2021 06:07:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619183270; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=HrEvCjKrNvU8f2Kdeia0iPn8GHvkOfIv042jQr8u048=; b=MlYogAost8Ij70lyLqPWGGx0joZS4REWFQCUI8PZMnE9656B4FcR/KYueXD9Vs4LNtmYds 7RrKt2GKU2O1D/YIfCjeY60Nht2pJeRgSwTscRYFXjyzrNne444wIkIIoYa0OU1dresB56 i8+552DgpTNrdb4oHGWR5jnGoa2bRj0= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-128-p2aXp0xRN9iTLkrd4oJhkA-1; Fri, 23 Apr 2021 09:07:46 -0400 X-MC-Unique: p2aXp0xRN9iTLkrd4oJhkA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 269C61006C81; Fri, 23 Apr 2021 13:07:45 +0000 (UTC) Received: from horse.redhat.com (ovpn-115-86.rdu2.redhat.com [10.10.115.86]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1C37250DD2; Fri, 23 Apr 2021 13:07:38 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id A8368225FCD; Fri, 23 Apr 2021 09:07:37 -0400 (EDT) From: Vivek Goyal To: linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, dan.j.williams@intel.com Subject: [PATCH v4 3/3] dax: Wake up all waiters after invalidating dax entry Date: Fri, 23 Apr 2021 09:07:23 -0400 Message-Id: <20210423130723.1673919-4-vgoyal@redhat.com> In-Reply-To: <20210423130723.1673919-1-vgoyal@redhat.com> References: <20210423130723.1673919-1-vgoyal@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Message-ID-Hash: PW4KL56FD2XYIZ76NOBC4TXXWPIV3BOG X-Message-ID-Hash: PW4KL56FD2XYIZ76NOBC4TXXWPIV3BOG X-MailFrom: vgoyal@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; suspicious-header CC: linux-kernel@vger.kernel.org, virtio-fs@redhat.com, miklos@szeredi.hu, jack@suse.cz, willy@infradead.org, slp@redhat.com, groug@kaod.org X-Mailman-Version: 3.1.1 Precedence: list List-Id: "Linux-nvdimm developer list." Archived-At: List-Archive: List-Help: List-Post: List-Subscribe: List-Unsubscribe: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit I am seeing missed wakeups which ultimately lead to a deadlock when I am using virtiofs with DAX enabled and running "make -j". I had to mount virtiofs as rootfs and also reduce to dax window size to 256M to reproduce the problem consistently. So here is the problem. put_unlocked_entry() wakes up waiters only if entry is not null as well as !dax_is_conflict(entry). But if I call multiple instances of invalidate_inode_pages2() in parallel, then I can run into a situation where there are waiters on this index but nobody will wake these waiters. invalidate_inode_pages2() invalidate_inode_pages2_range() invalidate_exceptional_entry2() dax_invalidate_mapping_entry_sync() __dax_invalidate_entry() { xas_lock_irq(&xas); entry = get_unlocked_entry(&xas, 0); ... ... dax_disassociate_entry(entry, mapping, trunc); xas_store(&xas, NULL); ... ... put_unlocked_entry(&xas, entry); xas_unlock_irq(&xas); } Say a fault in in progress and it has locked entry at offset say "0x1c". Now say three instances of invalidate_inode_pages2() are in progress (A, B, C) and they all try to invalidate entry at offset "0x1c". Given dax entry is locked, all tree instances A, B, C will wait in wait queue. When dax fault finishes, say A is woken up. It will store NULL entry at index "0x1c" and wake up B. When B comes along it will find "entry=0" at page offset 0x1c and it will call put_unlocked_entry(&xas, 0). And this means put_unlocked_entry() will not wake up next waiter, given the current code. And that means C continues to wait and is not woken up. This patch fixes the issue by waking up all waiters when a dax entry has been invalidated. This seems to fix the deadlock I am facing and I can make forward progress. Reported-by: Sergio Lopez Fixes: ac401cc78242 ("dax: New fault locking") Reviewed-by: Jan Kara Suggested-by: Dan Williams Signed-off-by: Vivek Goyal --- fs/dax.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/dax.c b/fs/dax.c index 96e896de8f18..83daa57d37d3 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -675,7 +675,7 @@ static int __dax_invalidate_entry(struct address_space *mapping, mapping->nrexceptional--; ret = 1; out: - put_unlocked_entry(&xas, entry, WAKE_NEXT); + put_unlocked_entry(&xas, entry, WAKE_ALL); xas_unlock_irq(&xas); return ret; } -- 2.25.4 _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org