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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id F15D2C41535 for ; Tue, 19 Dec 2023 15:46:45 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 5DD6C6B007D; Tue, 19 Dec 2023 10:46:45 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 58D776B007E; Tue, 19 Dec 2023 10:46:45 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 47C586B0080; Tue, 19 Dec 2023 10:46:45 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 395F66B007D for ; Tue, 19 Dec 2023 10:46:45 -0500 (EST) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id EBFE0120B7A for ; Tue, 19 Dec 2023 15:46:44 +0000 (UTC) X-FDA: 81583995528.10.BC575B5 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf04.hostedemail.com (Postfix) with ESMTP id 8CF7B40014 for ; Tue, 19 Dec 2023 15:46:41 +0000 (UTC) Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=CFvSoo6U; spf=pass (imf04.hostedemail.com: domain of dhowells@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=dhowells@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1703000803; a=rsa-sha256; cv=none; b=LC0Y0fZSiyGEOkpXVPDrjyERf16b02McrmpeIvglCIgOFvmoeSB49Fs8ZHlXrubH951YeH OjPe0qEtTPw4k0xRXGdCIrJSAk37r3Kod5cSlVTOfxu3TNyCUNZuTlJx0BcEpVEKi6CKjD 6LNsRez/YyDaqyQsGvX+2F7BNL5s/98= ARC-Authentication-Results: i=1; imf04.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=CFvSoo6U; spf=pass (imf04.hostedemail.com: domain of dhowells@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=dhowells@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1703000803; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=wZJGy675CLReZdRFDQqYih3Khpsr0+z+wYGm8WjxUuI=; b=NUf8ycl+iMcA5HvltaD4AUV2onodFDlih7x86c2aOsXtj6W0O8nwZFcXeCQndhmByOA4Zs mq6monyfXYhcGV7mYrh0AbcHhcjEns1knqEAH+k5hjTwGj2VeJkkkGaUuxVS4plxnl5Q7A 0d7/6Xpzf30OiP/K+3t/WJB5f8onf98= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1703000800; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=wZJGy675CLReZdRFDQqYih3Khpsr0+z+wYGm8WjxUuI=; b=CFvSoo6U80LwJYjfkGOiCZWXCB3s1rz6JAuCgqO6QC2ouwT7PJr16NT/fMZabS3Br4KpOw fTdk99MGRpB/ERq80jw8V5FtHMJJ7nMZtKTh9T+JpC46lwENGtJVIMQJ4tdtH93YzB4rCC UvSQgZ5ExtuKQx/FaugaXImDeF4Zxu0= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-649-IJX7nCWPOzWJ4d7l3Db6MQ-1; Tue, 19 Dec 2023 10:46:35 -0500 X-MC-Unique: IJX7nCWPOzWJ4d7l3Db6MQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 936DD1C0513E; Tue, 19 Dec 2023 15:46:33 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.39.195.169]) by smtp.corp.redhat.com (Postfix) with ESMTP id B5C1E3C25; Tue, 19 Dec 2023 15:46:30 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <36ba1d9f8668e701a9eebcc6cbaa9367e7ccb182.camel@kernel.org> References: <36ba1d9f8668e701a9eebcc6cbaa9367e7ccb182.camel@kernel.org> <20231213152350.431591-1-dhowells@redhat.com> <20231213152350.431591-29-dhowells@redhat.com> To: Jeff Layton Cc: dhowells@redhat.com, Steve French , Matthew Wilcox , Marc Dionne , Paulo Alcantara , Shyam Prasad N , Tom Talpey , Dominique Martinet , Eric Van Hensbergen , Ilya Dryomov , Christian Brauner , linux-cachefs@redhat.com, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, v9fs@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 28/39] netfs: Implement support for unbuffered/DIO read MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <844304.1703000788.1@warthog.procyon.org.uk> Date: Tue, 19 Dec 2023 15:46:28 +0000 Message-ID: <844305.1703000788@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.1 X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 8CF7B40014 X-Stat-Signature: 8zarnpdqskadrtprthf1rce79shkyid5 X-Rspam-User: X-HE-Tag: 1703000801-157230 X-HE-Meta: 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 q5vFK99c tOcgOfHXO2okm5oPlHtLDHJC7H2lZzovNGy894s3GYy1ek6Y+46UQ0rBQGleHNCxzQeETPDAcfJ+62dRTxFcZh6ovkGh1t84+qwK0p+ewAB19pS+Pv6a3UEo6rekTAqCe5vvF2cj45X5xzLNXIE60EHpiYP1YJZnc2I4nTwzGg8sBBPcZ+PSQOMXBDCY+IiH1O5YwjA2gqUDZsr+j//Ejzvnezg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Jeff Layton wrote: > > +static int netfs_copy_xarray_to_iter(struct netfs_io_request *rreq, > > + struct xarray *xa, struct iov_iter *dst, > > + unsigned long long start, size_t avail) > ... > > + xas_for_each(&xas, folio, ULONG_MAX) { > > + size_t offset; > > + > > + if (xas_retry(&xas, folio)) > > + continue; > > + > > + /* There shouldn't be a need to call xas_pause() as no one else > > + * should be modifying the xarray we're iterating over. > > + * Really, we only need the RCU readlock to keep lockdep happy > > + * inside xas_for_each(). > > + */ > > + rcu_read_unlock(); > > + > > Are you sure it's still safe to access "folio" once you've dropped the > rcu_read_lock? I wonder if you need to take a reference or something. > > I guess if this is a "private" xarray then nothing should be modifying > it? It is a private xarray in this case. The only reason I need the RCU read lock is because the xarray code will complain if we're not holding it:-/. Actually, I can probably excise the bounce buffer code for this series as nothing in 9p or afs currently uses it. It's needed for content crypto - so ceph will need it. David