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 0143AC4332F for ; Tue, 10 May 2022 12:51:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242036AbiEJMzZ (ORCPT ); Tue, 10 May 2022 08:55:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40028 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242043AbiEJMzE (ORCPT ); Tue, 10 May 2022 08:55:04 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id BF2EB2B94EE for ; Tue, 10 May 2022 05:50:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1652187030; 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=Xkxzad1cbht/jlusqrH8a1D+QFGOt7FrMJEjOw9H5po=; b=HHHf8Isqc8ai/eA1nvXoycUo6wYw6T0TOWn5/O9tuX/YnrRGyzkr+wn0abuAND8kawzkC9 R7+WJFqnjWlDzOIuumrruUXLnbAQtW2NiJCexkc2XKNxXl6Asv5DbRylRTqcYtbXz+HZcZ fN7VAMzEliLQPWBxnSxlETBL5ZCQJ6M= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-210-Isfs8HFjNPW5aaZjgDRhpA-1; Tue, 10 May 2022 08:50:20 -0400 X-MC-Unique: Isfs8HFjNPW5aaZjgDRhpA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 1F3C71C06910; Tue, 10 May 2022 12:50:19 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.33.37.67]) by smtp.corp.redhat.com (Postfix) with ESMTP id 483D714C1D4D; Tue, 10 May 2022 12:50:16 +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: <20220509074028.74954-3-jefflexu@linux.alibaba.com> References: <20220509074028.74954-3-jefflexu@linux.alibaba.com> <20220509074028.74954-1-jefflexu@linux.alibaba.com> To: Jeffle Xu Cc: dhowells@redhat.com, linux-cachefs@redhat.com, xiang@kernel.org, chao@kernel.org, linux-erofs@lists.ozlabs.org, torvalds@linux-foundation.org, gregkh@linuxfoundation.org, willy@infradead.org, linux-fsdevel@vger.kernel.org, joseph.qi@linux.alibaba.com, bo.liu@linux.alibaba.com, tao.peng@linux.alibaba.com, gerry@linux.alibaba.com, eguan@linux.alibaba.com, linux-kernel@vger.kernel.org, luodaowen.backend@bytedance.com, tianzichen@kuaishou.com, yinxin.x@bytedance.com, zhangjiachen.jaycee@bytedance.com, zhujia.zj@bytedance.com Subject: Re: [PATCH v11 02/22] cachefiles: notify the user daemon when looking up cookie MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3509080.1652187015.1@warthog.procyon.org.uk> Date: Tue, 10 May 2022 13:50:15 +0100 Message-ID: <3509081.1652187015@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.85 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jeffle Xu wrote: > Fscache/CacheFiles used to serve as a local cache for a remote > networking fs. A new on-demand read mode will be introduced for > CacheFiles, which can boost the scenario where on-demand read semantics > are needed, e.g. container image distribution. > > The essential difference between these two modes is seen when a cache > miss occurs: In the original mode, the netfs will fetch the data from > the remote server and then write it to the cache file; in on-demand > read mode, fetching the data and writing it into the cache is delegated > to a user daemon. > > As the first step, notify the user daemon when looking up cookie. In > this case, an anonymous fd is sent to the user daemon, through which the > user daemon can write the fetched data to the cache file. Since the user > daemon may move the anonymous fd around, e.g. through dup(), an object > ID uniquely identifying the cache file is also attached. > > Also add one advisory flag (FSCACHE_ADV_WANT_CACHE_SIZE) suggesting that > the cache file size shall be retrieved at runtime. This helps the > scenario where one cache file contains multiple netfs files, e.g. for > the purpose of deduplication. In this case, netfs itself has no idea the > size of the cache file, whilst the user daemon should give the hint on > it. > > Signed-off-by: Jeffle Xu Acked-by: David Howells