From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-193552-1521647899-2-10289336860653920522 X-Sieve: CMU Sieve 3.0 X-Spam-known-sender: no X-Spam-score: 0.0 X-Spam-hits: BAYES_00 -1.9, HEADER_FROM_DIFFERENT_DOMAINS 0.25, ME_NOAUTH 0.01, RCVD_IN_DNSWL_HI -5, T_RP_MATCHES_RCVD -0.01, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='198.145.29.99', Host='mail.kernel.org', Country='US', FromHeader='com', MailFrom='org' X-Spam-charsets: plain='us-ascii' X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: SRS0=Ew++=GL=redhat.com=oleg@kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=arctest; t=1521647898; b=iTEMQsUwvYJAzgHcigOae0J5BHNL6Su1eM2bDpBRkKI3IN3 +UPtjXF9lSQbTZcjJBf9foLjIjk+K71o1fUTdFtt86606ldXML54U2yBS+ebuIxI 4HHikcV4KaLO/NwbtiNHkZ0ZO7zpZNZNPksUkb1rmAo3Jstl4Fgsn6G9HAqtVFk4 Ub2VvSBdWUySUvJ+6NthAp9/0KWw1rCeKK0ygdcQRHqpI9P79CX9ah+eTlBlZMV9 ac4rArY9IvZw8A/xQ+z4lcyzCTSKV8ggJ0rjKb6eYC3dOtSENVEPSnoZGmA6x44H so1sdldSn6DycwQ9s2biRiUnGZ41/k59oAUXFcg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=date:from:to:cc:subject:message-id :references:mime-version:content-type:in-reply-to; s=arctest; t= 1521647898; bh=SemN5feSBZmHoBAYz+0cAaf9iIZZ48aHqidxurqvpG8=; b=W qgmeaqIaLiHuJLdS2ZXDPCtlzpftG9wpXA3zkIr5FORsNPKLJ91RvHpNkNlEeZCn zwteUN2HPP4NpSfu43Vr0LpFvVvMRuv/545F5QoFuGmg1Mq2P+vUVDzPTvAC/OEC HSWOCc2X4H6lEA6UCOpEhwUU0Y82a/hkQY8IbssB/ZMbwas9Y7vav8tfF5B2eNLu N2fueXYLe7jQDYc8rI5idtwywP3gfUYVw+J0PJIxfR4i7cY+d24cn07zWEJr8Y59 2GTZNH/fm1up79/RJMh/XoDe9fB3ak3ysB5z3Zdv+O1ocjk28/IHgwYsXBW5Wo1q LVh87Axb1XyDrsYYdMBwg== ARC-Authentication-Results: i=1; mx2.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,d=none) header.from=redhat.com; iprev=pass policy.iprev=198.145.29.99 (mail.kernel.org); spf=none smtp.mailfrom="SRS0=Ew++=GL=redhat.com=oleg@kernel.org" smtp.helo=mail.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=mail.kernel.org x-ptr-lookup=mail.kernel.org; x-return-mx=pass smtp.domain=kernel.org smtp.result=pass smtp_is_org_domain=yes header.domain=redhat.com header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128; x-vs=clean score=0 state=0 Authentication-Results: mx2.messagingengine.com; arc=none (no signatures found); dkim=none (no signatures found); dmarc=fail (p=none,d=none) header.from=redhat.com; iprev=pass policy.iprev=198.145.29.99 (mail.kernel.org); spf=none smtp.mailfrom="SRS0=Ew++=GL=redhat.com=oleg@kernel.org" smtp.helo=mail.kernel.org; x-aligned-from=fail; x-ptr=pass x-ptr-helo=mail.kernel.org x-ptr-lookup=mail.kernel.org; x-return-mx=pass smtp.domain=kernel.org smtp.result=pass smtp_is_org_domain=yes header.domain=redhat.com header.result=pass header_is_org_domain=yes; x-tls=pass version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128; x-vs=clean score=0 state=0 X-ME-VSCategory: clean X-Remote-Delivered-To: security@kernel.org DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6582A2177B Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=oleg@redhat.com Date: Wed, 21 Mar 2018 16:58:13 +0100 From: Oleg Nesterov To: Tejun Heo Cc: torvalds@linux-foundation.org, jannh@google.com, paulmck@linux.vnet.ibm.com, bcrl@kvack.org, viro@zeniv.linux.org.uk, kent.overstreet@gmail.com, security@kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 8/8] fs/aio: Use rcu_work instead of explicit rcu and work item Message-ID: <20180321155812.GA9382@redhat.com> References: <20180314194205.1651587-1-tj@kernel.org> <20180314194515.1661824-1-tj@kernel.org> <20180314194515.1661824-8-tj@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180314194515.1661824-8-tj@kernel.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: Hi Tejun, sorry for late reply. On 03/14, Tejun Heo wrote: > > Workqueue now has rcu_work. Use it instead of open-coding rcu -> work > item bouncing. Yes, but a bit of open-coding may be more efficient... > --- a/fs/aio.c > +++ b/fs/aio.c > @@ -115,8 +115,7 @@ struct kioctx { > struct page **ring_pages; > long nr_pages; > > - struct rcu_head free_rcu; > - struct work_struct free_work; /* see free_ioctx() */ > + struct rcu_work free_rwork; /* see free_ioctx() */ IIUC, you can't easily share rcu_work's, thus every kioctx needs its own ->free_rwork and this looks sub-optimal. What do you think about the (untested) patch below? Oleg. --- a/fs/aio.c +++ b/fs/aio.c @@ -115,8 +115,10 @@ struct kioctx { struct page **ring_pages; long nr_pages; - struct rcu_head free_rcu; - struct work_struct free_work; /* see free_ioctx() */ + union { + struct rcu_head free_rcu; + struct llist_node free_llist; + }; /* * signals when all in-flight requests are done @@ -589,31 +591,38 @@ static int kiocb_cancel(struct aio_kiocb *kiocb) return cancel(&kiocb->common); } +static struct llist_head free_ioctx_llist; + /* * free_ioctx() should be RCU delayed to synchronize against the RCU * protected lookup_ioctx() and also needs process context to call * aio_free_ring(), so the double bouncing through kioctx->free_rcu and * ->free_work. */ -static void free_ioctx(struct work_struct *work) +static void free_ioctx_workfn(struct work_struct *work) { - struct kioctx *ctx = container_of(work, struct kioctx, free_work); + struct llist_node *llist = llist_del_all(&free_ioctx_llist); + struct kioctx *ctx, *tmp; - pr_debug("freeing %p\n", ctx); + llist_for_each_entry_safe(ctx, tmp, llist, free_llist) { + pr_debug("freeing %p\n", ctx); - aio_free_ring(ctx); - free_percpu(ctx->cpu); - percpu_ref_exit(&ctx->reqs); - percpu_ref_exit(&ctx->users); - kmem_cache_free(kioctx_cachep, ctx); + aio_free_ring(ctx); + free_percpu(ctx->cpu); + percpu_ref_exit(&ctx->reqs); + percpu_ref_exit(&ctx->users); + kmem_cache_free(kioctx_cachep, ctx); + } } +static DECLARE_WORK(free_ioctx_work, free_ioctx_workfn); + static void free_ioctx_rcufn(struct rcu_head *head) { struct kioctx *ctx = container_of(head, struct kioctx, free_rcu); - INIT_WORK(&ctx->free_work, free_ioctx); - schedule_work(&ctx->free_work); + if (llist_add(&ctx->free_llist, &free_ioctx_llist)) + schedule_work(&free_ioctx_work); } static void free_ioctx_reqs(struct percpu_ref *ref)