From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-3731766-1522424288-2-10182806913026150915 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 0.249, 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='209.132.180.67', Host='vger.kernel.org', Country='CN', FromHeader='de', MailFrom='org' X-Spam-charsets: X-Resolved-to: greg@kroah.com X-Delivered-to: greg@kroah.com X-Mail-from: linux-api-owner@vger.kernel.org ARC-Seal: i=1; a=rsa-sha256; cv=none; d=messagingengine.com; s=fm2; t= 1522424287; b=WpgTHHRppPc6BaRLqKiC3a9SdFsyMS7vun5EBaxUQCKXJP8OXm Cb7mdSPcS5JRLdUbahtBhehQS6afQFnhHs+WPSZ7y0lXCeM510L52MFxQ+P7EkBf mUNRrMpJ0zvyknX4NbDa4mAvLvb9pGfSVN7L+TeU2wcIOhz7sMUB0YJpL8an8sBl cKIFPcY1hyOm6w5NMIEoKgN5xYrDlRXFgUsk0CJS0B69secGlOJF/VPUE//A7hxX 9vH3pTEoORveZ3rkM4mbQnvoExSTNhmNse5binwBrlPYw/qlU3qu59gJ3SbjDQms mqRyyNBrHNPs2v1fw3GhS4mE/aaEQfgnaEQg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d= messagingengine.com; h=from:to:cc:subject:date:message-id :in-reply-to:references:sender:list-id; s=fm2; t=1522424287; bh= CAbU3lYsdRoDcKC4RkkbxT6TU6mQFf9vtA+joND4th0=; b=Llhh1ft8hxR3zyhi shTg8+/6MTfnhUfHHnRmrFrHJTzutyRsZ7Cev0dY0N9nODFivfrSO1z6Q+xFIjef jyKTQbF1CCHsjyBCNL42Ne2KbuHm6ffpIwHyDhFJ7JISHnZwgDtKn4epeVf9A81g SNI/Z80oM9gBzentCcqoLyDODGibKXce2azFl9jHtkeTstKgCylnC9SLiqxUG74S VDGw9+oLS7D8vFD1CxgrD4gvEMFbLajeeYmlYq3Hcp+OMwyBs/eUnBhU54/zBBhe 0COJmgt5+CvYnaQ9E0JukAX+RYXt2x3WG6lK0+ckqOtaFSawEoLJ5VoqkikRbZOP seIGiQ== ARC-Authentication-Results: i=1; mx1.messagingengine.com; arc=none (no signatures found); dkim=fail (message has been altered, 2048-bit rsa key sha256) header.d=infradead.org header.i=@infradead.org header.b=If1Lthod x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=bombadil.20170209; dmarc=none (p=none,has-list-id=yes,d=none) header.from=lst.de; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-api-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=lst.de header.result=pass header_is_org_domain=yes; x-vs=clean score=0 state=0 Authentication-Results: mx1.messagingengine.com; arc=none (no signatures found); dkim=fail (message has been altered, 2048-bit rsa key sha256) header.d=infradead.org header.i=@infradead.org header.b=If1Lthod x-bits=2048 x-keytype=rsa x-algorithm=sha256 x-selector=bombadil.20170209; dmarc=none (p=none,has-list-id=yes,d=none) header.from=lst.de; iprev=pass policy.iprev=209.132.180.67 (vger.kernel.org); spf=none smtp.mailfrom=linux-api-owner@vger.kernel.org smtp.helo=vger.kernel.org; x-aligned-from=fail; x-cm=none score=0; x-ptr=pass x-ptr-helo=vger.kernel.org x-ptr-lookup=vger.kernel.org; x-return-mx=pass smtp.domain=vger.kernel.org smtp.result=pass smtp_org.domain=kernel.org smtp_org.result=pass smtp_is_org_domain=no header.domain=lst.de header.result=pass header_is_org_domain=yes; x-vs=clean score=0 state=0 X-ME-VSCategory: clean X-CM-Envelope: MS4wfId5oI5sGKxWtMpjxeVQePztE1JSo0jwm2ZC2OAdumb2YZ0F6qNM59eQhz4KxdYZBCKtD8/zJ3Kx25+hF8d86d/hgc65AqSAJt1/83p6aMnpSQYGa0i+ mhY08RhiIHQERPSat416/LXYtC3GVoRWuX5DJnEIj8g7wLQQ0OqCKJOQgmf3nHNioempUqZZaMPEkS2kUCLOO6c6xI36AeGcUcj0o9hiYgVgIHIda11bqyXt X-CM-Analysis: v=2.3 cv=WaUilXpX c=1 sm=1 tr=0 a=UK1r566ZdBxH71SXbqIOeA==:117 a=UK1r566ZdBxH71SXbqIOeA==:17 a=v2DPQv5-lfwA:10 a=VwQbUJbxAAAA:8 a=ngUzud9BF-H0qhY5OAkA:9 a=x8gzFH9gYPwA:10 a=AjGcO6oz07-iQ99wixmX:22 X-ME-CMScore: 0 X-ME-CMCategory: none Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752300AbeC3PeJ (ORCPT ); Fri, 30 Mar 2018 11:34:09 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:42738 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751129AbeC3PeF (ORCPT ); Fri, 30 Mar 2018 11:34:05 -0400 From: Christoph Hellwig To: viro@zeniv.linux.org.uk Cc: Avi Kivity , linux-aio@kvack.org, linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH 07/32] aio: simplify cancellation Date: Fri, 30 Mar 2018 17:07:44 +0200 Message-Id: <20180330150809.28094-8-hch@lst.de> X-Mailer: git-send-email 2.14.2 In-Reply-To: <20180330150809.28094-1-hch@lst.de> References: <20180330150809.28094-1-hch@lst.de> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-api-owner@vger.kernel.org X-Mailing-List: linux-api@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: With the current aio code there is no need for the magic KIOCB_CANCELLED value, as a cancelation just kicks the driver to queue the completion ASAP, with all actual completion handling done in another thread. Given that both the completion path and cancelation take the context lock there is no need for magic cmpxchg loops either. If we remove iocbs from the active list before calling ->ki_cancel we can also rely on the invariant thay anything found on the list has a ->ki_cancel callback and can be cancelled, further simplifing the code. Signed-off-by: Christoph Hellwig --- fs/aio.c | 49 ++++++------------------------------------------- 1 file changed, 6 insertions(+), 43 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index cec42b4e3c3a..5a5d537cec2e 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -164,19 +164,6 @@ struct fsync_iocb { bool datasync; }; -/* - * We use ki_cancel == KIOCB_CANCELLED to indicate that a kiocb has been either - * cancelled or completed (this makes a certain amount of sense because - * successful cancellation - io_cancel() - does deliver the completion to - * userspace). - * - * And since most things don't implement kiocb cancellation and we'd really like - * kiocb completion to be lockless when possible, we use ki_cancel to - * synchronize cancellation and completion - we only set it to KIOCB_CANCELLED - * with xchg() or cmpxchg(), see batch_complete_aio() and kiocb_cancel(). - */ -#define KIOCB_CANCELLED ((void *) (~0ULL)) - struct aio_kiocb { union { struct kiocb rw; @@ -574,27 +561,6 @@ void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel) } EXPORT_SYMBOL(kiocb_set_cancel_fn); -static int kiocb_cancel(struct aio_kiocb *kiocb) -{ - kiocb_cancel_fn *old, *cancel; - - /* - * Don't want to set kiocb->ki_cancel = KIOCB_CANCELLED unless it - * actually has a cancel function, hence the cmpxchg() - */ - - cancel = READ_ONCE(kiocb->ki_cancel); - do { - if (!cancel || cancel == KIOCB_CANCELLED) - return -EINVAL; - - old = cancel; - cancel = cmpxchg(&kiocb->ki_cancel, old, KIOCB_CANCELLED); - } while (cancel != old); - - return cancel(&kiocb->rw); -} - static void free_ioctx(struct work_struct *work) { struct kioctx *ctx = container_of(work, struct kioctx, free_work); @@ -635,9 +601,8 @@ static void free_ioctx_users(struct percpu_ref *ref) while (!list_empty(&ctx->active_reqs)) { req = list_first_entry(&ctx->active_reqs, struct aio_kiocb, ki_list); - list_del_init(&req->ki_list); - kiocb_cancel(req); + req->ki_cancel(&req->rw); } spin_unlock_irq(&ctx->ctx_lock); @@ -1836,8 +1801,8 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb, { struct kioctx *ctx; struct aio_kiocb *kiocb; + int ret = -EINVAL; u32 key; - int ret; if (unlikely(get_user(key, &iocb->aio_key))) return -EFAULT; @@ -1849,13 +1814,11 @@ SYSCALL_DEFINE3(io_cancel, aio_context_t, ctx_id, struct iocb __user *, iocb, return -EINVAL; spin_lock_irq(&ctx->ctx_lock); - kiocb = lookup_kiocb(ctx, iocb); - if (kiocb) - ret = kiocb_cancel(kiocb); - else - ret = -EINVAL; - + if (kiocb) { + list_del_init(&kiocb->ki_list); + ret = kiocb->ki_cancel(&kiocb->rw); + } spin_unlock_irq(&ctx->ctx_lock); if (!ret) { -- 2.14.2