From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-2401354-1526989323-2-14987974784131241759 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 0.248, MAILING_LIST_MULTI -1, RCVD_IN_DNSWL_HI -5, LANGUAGES en, BAYES_USED global, SA_VERSION 3.4.0 X-Spam-source: IP='209.132.180.67', Host='vger.kernel.org', Country='US', 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= 1526989322; b=BqKbBC6gORDKyxkZ2I2pB21ZG4mTzUnoWxBT+xXet9XC+gcCNZ MV26kcoEA+ezRgzWfyosHaLM8teC27rrM8YD5WyBEPoyQoFAgLPuM4hlW1UeHwce 7ZsMtDh8DEq+mUttghXD/+pqhQfcutrRNK0WrqYYz1SaongAlMBx8K9JSZq7Nh0v AxVBBTHUKDrwxjIs19/O+oiDftXofd0VTVDCYP7Z0xzuID45MAYBs4MM2P3Rg9e8 TK736mCAPmDNpCtbA3rOHxtpEWgIyI5LNv08P0VSw/7TaeM42Hy4Rpvk3BON5Zmo ff2JnGwENWJ1BBBQTlC6xawregX8I0Vs1mjA== 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=1526989322; bh= 0ob2WQm2AgVNQ5XJyZo3Y2Wpfxx8gVO78HFzg6K7eSI=; b=YqfjcQRlpHoe8zLD z8cf/uOuRYSx4JN56uRnIM82tr/JF2eN4naxvyKyICRGTme21U79jjp1KDvhQIhX uBcqS7I+qW9SkkMTJmcUGBInSw+zD5Zcvbt+OcMlXA9MpUt1bSkvqR3sbAALWrXe 6BXdmtV2+dI3qvhbWfdlcLv1dcmI9ZkVKkTufza6GPctkga4h3KPXb7EJkXYAYKV ZvKMpmuOpYJn0h93iz/0hvXNkXg9viYi06PulhsBDsbJafu0mC/e2NLzfnubw1/s Ln6JiZHz/TVISvLZ4SerS6DRiKY/EqjXOcpg8O2yOOZTRo+g++fMxFJ1Tvc/2k1n iVRERw== ARC-Authentication-Results: i=1; mx5.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=F8koA7z0 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: mx5.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=F8koA7z0 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: MS4wfPNhU323U7bm8He91sXPYGcUQJLJ8zboWr9GHOgp4tK5EPJ3l9KexE5kTwaGecGMku1yqngwUn0Fs+LD3J0QWECmyD9UHV9z+erEysnp5ElqkNMEIt0/ 0TjrYnifAQEhy2TOW/sXdZbaCd0Dh/Wbqb52ZJwdvRkwqNVcdBqBvJs1hxrvIshXaNOaVbo9Yg0X519iKOGUt0NfgGOaJLeGQA83RGAyj/q3az6eNAoNEgXn X-CM-Analysis: v=2.3 cv=NPP7BXyg c=1 sm=1 tr=0 a=UK1r566ZdBxH71SXbqIOeA==:117 a=UK1r566ZdBxH71SXbqIOeA==:17 a=VUJBJC2UJ8kA: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 S1752600AbeEVLlm (ORCPT ); Tue, 22 May 2018 07:41:42 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:36630 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751738AbeEVLbs (ORCPT ); Tue, 22 May 2018 07:31:48 -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 07/31] aio: simplify cancellation Date: Tue, 22 May 2018 13:30:44 +0200 Message-Id: <20180522113108.25713-8-hch@lst.de> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180522113108.25713-1-hch@lst.de> References: <20180522113108.25713-1-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 2e0bc04f7920..8991baa38d5d 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); -} - /* * free_ioctx() should be RCU delayed to synchronize against the RCU * protected lookup_ioctx() and also needs process context to call @@ -641,9 +607,8 @@ 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); @@ -1843,8 +1808,8 @@ 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; @@ -1856,13 +1821,11 @@ 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) { -- 2.17.0