From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-2348587-1516651991-2-5766685866276504041 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, 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='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=arctest; t=1516651990; b=vYYV/MAuB1+RvMlkpZ5WJm1Pml+2lYp7FsAhzjyd4j3hoQD 1naULaXZ1Wf4kYYS4LhkUW1Cpqvc69llG3Q5Tg6MtqGuZxfl7HJDfTlBNIBV+JF3 mAwoFfY3zgTFhBgC73m89jdwtfjBayfJG9DAGT8fydOYBLYGL6aYNV0s1azHqWKX fwGxTG33tKgaHYVLvhAKpALkNsbGuITEMnd4eqzKhfreCBsCvf7run4xQTSOxnfL hR8Bz+7Bqyu+3mJA1+HWx993PyxVy0+83CWW5TaTN8PdeO3XA5qfz9D9VE6e/I4d Ruj2CrSVXoRUiiv9jqFahQtzl6Stds0jLkLSJDg== 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=arctest; t=1516651990; bh=8tobXlXxyQZbJkdjl3yVb2Bh3VaOvmlK+hRnKh1paw0=; b=pl/fqAaYylw8 b5c4WS4FfU2IGIR9fWCaYs+q2em5nphTOJTT/E4TuXpIGKcl9yfzEAj0fcQhRrIX 5nfsPIfrbFLshErwA7jDlVrOsrizedsKyDXmvrogrvajZSaV+PhVljSaMcVfUqJO PJc7eH/ZV0AEj2nXe80aqRwuYCAS2JPlIxqcneGXOQOEdqSrrs4MU6zlRo5h5FH0 HoX4j6euPWc+uQkDrGwYmShD2JY3wHfRr2Owk2GdyQN3YFcSQiVw0TRUKVx1HPIQ YNrbP3oJvufQkv/BtdwjkjNnHM6yONiJrb+Um1CLCic/G2XMH3dax7XbPy+tno6T f7d6zbgAuw== 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=aSoQ20rM 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-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 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=aSoQ20rM 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-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 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750909AbeAVUNG (ORCPT ); Mon, 22 Jan 2018 15:13:06 -0500 Received: from bombadil.infradead.org ([65.50.211.133]:47763 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751183AbeAVUNE (ORCPT ); Mon, 22 Jan 2018 15:13:04 -0500 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 05/36] aio: simplify cancellation Date: Mon, 22 Jan 2018 21:12:12 +0100 Message-Id: <20180122201243.31610-6-hch@lst.de> X-Mailer: git-send-email 2.14.2 In-Reply-To: <20180122201243.31610-1-hch@lst.de> References: <20180122201243.31610-1-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. Signed-off-by: Christoph Hellwig Acked-by: Jeff Moyer --- fs/aio.c | 37 +++++++++---------------------------- 1 file changed, 9 insertions(+), 28 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index c32c315f05b5..2d40cf5dd4ec 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -156,19 +156,6 @@ struct kioctx { unsigned id; }; -/* - * 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; @@ -565,24 +552,18 @@ void kiocb_set_cancel_fn(struct kiocb *iocb, kiocb_cancel_fn *cancel) } EXPORT_SYMBOL(kiocb_set_cancel_fn); +/* + * Only cancel if there ws a ki_cancel function to start with, and we + * are the one how managed to clear it (to protect against simulatinious + * cancel calls). + */ 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); + kiocb_cancel_fn *cancel = kiocb->ki_cancel; + if (!cancel) + return -EINVAL; + kiocb->ki_cancel = NULL; return cancel(&kiocb->rw); } -- 2.14.2