From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Cyrus-Session-Id: sloti22d1t05-604614-1527103943-2-1777055821397211227 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= 1527103942; b=fuxhLh8og7uPO5eI32gFendL6Fm93Ah8d3tI/J+i6Y8vq9RkS0 2HoZQeAnA2nGBSoaQupTo74bN+feHE6wD62kyQBFYQOsL7vjIDDgK5iYNZdjeLik Q2Q/rWQdQsHs8YqVKzYAXbFRvsxf/d1sO+bFdPLppS8uuuems1l9yLGrrcfub1N5 1rLgAu7qXRzLp790YjP+76jbk2FnWlLF7BFxK1d3mlrcn/Bd+AXeBv7XeHN0jIhm bu46QcVsASY21PMhOX7Zf11tBklpGBv/sEGH8Jdol3zeB6iTxaTOXnK4qS0fdgLc iQsDalyJANlKBBvgDWzJoTBURxvpVkVlINtw== 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=1527103942; bh= xI46qGU26MaJxXo5Ad9EGoYM8RJzYjtVPHndIptCvXE=; b=Hm8/z+HccXsfxxwQ CYlCPmxr6xJiFE4GSlJK9Zt11NbaM8AKiZS5OIhNTugsMKO/E+egltwFHwwHL33C OKYkbHWYu68mBe+2QyTLDTUKhaMJwUrAyswouIi7j2ao0Iql0amgT6CsyCopA8lm 1RRakpHL65e/VcvlU2G8tucAEsLIuymndk7EfGwFCL0FvhWagJa6AMUsWPpT9gnU mzbArUFEzWORh2hIVEtrRFg6k1eS0g2578tKHsgqbHzWC7z/vThig0nKnCNQouYO O18V7lI/yYY9g02Y7YY4Zoa4Yt9N/3UAIx0UV75gRrpoAFO7gvN3YpQNYKfxcLaY z3OfDQ== 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=TIMTPWRQ 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=TIMTPWRQ 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: MS4wfF8KSewv/vxwJ8923dktsJTgH/UfSCF1q2hCIDWv3lPEIRRcGw1WEPPy2tuYrKlL0T9uYLjp9eos28DnyLLvc7McJU2v7thLk/TpVA0BAXRd3ZgpnVDd WC08axN0PcG+540cfkgcppDZ/Rdwv8quq24n9aR9P6hDUhGBy8g8Of9JW607xTVJcWC6L7GrKARdUPAcX0Li7488OLko013qqjwXzPLugN1kf8yQZmFqaEp8 X-CM-Analysis: v=2.3 cv=WaUilXpX 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 S934586AbeEWTbo (ORCPT ); Wed, 23 May 2018 15:31:44 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:40736 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934288AbeEWTUw (ORCPT ); Wed, 23 May 2018 15:20:52 -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 09/33] aio: simplify cancellation Date: Wed, 23 May 2018 21:19:58 +0200 Message-Id: <20180523192022.1703-10-hch@lst.de> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180523192022.1703-1-hch@lst.de> References: <20180523192022.1703-1-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 after calling ->ki_cancel (but with ctx_lock still held), 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 | 48 ++++++------------------------------------------ 1 file changed, 6 insertions(+), 42 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 50a90e5581ed..0633cf3b325c 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 @@ -641,7 +607,7 @@ 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); - kiocb_cancel(req); + req->ki_cancel(&req->rw); list_del_init(&req->ki_list); } @@ -1842,8 +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; @@ -1855,13 +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) { + ret = kiocb->ki_cancel(&kiocb->rw); + list_del_init(&kiocb->ki_list); + } spin_unlock_irq(&ctx->ctx_lock); if (!ret) { -- 2.17.0