From patchwork Thu Nov 7 13:36:33 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 11232881 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8F30314E5 for ; Thu, 7 Nov 2019 13:36:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6EBA621D7B for ; Thu, 7 Nov 2019 13:36:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="BOKllaWE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389173AbfKGNgq (ORCPT ); Thu, 7 Nov 2019 08:36:46 -0500 Received: from us-smtp-1.mimecast.com ([205.139.110.61]:42084 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730937AbfKGNgq (ORCPT ); Thu, 7 Nov 2019 08:36:46 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1573133805; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=nb0Y0v4Wx0arNtIyqYDVHhABDd0ChPNhAeRPBiCtjEA=; b=BOKllaWECRXrzIlScxy9ypDS+gjyHNuih83uKGozMh070qq6TRsrDuA5i2rAJl5tEOZGIm t5TSnBeZ9nBn0rYNox9GC9jmV5SlSD0eoBkx6F8wfcWaFjWdY/4xgw4IZfDjNlvZweAgrj UnihFgHGcNx1QumZe3jxTTXNoo7XNKc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-28--xtrLlxmOUGa4-p7Shz2dA-1; Thu, 07 Nov 2019 08:36:41 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AA02C8017DD; Thu, 7 Nov 2019 13:36:36 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-120-254.rdu2.redhat.com [10.10.120.254]) by smtp.corp.redhat.com (Postfix) with ESMTP id 104E15DA2C; Thu, 7 Nov 2019 13:36:33 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [RFC PATCH 08/14] pipe: Allow buffers to be marked read-whole-or-error for notifications [ver #2] From: David Howells To: torvalds@linux-foundation.org Cc: dhowells@redhat.com, Greg Kroah-Hartman , Casey Schaufler , Stephen Smalley , nicolas.dichtel@6wind.com, raven@themaw.net, Christian Brauner , dhowells@redhat.com, keyrings@vger.kernel.org, linux-usb@vger.kernel.org, linux-block@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 07 Nov 2019 13:36:33 +0000 Message-ID: <157313379331.29677.5209561321495531328.stgit@warthog.procyon.org.uk> In-Reply-To: <157313371694.29677.15388731274912671071.stgit@warthog.procyon.org.uk> References: <157313371694.29677.15388731274912671071.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-MC-Unique: -xtrLlxmOUGa4-p7Shz2dA-1 X-Mimecast-Spam-Score: 0 Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Allow a buffer to be marked such that read() must return the entire buffer in one go or return ENOBUFS. Multiple buffers can be amalgamated into a single read, but a short read will occur if the next "whole" buffer won't fit. This is useful for watch queue notifications to make sure we don't split a notification across multiple reads, especially given that we need to fabricate an overrun record under some circumstances - and that isn't in the buffers. Signed-off-by: David Howells --- fs/pipe.c | 8 +++++++- include/linux/pipe_fs_i.h | 1 + kernel/watch_queue.c | 2 +- samples/watch_queue/watch_test.c | 2 +- 4 files changed, 10 insertions(+), 3 deletions(-) diff --git a/fs/pipe.c b/fs/pipe.c index 099bf4b657dd..588355c24ee0 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -298,8 +298,14 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) size_t written; int error; - if (chars > total_len) + if (chars > total_len) { + if (buf->flags & PIPE_BUF_FLAG_WHOLE) { + if (ret == 0) + ret = -ENOBUFS; + break; + } chars = total_len; + } error = pipe_buf_confirm(pipe, buf); if (error) { diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h index 816bc0d3aecd..a19d60a06869 100644 --- a/include/linux/pipe_fs_i.h +++ b/include/linux/pipe_fs_i.h @@ -8,6 +8,7 @@ #define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */ #define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */ #define PIPE_BUF_FLAG_PACKET 0x08 /* read() as a packet */ +#define PIPE_BUF_FLAG_WHOLE 0x10 /* read() must return entire buffer or error */ /** * struct pipe_buffer - a linux kernel pipe buffer diff --git a/kernel/watch_queue.c b/kernel/watch_queue.c index b73fbfe0d467..b1d30296e29b 100644 --- a/kernel/watch_queue.c +++ b/kernel/watch_queue.c @@ -115,7 +115,7 @@ static bool post_one_notification(struct watch_queue *wqueue, buf->ops = &watch_queue_pipe_buf_ops; buf->offset = offset; buf->len = len; - buf->flags = 0; + buf->flags = PIPE_BUF_FLAG_WHOLE; pipe->head = head + 1; if (!test_and_clear_bit(note, wqueue->notes_bitmap)) { diff --git a/samples/watch_queue/watch_test.c b/samples/watch_queue/watch_test.c index 8925593bdb9b..f6fb6e813551 100644 --- a/samples/watch_queue/watch_test.c +++ b/samples/watch_queue/watch_test.c @@ -63,7 +63,7 @@ static void saw_key_change(struct watch_notification *n, size_t len) */ static void consumer(int fd) { - unsigned char buffer[4096], *p, *end; + unsigned char buffer[433], *p, *end; union { struct watch_notification n; unsigned char buf1[128];