From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id EC5ABC433F5 for ; Wed, 9 Mar 2022 05:28:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229634AbiCIF3o (ORCPT ); Wed, 9 Mar 2022 00:29:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39690 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229498AbiCIF3m (ORCPT ); Wed, 9 Mar 2022 00:29:42 -0500 Received: from alexa-out.qualcomm.com (alexa-out.qualcomm.com [129.46.98.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0CB1F3D1E0 for ; Tue, 8 Mar 2022 21:28:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; i=@quicinc.com; q=dns/txt; s=qcdkim; t=1646803725; x=1678339725; h=from:to:cc:subject:date:message-id:mime-version; bh=97CBgfKzG/hf6ld2R9U1iapWBregjuYMrjFowuf2y98=; b=bBIoHKI8wQExxUnJoW2lFgxsDn2BjXC9lqQXcLv1SEW5Yj7YwbsHnxd2 baeu1dCmhuHTkTT0RmO4c3DLOXhzCviQSCU4gQY13oNv9ZU1Vc9ljqN4A QaSn0WDnfHRgVrmhtVd3pzkQt/GCSqYlHzuIEJ8CKWLPNmL6AignQAPXn 4=; Received: from ironmsg08-lv.qualcomm.com ([10.47.202.152]) by alexa-out.qualcomm.com with ESMTP; 08 Mar 2022 21:28:43 -0800 X-QCInternal: smtphost Received: from nasanex01c.na.qualcomm.com ([10.47.97.222]) by ironmsg08-lv.qualcomm.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Mar 2022 21:28:44 -0800 Received: from nalasex01a.na.qualcomm.com (10.47.209.196) by nasanex01c.na.qualcomm.com (10.47.97.222) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.15; Tue, 8 Mar 2022 21:28:42 -0800 Received: from hu-charante-hyd.qualcomm.com (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.986.15; Tue, 8 Mar 2022 21:28:38 -0800 From: Charan Teja Kalla To: , , , , , , CC: , , Charan Teja Kalla Subject: [PATCH] mm: madvise: return correct bytes advised with process_madvise Date: Wed, 9 Mar 2022 10:57:59 +0530 Message-ID: <1646803679-11433-1-git-send-email-quic_charante@quicinc.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01a.na.qualcomm.com (10.52.223.231) To nalasex01a.na.qualcomm.com (10.47.209.196) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The process_madvise() system call returns error even after processing some VMA's passed in the 'struct iovec' vector list which leaves the user confused to know where to restart the advise next. It is also against this syscall man page[1] documentation where it mentions that "return value may be less than the total number of requested bytes, if an error occurred after some iovec elements were already processed.". Consider a user passed 10 VMA's in the 'struct iovec' vector list of which 9 are processed but one. Then it just returns the error caused on that failed VMA despite the first 9 VMA's processed, leaving the user confused about on which VMA it is failed. Returning the number of bytes processed here can help the user to know which VMA it is failed on and thus can retry/skip the advise on that VMA. [1]https://man7.org/linux/man-pages/man2/process_madvise.2.html. Fixes: ecb8ac8b1f14("mm/madvise: introduce process_madvise() syscall: an external memory hinting API" Signed-off-by: Charan Teja Kalla --- mm/madvise.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 38d0f51..d3b49b3 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1426,15 +1426,21 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec, while (iov_iter_count(&iter)) { iovec = iov_iter_iovec(&iter); + /* + * Even when [start, end) passed to do_madvise covers + * some unmapped addresses, it continues processing with + * returning ENOMEM at the end. Thus consider the range + * as processed when do_madvise() returns ENOMEM. + * This makes process_madvise() never returns ENOMEM. + */ ret = do_madvise(mm, (unsigned long)iovec.iov_base, iovec.iov_len, behavior); - if (ret < 0) + if (ret < 0 && ret != -ENOMEM) break; iov_iter_advance(&iter, iovec.iov_len); } - if (ret == 0) - ret = total_len - iov_iter_count(&iter); + ret = (total_len - iov_iter_count(&iter)) ? : ret; release_mm: mmput(mm); -- 2.7.4