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 3C2F9C433EF for ; Fri, 11 Mar 2022 15:31:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235632AbiCKPcT (ORCPT ); Fri, 11 Mar 2022 10:32:19 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47214 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349173AbiCKPcM (ORCPT ); Fri, 11 Mar 2022 10:32:12 -0500 Received: from alexa-out.qualcomm.com (alexa-out.qualcomm.com [129.46.98.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B1D2A1C025E; Fri, 11 Mar 2022 07:31:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; i=@quicinc.com; q=dns/txt; s=qcdkim; t=1647012667; x=1678548667; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version; bh=sxa44dfwh+7OfJVU2hGG661tCEMXjNsht7SbfX+FjMQ=; b=m9oFnRR8m9MCwDodx1GEkT4N4eRqxIM4pnZW9Gb9oreYDJylmZzgmVup kV07laFxjOBqiuaTmWEkSmybqZtujewfXgWrpXaJctlg5HDoPhHwFXqFN DUAQBQxzm8WP6RKSgeaXK+TsYRb+8NKfvZMmyk74ViprSwTrG/iY3b6m2 k=; Received: from ironmsg09-lv.qualcomm.com ([10.47.202.153]) by alexa-out.qualcomm.com with ESMTP; 11 Mar 2022 07:31:06 -0800 X-QCInternal: smtphost Received: from nasanex01c.na.qualcomm.com ([10.47.97.222]) by ironmsg09-lv.qualcomm.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Mar 2022 07:31:06 -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; Fri, 11 Mar 2022 07:31:05 -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; Fri, 11 Mar 2022 07:31:01 -0800 From: Charan Teja Kalla To: , , , , , , , , CC: , , Charan Teja Kalla , "# 5 . 10+" Subject: [PATCH V2,1/2] mm: madvise: return correct bytes advised with process_madvise Date: Fri, 11 Mar 2022 20:59:05 +0530 Message-ID: <125b61a0edcee5c2db8658aed9d06a43a19ccafc.1647008754.git.quic_charante@quicinc.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) 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") Cc: # 5.10+ Signed-off-by: Charan Teja Kalla --- Changes in V2: -- Separated the ENOMEM handling and return bytes processed, as per Minchan comments. -- This contains correcting return bytes processed with process_madvise(). Changes in V1: -- Fixed the ENOMEM handling and return bytes processed by process_madvise. -- https://patchwork.kernel.org/project/linux-mm/patch/1646803679-11433-1-git-send-email-quic_charante@quicinc.com/ mm/madvise.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 38d0f51..e97e6a9 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1433,8 +1433,7 @@ SYSCALL_DEFINE5(process_madvise, int, pidfd, const struct iovec __user *, vec, 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