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 34831C433F5 for ; Tue, 5 Apr 2022 08:01:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234441AbiDEH6d (ORCPT ); Tue, 5 Apr 2022 03:58:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46908 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233014AbiDEHrV (ORCPT ); Tue, 5 Apr 2022 03:47:21 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 61B53972CA; Tue, 5 Apr 2022 00:43:29 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 1468CB81A22; Tue, 5 Apr 2022 07:43:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3E0DEC340EE; Tue, 5 Apr 2022 07:43:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649144606; bh=67+iwn21hU+eAf9Hn/ExM4fEOGIQZGPFuRfiibRg3lM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=rDq+k9gy3jfg4azHKN+k9IWPjM0GvHH7Yckfpfdaw4KqxguM01w6NkPWfA5mK/uQU QDJix0QbsSjLTIT+f/Kqo4w04KPtlxLw3iStvWRFvxlQPTtFfPmJPHJfSUogR9GHkx vXAOypGNx6m5eSMqUCT0Wyw/njtonxLZ/lGdrs8s= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Charan Teja Kalla , Suren Baghdasaryan , Vlastimil Babka , David Rientjes , Stephen Rothwell , Minchan Kim , Nadav Amit , Michal Hocko , Andrew Morton , Linus Torvalds Subject: [PATCH 5.17 0106/1126] mm: madvise: return correct bytes advised with process_madvise Date: Tue, 5 Apr 2022 09:14:13 +0200 Message-Id: <20220405070410.681670271@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220405070407.513532867@linuxfoundation.org> References: <20220405070407.513532867@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Charan Teja Kalla commit 5bd009c7c9a9e888077c07535dc0c70aeab242c3 upstream. Patch series "mm: madvise: return correct bytes processed with process_madvise", v2. With the process_madvise(), always choose to return non zero processed bytes over an error. This can help the user to know on which VMA, passed in the 'struct iovec' vector list, is failed to advise thus can take the decission of retrying/skipping on that VMA. This patch (of 2): 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. Link: https://lkml.kernel.org/r/cover.1647008754.git.quic_charante@quicinc.com Link: https://lkml.kernel.org/r/125b61a0edcee5c2db8658aed9d06a43a19ccafc.1647008754.git.quic_charante@quicinc.com Fixes: ecb8ac8b1f14("mm/madvise: introduce process_madvise() syscall: an external memory hinting API") Signed-off-by: Charan Teja Kalla Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: David Rientjes Cc: Stephen Rothwell Cc: Minchan Kim Cc: Nadav Amit Cc: Michal Hocko Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/madvise.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/mm/madvise.c +++ b/mm/madvise.c @@ -1440,8 +1440,7 @@ SYSCALL_DEFINE5(process_madvise, int, pi 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);