From patchwork Tue Mar 22 21:46:44 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 12789246 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56965C4332F for ; Tue, 22 Mar 2022 21:46:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DE8C66B0168; Tue, 22 Mar 2022 17:46:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D984F6B0169; Tue, 22 Mar 2022 17:46:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C87EB6B016A; Tue, 22 Mar 2022 17:46:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0224.hostedemail.com [216.40.44.224]) by kanga.kvack.org (Postfix) with ESMTP id B87166B0168 for ; Tue, 22 Mar 2022 17:46:48 -0400 (EDT) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 784031828AE2E for ; Tue, 22 Mar 2022 21:46:48 +0000 (UTC) X-FDA: 79273357296.28.24C0530 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf09.hostedemail.com (Postfix) with ESMTP id EB957140012 for ; Tue, 22 Mar 2022 21:46:47 +0000 (UTC) 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 D4C9BB81DAF; Tue, 22 Mar 2022 21:46:46 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 900B1C340F2; Tue, 22 Mar 2022 21:46:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1647985605; bh=DcWI2doj2SlVH2dL49MiEISyaQO5oHBqgS/a2Bax58s=; h=Date:To:From:In-Reply-To:Subject:From; b=Lj+WZW9cQsxX+l0SVoKezLDRzmLNPDQKjVGPX8f2Q2pPxN643MYyrO71m+5snAand NWqIbJCJcx4H7BEWntc4G7cYt25xD+prJRwrv31ZrCZluo7syPPU3HbfJAnz3uQ+Um eRKYG65KVQaVU356yXB4Nrrk9dLiOYn7R6DMJunQ= Date: Tue, 22 Mar 2022 14:46:44 -0700 To: vbabka@suse.cz,surenb@google.com,stable@vger.kernel.org,sfr@canb.auug.org.au,rientjes@google.com,nadav.amit@gmail.com,minchan@kernel.org,mhocko@suse.com,quic_charante@quicinc.com,akpm@linux-foundation.org,patches@lists.linux.dev,linux-mm@kvack.org,mm-commits@vger.kernel.org,torvalds@linux-foundation.org,akpm@linux-foundation.org From: Andrew Morton In-Reply-To: <20220322143803.04a5e59a07e48284f196a2f9@linux-foundation.org> Subject: [patch 162/227] mm: madvise: return correct bytes advised with process_madvise Message-Id: <20220322214645.900B1C340F2@smtp.kernel.org> Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=Lj+WZW9c; spf=pass (imf09.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org; dmarc=none X-Stat-Signature: pzn9fd9jeek1rm4gieo3ydt3rrdb69gk X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: EB957140012 X-HE-Tag: 1647985607-832485 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Charan Teja Kalla Subject: mm: madvise: return correct bytes advised with process_madvise 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 --- mm/madvise.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- a/mm/madvise.c~mm-madvise-return-correct-bytes-advised-with-process_madvise +++ a/mm/madvise.c @@ -1435,8 +1435,7 @@ 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);