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: 553725 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 38AC5C433EF for ; Tue, 22 Mar 2022 21:46:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236584AbiCVVsV (ORCPT ); Tue, 22 Mar 2022 17:48:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34718 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236712AbiCVVsP (ORCPT ); Tue, 22 Mar 2022 17:48:15 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9F7CC5FF0F; Tue, 22 Mar 2022 14:46:46 -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 dfw.source.kernel.org (Postfix) with ESMTPS id 3AF186100A; 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> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 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);