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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6BEB8C48BE4 for ; Sun, 14 Aug 2022 16:32:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id A072B6B0073; Sun, 14 Aug 2022 12:32:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9B6F86B0074; Sun, 14 Aug 2022 12:32:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8A5618D0001; Sun, 14 Aug 2022 12:32:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 7A5C66B0073 for ; Sun, 14 Aug 2022 12:32:40 -0400 (EDT) Received: from smtpin20.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 42609804D9 for ; Sun, 14 Aug 2022 16:32:40 +0000 (UTC) X-FDA: 79798741680.20.D8B292B Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf06.hostedemail.com (Postfix) with ESMTP id B3F9318018D for ; Sun, 14 Aug 2022 16:32:39 +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 dfw.source.kernel.org (Postfix) with ESMTPS id 96A8E60FD3; Sun, 14 Aug 2022 16:32:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 39C1BC4347C; Sun, 14 Aug 2022 16:32:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1660494757; bh=K+V/saPPEc+WOP8oR9l0FSWA4cYcXwvC82LX7l+Tvx8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Xxz9eagHR1eQIn1IxyEg1CIPNfd0oOT6EJFI7ZKsanNgJpgTqAULbFGftvTTxPcCp gmlPVCLYgBrCzD32k9Y8zFi6RGi8kD+KpJ0he3bxCRFUCswOYx35HZ6cFZfGJoGoCj 04c5EJ6eMLQaisZGvygKZ6X8zrmH8tX6szOJ7BHxvw8f+5rN9exZ3dMjdoGw8rErQl XcSI/5KrJtSDspCJ+TRtyCGBm6LdS82omvjdCrmVA/V9tQjBV1p+X6ga9m1yqWDHHj 8tLcUdkCoDcwakSNtnKE4ZERIilmQTQqPLGETZNDH7qo3EUUrmw1AZnNdOOMqMNof9 UK4Oy6IWbIBGQ== From: SeongJae Park To: "Pulavarty, Badari" Cc: "damon@lists.linux.dev" , "linux-mm@kvack.org" Subject: Re: [PATCH] DAMON dbgfs_mk_context() error handling Date: Sun, 14 Aug 2022 16:32:34 +0000 Message-Id: <20220814163234.52190-1-sj@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660494759; a=rsa-sha256; cv=none; b=qNFbg4M7Vab9xKrEwZX+g0peK5+lzPI5+oZ3WAMw4OrJ3GO85CtJ7o/FG4hWINO1wRzL+0 4Eo9L8ZaIPSA39w12toLKwrS+wyeeDK+VHDlfHmgFv+0y1jQ55DrvOD13Do6bfA1caj3B8 BJ7iLOQsiVknbdP8pp0zucYwDG+qzws= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Xxz9eagH; spf=pass (imf06.hostedemail.com: domain of sj@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=sj@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660494759; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=LEBY6sDouZFKGWlZ/Rk9hXwIxiPVYWY0b28n8pzXyQ0=; b=DWyvSqJLCq0bz8uLi5gXa0WTogpOyXB0r9PEmHxKOApILHNYNPGGseBULGX2AAcPC8tS5I otPTRYwYIO6Znes3fYdw7AcAdBaEmSzIhPptRmxP0cO508IjlNi4c/kfkY69Kt5Om1cLr8 2MReF2jl/t2fU7ffV9Y5vMSVlY5tviE= X-Stat-Signature: arykkf5cgsym3m9mnkh19utip5xqe9p5 X-Rspamd-Queue-Id: B3F9318018D X-Rspam-User: X-Rspamd-Server: rspam03 Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=Xxz9eagH; spf=pass (imf06.hostedemail.com: domain of sj@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=sj@kernel.org; dmarc=pass (policy=none) header.from=kernel.org X-HE-Tag: 1660494759-935044 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: Hi Badari, On Fri, 12 Aug 2022 18:01:25 +0000 "Pulavarty, Badari" wrote: > damon dbgfs_mk_context() does not handle error from debugfs_create_dir() correctly. Let's wrpa the body lines at 75 columns[1]. > > For example, if one tries to create a context with existing name, debugfs_create_dir() fails > with -EEXIST, but dbgfs_mk_context() assumes the call is successful and adds another entry - which > will cause failures when try to enable the monitor. > > Test case: > > echo "off" > /sys/kernel/debug/damon/monitor_on > echo "abc" > /sys/kernel/debug/damon/mk_context > echo "abc" > /sys/kernel/debug/damon/mk_context > echo > /sys/kernel/debug/damon/target_ids > echo "on" > /sys/kernel/debug/damon/monitor_on <<< fails to enable monitor > > Signed-off-by: Badari Pulavarty badari.pulavarty@intel.com > --- > --- orig/mm/damon/dbgfs.c 2022-08-05 13:35:54.416831666 -0400 > +++ new/mm/damon/dbgfs.c 2022-08-05 13:44:25.121849930 -0400 > @@ -721,6 +721,9 @@ static int dbgfs_mk_context(char *name) > return -ENOENT; > > new_dir = debugfs_create_dir(name, root); > + if (IS_ERR(new_dir)) { > + return PTR_ERR(new_dir); > + } Nice finding, thank you! But, the return value of the debugfs call is intentionally ignored[2]. How about doing the duplicated name check in dbgfs_mk_context() itself before the debugfs_create_dir() call? [1] https://docs.kernel.org/process/submitting-patches.html#the-canonical-patch-format [2] https://lore.kernel.org/linux-mm/20210205155902.31102-1-sjpark@amazon.com/ Thanks, SJ > dbgfs_dirs[dbgfs_nr_ctxs] = new_dir; > > new_ctx = dbgfs_new_ctx();