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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 772C6C433EF for ; Wed, 20 Oct 2021 01:22:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4D9C3610CC for ; Wed, 20 Oct 2021 01:22:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229756AbhJTBYw (ORCPT ); Tue, 19 Oct 2021 21:24:52 -0400 Received: from out30-57.freemail.mail.aliyun.com ([115.124.30.57]:55522 "EHLO out30-57.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229555AbhJTBYv (ORCPT ); Tue, 19 Oct 2021 21:24:51 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R131e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04426;MF=xhao@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0Ut-jCe8_1634692955; Received: from B-X3VXMD6M-2058.local(mailfrom:xhao@linux.alibaba.com fp:SMTPD_---0Ut-jCe8_1634692955) by smtp.aliyun-inc.com(127.0.0.1); Wed, 20 Oct 2021 09:22:35 +0800 From: Xin Hao Reply-To: xhao@linux.alibaba.com Subject: Re: [PATCH v2 2/2] mm/damon/dbgfs: Add adaptive_targets list check before enable monitor_on To: SeongJae Park Cc: sjpark@amazon.de, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20211019154951.17570-1-sj@kernel.org> Message-ID: Date: Wed, 20 Oct 2021 09:22:34 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <20211019154951.17570-1-sj@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/10/19 下午11:49, SeongJae Park wrote: > On Tue, 19 Oct 2021 15:42:43 +0000 SeongJae Park wrote: > >> Hello Xin, >> >> On Tue, 19 Oct 2021 22:26:04 +0800 Xin Hao wrote: >> >>> When the ctx->adaptive_targets list is empty, >>> i did some test on monitor_on interface like this. >> s/i/I/ >> >>> echo on > /sys/kernel/debug/damon/monitor_on >>> [ 851.988307] damon: kdamond (5390) starts >> Could you please add four spaces in the beginning of this example terminal >> outputs? Also, I think confirming targets are empty like below before writing >> 'on' could make this example better. >> >> # cat /sys/kernel/debug/damon/target_ids >> # >> >> or, like below. >> >> # echo > /sys/kernel/debug/damon/target_ids >> >>> Though the ctx->adaptive_targets list is empty, but the >>> kthread_run still be called, and the kdamond.x thread still >>> be created, this is meaningless. >>> >>> So there adds a judgment in 'dbgfs_monitor_on_write', >>> if the ctx->adaptive_targets list is empty, return -EINVAL. >>> >>> Signed-off-by: Xin Hao >>> --- >>> include/linux/damon.h | 1 + >>> mm/damon/core.c | 5 +++++ >>> mm/damon/dbgfs.c | 10 ++++++++-- >>> 3 files changed, 14 insertions(+), 2 deletions(-) >>> >>> diff --git a/include/linux/damon.h b/include/linux/damon.h >>> index 715dadd21f7c..06acf73fe9db 100644 >>> --- a/include/linux/damon.h >>> +++ b/include/linux/damon.h >>> @@ -316,6 +316,7 @@ void damon_destroy_scheme(struct damos *s); >>> >>> struct damon_target *damon_new_target(unsigned long id); >>> void damon_add_target(struct damon_ctx *ctx, struct damon_target *t); >>> +int damon_target_empty(struct damon_ctx *ctx); >> Seems 'bool' would be better for the return type? > Also, I think 'damon_targets_empty()' (s/target/targets/) might be a better > naming? Yeah, thanks. > > > Thanks, > SJ > >>> void damon_free_target(struct damon_target *t); >>> void damon_destroy_target(struct damon_target *t); >>> unsigned int damon_nr_regions(struct damon_target *t); >>> diff --git a/mm/damon/core.c b/mm/damon/core.c >>> index 2f6785737902..c651b49249e5 100644 >>> --- a/mm/damon/core.c >>> +++ b/mm/damon/core.c >>> @@ -156,6 +156,11 @@ void damon_add_target(struct damon_ctx *ctx, struct damon_target *t) >>> list_add_tail(&t->list, &ctx->adaptive_targets); >>> } >>> >>> +int damon_target_empty(struct damon_ctx *ctx) >>> +{ >>> + return list_empty(&ctx->adaptive_targets); >>> +} >>> + >>> static void damon_del_target(struct damon_target *t) >>> { >>> list_del(&t->list); >>> diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c >>> index 38188347d8ab..bac42dd358d1 100644 >>> --- a/mm/damon/dbgfs.c >>> +++ b/mm/damon/dbgfs.c >>> @@ -865,9 +865,15 @@ static ssize_t dbgfs_monitor_on_write(struct file *file, >>> return -EINVAL; >>> } >>> >>> - if (!strncmp(kbuf, "on", count)) >>> + if (!strncmp(kbuf, "on", count)) { >>> + int i; >>> + >>> + for (i = 0; i < dbgfs_nr_ctxs; i++) { >>> + if (damon_target_empty(dbgfs_ctxs[i])) >>> + return -EINVAL; >>> + } >>> err = damon_start(dbgfs_ctxs, dbgfs_nr_ctxs); >>> - else if (!strncmp(kbuf, "off", count)) >>> + } else if (!strncmp(kbuf, "off", count)) >>> err = damon_stop(dbgfs_ctxs, dbgfs_nr_ctxs); >>> else >>> err = -EINVAL; >> Please use braces for all above branches: >> >> https://docs.kernel.org/process/coding-style.html#placing-braces-and-spaces >> >> >> Thanks, >> SJ >> >>> -- >>> 2.31.0 -- Best Regards! Xin Hao