Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751334AbdIQJxC (ORCPT ); Sun, 17 Sep 2017 05:53:02 -0400 Received: from mail-pg0-f65.google.com ([74.125.83.65]:36384 "EHLO mail-pg0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750793AbdIQJxA (ORCPT ); Sun, 17 Sep 2017 05:53:00 -0400 X-Google-Smtp-Source: AOwi7QArYWMTDj/CPk7Z0kIukv2a4iImRQ04Jm35b3QSMeXBgpqN9cHHx6T5DvgjfoABi+DiumaDdg== From: Yafang Shao To: akpm@linux-foundation.org, jack@suse.cz, hannes@cmpxchg.org, mhocko@suse.com, vdavydov.dev@gmail.com, jlayton@redhat.com, nborisov@suse.com, tytso@mit.edu, mawilcox@microsoft.com Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, laoar.shao@gmail.com Subject: [PATCH] mm: introduce sanity check on dirty ratio sysctl value Date: Mon, 18 Sep 2017 01:39:28 +0800 Message-Id: <1505669968-12593-1-git-send-email-laoar.shao@gmail.com> X-Mailer: git-send-email 1.8.3.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4789 Lines: 173 we can find the logic in domain_dirty_limits() that when dirty bg_thresh is bigger than dirty thresh, bg_thresh will be set as thresh * 1 / 2. if (bg_thresh >= thresh) bg_thresh = thresh / 2; But actually we can set dirty_background_raio bigger than dirty_ratio successfully. This behavior may mislead us. So we should do this sanity check at the beginning. Signed-off-by: Yafang Shao --- Documentation/sysctl/vm.txt | 5 +++ mm/page-writeback.c | 84 ++++++++++++++++++++++++++++++++++++++++----- 2 files changed, 81 insertions(+), 8 deletions(-) diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt index 9baf66a..b87e238 100644 --- a/Documentation/sysctl/vm.txt +++ b/Documentation/sysctl/vm.txt @@ -156,6 +156,8 @@ read. Note: the minimum value allowed for dirty_bytes is two pages (in bytes); any value lower than this limit will be ignored and the old configuration will be retained. +dirty_bytes can't less than dirty_background_bytes or +dirty_ratio * available_memory / 100. ============================================================== @@ -176,6 +178,9 @@ generating disk writes will itself start writing out dirty data. The total available memory is not equal to total system memory. +Note: dirty_ratio can't less than dirty_background_ratio or +dirty_background_bytes / available_memory * 100. + ============================================================== dirty_writeback_centisecs diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 0b9c5cb..1dcb8f7 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -515,11 +515,29 @@ int dirty_background_ratio_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { + int old_ratio = dirty_background_ratio; + unsigned long bytes; int ret; ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); - if (ret == 0 && write) - dirty_background_bytes = 0; + + if (ret == 0 && write) { + if (vm_dirty_ratio > 0) { + if (dirty_background_ratio >= vm_dirty_ratio) + ret = -EINVAL; + } else if (vm_dirty_bytes > 0) { + bytes = global_dirtyable_memory() * PAGE_SIZE * + dirty_background_ratio / 100; + if (bytes >= vm_dirty_bytes) + ret = -EINVAL; + } + + if (ret == 0) + dirty_background_bytes = 0; + else + dirty_background_ratio = old_ratio; + } + return ret; } @@ -527,11 +545,29 @@ int dirty_background_bytes_handler(struct ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { + unsigned long old_bytes = dirty_background_bytes; + unsigned long bytes; int ret; ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); - if (ret == 0 && write) - dirty_background_ratio = 0; + + if (ret == 0 && write) { + if (vm_dirty_bytes > 0) { + if (dirty_background_bytes >= vm_dirty_bytes) + ret = -EINVAL; + } else if (vm_dirty_ratio > 0) { + bytes = global_dirtyable_memory() * PAGE_SIZE * + vm_dirty_ratio / 100; + if (dirty_background_bytes >= bytes) + ret = -EINVAL; + } + + if (ret == 0) + dirty_background_ratio = 0; + else + dirty_background_bytes = old_bytes; + } + return ret; } @@ -540,13 +576,29 @@ int dirty_ratio_handler(struct ctl_table *table, int write, loff_t *ppos) { int old_ratio = vm_dirty_ratio; + unsigned long bytes; int ret; ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); + if (ret == 0 && write && vm_dirty_ratio != old_ratio) { - writeback_set_ratelimit(); - vm_dirty_bytes = 0; + if (dirty_background_ratio > 0) { + if (vm_dirty_ratio <= dirty_background_ratio) + ret = -EINVAL; + } else if (dirty_background_bytes > 0) { + bytes = global_dirtyable_memory() * PAGE_SIZE * + vm_dirty_ratio / 100; + if (bytes <= dirty_background_bytes) + ret = -EINVAL; + } + + if (ret == 0) { + writeback_set_ratelimit(); + vm_dirty_bytes = 0; + } else + vm_dirty_ratio = old_ratio; } + return ret; } @@ -555,13 +607,29 @@ int dirty_bytes_handler(struct ctl_table *table, int write, loff_t *ppos) { unsigned long old_bytes = vm_dirty_bytes; + unsigned long bytes; int ret; ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos); + if (ret == 0 && write && vm_dirty_bytes != old_bytes) { - writeback_set_ratelimit(); - vm_dirty_ratio = 0; + if (dirty_background_ratio > 0) { + bytes = global_dirtyable_memory() * PAGE_SIZE * + dirty_background_ratio / 100; + if (vm_dirty_bytes <= bytes) + ret = -EINVAL; + } else if (dirty_background_bytes > 0) { + if (vm_dirty_bytes <= dirty_background_bytes) + ret = -EINVAL; + } + + if (ret == 0) { + writeback_set_ratelimit(); + vm_dirty_ratio = 0; + } else + vm_dirty_bytes = old_bytes; } + return ret; } -- 1.8.3.1