From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751736AbcFUJ20 (ORCPT ); Tue, 21 Jun 2016 05:28:26 -0400 Received: from out4133-66.mail.aliyun.com ([42.120.133.66]:19359 "EHLO out4133-66.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751694AbcFUJ2W (ORCPT ); Tue, 21 Jun 2016 05:28:22 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R131e4;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e02c03294;MF=hillf.zj@alibaba-inc.com;NM=1;PH=DS;RN=4;SR=0;TI=SMTPD_----4wyLZwJ_1466501277; Reply-To: "Hillf Danton" From: "Hillf Danton" To: "'Michal Hocko'" Cc: "'Oleg Nesterov'" , "linux-kernel" , References: <06be01d1cb9c$8f235850$ad6a08f0$@alibaba-inc.com> In-Reply-To: <06be01d1cb9c$8f235850$ad6a08f0$@alibaba-inc.com> Subject: Re: [PATCH 03/10] proc, oom_adj: extract oom_score_adj setting into a helper Date: Tue, 21 Jun 2016 17:27:57 +0800 Message-ID: <06bf01d1cb9f$32a49320$97edb960$@alibaba-inc.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQIyWb/3a0/9cuSb2i9D7m6Wp+9qVp8yhbCg Content-Language: zh-cn Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > From: Michal Hocko > > Currently we have two proc interfaces to set oom_score_adj. The legacy > /proc//oom_adj and /proc//oom_score_adj which both have their > specific handlers. Big part of the logic is duplicated so extract the > common code into __set_oom_adj helper. Legacy knob still expects some > details slightly different so make sure those are handled same way - e.g. > the legacy mode ignores oom_score_adj_min and it warns about the usage. > > This patch shouldn't introduce any functional changes. > > Acked-by: Oleg Nesterov > Signed-off-by: Michal Hocko > --- > fs/proc/base.c | 94 +++++++++++++++++++++++++++------------------------------- > 1 file changed, 43 insertions(+), 51 deletions(-) > > diff --git a/fs/proc/base.c b/fs/proc/base.c > index 968d5ea06e62..a6a8fbdd5a1b 100644 > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -1037,7 +1037,47 @@ static ssize_t oom_adj_read(struct file *file, char __user *buf, size_t count, > return simple_read_from_buffer(buf, count, ppos, buffer, len); > } > > -static DEFINE_MUTEX(oom_adj_mutex); > +static int __set_oom_adj(struct file *file, int oom_adj, bool legacy) > +{ > + static DEFINE_MUTEX(oom_adj_mutex); Writers are not excluded for readers! Is this a hot path? > + struct task_struct *task; > + int err = 0; > + > + task = get_proc_task(file_inode(file)); > + if (!task) > + return -ESRCH; > + > + mutex_lock(&oom_adj_mutex); > + if (legacy) { > + if (oom_adj < task->signal->oom_score_adj && > + !capable(CAP_SYS_RESOURCE)) { > + err = -EACCES; > + goto err_unlock; > + } > + /* > + * /proc/pid/oom_adj is provided for legacy purposes, ask users to use > + * /proc/pid/oom_score_adj instead. > + */ > + pr_warn_once("%s (%d): /proc/%d/oom_adj is deprecated, please use /proc/%d/oom_score_adj instead.\n", > + current->comm, task_pid_nr(current), task_pid_nr(task), > + task_pid_nr(task)); > + } else { > + if ((short)oom_adj < task->signal->oom_score_adj_min && > + !capable(CAP_SYS_RESOURCE)) { > + err = -EACCES; > + goto err_unlock; > + } > + } > + > + task->signal->oom_score_adj = oom_adj; > + if (!legacy && has_capability_noaudit(current, CAP_SYS_RESOURCE)) > + task->signal->oom_score_adj_min = (short)oom_adj; > + trace_oom_score_adj_update(task); > +err_unlock: > + mutex_unlock(&oom_adj_mutex); > + put_task_struct(task); > + return err; > +} > > /* > * /proc/pid/oom_adj exists solely for backwards compatibility with previous > @@ -1052,7 +1092,6 @@ static DEFINE_MUTEX(oom_adj_mutex); > static ssize_t oom_adj_write(struct file *file, const char __user *buf, > size_t count, loff_t *ppos) > { > - struct task_struct *task; > char buffer[PROC_NUMBUF]; > int oom_adj; > int err; > @@ -1074,12 +1113,6 @@ static ssize_t oom_adj_write(struct file *file, const char __user *buf, > goto out; > } > > - task = get_proc_task(file_inode(file)); > - if (!task) { > - err = -ESRCH; > - goto out; > - } > - > /* > * Scale /proc/pid/oom_score_adj appropriately ensuring that a maximum > * value is always attainable. > @@ -1089,26 +1122,7 @@ static ssize_t oom_adj_write(struct file *file, const char __user *buf, > else > oom_adj = (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE; > > - mutex_lock(&oom_adj_mutex); > - if (oom_adj < task->signal->oom_score_adj && > - !capable(CAP_SYS_RESOURCE)) { > - err = -EACCES; > - goto err_unlock; > - } > - > - /* > - * /proc/pid/oom_adj is provided for legacy purposes, ask users to use > - * /proc/pid/oom_score_adj instead. > - */ > - pr_warn_once("%s (%d): /proc/%d/oom_adj is deprecated, please use /proc/%d/oom_score_adj instead.\n", > - current->comm, task_pid_nr(current), task_pid_nr(task), > - task_pid_nr(task)); > - > - task->signal->oom_score_adj = oom_adj; > - trace_oom_score_adj_update(task); > -err_unlock: > - mutex_unlock(&oom_adj_mutex); > - put_task_struct(task); > + err = __set_oom_adj(file, oom_adj, true); > out: > return err < 0 ? err : count; > } > @@ -1138,7 +1152,6 @@ static ssize_t oom_score_adj_read(struct file *file, char __user *buf, > static ssize_t oom_score_adj_write(struct file *file, const char __user *buf, > size_t count, loff_t *ppos) > { > - struct task_struct *task; > char buffer[PROC_NUMBUF]; > int oom_score_adj; > int err; > @@ -1160,28 +1173,7 @@ static ssize_t oom_score_adj_write(struct file *file, const char __user *buf, > goto out; > } > > - task = get_proc_task(file_inode(file)); > - if (!task) { > - err = -ESRCH; > - goto out; > - } > - > - mutex_lock(&oom_adj_mutex); > - if ((short)oom_score_adj < task->signal->oom_score_adj_min && > - !capable(CAP_SYS_RESOURCE)) { > - err = -EACCES; > - goto err_unlock; > - } > - > - task->signal->oom_score_adj = (short)oom_score_adj; > - if (has_capability_noaudit(current, CAP_SYS_RESOURCE)) > - task->signal->oom_score_adj_min = (short)oom_score_adj; > - > - trace_oom_score_adj_update(task); > - > -err_unlock: > - mutex_unlock(&oom_adj_mutex); > - put_task_struct(task); > + err = __set_oom_adj(file, oom_score_adj, false); > out: > return err < 0 ? err : count; > } > -- > 2.8.1 > >