From patchwork Mon Sep 9 16:28:04 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mike Christie X-Patchwork-Id: 11138277 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id F3F5F14E5 for ; Mon, 9 Sep 2019 16:28:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D2B0321A4A for ; Mon, 9 Sep 2019 16:28:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728121AbfIIQ2M (ORCPT ); Mon, 9 Sep 2019 12:28:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35904 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726148AbfIIQ2L (ORCPT ); Mon, 9 Sep 2019 12:28:11 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9E1F020EF; Mon, 9 Sep 2019 16:28:10 +0000 (UTC) Received: from rh2.redhat.com (ovpn-124-7.rdu2.redhat.com [10.10.124.7]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6D2B75D6B7; Mon, 9 Sep 2019 16:28:09 +0000 (UTC) From: Mike Christie To: axboe@kernel.dk, James.Bottomley@HansenPartnership.com, martin.petersen@oracle.com, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-block@vger.kernel.org Cc: Mike Christie Subject: [RFC PATCH] Add proc interface to set PF_MEMALLOC flags Date: Mon, 9 Sep 2019 11:28:04 -0500 Message-Id: <20190909162804.5694-1-mchristi@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.71]); Mon, 09 Sep 2019 16:28:10 +0000 (UTC) Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org There are several storage drivers like dm-multipath, iscsi, and nbd that have userspace components that can run in the IO path. For example, iscsi and nbd's userspace deamons may need to recreate a socket and/or send IO on it, and dm-multipath's daemon multipathd may need to send IO to figure out the state of paths and re-set them up. In the kernel these drivers have access to GFP_NOIO/GFP_NOFS and the memalloc_*_save/restore functions to control the allocation behavior, but for userspace we would end up hitting a allocation that ended up writing data back to the same device we are trying to allocate for. This patch allows the userspace deamon to set the PF_MEMALLOC* flags through procfs. It currently only supports PF_MEMALLOC_NOIO, but depending on what other drivers and userspace file systems need, for the final version I can add the other flags for that file or do a file per flag or just do a memalloc_noio file. Signed-off-by: Mike Christie --- Documentation/filesystems/proc.txt | 6 ++++ fs/proc/base.c | 53 ++++++++++++++++++++++++++++++ 2 files changed, 59 insertions(+) diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 99ca040e3f90..b5456a61a013 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -46,6 +46,7 @@ Table of Contents 3.10 /proc//timerslack_ns - Task timerslack value 3.11 /proc//patch_state - Livepatch patch operation state 3.12 /proc//arch_status - Task architecture specific information + 3.13 /proc//memalloc - Control task's memory reclaim behavior 4 Configuring procfs 4.1 Mount options @@ -1980,6 +1981,11 @@ Example $ cat /proc/6753/arch_status AVX512_elapsed_ms: 8 +3.13 /proc//memalloc - Control task's memory reclaim behavior +----------------------------------------------------------------------- +A value of "noio" indicates that when a task allocates memory it will not +reclaim memory that requires starting phisical IO. + Description ----------- diff --git a/fs/proc/base.c b/fs/proc/base.c index ebea9501afb8..c4faa3464602 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1223,6 +1223,57 @@ static const struct file_operations proc_oom_score_adj_operations = { .llseek = default_llseek, }; +static ssize_t memalloc_read(struct file *file, char __user *buf, size_t count, + loff_t *ppos) +{ + struct task_struct *task; + ssize_t rc = 0; + + task = get_proc_task(file_inode(file)); + if (!task) + return -ESRCH; + + if (task->flags & PF_MEMALLOC_NOIO) + rc = simple_read_from_buffer(buf, count, ppos, "noio", 4); + put_task_struct(task); + return rc; +} + +static ssize_t memalloc_write(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct task_struct *task; + char buffer[5]; + int rc = count; + + memset(buffer, 0, sizeof(buffer)); + if (count != sizeof(buffer) - 1) + return -EINVAL; + + if (copy_from_user(buffer, buf, count)) + return -EFAULT; + buffer[count] = '\0'; + + task = get_proc_task(file_inode(file)); + if (!task) + return -ESRCH; + + if (!strcmp(buffer, "noio")) { + task->flags |= PF_MEMALLOC_NOIO; + } else { + rc = -EINVAL; + } + + put_task_struct(task); + return rc; +} + +static const struct file_operations proc_memalloc_operations = { + .read = memalloc_read, + .write = memalloc_write, + .llseek = default_llseek, +}; + #ifdef CONFIG_AUDIT #define TMPBUFLEN 11 static ssize_t proc_loginuid_read(struct file * file, char __user * buf, @@ -3097,6 +3148,7 @@ static const struct pid_entry tgid_base_stuff[] = { #ifdef CONFIG_PROC_PID_ARCH_STATUS ONE("arch_status", S_IRUGO, proc_pid_arch_status), #endif + REG("memalloc", S_IRUGO|S_IWUSR, proc_memalloc_operations), }; static int proc_tgid_base_readdir(struct file *file, struct dir_context *ctx) @@ -3487,6 +3539,7 @@ static const struct pid_entry tid_base_stuff[] = { #ifdef CONFIG_PROC_PID_ARCH_STATUS ONE("arch_status", S_IRUGO, proc_pid_arch_status), #endif + REG("memalloc", S_IRUGO|S_IWUSR, proc_memalloc_operations), }; static int proc_tid_base_readdir(struct file *file, struct dir_context *ctx)