From patchwork Mon Oct 21 21:41:37 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mike Christie X-Patchwork-Id: 11203029 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 B4A16112B for ; Mon, 21 Oct 2019 21:41:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 92DCC2084B for ; Mon, 21 Oct 2019 21:41:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="EA8vKtU8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730406AbfJUVlr (ORCPT ); Mon, 21 Oct 2019 17:41:47 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:31316 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730052AbfJUVlr (ORCPT ); Mon, 21 Oct 2019 17:41:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1571694106; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=IWeM12SnjaxnROOhjKG0uzMoH/1pwew4flz84hu3l0k=; b=EA8vKtU8iQd2X3J6MWu7z3azMx0YgPt7zpBAms3aKTuzXSvMutK5X7fjnJkQGkeivXxoj9 7qCVfB5vLcvURXKOdKaH0RyvV9DvFKYZQIoUh22j9vXdGdcyUtR+V3L9vIxRNJrJ8tFKpp RCodsuiGw5rdWeFvmd0rOBGmhmR1UsE= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-270-WEhns1CVOLONzpz_CDZEpg-1; Mon, 21 Oct 2019 17:41:41 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 2B3CF2B6; Mon, 21 Oct 2019 21:41:40 +0000 (UTC) Received: from rh2.redhat.com (ovpn-123-171.rdu2.redhat.com [10.10.123.171]) by smtp.corp.redhat.com (Postfix) with ESMTP id D2A8560126; Mon, 21 Oct 2019 21:41:38 +0000 (UTC) From: Mike Christie To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, martin@urbackup.org, Damien.LeMoal@wdc.com Cc: Mike Christie Subject: [PATCH] Add prctl support for controlling PF_MEMALLOC V2 Date: Mon, 21 Oct 2019 16:41:37 -0500 Message-Id: <20191021214137.8172-1-mchristi@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: WEhns1CVOLONzpz_CDZEpg-1 X-Mimecast-Spam-Score: 0 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, tcmu-runner, amd 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 with prctl during their initialization so later allocations cannot calling back into them. Signed-off-by: Mike Christie --- V2: - Use prctl instead of procfs. - Add support for NOFS for fuse. - Check permissions. include/uapi/linux/prctl.h | 8 +++++++ kernel/sys.c | 44 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 52 insertions(+) diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 7da1b37b27aa..6f6b3af6633a 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -234,4 +234,12 @@ struct prctl_mm_map { #define PR_GET_TAGGED_ADDR_CTRL 56 # define PR_TAGGED_ADDR_ENABLE (1UL << 0) +/* Control reclaim behavior when allocating memory */ +#define PR_SET_MEMALLOC 57 +#define PR_GET_MEMALLOC 58 +#define PR_MEMALLOC_SET_NOIO (1UL << 0) +#define PR_MEMALLOC_CLEAR_NOIO (1UL << 1) +#define PR_MEMALLOC_SET_NOFS (1UL << 2) +#define PR_MEMALLOC_CLEAR_NOFS (1UL << 3) + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/sys.c b/kernel/sys.c index a611d1d58c7d..34fedc9fc7e4 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2486,6 +2486,50 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, return -EINVAL; error = GET_TAGGED_ADDR_CTRL(); break; + case PR_SET_MEMALLOC: + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + if (arg3 || arg4 || arg5) + return -EINVAL; + + switch (arg2) { + case PR_MEMALLOC_SET_NOIO: + if (current->flags & PF_MEMALLOC_NOFS) + return -EINVAL; + + current->flags |= PF_MEMALLOC_NOIO; + break; + case PR_MEMALLOC_CLEAR_NOIO: + current->flags &= ~PF_MEMALLOC_NOIO; + break; + case PR_MEMALLOC_SET_NOFS: + if (current->flags & PF_MEMALLOC_NOIO) + return -EINVAL; + + current->flags |= PF_MEMALLOC_NOFS; + break; + case PR_MEMALLOC_CLEAR_NOFS: + current->flags &= ~PF_MEMALLOC_NOFS; + break; + default: + return -EINVAL; + } + break; + case PR_GET_MEMALLOC: + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + if (arg2 || arg3 || arg4 || arg5) + return -EINVAL; + + if (current->flags & PF_MEMALLOC_NOIO) + error = PR_MEMALLOC_SET_NOIO; + else if (current->flags & PF_MEMALLOC_NOFS) + error = PR_MEMALLOC_SET_NOFS; + else + error = 0; + break; default: error = -EINVAL; break;