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 X-Spam-Level: X-Spam-Status: No, score=-6.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A9582C5DF60 for ; Fri, 8 Nov 2019 19:23:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7381A2067B for ; Fri, 8 Nov 2019 19:23:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="ixqLj5/q" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389271AbfKHTX6 (ORCPT ); Fri, 8 Nov 2019 14:23:58 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:46511 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1732379AbfKHSxc (ORCPT ); Fri, 8 Nov 2019 13:53:32 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1573239211; 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=9FwgetzyW8P48cGLGqGtD4GfxfTRlJoRiG4n2Dado8Y=; b=ixqLj5/qZDjREgmFuroudJ1XpJJThA7TmnfmjNiz/xXh0D5/QaD8nmFy3+UxkfB05PebK8 4V7uYVbTuhfhpbR+9T2I29gTw3mIakBVJAROwWFQXv2UaGUtRlIbsOxuh+BPQ0z6bVV4jy I5ul+Cx5+KjskUkgnJ9q5bBA0jM3bw4= 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-225-RDOnMV84OlO0Y-tz_4aX-A-1; Fri, 08 Nov 2019 13:53:28 -0500 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 5C2C88017E0; Fri, 8 Nov 2019 18:53:26 +0000 (UTC) Received: from rh2.redhat.com (ovpn-125-42.rdu2.redhat.com [10.10.125.42]) by smtp.corp.redhat.com (Postfix) with ESMTP id CF6A1600C9; Fri, 8 Nov 2019 18:53:24 +0000 (UTC) From: Mike Christie To: mhocko@kernel.org, david@fromorbit.com, 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 mem reclaim V3 Date: Fri, 8 Nov 2019 12:53:19 -0600 Message-Id: <20191108185319.9326-1-mchristi@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: RDOnMV84OlO0Y-tz_4aX-A-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@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 SG IO or read/write 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 an allocation that ended up writing data back to the same device we are trying to allocate for. The device is then in a state of deadlock, because to execute IO the device needs to allocate memory, but to allocate memory the memory layers want execute IO to the device. Here is an example with nbd using a local userspace daemon that performs network IO to a remote server. We are using XFS on top of the nbd device, but it can happen with any FS or other modules layered on top of the nbd device that can write out data to free memory. Here a nbd daemon helper thread, msgr-worker-1, is performing a write/sendmsg on a socket to execute a request. This kicks off a reclaim operation which results in a WRITE to the nbd device and the nbd thread calling back into the mm layer. [ 1626.609191] msgr-worker-1 D 0 1026 1 0x00004000 [ 1626.609193] Call Trace: [ 1626.609195] ? __schedule+0x29b/0x630 [ 1626.609197] ? wait_for_completion+0xe0/0x170 [ 1626.609198] schedule+0x30/0xb0 [ 1626.609200] schedule_timeout+0x1f6/0x2f0 [ 1626.609202] ? blk_finish_plug+0x21/0x2e [ 1626.609204] ? _xfs_buf_ioapply+0x2e6/0x410 [ 1626.609206] ? wait_for_completion+0xe0/0x170 [ 1626.609208] wait_for_completion+0x108/0x170 [ 1626.609210] ? wake_up_q+0x70/0x70 [ 1626.609212] ? __xfs_buf_submit+0x12e/0x250 [ 1626.609214] ? xfs_bwrite+0x25/0x60 [ 1626.609215] xfs_buf_iowait+0x22/0xf0 [ 1626.609218] __xfs_buf_submit+0x12e/0x250 [ 1626.609220] xfs_bwrite+0x25/0x60 [ 1626.609222] xfs_reclaim_inode+0x2e8/0x310 [ 1626.609224] xfs_reclaim_inodes_ag+0x1b6/0x300 [ 1626.609227] xfs_reclaim_inodes_nr+0x31/0x40 [ 1626.609228] super_cache_scan+0x152/0x1a0 [ 1626.609231] do_shrink_slab+0x12c/0x2d0 [ 1626.609233] shrink_slab+0x9c/0x2a0 [ 1626.609235] shrink_node+0xd7/0x470 [ 1626.609237] do_try_to_free_pages+0xbf/0x380 [ 1626.609240] try_to_free_pages+0xd9/0x1f0 [ 1626.609245] __alloc_pages_slowpath+0x3a4/0xd30 [ 1626.609251] ? ___slab_alloc+0x238/0x560 [ 1626.609254] __alloc_pages_nodemask+0x30c/0x350 [ 1626.609259] skb_page_frag_refill+0x97/0xd0 [ 1626.609274] sk_page_frag_refill+0x1d/0x80 [ 1626.609279] tcp_sendmsg_locked+0x2bb/0xdd0 [ 1626.609304] tcp_sendmsg+0x27/0x40 [ 1626.609307] sock_sendmsg+0x54/0x60 [ 1626.609308] ___sys_sendmsg+0x29f/0x320 [ 1626.609313] ? sock_poll+0x66/0xb0 [ 1626.609318] ? ep_item_poll.isra.15+0x40/0xc0 [ 1626.609320] ? ep_send_events_proc+0xe6/0x230 [ 1626.609322] ? hrtimer_try_to_cancel+0x54/0xf0 [ 1626.609324] ? ep_read_events_proc+0xc0/0xc0 [ 1626.609326] ? _raw_write_unlock_irq+0xa/0x20 [ 1626.609327] ? ep_scan_ready_list.constprop.19+0x218/0x230 [ 1626.609329] ? __hrtimer_init+0xb0/0xb0 [ 1626.609331] ? _raw_spin_unlock_irq+0xa/0x20 [ 1626.609334] ? ep_poll+0x26c/0x4a0 [ 1626.609337] ? tcp_tsq_write.part.54+0xa0/0xa0 [ 1626.609339] ? release_sock+0x43/0x90 [ 1626.609341] ? _raw_spin_unlock_bh+0xa/0x20 [ 1626.609342] __sys_sendmsg+0x47/0x80 [ 1626.609347] do_syscall_64+0x5f/0x1c0 [ 1626.609349] ? prepare_exit_to_usermode+0x75/0xa0 [ 1626.609351] entry_SYSCALL_64_after_hwframe+0x44/0xa9 This patch adds a new prctl command that daemons can use after they have done their initial setup, and before they start to do allocations that are in the IO path. It sets the PF_MEMALLOC_NOIO and PF_LESS_THROTTLE flags so both userspace block and FS threads can use it to avoid the allocation recursion and try to prevent from being throttled while writing out data to free up memory. Signed-off-by: Mike Christie --- V3=20 - Drop NOFS, set PF_LESS_THROTTLE and rename prctl flag to reflect it is more general and can support both FS and block devices. Both fuse and block device daemons, nbd and tcmu-runner, have been tested to confirm the more restrictive PF_MEMALLOC_NOIO also works for fuse. - Use CAP_SYS_RESOURCE instead of admin. V2: - Use prctl instead of procfs. - Add support for NOFS for fuse. - Check permissions. include/uapi/linux/capability.h | 1 + include/uapi/linux/prctl.h | 4 ++++ kernel/sys.c | 26 ++++++++++++++++++++++++++ 3 files changed, 31 insertions(+) diff --git a/include/uapi/linux/capability.h b/include/uapi/linux/capabilit= y.h index 240fdb9a60f6..272dc69fa080 100644 --- a/include/uapi/linux/capability.h +++ b/include/uapi/linux/capability.h @@ -301,6 +301,7 @@ struct vfs_ns_cap_data { /* Allow more than 64hz interrupts from the real-time clock */ /* Override max number of consoles on console allocation */ /* Override max number of keymaps */ +/* Control memory reclaim behavior */ =20 #define CAP_SYS_RESOURCE 24 =20 diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 7da1b37b27aa..07b4f8131e36 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -234,4 +234,8 @@ struct prctl_mm_map { #define PR_GET_TAGGED_ADDR_CTRL=09=0956 # define PR_TAGGED_ADDR_ENABLE=09=09(1UL << 0) =20 +/* Control reclaim behavior when allocating memory */ +#define PR_SET_IO_FLUSHER=09=0957 +#define PR_GET_IO_FLUSHER=09=0958 + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/sys.c b/kernel/sys.c index a611d1d58c7d..08c6b682fa99 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2486,6 +2486,32 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, a= rg2, unsigned long, arg3, =09=09=09return -EINVAL; =09=09error =3D GET_TAGGED_ADDR_CTRL(); =09=09break; +=09case PR_SET_IO_FLUSHER: +=09=09if (!capable(CAP_SYS_RESOURCE)) +=09=09=09return -EPERM; + +=09=09if (arg3 || arg4 || arg5) +=09=09=09return -EINVAL; + +=09=09if (arg2 =3D=3D 1) +=09=09=09current->flags |=3D PF_MEMALLOC_NOIO | PF_LESS_THROTTLE; +=09=09else if (!arg2) +=09=09=09current->flags &=3D ~(PF_MEMALLOC_NOIO | PF_LESS_THROTTLE); +=09=09else +=09=09=09return -EINVAL; +=09=09break; +=09case PR_GET_IO_FLUSHER: +=09=09if (!capable(CAP_SYS_RESOURCE)) +=09=09=09return -EPERM; + +=09=09if (arg2 || arg3 || arg4 || arg5) +=09=09=09return -EINVAL; + +=09=09if (current->flags & (PF_MEMALLOC_NOIO | PF_LESS_THROTTLE)) +=09=09=09error =3D 1; +=09=09else +=09=09=09error =3D 0; +=09=09break; =09default: =09=09error =3D -EINVAL; =09=09break; --=20 2.20.1