From patchwork Thu Aug 27 01:34:43 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 11739803 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 9B72B13B1 for ; Thu, 27 Aug 2020 01:35:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 82E3E2087C for ; Thu, 27 Aug 2020 01:35:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="k6dwmBVs" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726802AbgH0BfL (ORCPT ); Wed, 26 Aug 2020 21:35:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49342 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726784AbgH0BfI (ORCPT ); Wed, 26 Aug 2020 21:35:08 -0400 Received: from mail-qv1-xf41.google.com (mail-qv1-xf41.google.com [IPv6:2607:f8b0:4864:20::f41]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3D215C0617BB; Wed, 26 Aug 2020 18:35:08 -0700 (PDT) Received: by mail-qv1-xf41.google.com with SMTP id o2so1972501qvk.6; Wed, 26 Aug 2020 18:35:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=859mhnP8u9rodAzdukpHAhCDlaIXdEIMkMf65c9ms04=; b=k6dwmBVsmvY58/1KhZx8eVLxr1b8SKUWz6ZGelSvEl8OST103ZFGYtQ7M5uCa2Wt+u cZ4N+KeTVOc6IIbz0lu2DaqSFFP2mWfN5UaypUUatk//5JfJUFuBllhlVx55e/sBdkYr zrQYbtjb20JcwykQleBIcZ3OJAguWiAyzuNWldaXXy8uEsHhSRMsMAPcI7n1eN2nYaOy EF8558pTT2XoOvtfZHblRPINv0rYusnq13+D61lJXb41ozg3qzpfoeWNyLxpR4UnRCmx 7voHN16ZAveN1lp1NhqdXd7zEMOVCfFKOTcuXOfNdWQBz2JfLLFfBDiA7j5Lhj62JWtk aBbw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=859mhnP8u9rodAzdukpHAhCDlaIXdEIMkMf65c9ms04=; b=RR78OSTSc64KeZFfWnrvJDvN+Zg3WFSbyliD7PhUmu9PmRnkmGrU4/CTq/mnYHa4sq bXRDs+tvHUFHz5fCsxSJEids3iHRMpigYhsXV3g0b8do1Ral/XsQJDu4jKXHQX6/46vS nKWmSwYbyostA22PE8ShqSeUy/xRi1K72K+2GY5P2Xbh1R9eVYwzACmbWCBtV8hNrUqo 4iePYEnmMIz6q1WBAR8KDMsXn20rmmCSRTIT3lwTLi775EfJ4SzQ/VK/rPqqRcRZezYb fmG5QQCCM4/lsqz6ekb3uVLxF2xNRfy+ZEePHdrWax1imm4eSvWGPoimsD7XAXXGDj0I CnjA== X-Gm-Message-State: AOAM531o4oh01poMI/F3lTkEnfiZtNzDHzGY1xdsUAu5F3f/P/r1p4gn VpCjMQYW4Gjbjs/eZooWltM= X-Google-Smtp-Source: ABdhPJz/2AVTAxCYK2a/koRZs00sb0kfe7WN5CEQOBh/yfgGy/tDE8zCrd2oqbfWJYCqjBfcY2iS+Q== X-Received: by 2002:ad4:4cc9:: with SMTP id i9mr16521667qvz.131.1598492107244; Wed, 26 Aug 2020 18:35:07 -0700 (PDT) Received: from localhost.localdomain ([50.236.19.102]) by smtp.gmail.com with ESMTPSA id i18sm631846qtv.39.2020.08.26.18.35.02 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 26 Aug 2020 18:35:06 -0700 (PDT) From: Yafang Shao To: david@fromorbit.com, hch@infradead.org, darrick.wong@oracle.com, willy@infradead.org, mhocko@kernel.org, akpm@linux-foundation.org Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Yafang Shao Subject: [PATCH v7 1/2] mm: Add become_kswapd and restore_kswapd Date: Thu, 27 Aug 2020 09:34:43 +0800 Message-Id: <20200827013444.24270-2-laoar.shao@gmail.com> X-Mailer: git-send-email 2.17.2 (Apple Git-113) In-Reply-To: <20200827013444.24270-1-laoar.shao@gmail.com> References: <20200827013444.24270-1-laoar.shao@gmail.com> Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org From: "Matthew Wilcox (Oracle)" Since XFS needs to pretend to be kswapd in some of its worker threads, create methods to save & restore kswapd state. Don't bother restoring kswapd state in kswapd -- the only time we reach this code is when we're exiting and the task_struct is about to be destroyed anyway. Cc: Dave Chinner Cc: Christoph Hellwig Cc: Darrick J. Wong Cc: Matthew Wilcox Acked-by: Michal Hocko Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Yafang Shao --- fs/xfs/libxfs/xfs_btree.c | 14 ++++++++------ include/linux/sched/mm.h | 23 +++++++++++++++++++++++ mm/vmscan.c | 16 +--------------- 3 files changed, 32 insertions(+), 21 deletions(-) diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c index 2d25bab68764..a04a44238aab 100644 --- a/fs/xfs/libxfs/xfs_btree.c +++ b/fs/xfs/libxfs/xfs_btree.c @@ -2813,8 +2813,9 @@ xfs_btree_split_worker( { struct xfs_btree_split_args *args = container_of(work, struct xfs_btree_split_args, work); + bool is_kswapd = args->kswapd; unsigned long pflags; - unsigned long new_pflags = PF_MEMALLOC_NOFS; + int memalloc_nofs; /* * we are in a transaction context here, but may also be doing work @@ -2822,16 +2823,17 @@ xfs_btree_split_worker( * temporarily to ensure that we don't block waiting for memory reclaim * in any way. */ - if (args->kswapd) - new_pflags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; - - current_set_flags_nested(&pflags, new_pflags); + if (is_kswapd) + pflags = become_kswapd(); + memalloc_nofs = memalloc_nofs_save(); args->result = __xfs_btree_split(args->cur, args->level, args->ptrp, args->key, args->curp, args->stat); complete(args->done); - current_restore_flags_nested(&pflags, new_pflags); + memalloc_nofs_restore(memalloc_nofs); + if (is_kswapd) + restore_kswapd(pflags); } /* diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index f889e332912f..b38fdcb977a4 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -303,6 +303,29 @@ static inline void memalloc_nocma_restore(unsigned int flags) } #endif +/* + * Tell the memory management code that this thread is working on behalf + * of background memory reclaim (like kswapd). That means that it will + * get access to memory reserves should it need to allocate memory in + * order to make forward progress. With this great power comes great + * responsibility to not exhaust those reserves. + */ +#define KSWAPD_PF_FLAGS (PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD) + +static inline unsigned long become_kswapd(void) +{ + unsigned long flags = current->flags & KSWAPD_PF_FLAGS; + + current->flags |= KSWAPD_PF_FLAGS; + + return flags; +} + +static inline void restore_kswapd(unsigned long flags) +{ + current->flags &= ~(flags ^ KSWAPD_PF_FLAGS); +} + #ifdef CONFIG_MEMCG /** * memalloc_use_memcg - Starts the remote memcg charging scope. diff --git a/mm/vmscan.c b/mm/vmscan.c index 99e1796eb833..3a2615bfde35 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3859,19 +3859,7 @@ static int kswapd(void *p) if (!cpumask_empty(cpumask)) set_cpus_allowed_ptr(tsk, cpumask); - /* - * Tell the memory management that we're a "memory allocator", - * and that if we need more memory we should get access to it - * regardless (see "__alloc_pages()"). "kswapd" should - * never get caught in the normal page freeing logic. - * - * (Kswapd normally doesn't need memory anyway, but sometimes - * you need a small amount of memory in order to be able to - * page out something else, and this flag essentially protects - * us from recursively trying to free more memory as we're - * trying to free the first piece of memory in the first place). - */ - tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; + become_kswapd(); set_freezable(); WRITE_ONCE(pgdat->kswapd_order, 0); @@ -3921,8 +3909,6 @@ static int kswapd(void *p) goto kswapd_try_sleep; } - tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD); - return 0; }