From patchwork Tue Nov 3 13:17:53 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 11877455 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 C7BED6A2 for ; Tue, 3 Nov 2020 13:18:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9D3212224E for ; Tue, 3 Nov 2020 13:18:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="U4Sq0WIh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728245AbgKCNS1 (ORCPT ); Tue, 3 Nov 2020 08:18:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729183AbgKCNS0 (ORCPT ); Tue, 3 Nov 2020 08:18:26 -0500 Received: from mail-oi1-x241.google.com (mail-oi1-x241.google.com [IPv6:2607:f8b0:4864:20::241]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BA251C0613D1; Tue, 3 Nov 2020 05:18:26 -0800 (PST) Received: by mail-oi1-x241.google.com with SMTP id t16so957206oie.11; Tue, 03 Nov 2020 05:18:26 -0800 (PST) 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=wcewLsncu9ZYLAdf8Dj+b3i3xIrhlEzCNXPbs1EqjSc=; b=U4Sq0WIhR9xhMN9zPWhvg/zls9REX7I5XS/eUk2Dmrg1PTGMlH1hqkaQhkJsZW4aFs HrzLLXJxQx4kGNkUK94cTwvSumfEUW+OSbdZYyoZx3Qqee+1b7NjQowPXNXKtQlMcqqs iIwgdq+MNQBS+u0Kn4Wn/U+aAR5ZdkGh1ICGYhD3fNGn8gb9XE2GKYGBV8WcpbRtaw/c htJYPkbAEBUYmJK0SGX2FdKMPK33YSZtRS1HdZ836qNuvDSdrIw2S1FOvdcd053EIuuK 6A+2buP86nqP0qO5t2ucS15ZhxZM9yku26PMyApS3/c48JLNnV9oo4FYG8a1AhbrcZwm UGtA== 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=wcewLsncu9ZYLAdf8Dj+b3i3xIrhlEzCNXPbs1EqjSc=; b=KjEgh4d7UfB0ycaOsIZSjUv6W2Ru0Io8N2GdvjzpYhKvqh6zDmpRuHp0+5+nGaplLo /Fyf2+S1vaSW1NvFRYS9410Qp6iz7j4X6nkEa+PkKxFEZY1kn0X4fc1e4yYl34Vv7VnU BbquqQQysV3hpAXAYU/KeGzU2v4HWh7sYDcqTbQICh9Th8CfIJjFzKeMto4Sntf8tK+R tKZrKGpVsyu9zP/ALPbD8juxDsYbEtJ3YJncKULsX8WCcXtz4S+ypJYGMwwlKgdN2wM6 3rjz1n85ATmhhoFm8y3Cpf51lDvGV7aFbjIiwsCQYLWKPOr+I6gcyd6efCpVqpdKQFH0 A1kg== X-Gm-Message-State: AOAM530hPtbKdfgva52q7NGs2UX3MH+hwfT6l+3kW3UXgygmjYKqh3Ba WiLJQFSn8LvGEs4YFQUEe4g= X-Google-Smtp-Source: ABdhPJxxY1oARG/kzprtfN6LQpvSv/dkZkBdU/f6ENapc5lPESBoit+o9PJKuZzR/35lv0PKgZQ8Aw== X-Received: by 2002:aca:1e08:: with SMTP id m8mr1763659oic.168.1604409506161; Tue, 03 Nov 2020 05:18:26 -0800 (PST) Received: from localhost.localdomain ([50.236.19.102]) by smtp.gmail.com with ESMTPSA id f18sm4396138otf.55.2020.11.03.05.18.22 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 03 Nov 2020 05:18:25 -0800 (PST) From: Yafang Shao To: akpm@linux-foundation.org Cc: david@fromorbit.com, hch@infradead.org, darrick.wong@oracle.com, willy@infradead.org, mhocko@kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, Yafang Shao Subject: [PATCH v8 resend 1/2] mm: Add become_kswapd and restore_kswapd Date: Tue, 3 Nov 2020 21:17:53 +0800 Message-Id: <20201103131754.94949-2-laoar.shao@gmail.com> X-Mailer: git-send-email 2.17.2 (Apple Git-113) In-Reply-To: <20201103131754.94949-1-laoar.shao@gmail.com> References: <20201103131754.94949-1-laoar.shao@gmail.com> 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 Acked-by: Michal Hocko Reviewed-by: Darrick J. Wong Reviewed-by: Christoph Hellwig 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 2d25bab..a04a442 100644 --- a/fs/xfs/libxfs/xfs_btree.c +++ b/fs/xfs/libxfs/xfs_btree.c @@ -2813,8 +2813,9 @@ struct xfs_btree_split_args { { 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 @@ struct xfs_btree_split_args { * 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 d5ece7a..2faf03e 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -278,6 +278,29 @@ 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 DECLARE_PER_CPU(struct mem_cgroup *, int_active_memcg); /** diff --git a/mm/vmscan.c b/mm/vmscan.c index 1b8f0e0..77bc1dd 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3869,19 +3869,7 @@ 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); @@ -3931,8 +3919,6 @@ static int kswapd(void *p) goto kswapd_try_sleep; } - tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD); - return 0; }