From patchwork Wed Aug 19 02:24:24 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 11722385 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 901E813B1 for ; Wed, 19 Aug 2020 02:25:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 77AB7207BB for ; Wed, 19 Aug 2020 02:25:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="g6IVo8SN" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726870AbgHSCZR (ORCPT ); Tue, 18 Aug 2020 22:25:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51208 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726372AbgHSCZR (ORCPT ); Tue, 18 Aug 2020 22:25:17 -0400 Received: from mail-qv1-xf44.google.com (mail-qv1-xf44.google.com [IPv6:2607:f8b0:4864:20::f44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6CEFBC061389; Tue, 18 Aug 2020 19:25:16 -0700 (PDT) Received: by mail-qv1-xf44.google.com with SMTP id t6so10626318qvw.1; Tue, 18 Aug 2020 19:25:16 -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=NRcr1uR+jWrXWzQj4QCI0O5tOCY1uyw+iu2TAziMeTw=; b=g6IVo8SNkSoc13ObF7oUgd3Gzgh8q53F3K8BgSOlps6OhWtNQvqUcss/Mk7DyGZfEz HtWw2IuxUFN0sB1Rh3IkVT28nccCyK3Kgg1tdvz39hIf6SqKI2dVu5IY2nUZFDookii7 JfZ57jQZmunF9GVf9ezeTqLvNv8H6vxr/Z910Pidty32BYdKrhmXbxgkp1KfG+chdf/V 0r/jLVtedaMf86ZlvC+i2W+ctu0gOyOrTo999TaPg3tUmR6P1APbTKy4Dw9blV/kRWpZ ZPpUH8i2JCMN/rrs1PsDi1yypkfPESV5qMhOI6tqCTOX7MmTwlFDBfjlK1nAaKK8jAKK T1xQ== 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=NRcr1uR+jWrXWzQj4QCI0O5tOCY1uyw+iu2TAziMeTw=; b=qQqlA1xmfvgZGYKPrX2uNVzmKQU61iZkeCgyAOnUt2Eoe5ZJVfc2JWKDWPduv9wFdZ nyqAdADqchO6T669yw3Z83g+GuANCZkQl8f3h2uAwJdxEwZ4EZdXY23vp470ZQibqsFt NqerYWG2449jBz3hdwlPTR8jBON6VKLOpSym5O+BHR8C9S3wGYw7J8lRvVkvqPGF72X+ e8Ga5jxP1DRHcALnw2KY/FJ55YL/tPM8Zs2MuSUAusIOXTwToQVGyJziaBe1w0SDDCMC wl2HlMtO2aPtUDBnmVHyGuKYT3JvRZGnOxnMRUXs8utX0+hxNkgliXYHoR3GXU9QeD+w Dv6w== X-Gm-Message-State: AOAM532GVO3PNWn3xcTcGETuz03jhJH5CVCTIXKezTF+wYQv5vV6JAQU oOx1avjoJsCcPOQhs7HjbQs= X-Google-Smtp-Source: ABdhPJx8Kw+IH+QeI3+5U/fnvkMljo7NN7EJojoUfStufzv8ixioHaLNelz+8ih/iIifgLjuJC7kbw== X-Received: by 2002:a0c:8b51:: with SMTP id d17mr22126354qvc.107.1597803915736; Tue, 18 Aug 2020 19:25:15 -0700 (PDT) Received: from localhost.localdomain ([50.236.19.102]) by smtp.gmail.com with ESMTPSA id t12sm21988275qkt.56.2020.08.18.19.25.10 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Aug 2020 19:25:15 -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 v5 1/2] mm: Add become_kswapd and restore_kswapd Date: Wed, 19 Aug 2020 10:24:24 +0800 Message-Id: <20200819022425.25188-2-laoar.shao@gmail.com> X-Mailer: git-send-email 2.17.2 (Apple Git-113) In-Reply-To: <20200819022425.25188-1-laoar.shao@gmail.com> References: <20200819022425.25188-1-laoar.shao@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@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: Michal Hocko Cc: Darrick J. Wong Cc: Matthew Wilcox Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Yafang Shao Acked-by: Michal Hocko --- fs/xfs/libxfs/xfs_btree.c | 14 ++++++++------ include/linux/sched/mm.h | 28 ++++++++++++++++++++++++++++ mm/vmscan.c | 16 +--------------- 3 files changed, 37 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..80cc132f13a1 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -303,6 +303,34 @@ static inline void memalloc_nocma_restore(unsigned int flags) } #endif +/* + * 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). + */ +#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; }