From patchwork Tue Dec 8 02:15:40 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 11957437 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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 3E13FC433FE for ; Tue, 8 Dec 2020 02:17:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0A4A623A33 for ; Tue, 8 Dec 2020 02:17:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727739AbgLHCQ7 (ORCPT ); Mon, 7 Dec 2020 21:16:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37638 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725877AbgLHCQ7 (ORCPT ); Mon, 7 Dec 2020 21:16:59 -0500 Received: from mail-ua1-x941.google.com (mail-ua1-x941.google.com [IPv6:2607:f8b0:4864:20::941]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3212CC0613D6; Mon, 7 Dec 2020 18:16:19 -0800 (PST) Received: by mail-ua1-x941.google.com with SMTP id t15so5164799ual.6; Mon, 07 Dec 2020 18:16:19 -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 :mime-version:content-transfer-encoding; bh=m+1GohZiu08TBGb+QZ95Ht2UJWzVkthZE/EPME/oCwk=; b=p+Vo22Ajj0KnaKJDOjLCWdum9GRkWkLPGj0o9AcWdZtvcNVz5rGJDgCkqCrDKLb6HR 07gGPDmiz2npXEvGiA+LDy6Q3KvxzbzsexQe9RGeUpO4N8m7NixtQO6T5Dz0cArVtPAP eQRdT+IHaBkiCRTp+o+TxWgV9tKTj5kqEH+5oYd73+kY92dYa6nEvqMvMuHx56CTVnUr Hk0TaAwkFS0UZTfOtYx5/E5922Q+9vBv7uRctfagykQXrwS1p4y7enLf/R5hxBwuTvne +M4EURRe7uj3g2Bxb1bXSHY/XZ+1Fl+o3pZ42FIMuGw/YpMc4nNW9gP+ppH01AUZzEZ4 Le/g== 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:mime-version:content-transfer-encoding; bh=m+1GohZiu08TBGb+QZ95Ht2UJWzVkthZE/EPME/oCwk=; b=qhNq4x8/e3CbP0sBWB4HVWCEMGuR7m+TcmZ4Uz75oKGh8elIlAf1v3BMIQl7Zke1e2 puqJhJRF1LSYjkUF2I0JQuco/g8HnPg4a5QZC6poXV3rTjXHAaQiAOXonlQdu9+RxmLr aiIb3Sk7DZ6qYPZycZIlpLk6cSrrQnEZKbgi2vFyxhDNPTvf6SNGiKK0u3ONQU+M+jR0 U/9ZGaXac0Zwx13XIbe6uZ1aAM8Z2nRfDEep3cRAFvxW4GwuSxOzrQPnNMmmFh0iGq2N 4y103P+7m/Dli7wQipaHyMwx8Gf4HmXRWCwa/U7RsHMEHmE5uS26B+JjY6TNB7P0hs/l p+JA== X-Gm-Message-State: AOAM530w5XTpRoTo/pyiSYn44gEESqAsKrmlR6FuSdlIyNbPTRqQufce IVlRxRFAiG/WLRlS3mM2pto= X-Google-Smtp-Source: ABdhPJykWOCUKyytu1BnOcC+NQiG9kaP5230ROkGfHRFt5Xw95zgweMCGNA0vNbhM+PCV+YvuSadfg== X-Received: by 2002:a9f:26c5:: with SMTP id 63mr15305401uay.25.1607393778460; Mon, 07 Dec 2020 18:16:18 -0800 (PST) Received: from localhost.localdomain ([50.236.19.102]) by smtp.gmail.com with ESMTPSA id o192sm1936000vko.19.2020.12.07.18.16.12 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 07 Dec 2020 18:16:17 -0800 (PST) From: Yafang Shao To: darrick.wong@oracle.com, willy@infradead.org, david@fromorbit.com, hch@infradead.org, mhocko@kernel.org, akpm@linux-foundation.org, dhowells@redhat.com, jlayton@redhat.com Cc: linux-fsdevel@vger.kernel.org, linux-cachefs@redhat.com, linux-xfs@vger.kernel.org, linux-mm@kvack.org, Michal Hocko , Christoph Hellwig , Yafang Shao Subject: [PATCH v10 1/4] mm: Add become_kswapd and restore_kswapd Date: Tue, 8 Dec 2020 10:15:40 +0800 Message-Id: <20201208021543.76501-2-laoar.shao@gmail.com> X-Mailer: git-send-email 2.24.3 (Apple Git-128) In-Reply-To: <20201208021543.76501-1-laoar.shao@gmail.com> References: <20201208021543.76501-1-laoar.shao@gmail.com> MIME-Version: 1.0 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 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 d5ece7a9a403..2faf03e79a1e 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 1b8f0e059767..77bc1dda75bf 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; }