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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, 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 1AF7AC43467 for ; Fri, 9 Oct 2020 12:52:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B6EBA222C2 for ; Fri, 9 Oct 2020 12:52:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="h5vw1Q6e" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732256AbgJIMwD (ORCPT ); Fri, 9 Oct 2020 08:52:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38304 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387784AbgJIMv4 (ORCPT ); Fri, 9 Oct 2020 08:51:56 -0400 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 7B99FC0613D2; Fri, 9 Oct 2020 05:51:54 -0700 (PDT) Received: by mail-oi1-x241.google.com with SMTP id w141so10105600oia.2; Fri, 09 Oct 2020 05:51:54 -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=IWHS/EzbCD9llYg4YvlRdsM69gVjza4DYN+VKGEIyMg=; b=h5vw1Q6ehhkRgK4e44tdZ+0HbAzNFI8qUb/ZJPMtabBsNhLZC9e6HKpsztK7jAt9zr 2i5M2i1Oye0qU6ht4nMYcGYcAE0YpADJFHp5owXWgqW3dlo/rZZdsks5gs+2L236iPcN jjP3G3gxh+mnqrv76oor3DuZqjElcgaj0ZCnJQ6m28rRrFFpIP0GFGFifKC2y7xCWFYx PAw2DtxrYxJqHsoLsy2EuN36BFX6medYFN/26vXu0owsFjZk6d1QQPaJYSKGnqiytOYJ TotWyoiAkkcLcnpGh58jepjHzi7wotjSkrgEixplaUz9oNutWevFbhGwTtO44U89wgAq grDA== 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=IWHS/EzbCD9llYg4YvlRdsM69gVjza4DYN+VKGEIyMg=; b=S+HuG1xLBrmgpVzeXklKEnORa4t0w2qcJDqIV5OLnpndMGQHYK5uu+8jAddFB8QOIF 5oQWjqz6X4PTwf9s5kBLi4dDo8ZtIfUmDrCTikgYXEzNGbVYlfkWMYyTMGXvdm9iDx2/ T1MdhHqELQMFvkqBA1901xT9m6JnecjRSaLKM12aPmwOZNJfocZg/Vl4dYPlKOcG9c9I 1q6JoDyy2WHJBpDvNz37c7pc3r6YrveT5MSmCWZ7oxQGVFMhpLDdGXwKUYiFpgDnA25h cCz6zLuL4Qq6xVMM++sSQMS07lOyLYz2G0TwHhpsk37Qx1hL0e9pRzi7w0tSR7pgt6Ah oozg== X-Gm-Message-State: AOAM532GZ3HLW4adKmZ1iu+4VWtZ8VHh651I7Q8P6D8VBZE7+3sLHVVR MQQoU+QXxwoL3YxsptYGE9w= X-Google-Smtp-Source: ABdhPJywSKrlmzTUV7BRYRzAJplTpQbx7iJIc7TG42ucjslz9rub42PFEY/nsBW/GI1ccLRmnf4a3w== X-Received: by 2002:aca:4ad0:: with SMTP id x199mr2315208oia.113.1602247913752; Fri, 09 Oct 2020 05:51:53 -0700 (PDT) Received: from localhost.localdomain ([50.236.19.102]) by smtp.gmail.com with ESMTPSA id l25sm6736861otb.4.2020.10.09.05.51.49 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 09 Oct 2020 05:51:52 -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 v8 1/2] mm: Add become_kswapd and restore_kswapd Date: Fri, 9 Oct 2020 20:51:26 +0800 Message-Id: <20201009125127.37435-2-laoar.shao@gmail.com> X-Mailer: git-send-email 2.17.2 (Apple Git-113) In-Reply-To: <20201009125127.37435-1-laoar.shao@gmail.com> References: <20201009125127.37435-1-laoar.shao@gmail.com> 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: 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 466fc3144fff..eb6f6e8103c1 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3867,19 +3867,7 @@ 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); @@ -3929,8 +3917,6 @@ static int kswapd(void *p) goto kswapd_try_sleep; } - tsk->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD); - return 0; } -- 2.17.1