From patchwork Tue Dec 8 12:28:21 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 11958491 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 F3250C2BB40 for ; Tue, 8 Dec 2020 12:29:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B7C3023AFB for ; Tue, 8 Dec 2020 12:29:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728362AbgLHM3h (ORCPT ); Tue, 8 Dec 2020 07:29:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47200 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727132AbgLHM3g (ORCPT ); Tue, 8 Dec 2020 07:29:36 -0500 Received: from mail-ua1-x943.google.com (mail-ua1-x943.google.com [IPv6:2607:f8b0:4864:20::943]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C4D89C061793; Tue, 8 Dec 2020 04:28:55 -0800 (PST) Received: by mail-ua1-x943.google.com with SMTP id x13so5555557uar.4; Tue, 08 Dec 2020 04:28:55 -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=YEmgihWu/wyME49Crb+Ui5skh2RdMWbWg2K3AhmtC/CFf02gcWUiLcLHyMf5BV9baW HxLDWnal78Tb1+b0V4OFd1uWOhOZrXPwa9ZgnCeTqa7d3vTykuaipdlmhup/s37Mxpc5 wIEaXZEtnHqexxSDy+4GSO+KtsLfm8z14U05euSod0UjN+4ZJEimAP0ykzOJ37gi7/Pe 6czzyd15HDLhcQvSjsMkkjeCzHqJ50g+okrNzSFIkTj3tPCKl5MUt/y/Ew2fzpoZdqXT N97LtMtioLe7MgWcPSGwjmXWDpnWxGdsXXR9+ndl310kUPDVqi7yT+4LwGu0OY9lAgTC 5xTg== 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=o1AGn/poc2x3FvPWuRAeByOt0LSIvTXaEJJYsIWciiYhwg5xtY7cma09C/uQXcq5wa 9jBizLO1Vn0MZpQa/6zHTBaQpLI1r33s4aIn4Q58ysQGaqIr4Ju9EDoX9GhlmxOn3De1 pxvtZGbHQEsqqu097O+Rlbo/Z56o6uPMfRzkJZRPS1ODb8Xh+TQzlmnBiOFCL5HXbtbl pqXqnDV3d47q8TX4ObB+u+5ofKdY8PAnVbLk/FbKbCZRVBc7uwddKeT6x/+oNHvWTJd5 D9jU/Ckf3u6fZHxDn4kA9aDQQjsNTmOk06drW7+piagl8nncJoQLSUyLk3208VsVyaFp Ne6A== X-Gm-Message-State: AOAM533ycU4ptzL1nNrvCEf5WVM43fKrvri4YrHOCBGgz9F6QKJyylZN rLOCjNDauvGzeOnxAO+nzRE= X-Google-Smtp-Source: ABdhPJwyTfuHVqxNaklmZUbRSVY+4dw2M5F4PnVl8WHL3hn8HrKwFuRflsBxvRdIlZG2xwXQ2agulQ== X-Received: by 2002:ab0:2707:: with SMTP id s7mr368576uao.65.1607430535014; Tue, 08 Dec 2020 04:28:55 -0800 (PST) Received: from localhost.localdomain ([50.236.19.102]) by smtp.gmail.com with ESMTPSA id w202sm2001106vkd.25.2020.12.08.04.28.48 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 08 Dec 2020 04:28:54 -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 v11 1/4] mm: Add become_kswapd and restore_kswapd Date: Tue, 8 Dec 2020 20:28:21 +0800 Message-Id: <20201208122824.16118-2-laoar.shao@gmail.com> X-Mailer: git-send-email 2.24.3 (Apple Git-128) In-Reply-To: <20201208122824.16118-1-laoar.shao@gmail.com> References: <20201208122824.16118-1-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; }