From patchwork Mon Mar 16 10:39:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 11440115 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 819261667 for ; Mon, 16 Mar 2020 10:40:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5818620724 for ; Mon, 16 Mar 2020 10:40:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="DS6qyJAV" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730653AbgCPKka (ORCPT ); Mon, 16 Mar 2020 06:40:30 -0400 Received: from mail-pf1-f193.google.com ([209.85.210.193]:41297 "EHLO mail-pf1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730497AbgCPKka (ORCPT ); Mon, 16 Mar 2020 06:40:30 -0400 Received: by mail-pf1-f193.google.com with SMTP id z65so9692765pfz.8 for ; Mon, 16 Mar 2020 03:40:30 -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=2GXt5l0BnU2RaVncy40HZUiqISCrmfLRyzDrfxLSYfo=; b=DS6qyJAVsjhyGFLKknVXpXrpm8SXdExRu5smq/INJvlVQNIksj/Z/DLTRGiDCGpf1g CJDalo4ezR0dkUepeQbBTC6a+nWdpToG3zBO+Cw4NpW38yZ7UNAAx/yOVopse2BmkcTR 0ag3iz6UBPaArUSqXLv6c4I50C65K1jEUDXZFBkjRiZMmaf6tHafTYptAhenll4rwRR+ vD86Fumx1e1+kMiqv0bUHeeS1hf8OgTtKSzwQ5VpkKvOmxsbQCzRV//YZObofz82x2k7 a1ItwC4dOxG4+53n6ZEmiv86CW2ZtPOE3lBWbIQ3iqNvXw+uz4yVnVVMLbPCz+OjLZrA WXJQ== 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=2GXt5l0BnU2RaVncy40HZUiqISCrmfLRyzDrfxLSYfo=; b=Auzi47AHzemAoqJV4AItmD0T10ego9mIAxS3DU0V+UG3sxtFMxo7r03odbtA1a/+1F L0jCN2kcTOFcOyy184zj50Ckwf6ZApT0CpZ9aKKnwHbYjNL7fi/8cmdNFQsTdJYAxChO 8usYC7wWCtlZXIZ6twksRPZ0KYzIQfmEYFVilpzFxNs5zU3aM2lUQm0WCVJYVs5kTYbM KwVvUMzDjo/FbDFreZOLxO2gIy3++FLK6kSadL37ejFCV/22HiLlVCq8ejdMO/+19aVT u7bqD2XIXcDY1XJbP4banvoClOBWkgojZgTC6H23WhXMxOXrfJUNtXAsHTOZNeBO59wl tKHg== X-Gm-Message-State: ANhLgQ3ZujBcw1DZcyd98hvHt4eix/oBy9LZ7MOMF/hkwOpaMel8F3J3 Tn5IuH1ClcwW0FrvgXVrzwE= X-Google-Smtp-Source: ADFU+vsDFwodClKlUJFRep/E7/L5Oz3gg/x0Pio8rVsxenPZ+WUNteouZKf+PQdwdm5z0p4Mb76Hdg== X-Received: by 2002:a62:1dd3:: with SMTP id d202mr5005931pfd.47.1584355229901; Mon, 16 Mar 2020 03:40:29 -0700 (PDT) Received: from dev.localdomain ([203.100.54.194]) by smtp.gmail.com with ESMTPSA id h2sm19834276pjc.7.2020.03.16.03.40.26 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 16 Mar 2020 03:40:29 -0700 (PDT) From: Yafang Shao To: dchinner@redhat.com, hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, guro@fb.com, akpm@linux-foundation.org, viro@zeniv.linux.org.uk, willy@infradead.org Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Yafang Shao Subject: [PATCH v6 1/3] mm, list_lru: make memcg visible to lru walker isolation function Date: Mon, 16 Mar 2020 06:39:56 -0400 Message-Id: <1584355198-10137-2-git-send-email-laoar.shao@gmail.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1584355198-10137-1-git-send-email-laoar.shao@gmail.com> References: <1584355198-10137-1-git-send-email-laoar.shao@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org The lru walker isolation function may use this memcg to do something, e.g. the inode isolatation function will use the memcg to do inode protection in followup patch. So make memcg visible to the lru walker isolation function. Something should be emphasized in this patch is it replaces for_each_memcg_cache_index() with for_each_mem_cgroup() in list_lru_walk_node(). Because there's a gap between these two MACROs that for_each_mem_cgroup() depends on CONFIG_MEMCG while the other one depends on CONFIG_MEMCG_KMEM. But as list_lru_memcg_aware() returns false if CONFIG_MEMCG_KMEM is not configured, it is safe to this replacement. Another difference between for_each_memcg_cache_index() and for_each_mem_cgroup() is that for_each_memcg_cache_index() excludes the root_mem_cgroup because its kmemcg_id is -1, while for_each_mem_cgroup() includes the root_mem_cgroup. So we need to skip the root_mem_cgroup explicitly in the for loop. Cc: Matthew Wilcox Cc: Dave Chinner Signed-off-by: Yafang Shao --- include/linux/memcontrol.h | 18 ++++++++++++++++++ mm/list_lru.c | 47 +++++++++++++++++++++++++++------------------- mm/memcontrol.c | 15 --------------- 3 files changed, 46 insertions(+), 34 deletions(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index a7a0a1a5..39be2e4 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -445,6 +445,21 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *, int mem_cgroup_scan_tasks(struct mem_cgroup *, int (*)(struct task_struct *, void *), void *); +/* + * Iteration constructs for visiting all cgroups (under a tree). If + * loops are exited prematurely (break), mem_cgroup_iter_break() must + * be used for reference counting. + */ +#define for_each_mem_cgroup_tree(iter, root) \ + for (iter = mem_cgroup_iter(root, NULL, NULL); \ + iter != NULL; \ + iter = mem_cgroup_iter(root, iter, NULL)) + +#define for_each_mem_cgroup(iter) \ + for (iter = mem_cgroup_iter(NULL, NULL, NULL); \ + iter != NULL; \ + iter = mem_cgroup_iter(NULL, iter, NULL)) + static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg) { if (mem_cgroup_disabled()) @@ -945,6 +960,9 @@ static inline int mem_cgroup_scan_tasks(struct mem_cgroup *memcg, return 0; } +#define for_each_mem_cgroup(iter) \ + for (iter = NULL; iter; ) + static inline unsigned short mem_cgroup_id(struct mem_cgroup *memcg) { return 0; diff --git a/mm/list_lru.c b/mm/list_lru.c index 0f1f6b0..6daa8c6 100644 --- a/mm/list_lru.c +++ b/mm/list_lru.c @@ -207,11 +207,11 @@ unsigned long list_lru_count_node(struct list_lru *lru, int nid) EXPORT_SYMBOL_GPL(list_lru_count_node); static unsigned long -__list_lru_walk_one(struct list_lru_node *nlru, int memcg_idx, +__list_lru_walk_one(struct list_lru_node *nlru, struct mem_cgroup *memcg, list_lru_walk_cb isolate, void *cb_arg, unsigned long *nr_to_walk) { - + int memcg_idx = memcg_cache_id(memcg); struct list_lru_one *l; struct list_head *item, *n; unsigned long isolated = 0; @@ -273,7 +273,7 @@ unsigned long list_lru_count_node(struct list_lru *lru, int nid) unsigned long ret; spin_lock(&nlru->lock); - ret = __list_lru_walk_one(nlru, memcg_cache_id(memcg), isolate, cb_arg, + ret = __list_lru_walk_one(nlru, memcg, isolate, cb_arg, nr_to_walk); spin_unlock(&nlru->lock); return ret; @@ -289,7 +289,7 @@ unsigned long list_lru_count_node(struct list_lru *lru, int nid) unsigned long ret; spin_lock_irq(&nlru->lock); - ret = __list_lru_walk_one(nlru, memcg_cache_id(memcg), isolate, cb_arg, + ret = __list_lru_walk_one(nlru, memcg, isolate, cb_arg, nr_to_walk); spin_unlock_irq(&nlru->lock); return ret; @@ -299,25 +299,34 @@ unsigned long list_lru_walk_node(struct list_lru *lru, int nid, list_lru_walk_cb isolate, void *cb_arg, unsigned long *nr_to_walk) { - long isolated = 0; - int memcg_idx; + struct list_lru_node *nlru; + struct mem_cgroup *memcg; + long isolated; - isolated += list_lru_walk_one(lru, nid, NULL, isolate, cb_arg, - nr_to_walk); - if (*nr_to_walk > 0 && list_lru_memcg_aware(lru)) { - for_each_memcg_cache_index(memcg_idx) { - struct list_lru_node *nlru = &lru->node[nid]; + /* iterate the global lru first */ + isolated = list_lru_walk_one(lru, nid, NULL, isolate, cb_arg, + nr_to_walk); - spin_lock(&nlru->lock); - isolated += __list_lru_walk_one(nlru, memcg_idx, - isolate, cb_arg, - nr_to_walk); - spin_unlock(&nlru->lock); + if (!list_lru_memcg_aware(lru)) + goto out; - if (*nr_to_walk <= 0) - break; - } + nlru = &lru->node[nid]; + for_each_mem_cgroup(memcg) { + /* already scanned the root memcg above */ + if (mem_cgroup_is_root(memcg)) + continue; + + if (*nr_to_walk <= 0) + break; + + spin_lock(&nlru->lock); + isolated += __list_lru_walk_one(nlru, memcg, + isolate, cb_arg, + nr_to_walk); + spin_unlock(&nlru->lock); } + +out: return isolated; } EXPORT_SYMBOL_GPL(list_lru_walk_node); diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 2058b8d..587c6b2 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -222,21 +222,6 @@ enum res_type { /* Used for OOM nofiier */ #define OOM_CONTROL (0) -/* - * Iteration constructs for visiting all cgroups (under a tree). If - * loops are exited prematurely (break), mem_cgroup_iter_break() must - * be used for reference counting. - */ -#define for_each_mem_cgroup_tree(iter, root) \ - for (iter = mem_cgroup_iter(root, NULL, NULL); \ - iter != NULL; \ - iter = mem_cgroup_iter(root, iter, NULL)) - -#define for_each_mem_cgroup(iter) \ - for (iter = mem_cgroup_iter(NULL, NULL, NULL); \ - iter != NULL; \ - iter = mem_cgroup_iter(NULL, iter, NULL)) - static inline bool should_force_charge(void) { return tsk_is_oom_victim(current) || fatal_signal_pending(current) || From patchwork Mon Mar 16 10:39:57 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 11440121 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 6E1151668 for ; Mon, 16 Mar 2020 10:40:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4CFB12071C for ; Mon, 16 Mar 2020 10:40:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="IkCicFVa" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730654AbgCPKkh (ORCPT ); Mon, 16 Mar 2020 06:40:37 -0400 Received: from mail-pg1-f194.google.com ([209.85.215.194]:38230 "EHLO mail-pg1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730497AbgCPKkh (ORCPT ); Mon, 16 Mar 2020 06:40:37 -0400 Received: by mail-pg1-f194.google.com with SMTP id x7so9523431pgh.5 for ; Mon, 16 Mar 2020 03:40:37 -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=vY2V4Msx6oxN9LJCRiKwHFiisubxDrfzwxG6lOa9dNU=; b=IkCicFVaHxkWKrGSUxrZpHqQj9D/t3mOLXb5kShBej3eTD5sYwXm9X3p4YWr5Gzm+x uJP3PkLtPqj7wDEK5JGRSu5vutp/fJZhT5xhC4wL1ARSWkiOTebAc7xq8wVFfb7opWtP bYkyFe8nefFlO094Bs/19gEBgiYAIn0974G/QbHc43y4F5+dsheomEAyaEl1D3BeaFn2 qX1pF0ENmCLYXTiKmQl2A2ipBjagoqoO5qQUYLd4ra0pSq3EURChDalYBAlj70XEb3Ku wJ9Y5CvNB1huHe7dqfHdRHqWFgag3RD7kY0Q1m+TwboHVdFlsLyX6zKRWR0/0iPP/Lud m/sw== 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=vY2V4Msx6oxN9LJCRiKwHFiisubxDrfzwxG6lOa9dNU=; b=K6e7/d/OgoL+0dxB4UrauWxIG6RtCSnY05hvAtQzYyfUjFUYMW5fe2xf2iYnulTfhG /rsHRQFUjPBbOvGGdqkafyYmeOoSy5ehUQgGamUL8Oop1f2J5wrIQSYPM8qqEZK6R9zi G5iBq4JPcasOSmIvKOH5rsdhwEaoXOuFuzUs8+NeLVbt/pXMOR53knBIdwHTnX7xbU9H XQztPg3Ek5hmVLM1KxeAEYFglnbcqp0/ap78JSLkZbNFUfXI/q7Rpg4wDbh9yMFc8YZv ORsfITzIEL8Kjr6AkHEyKGf3Xva8BtlhKFUI2EBDFzWmcwsWT/JYEg/Jnnwv/CDP43ey g+5Q== X-Gm-Message-State: ANhLgQ3ZplP2O6G5qLbZhOlmR3JGvKWCPwsRbg4c0erUM7t/XfspT8Oa JYSQuoB6YQVyJg3yxzaxDsM= X-Google-Smtp-Source: ADFU+vvuCGJScZZkfVQplCLS3rrwKochvebnJHsILTRfc2PNbM4o3inEYYU3KocRr5PPgQyktY6Cdw== X-Received: by 2002:a62:5544:: with SMTP id j65mr28084461pfb.121.1584355236772; Mon, 16 Mar 2020 03:40:36 -0700 (PDT) Received: from dev.localdomain ([203.100.54.194]) by smtp.gmail.com with ESMTPSA id h2sm19834276pjc.7.2020.03.16.03.40.33 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 16 Mar 2020 03:40:36 -0700 (PDT) From: Yafang Shao To: dchinner@redhat.com, hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, guro@fb.com, akpm@linux-foundation.org, viro@zeniv.linux.org.uk, willy@infradead.org Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Yafang Shao Subject: [PATCH v6 2/3] mm, shrinker: make memcg low reclaim visible to lru walker isolation function Date: Mon, 16 Mar 2020 06:39:57 -0400 Message-Id: <1584355198-10137-3-git-send-email-laoar.shao@gmail.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1584355198-10137-1-git-send-email-laoar.shao@gmail.com> References: <1584355198-10137-1-git-send-email-laoar.shao@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org A new member memcg_low_reclaim is introduced in shrink_control struct, which is derived from scan_control struct, in order to tell the shrinker whether the reclaim session is under memcg low reclaim or not. The followup patch will use this new member. Cc: Dave Chinner Signed-off-by: Yafang Shao --- include/linux/shrinker.h | 3 +++ mm/vmscan.c | 27 ++++++++++++++++----------- 2 files changed, 19 insertions(+), 11 deletions(-) diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h index 0f80123..dc42ae5 100644 --- a/include/linux/shrinker.h +++ b/include/linux/shrinker.h @@ -31,6 +31,9 @@ struct shrink_control { /* current memcg being shrunk (for memcg aware shrinkers) */ struct mem_cgroup *memcg; + + /* derived from struct scan_control */ + bool memcg_low_reclaim; }; #define SHRINK_STOP (~0UL) diff --git a/mm/vmscan.c b/mm/vmscan.c index 8763705..3857508 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -625,10 +625,9 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, /** * shrink_slab - shrink slab caches - * @gfp_mask: allocation context - * @nid: node whose slab caches to target * @memcg: memory cgroup whose slab caches to target - * @priority: the reclaim priority + * @sc: scan_control struct for this reclaim session + * @nid: node whose slab caches to target * * Call the shrink functions to age shrinkable caches. * @@ -638,15 +637,18 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, * @memcg specifies the memory cgroup to target. Unaware shrinkers * are called only if it is the root cgroup. * - * @priority is sc->priority, we take the number of objects and >> by priority - * in order to get the scan target. + * @sc is the scan_control struct, we take the number of objects + * and >> by sc->priority in order to get the scan target. * * Returns the number of reclaimed slab objects. */ -static unsigned long shrink_slab(gfp_t gfp_mask, int nid, - struct mem_cgroup *memcg, - int priority) +static unsigned long shrink_slab(struct mem_cgroup *memcg, + struct scan_control *sc, + int nid) { + bool memcg_low_reclaim = sc->memcg_low_reclaim; + gfp_t gfp_mask = sc->gfp_mask; + int priority = sc->priority; unsigned long ret, freed = 0; struct shrinker *shrinker; @@ -668,6 +670,7 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, .gfp_mask = gfp_mask, .nid = nid, .memcg = memcg, + .memcg_low_reclaim = memcg_low_reclaim, }; ret = do_shrink_slab(&sc, shrinker, priority); @@ -694,6 +697,9 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid, void drop_slab_node(int nid) { unsigned long freed; + struct scan_control sc = { + .gfp_mask = GFP_KERNEL, + }; do { struct mem_cgroup *memcg = NULL; @@ -701,7 +707,7 @@ void drop_slab_node(int nid) freed = 0; memcg = mem_cgroup_iter(NULL, NULL, NULL); do { - freed += shrink_slab(GFP_KERNEL, nid, memcg, 0); + freed += shrink_slab(memcg, &sc, nid); } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); } while (freed > 10); } @@ -2673,8 +2679,7 @@ static void shrink_node_memcgs(pg_data_t *pgdat, struct scan_control *sc) shrink_lruvec(lruvec, sc); - shrink_slab(sc->gfp_mask, pgdat->node_id, memcg, - sc->priority); + shrink_slab(memcg, sc, pgdat->node_id); /* Record the group's reclaim efficiency */ vmpressure(sc->gfp_mask, memcg, false, From patchwork Mon Mar 16 10:39:58 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yafang Shao X-Patchwork-Id: 11440125 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 B0B4992A for ; 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Mon, 16 Mar 2020 03:40:43 -0700 (PDT) From: Yafang Shao To: dchinner@redhat.com, hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, guro@fb.com, akpm@linux-foundation.org, viro@zeniv.linux.org.uk, willy@infradead.org Cc: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Yafang Shao Subject: [PATCH v6 3/3] inode: protect page cache from freeing inode Date: Mon, 16 Mar 2020 06:39:58 -0400 Message-Id: <1584355198-10137-4-git-send-email-laoar.shao@gmail.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <1584355198-10137-1-git-send-email-laoar.shao@gmail.com> References: <1584355198-10137-1-git-send-email-laoar.shao@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On my server there're some running MEMCGs protected by memory.{min, low}, but I found the usage of these MEMCGs abruptly became very small, which were far less than the protect limit. It confused me and finally I found that was because of inode stealing. Once an inode is freed, all its belonging page caches will be dropped as well, no matter how may page caches it has. So if we intend to protect the page caches in a memcg, we must protect their host (the inode) first. Otherwise the memcg protection can be easily bypassed with freeing inode, especially if there're big files in this memcg. Supposes we have a memcg, and the stat of this memcg is, memory.current = 1024M memory.min = 512M And in this memcg there's a inode with 800M page caches. Once this memcg is scanned by kswapd or other regular reclaimers, kswapd <<<< It can be either of the regular reclaimers. shrink_node_memcgs switch (mem_cgroup_protected()) <<<< Not protected case MEMCG_PROT_NONE: <<<< Will scan this memcg beak; shrink_lruvec() <<<< Reclaim the page caches shrink_slab() <<<< It may free this inode and drop all its page caches(800M). So we must protect the inode first if we want to protect page caches. Note that this inode may be a cold inode (in the tail of list lru), because memcg protection protects all slabs and page cache pages whatever they are cold or hot. IOW, this is a memcg-protection-specific issue. The inherent mismatch between memcg and inode is a trouble. One inode can be shared by different MEMCGs, but it is a very rare case. If an inode is shared, its belonging page caches may be charged to different MEMCGs. Currently there's no perfect solution to fix this kind of issue, but the inode majority-writer ownership switching can help it more or less. Cc: Dave Chinner Cc: Johannes Weiner Signed-off-by: Yafang Shao --- fs/inode.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 72 insertions(+), 3 deletions(-) diff --git a/fs/inode.c b/fs/inode.c index 93d9252..f5a9537 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -55,6 +55,12 @@ * inode_hash_lock */ +struct inode_isolate_control { + struct list_head *freeable; + struct mem_cgroup *memcg; /* derived from shrink_control */ + bool memcg_low_reclaim; /* derived from scan_control */ +}; + static unsigned int i_hash_mask __read_mostly; static unsigned int i_hash_shift __read_mostly; static struct hlist_head *inode_hashtable __read_mostly; @@ -715,6 +721,58 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty) return busy; } +#ifdef CONFIG_MEMCG_KMEM +/* + * Once an inode is freed, all its belonging page caches will be dropped as + * well, even if there're lots of page caches. So if we intend to protect + * page caches in a memcg, we must protect their host(the inode) first. + * Otherwise the memcg protection can be easily bypassed with freeing inode, + * especially if there're big files in this memcg. + * Note that it may happen that the page caches are already charged to the + * memcg, but the inode hasn't been added to this memcg yet. In this case, + * this inode is not protected. + * The inherent mismatch between memcg and inode is a trouble. One inode + * can be shared by different MEMCGs, but it is a very rare case. If + * an inode is shared, its belonging page caches may be charged to + * different MEMCGs. Currently there's no perfect solution to fix this + * kind of issue, but the inode majority-writer ownership switching can + * help it more or less. + */ +static bool memcg_can_reclaim_inode(struct inode *inode, + struct inode_isolate_control *iic) +{ + unsigned long protection; + struct mem_cgroup *memcg; + bool reclaimable = true; + + if (!inode->i_data.nrpages) + goto out; + + /* Excludes freeing inode via drop_caches */ + if (!current->reclaim_state) + goto out; + + memcg = iic->memcg; + if (!memcg || memcg == root_mem_cgroup) + goto out; + + protection = mem_cgroup_protection(memcg, iic->memcg_low_reclaim); + if (!protection) + goto out; + + reclaimable = false; + +out: + return reclaimable; +} +#else /* CONFIG_MEMCG_KMEM */ +static bool memcg_can_reclaim_inode(struct inode *inode, + struct inode_isolate_control *iic) +{ + return true; +} +#endif /* CONFIG_MEMCG_KMEM */ + /* * Isolate the inode from the LRU in preparation for freeing it. * @@ -733,8 +791,9 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty) static enum lru_status inode_lru_isolate(struct list_head *item, struct list_lru_one *lru, spinlock_t *lru_lock, void *arg) { - struct list_head *freeable = arg; - struct inode *inode = container_of(item, struct inode, i_lru); + struct inode_isolate_control *iic = arg; + struct list_head *freeable = iic->freeable; + struct inode *inode = container_of(item, struct inode, i_lru); /* * we are inverting the lru lock/inode->i_lock here, so use a trylock. @@ -743,6 +802,11 @@ static enum lru_status inode_lru_isolate(struct list_head *item, if (!spin_trylock(&inode->i_lock)) return LRU_SKIP; + if (!memcg_can_reclaim_inode(inode, iic)) { + spin_unlock(&inode->i_lock); + return LRU_ROTATE; + } + /* * Referenced or dirty inodes are still in use. Give them another pass * through the LRU as we canot reclaim them now. @@ -800,9 +864,14 @@ long prune_icache_sb(struct super_block *sb, struct shrink_control *sc) { LIST_HEAD(freeable); long freed; + struct inode_isolate_control iic = { + .freeable = &freeable, + .memcg = sc->memcg, + .memcg_low_reclaim = sc->memcg_low_reclaim, + }; freed = list_lru_shrink_walk(&sb->s_inode_lru, sc, - inode_lru_isolate, &freeable); + inode_lru_isolate, &iic); dispose_list(&freeable); return freed; }