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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 80CF6C41513 for ; Thu, 17 Aug 2023 19:01:38 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C068D28004D; Thu, 17 Aug 2023 15:01:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BB64F940009; Thu, 17 Aug 2023 15:01:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A566528004D; Thu, 17 Aug 2023 15:01:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 97229940009 for ; Thu, 17 Aug 2023 15:01:37 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 58E48401E3 for ; Thu, 17 Aug 2023 19:01:37 +0000 (UTC) X-FDA: 81134515434.28.86BD0F1 Received: from mail-pl1-f176.google.com (mail-pl1-f176.google.com [209.85.214.176]) by imf15.hostedemail.com (Postfix) with ESMTP id 1AC48A0058 for ; Thu, 17 Aug 2023 19:01:28 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=gmail.com header.s=20221208 header.b=nOZ7OKlv; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf15.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.214.176 as permitted sender) smtp.mailfrom=nphamcs@gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1692298889; a=rsa-sha256; cv=none; b=RY+usQw//nLIh8NJj1Jyd3yrQbWAY1LDXpd/YsgLJZRXiaT36Wh6Rx4Ul51HcpIG/l+cr1 NkaGqLhv/d4qmulE3EkxlHhZekmvrOk4ULJkOs7XixCD65fCI4GjgMicsOsEeD/KQTAKv0 Kr4VxOT9NRY4Vmbsv6jKHB2L/dW5Nk0= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=gmail.com header.s=20221208 header.b=nOZ7OKlv; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf15.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.214.176 as permitted sender) smtp.mailfrom=nphamcs@gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1692298889; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=TnN9tn3E+lZE3Z+gBA1oF4t/xLxiuc+Fa8cmsOnhTHQ=; b=L5WTEgHBmS5QR+zfQg+H8FEMm+lXruDnnu4xdhixcem3mSWnNbJixCbJhEl1FYmmOVFmS/ HssyqEld4zRbzKTZGeJd1b9e0pw7EcyN+HD3/botdJsB8kAvGMNc+yc8EjiLF5HS2kTNsD EKP+OrW5QnmFAlY6Jds3/8nGbSAqxKA= Received: by mail-pl1-f176.google.com with SMTP id d9443c01a7336-1bc8045e09dso1171865ad.0 for ; Thu, 17 Aug 2023 12:01:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1692298888; x=1692903688; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=TnN9tn3E+lZE3Z+gBA1oF4t/xLxiuc+Fa8cmsOnhTHQ=; b=nOZ7OKlv2PWOQNbv4PSKJZ70Jyp3VyAYMSkj0iJHy+1r0+09v4yifOEk2dfxdJumsr Cv//QWru6lCLzj4g8Ktk4c4DVuiu/TlEirPJuj/5RKEKahM//XtOLHjGE03R12qG6ezU tWtRsolMny7MwHR1+pslK2LGidi0O1gDs4wLLMyHwE2EuLTI909gQ1olTTOHd+XHM65q r5GtMmNjmgjuaJjyEnguY1pswL8Ic48Q1ykQOzL5lgTzV1sMGJYgLD55i4zypYsWTa24 Y49EFaus514RBgeo4Jsse1xOhGRQ4+b2jxY5XYv9vOZOQxfVqnxmJhdT+hifJ7MW7mx8 ndow== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692298888; x=1692903688; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=TnN9tn3E+lZE3Z+gBA1oF4t/xLxiuc+Fa8cmsOnhTHQ=; b=C8Wl8fDXMPsVI0iZYT59Z2E55ze6eN/SV5TTdZqtLxZOqYZH47j+n8XHZK7hWWfBXh PUzmMBUiQa7oAYEmfISFjSt/hadWeLWdrKQ5TcSVamFeJ/iOP5lnmyuy3/lbaWJ5vYao x1/XzxuuGaSd5V8ymzLoqybcE8J17+Elt/hLhNcuf9jTDzfpiVMXOGVNl1U0yjO1yyjf EQmOsgcAmuCLtjgW8724F6RyLU1alT7SVMhrPLZU2WUODi8eTy7A7oguZaJsJXYA7AcD pRLDIafxui20RgmAA6G+n/a2r+F4mnX2NouFKU/mfXdMFi4BiURo+l1spqatoK1mBwFC Ezhg== X-Gm-Message-State: AOJu0YwYCjAqZKuDtuaYKdp+y/XjFl4pwXEF4KTgNwfTSzLl3FUEJ8dX keOsZgOhheLDAq8Hj2+Flx8= X-Google-Smtp-Source: AGHT+IEN3HhQw6hpzirmqQkGWxP0XW0xqs84MdRI2ViESw+CWI91mX+Tdr92devtl037fFtDqHYBJQ== X-Received: by 2002:a17:902:ce84:b0:1bd:f1ae:309d with SMTP id f4-20020a170902ce8400b001bdf1ae309dmr353147plg.9.1692298887462; Thu, 17 Aug 2023 12:01:27 -0700 (PDT) Received: from localhost (fwdproxy-prn-117.fbsv.net. [2a03:2880:ff:75::face:b00c]) by smtp.gmail.com with ESMTPSA id v4-20020a170902b7c400b001bdcd4b1616sm99005plz.260.2023.08.17.12.01.26 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 17 Aug 2023 12:01:27 -0700 (PDT) From: Nhat Pham To: akpm@linux-foundation.org Cc: hannes@cmpxchg.org, kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, yosryahmed@google.com Subject: [PATCH v2] workingset: ensure memcg is valid for recency check Date: Thu, 17 Aug 2023 12:01:26 -0700 Message-Id: <20230817190126.3155299-1-nphamcs@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230817164733.2475092-1-nphamcs@gmail.com> References: <20230817164733.2475092-1-nphamcs@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 1AC48A0058 X-Stat-Signature: ibm174umg5fdhhcqdsga7q1bbdgrw4kz X-HE-Tag: 1692298888-238588 X-HE-Meta: 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 u85aJhrJ 1WRzdhaIJub7S5yXJzXMhMwa5HpGOb5qC1sidoiZ8AvhDHw9HfmhiY9oGcpcuA0B8/vTDJanh/Jv8FuJvm5zsAz1OrYR2whd1tbBIUKPPQPDGxg6/LjQX1cwPmkm1XavgwOoIw3F0CVh18aDftEa6BVtKiPnZhPbo41gEIOZbeRsZXdf1DBTY6d7p9xh17uRlMz5dRgve5KmPkTT6bffeRHIE9XXjsgHqQ3K5K2+7K5VTVdBH8NFAmb8oUmjwYOWbSNPG5n4d5YTkd/8hOWyfXTaPZzX46KHX5n0Jba7pzHjk6s2Vyd61rpgb3o0+WXTrzu+hJABq9KAIa649e3EhcrLpE55QITi3lN6ejWT0kcgBIHP+0EAWxpXDwFeLffM8c6w451WriLVnHcnf+FGuQ/k4f10qjK6DHekov9ChtTbIjTt5mJHROZDvk+cqxuW1hFLofnimMgd0ed08KWhSkO52BtE9/QqZ3P47Q5qAWaLW6TM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: In eviction recency check, we are currently not holding a local reference to the memcg that the refaulted folio belonged to when it was evicted. This could cause serious memcg lifetime issues, for e.g in the memcg hierarchy traversal done in mem_cgroup_get_nr_swap_pages(). This has occurred in production: [ 155757.793456] BUG: kernel NULL pointer dereference, address: 00000000000000c0 [ 155757.807568] #PF: supervisor read access in kernel mode [ 155757.818024] #PF: error_code(0x0000) - not-present page [ 155757.828482] PGD 401f77067 P4D 401f77067 PUD 401f76067 PMD 0 [ 155757.839985] Oops: 0000 [#1] SMP [ 155757.846444] CPU: 7 PID: 1380944 Comm: ThriftSrv-pri3- Kdump: loaded Tainted: G S 6.4.3-0_fbk1_rc0_594_g8d0cbcaa67ba #1 [ 155757.870808] Hardware name: Wiwynn Twin Lakes MP/Twin Lakes Passive MP, BIOS YMM16 05/24/2021 [ 155757.887870] RIP: 0010:mem_cgroup_get_nr_swap_pages+0x3d/0xb0 [ 155757.899377] Code: 29 19 4a 02 48 39 f9 74 63 48 8b 97 c0 00 00 00 48 8b b7 58 02 00 00 48 2b b7 c0 01 00 00 48 39 f0 48 0f 4d c6 48 39 d1 74 42 <48> 8b b2 c0 00 00 00 48 8b ba 58 02 00 00 48 2b ba c0 01 00 00 48 [ 155757.937125] RSP: 0018:ffffc9002ecdfbc8 EFLAGS: 00010286 [ 155757.947755] RAX: 00000000003a3b1c RBX: 000007ffffffffff RCX: ffff888280183000 [ 155757.962202] RDX: 0000000000000000 RSI: 0007ffffffffffff RDI: ffff888bbc2d1000 [ 155757.976648] RBP: 0000000000000001 R08: 000000000000000b R09: ffff888ad9cedba0 [ 155757.991094] R10: ffffea0039c07900 R11: 0000000000000010 R12: ffff888b23a7b000 [ 155758.005540] R13: 0000000000000000 R14: ffff888bbc2d1000 R15: 000007ffffc71354 [ 155758.019991] FS: 00007f6234c68640(0000) GS:ffff88903f9c0000(0000) knlGS:0000000000000000 [ 155758.036356] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 155758.048023] CR2: 00000000000000c0 CR3: 0000000a83eb8004 CR4: 00000000007706e0 [ 155758.062473] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 155758.076924] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 155758.091376] PKRU: 55555554 [ 155758.096957] Call Trace: [ 155758.102016] [ 155758.106502] ? __die+0x78/0xc0 [ 155758.112793] ? page_fault_oops+0x286/0x380 [ 155758.121175] ? exc_page_fault+0x5d/0x110 [ 155758.129209] ? asm_exc_page_fault+0x22/0x30 [ 155758.137763] ? mem_cgroup_get_nr_swap_pages+0x3d/0xb0 [ 155758.148060] workingset_test_recent+0xda/0x1b0 [ 155758.157133] workingset_refault+0xca/0x1e0 [ 155758.165508] filemap_add_folio+0x4d/0x70 [ 155758.173538] page_cache_ra_unbounded+0xed/0x190 [ 155758.182919] page_cache_sync_ra+0xd6/0x1e0 [ 155758.191738] filemap_read+0x68d/0xdf0 [ 155758.199495] ? mlx5e_napi_poll+0x123/0x940 [ 155758.207981] ? __napi_schedule+0x55/0x90 [ 155758.216095] __x64_sys_pread64+0x1d6/0x2c0 [ 155758.224601] do_syscall_64+0x3d/0x80 [ 155758.232058] entry_SYSCALL_64_after_hwframe+0x46/0xb0 [ 155758.242473] RIP: 0033:0x7f62c29153b5 [ 155758.249938] Code: e8 48 89 75 f0 89 7d f8 48 89 4d e0 e8 b4 e6 f7 ff 41 89 c0 4c 8b 55 e0 48 8b 55 e8 48 8b 75 f0 8b 7d f8 b8 11 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 33 44 89 c7 48 89 45 f8 e8 e7 e6 f7 ff 48 8b [ 155758.288005] RSP: 002b:00007f6234c5ffd0 EFLAGS: 00000293 ORIG_RAX: 0000000000000011 [ 155758.303474] RAX: ffffffffffffffda RBX: 00007f628c4e70c0 RCX: 00007f62c29153b5 [ 155758.318075] RDX: 000000000003c041 RSI: 00007f61d2986000 RDI: 0000000000000076 [ 155758.332678] RBP: 00007f6234c5fff0 R08: 0000000000000000 R09: 0000000064d5230c [ 155758.347452] R10: 000000000027d450 R11: 0000000000000293 R12: 000000000003c041 [ 155758.362044] R13: 00007f61d2986000 R14: 00007f629e11b060 R15: 000000000027d450 [ 155758.376661] This patch fixes the issue by getting a local reference inside unpack_shadow(). Fixes: f78dfc7b77d5 ("workingset: fix confusion around eviction vs refault container") Signed-off-by: Nhat Pham Cc: stable@vger.kernel.org --- mm/workingset.c | 65 ++++++++++++++++++++++++++++++++----------------- 1 file changed, 43 insertions(+), 22 deletions(-) diff --git a/mm/workingset.c b/mm/workingset.c index da58a26d0d4d..03cadad4e484 100644 --- a/mm/workingset.c +++ b/mm/workingset.c @@ -206,10 +206,19 @@ static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction, return xa_mk_value(eviction); } -static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat, - unsigned long *evictionp, bool *workingsetp) +/* + * Unpacks the stored fields of a shadow entry into the given pointers. + * + * The memcg pointer is only populated if the memcg recorded in the shadow + * entry is valid. In this case, a reference to the memcg will be acquired, + * and a corresponding mem_cgroup_put() will be needed when we no longer + * need the memcg. + */ +static void unpack_shadow(void *shadow, struct mem_cgroup **memcgp, + pg_data_t **pgdat, unsigned long *evictionp, bool *workingsetp) { unsigned long entry = xa_to_value(shadow); + struct mem_cgroup *memcg; int memcgid, nid; bool workingset; @@ -220,7 +229,24 @@ static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat, memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1); entry >>= MEM_CGROUP_ID_SHIFT; - *memcgidp = memcgid; + /* + * Look up the memcg associated with the stored ID. It might + * have been deleted since the folio's eviction. + * + * Note that in rare events the ID could have been recycled + * for a new cgroup that refaults a shared folio. This is + * impossible to tell from the available data. However, this + * should be a rare and limited disturbance, and activations + * are always speculative anyway. Ultimately, it's the aging + * algorithm's job to shake out the minimum access frequency + * for the active cache. + */ + memcg = mem_cgroup_from_id(memcgid); + if (memcg && css_tryget(&memcg->css)) + *memcgp = memcg; + else + *memcgp = NULL; + *pgdat = NODE_DATA(nid); *evictionp = entry; *workingsetp = workingset; @@ -262,15 +288,16 @@ static void *lru_gen_eviction(struct folio *folio) static bool lru_gen_test_recent(void *shadow, bool file, struct lruvec **lruvec, unsigned long *token, bool *workingset) { - int memcg_id; unsigned long min_seq; struct mem_cgroup *memcg; struct pglist_data *pgdat; - unpack_shadow(shadow, &memcg_id, &pgdat, token, workingset); + unpack_shadow(shadow, &memcg, &pgdat, token, workingset); + if (!mem_cgroup_disabled() && !memcg) + return false; - memcg = mem_cgroup_from_id(memcg_id); *lruvec = mem_cgroup_lruvec(memcg, pgdat); + mem_cgroup_put(memcg); min_seq = READ_ONCE((*lruvec)->lrugen.min_seq[file]); return (*token >> LRU_REFS_WIDTH) == (min_seq & (EVICTION_MASK >> LRU_REFS_WIDTH)); @@ -421,36 +448,29 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset) unsigned long refault_distance; unsigned long workingset_size; unsigned long refault; - int memcgid; struct pglist_data *pgdat; unsigned long eviction; if (lru_gen_enabled()) return lru_gen_test_recent(shadow, file, &eviction_lruvec, &eviction, workingset); - unpack_shadow(shadow, &memcgid, &pgdat, &eviction, workingset); - eviction <<= bucket_order; - + unpack_shadow(shadow, &eviction_memcg, &pgdat, &eviction, workingset); /* - * Look up the memcg associated with the stored ID. It might - * have been deleted since the folio's eviction. + * When memcg is enabled, we only get !memcg here if the + * eviction group has been deleted. In that case, ignore + * the refault. * - * Note that in rare events the ID could have been recycled - * for a new cgroup that refaults a shared folio. This is - * impossible to tell from the available data. However, this - * should be a rare and limited disturbance, and activations - * are always speculative anyway. Ultimately, it's the aging - * algorithm's job to shake out the minimum access frequency - * for the active cache. + * When memcg is disabled, we always get NULL since there + * is no root_mem_cgroup for !CONFIG_MEMCG. Continue; the + * mem_cgroup_lruvec() will get us the global lruvec. * - * XXX: On !CONFIG_MEMCG, this will always return NULL; it - * would be better if the root_mem_cgroup existed in all + * XXX: It would be better if the root_mem_cgroup existed in all * configurations instead. */ - eviction_memcg = mem_cgroup_from_id(memcgid); if (!mem_cgroup_disabled() && !eviction_memcg) return false; + eviction <<= bucket_order; eviction_lruvec = mem_cgroup_lruvec(eviction_memcg, pgdat); refault = atomic_long_read(&eviction_lruvec->nonresident_age); @@ -493,6 +513,7 @@ bool workingset_test_recent(void *shadow, bool file, bool *workingset) } } + mem_cgroup_put(eviction_memcg); return refault_distance <= workingset_size; } -- 2.34.1