From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=103.209.128.28 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792581909; b=4qJyOzW6GvaUbAE+Ya4LaH5nBbKnCKtqG5YPFwnmytSaPYpwDoYp0Foy9mgp219QQJvY Np3zaYXItYzlxKSXMh3u4DRP35u1mEPlHYfrJixO4Z9wok1XdaXcSsIO9pxIDqbnLkBmp xHqSWUz8QgguA6DZjL12YJx3RpfQPXvc54WXdPfs3GR81IvpBGLmQlEFr68fixc/VEt59 jXThQnD7wTqNmku/0MBPaDLzdBJKKVft30pRS0iWaS/L4F+24fC9ZNi+vuRaYgImGvS8D AM+smBpxfvxTSApq9iNbcqLc9nYijqdV71fG4N8/sfDMazph5U8PlhVNEequcQ7zAxw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792581909; h=DMARC-Filter:Received:From:To:Cc:Subject:Date:Message-Id:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding: X-HM-Tid:X-HM-MType:X-HM-Spam-Status; bh=RAG/2ax1ucQUbAiCg/s1Qqe5BmQBfpQgRvDtOVmHwa4=; b=BGSVg4XSTJHGPLK6M4f8z9/hnVwxXQMwFy91aXSNjLS7S13KLAyFjpRO+AWCshT1++x7 G0lH19GwDTvf08V3zyH4PzH8V8YUyd8IupFsiF8enTJsLzQdJGguYnQ0Ba0utNDxB1B4m jTbSvx6513STcUqKbVaJ3rqYRkIgyZ4+WYUIRtd1o7SMyiCU0aWPVahHFJXQdCxh+RJcC oZ8ChjFb0TDoNnEDddnI9jGelUKy2t4eTLoQ3NvvTNNGC58WQ3xgye31EMFgoELY6lYB0 MMGVAOZDGKbarPiewgKuhQulyginh5CyQbgu8+kedyMxbCZ5U7SZdcgjiiEsKOPGtDg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=easystack.cn; spf=pass smtp.mailfrom=easystack.cn; arc=none smtp.remote-ip=103.209.128.28 Received: from mail-m12828.netease.com (mail-m12828.netease.com [103.209.128.28]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EE18A606A333; Wed, 21 Oct 2026 11:25:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org EE18A606A333 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=easystack.cn Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=easystack.cn Received: from localhost.localdomain (unknown [218.94.118.90]) by smtp.qiye.163.com (Hmail) with ESMTP id 204f151ae; Wed, 21 Oct 2026 19:24:56 +0800 (GMT+08:00) From: Zhen Ni To: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, eddyz87@gmail.com, memxor@gmail.com, martin.lau@linux.dev, song@kernel.org, yonghong.song@linux.dev, jolsa@kernel.org, emil@etsalapatis.com, ihor.solodrai@linux.dev, akpm@linux-foundation.org, vbabka@kernel.org, surenb@google.com, mhocko@suse.com, brendan.jackman@linux.dev, hannes@cmpxchg.org, ziy@nvidia.com, shuah@kernel.org Cc: bpf@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Zhen Ni Subject: [PATCH v3 6/7] mm/page_owner: add bpf_page_owner_get_memcg_info() kfunc Date: Wed, 21 Oct 2026 19:24:36 +0800 Message-Id: <20261021112437.1799213-7-zhen.ni@easystack.cn> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20261021112437.1799213-1-zhen.ni@easystack.cn> References: <20261021112437.1799213-1-zhen.ni@easystack.cn> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-HM-Tid: 0aa15e350a610229kunme08c1fd526acf1 X-HM-MType: 1 X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFJQjdXWRgWCB1ZQUpXWS1ZQUlXWQ8JGhUIEh9ZQVkaSUxJVhpLTBlLHxlJThhMT1YVFA kWGhdVGRETFhoSFyQUDg9ZV1kYEgtZQVlJSkNVQk9VSkpDVUJLWVdZFhoPEhUdFFlBWU9LSFVKS0 lPT09IVUpLS1VKQktLWQY+ Expose per-page memcg information to BPF programs, so that a bpf_iter over page_owner can aggregate and filter allocations by memcg. Attributing an allocation to a specific cgroup needs its full cgroup path, not just the memcg name. Split memcg info collection out of print_page_owner_memcg() into get_page_memcg_info(), which fills struct memcg_info and, when given a caller-provided buffer, writes the full cgroup path via cgroup_path(). print_page_owner_memcg() now consumes the struct; this introduces no functional change to the debugfs output. The helper takes a single READ_ONCE snapshot within one RCU read-side critical section, so the flags and cgroup path reflect a consistent view of the page. cgroup_path() returns the path relative to the cgroup hierarchy root, so memcg attribution works on both cgroup v1 and v2. Because scan->pfn is selected by a lockless scan, the kfunc re-resolves it with pfn_to_online_page() under get_online_mems() to avoid accessing a hot-removed section. If the PFN is offline or removed, the kfunc returns -ENODATA instead of dereferencing memcg_data. Signed-off-by: Zhen Ni --- Changes in v3: - Check the page_owner_inited static key. - Resolve the page with pfn_to_online_page() under get_online_mems(). Changes in v2: - bpf_page_owner_get_memcg_info() now resolves the page with pfn_to_online_page() for an offline or removed pfn. - Buffer/info args renamed to info__uninit/buf__uninit/buf__sz. v2: https://lore.kernel.org/linux-mm/20261013122125.843451-6-zhen.ni@easystack.cn/ v1: https://lore.kernel.org/linux-mm/20261009112308.240769-6-zhen.ni@easystack.cn/ --- kernel/bpf/helpers.c | 1 + mm/page_owner.c | 85 ++++++++++++++++++++++++++++++++++---------- mm/page_owner.h | 9 +++++ mm/page_owner_iter.c | 48 +++++++++++++++++++++++++ 4 files changed, 124 insertions(+), 19 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 0ba836f77957..bba9eeb076c3 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -4954,6 +4954,7 @@ BTF_ID_FLAGS(func, bpf_iter_page_owner_next, BTF_ID_FLAGS(func, bpf_iter_page_owner_destroy, KF_ITER_DESTROY | KF_SLEEPABLE | KF_PERFMON) BTF_ID_FLAGS(func, bpf_page_owner_stack_snprint, KF_SLEEPABLE | KF_PERFMON) +BTF_ID_FLAGS(func, bpf_page_owner_get_memcg_info, KF_SLEEPABLE | KF_PERFMON) #endif BTF_ID_FLAGS(func, __bpf_trap) BTF_ID_FLAGS(func, bpf_strcmp, KF_PERFMON); diff --git a/mm/page_owner.c b/mm/page_owner.c index 8bc15bcdc24e..7470b5d002be 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -538,16 +538,22 @@ void pagetypeinfo_showmixedcount_print(struct seq_file *m, #ifdef CONFIG_MEMCG /* - * Looking for memcg information and print it out + * Collect memcg information of @page into @info; when @buf and a + * nonzero @size are given, also copy the full cgroup path of the + * charged memcg into @buf. + * + * Return: 0 if @page is charged to an attributable memcg; -ENODATA + * otherwise. */ -static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret, - struct page *page) +int get_page_memcg_info(struct page *page, struct memcg_info *info, + char *buf, int size) { unsigned long memcg_data; struct obj_cgroup *objcg; struct mem_cgroup *memcg; - bool online; - char name[80]; + int ret = -ENODATA; + + *info = (struct memcg_info){}; rcu_read_lock(); memcg_data = READ_ONCE(page->memcg_data); @@ -555,31 +561,68 @@ static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret, goto out_unlock; if (memcg_data & MEMCG_DATA_OBJEXTS) { - ret += scnprintf(kbuf + ret, count - ret, - "Slab cache page\n"); + info->is_slab = true; goto out_unlock; } objcg = (void *)(memcg_data & ~OBJEXTS_FLAGS_MASK); - memcg = objcg ? obj_cgroup_memcg(objcg) : NULL; + if (!objcg) + goto out_unlock; + + memcg = obj_cgroup_memcg(objcg); if (!memcg) goto out_unlock; - online = css_is_online(&memcg->css); - cgroup_name(memcg->css.cgroup, name, sizeof(name)); - ret += scnprintf(kbuf + ret, count - ret, - "Charged %sto %smemcg %s\n", - (memcg_data & MEMCG_DATA_KMEM) ? "(via objcg) " : "", - online ? "" : "offline ", - name); + info->is_kmem = (memcg_data & MEMCG_DATA_KMEM) != 0; + info->is_online = css_is_online(&memcg->css); + cgroup_name(memcg->css.cgroup, info->name, sizeof(info->name)); + + if (buf && size) + cgroup_path(memcg->css.cgroup, buf, size); + ret = 0; out_unlock: rcu_read_unlock(); + if (ret < 0 && buf && size) + buf[0] = '\0'; + + return ret; +} + +/* + * Print memcg information from memcg_info + */ +static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret, + const struct memcg_info *info) +{ + if (!info) + return ret; + + if (info->is_slab) + ret += scnprintf(kbuf + ret, count - ret, + "Slab cache page\n"); + + if (info->name[0]) + ret += scnprintf(kbuf + ret, count - ret, + "Charged %sto %smemcg %s\n", + info->is_kmem ? "(via objcg) " : "", + info->is_online ? "" : "offline ", + info->name); + return ret; } #else +int get_page_memcg_info(struct page *page, struct memcg_info *info, + char *buf, int size) +{ + *info = (struct memcg_info){}; + if (buf && size) + buf[0] = '\0'; + return -EOPNOTSUPP; +} + static inline int print_page_owner_memcg(char *kbuf, size_t count, int ret, - struct page *page) + const struct memcg_info *info) { return ret; } @@ -589,7 +632,8 @@ static ssize_t print_page_owner(char __user *buf, size_t count, unsigned long pfn, struct page *page, struct page_owner *page_owner, depot_stack_handle_t handle, - struct page_owner_filter_state *state) + struct page_owner_filter_state *state, + const struct memcg_info *memcg_info) { int ret, pageblock_mt, page_mt; char *kbuf; @@ -639,7 +683,7 @@ print_page_owner(char __user *buf, size_t count, unsigned long pfn, migrate_reason_names[page_owner->last_migrate_reason]); } - ret = print_page_owner_memcg(kbuf, count, ret, page); + ret = print_page_owner_memcg(kbuf, count, ret, memcg_info); ret += snprintf(kbuf + ret, count - ret, "\n"); if (ret >= count) @@ -822,6 +866,7 @@ static ssize_t read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) { struct page_owner_scan scan; + struct memcg_info memcg_info; struct page_owner_filter_state *state = file->private_data; if (!static_branch_unlikely(&page_owner_inited)) @@ -855,8 +900,10 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) /* Record the next PFN to read in the file offset */ *ppos = scan.pfn + 1; + get_page_memcg_info(page, &memcg_info, NULL, 0); ret = print_page_owner(buf, count, scan.pfn, page, - &scan.po_snap, scan.po_snap.handle, state); + &scan.po_snap, scan.po_snap.handle, state, + &memcg_info); put_online_mems(); return ret; diff --git a/mm/page_owner.h b/mm/page_owner.h index 934bc9f84d6f..65598415af73 100644 --- a/mm/page_owner.h +++ b/mm/page_owner.h @@ -41,7 +41,16 @@ struct page_owner_scan { int nid; }; +struct memcg_info { + char name[80]; + bool is_slab; + bool is_kmem; + bool is_online; +}; + bool page_owner_next_eligible(struct page_owner_scan *scan); +int get_page_memcg_info(struct page *page, struct memcg_info *info, + char *buf, int size); /* * mm/page_owner_iter.c diff --git a/mm/page_owner_iter.c b/mm/page_owner_iter.c index b7e0ce1dfa80..a649e1207e24 100644 --- a/mm/page_owner_iter.c +++ b/mm/page_owner_iter.c @@ -181,4 +181,52 @@ __bpf_kfunc int bpf_page_owner_stack_snprint(struct page_owner_scan *scan, return len; } +/** + * bpf_page_owner_get_memcg_info - Report the memcg charged for the current page + * @scan: page_owner scan handle. + * @info__uninit: output buffer for the memcg_info. + * @buf__uninit: optional output buffer for the full cgroup path. + * @buf__sz: size of @buf__uninit. + * + * Fills @info__uninit with the memcg charged for the page backing + * @scan->pfn. If @buf__uninit and @buf__sz are provided, the full + * cgroup path is also copied out, so a BPF program can attribute a + * page_owner allocation to a specific cgroup. + * + * @scan->pfn is resolved to a struct page under get_online_mems(), + * so the page cannot be accessed after its memory section is offlined + * or removed. + * + * Returns: + * * 0 on success + * * -ENODATA if the page is not online or not charged to a memcg + * * -EOPNOTSUPP if built without CONFIG_MEMCG + */ +__bpf_kfunc int bpf_page_owner_get_memcg_info(struct page_owner_scan *scan, + struct memcg_info *info__uninit, + char *buf__uninit, u32 buf__sz) +{ + struct page *page; + int ret = -ENODATA; + + if (!static_branch_unlikely(&page_owner_inited)) + goto nodata; + + get_online_mems(); + page = pfn_to_online_page(scan->pfn); + if (!page) { + put_online_mems(); + goto nodata; + } + ret = get_page_memcg_info(page, info__uninit, buf__uninit, buf__sz); + put_online_mems(); + return ret; + +nodata: + *info__uninit = (struct memcg_info){}; + if (buf__uninit && buf__sz) + buf__uninit[0] = '\0'; + return ret; +} + __bpf_kfunc_end_defs(); -- 2.20.1