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a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1791894115; b=55NAcocvHeBytwbTB5GcV01lBWKgxBJwbxNJEYB491HhGYCayRCKOsxpRJQ/b0A1jv+Hu3 AnvzhLcUiDz6lTROhS2sqJGbguc3Opvj9SLkGcWfyGXrQNNBGCOiEacap3U1AY9FhQfqaO 79IxO8SKBQr+1Wp2rizXa+QQJIg0oWg= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=none; spf=pass (imf09.hostedemail.com: domain of zhen.ni@easystack.cn designates 160.236.53.229 as permitted sender) smtp.mailfrom=zhen.ni@easystack.cn; dmarc=pass (policy=none) header.from=easystack.cn Received: from localhost.localdomain (unknown [218.94.118.90]) by smtp.qiye.163.com (Hmail) with ESMTP id 200407ef2; Tue, 13 Oct 2026 20:21:49 +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 v2 5/6] mm/page_owner: add bpf_page_owner_get_memcg_info() kfunc Date: Tue, 13 Oct 2026 20:21:24 +0800 Message-Id: <20261013122125.843451-6-zhen.ni@easystack.cn> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20261013122125.843451-1-zhen.ni@easystack.cn> References: <20261013122125.843451-1-zhen.ni@easystack.cn> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-HM-Tid: 0aa135363c650229kunm0bc94a6a5264 X-HM-MType: 1 X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFJQjdXWRgWCB1ZQUpXWS1ZQUlXWQ8JGhUIEh9ZQVlDHxoaVkxMTR1DSR4aHktCSFYVFA kWGhdVGRETFhoSFyQUDg9ZV1kYEgtZQVlJSkNVQk9VSkpDVUJLWVdZFhoPEhUdFFlBWU9LSFVKS0 lPT09IVUpLS1VKQktLWQY+ X-Rspamd-Queue-Id: 9E25D140003 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: qxgojmgn19zptcidnrg8g8i7ad9o97iu X-HE-Tag: 1791894114-767111 X-HE-Meta: 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 W++Xmarh srwajwSGF5uog/8UdzKWIxdXUKlT9THp1ugeyNb8B2qToEY0Em3+7SmLyuTwgH/TCRnWI25EnylBqczI+12eYZCM+fIUN6W3QpjbAu2LZ5cAcajyAap1gU9qg35DWp495E3nq Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. The kfunc gets the page via pfn_to_online_page(), so an offline or removed pfn yields -ENODATA instead of a stale deref. Signed-off-by: Zhen Ni --- 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. 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 | 17 +++++++++ 4 files changed, 93 insertions(+), 19 deletions(-) diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 23a2d2d71f4d..b46822eac894 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -4951,6 +4951,7 @@ BTF_ID_FLAGS(func, bpf_iter_page_owner_new, KF_ITER_NEW | KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_iter_page_owner_next, KF_ITER_NEXT | KF_RET_NULL | KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_iter_page_owner_destroy, KF_ITER_DESTROY | KF_SLEEPABLE) BTF_ID_FLAGS(func, bpf_page_owner_stack_snprint, KF_SLEEPABLE) +BTF_ID_FLAGS(func, bpf_page_owner_get_memcg_info, KF_SLEEPABLE) #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 113e4e7e0b3a..664121be6686 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) @@ -811,6 +855,7 @@ 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)) @@ -832,8 +877,10 @@ 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(scan.page, &memcg_info, NULL, 0); return print_page_owner(buf, count, scan.pfn, scan.page, - &scan.po_snap, scan.po_snap.handle, state); + &scan.po_snap, scan.po_snap.handle, state, + &memcg_info); skip_continue: scan.pfn++; cond_resched(); diff --git a/mm/page_owner.h b/mm/page_owner.h index e8e52d22abed..febf1c2807de 100644 --- a/mm/page_owner.h +++ b/mm/page_owner.h @@ -39,7 +39,16 @@ 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 a2b90c874852..86e0b4b52bfc 100644 --- a/mm/page_owner_iter.c +++ b/mm/page_owner_iter.c @@ -177,4 +177,21 @@ __bpf_kfunc int bpf_page_owner_stack_snprint(struct page_owner_scan *scan, 0); } +__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) +{ + /* Guard against the section being offlined after scan. */ + struct page *page = pfn_to_online_page(scan->pfn); + + if (!page) { + *info__uninit = (struct memcg_info){}; + if (buf__uninit && buf__sz) + buf__uninit[0] = '\0'; + return -ENODATA; + } + + return get_page_memcg_info(page, info__uninit, buf__uninit, buf__sz); +} + __bpf_kfunc_end_defs(); -- 2.20.1