From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=156.224.81.104 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792581905; b=faQvv0RQaPuPC1K8DwTMnt1mtgPReYaZGRuopwdsTQAW7hgdNihEaNWaoDBeQWgnxffb y/Qx/e9RKYCd4Yk8gvnlzAPnOgKW78MBlfrqWmZ06WYSJ/TmdPw6CX0Zq0lhf/XYAVXSe ROIELklFH6QghhPF7OFAFIxCGhZ3zn7rWaD0grWmJPWaR8sc6hYGxnLZZ/Dz2vxpzZfux b0h9bCloWeXtgFrTcdYB/6SAE7m+3MPAzWq7Lv0zc7YYtpKYBrDXiixaGrq445SBexs2q TzmQ+Y51eSm9KB4jftNqiRhG7rkitEZVNDRsvUq2V8vCLe18WHeRTz6cwOQExh5K4ag== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792581905; 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=ND5EZj7JQ8YayZRBZb3U+AbUZ3EKzLPLjchuk2el9mM=; b=dAUJi+ARmgS4lHgTMChxCB5HAX0VSjni/ZmspKap2PbQs+xU6rNGtPajc7T8KZdpBEK7 ByuyMnwMavhbUXQHR2vvEtOf1y3rZBSdHbqCDO3uF+Ek4lyOp88AsFQS9usbm0GOwx6Ae 4fBlC9gSuqh7FvHYihxzTjopDOGnYftgnDh1/0vjp9Qr9fKblTYqXHW0rTm9IfxpdY47N y28zQAIT8Y2ThbmsxfuejDHy3KpYwMEM491hho+6a4TJVRrlQ20yzJHrw/NbUc3pzBNel HK9tupcpfF494omBzNqyFKRwiESA01DVexMktePZO6lFtRGNW8FT29ABawI9KmD16fQ== 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=156.224.81.104 Received: from mail-m81104.xmail.ntesmail.com (mail-m81104.xmail.ntesmail.com [156.224.81.104]) (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 A6EB2606A329; Wed, 21 Oct 2026 11:25:02 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org A6EB2606A329 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 204f151a8; Wed, 21 Oct 2026 19:24:52 +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 3/7] mm/page_owner: add bpf_iter target "page_owner" Date: Wed, 21 Oct 2026 19:24:33 +0800 Message-Id: <20261021112437.1799213-4-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: 0aa15e34f8690229kunme08c1fd526acdc X-HM-MType: 1 X-HM-Spam-Status: e1kfGhgUHx5ZQUpXWQgPGg8OCBgUHx5ZQUlOS1dZFg8aDwILHllBWSg2Ly tZV1koWUFJQjdXWRgWCB1ZQUpXWS1ZQUlXWQ8JGhUIEh9ZQVlCS08YVhlJQh0fTE9IGRgaH1YVFA kWGhdVGRETFhoSFyQUDg9ZV1kYEgtZQVlJSkNVQk9VSkpDVUJLWVdZFhoPEhUdFFlBWU9LSFVKS0 lPT09IVUpLS1VKQktLWQY+ Register a bpf_iter target "page_owner" that walks the pages eligible for page_owner output, with the same eligibility rules as the /sys/kernel/debug/page_owner read path. For each eligible page the attached BPF program receives the pfn and the page_owner record, and can freely filter and format output. The po_snap record in the scan cursor is taken inside the page_ext RCU window and handed to the BPF program as a copy, so no RCU window is needed at consumption time. Torn reads remain possible if the record is concurrently updated while it is copied, but this is the same best-effort behavior as the read path has always had. The target is registered from pageowner_init() when both CONFIG_PAGE_OWNER and CONFIG_BPF_SYSCALL are enabled; a registration failure only disables the bpf_iter target. Userspace tools such as bpftrace can attach to this target like any other bpf_iter. For example, to count pages owned by init (pid 1): bpftrace -e 'iter:page_owner / ctx->po->pid == 1 / { @ = sum(1 << ctx->po->order); }' Signed-off-by: Zhen Ni --- Changes in v3: - Drop the page pointer from the BPF context. - Enable BPF_ITER_RESCHED. - Fix the bpftrace example in the commit message. Changes in v2: - Drop the scan->pfn++. - Fill page/po/pfn only when v is non-NULL. - Implement page_owner_seq_stop(). v2: https://lore.kernel.org/linux-mm/20261013122125.843451-3-zhen.ni@easystack.cn/ v1: https://lore.kernel.org/linux-mm/20261009112308.240769-3-zhen.ni@easystack.cn/ --- mm/Makefile | 3 ++ mm/page_owner.c | 32 +++--------- mm/page_owner.h | 47 +++++++++++++++++ mm/page_owner_iter.c | 118 +++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 175 insertions(+), 25 deletions(-) create mode 100644 mm/page_owner.h create mode 100644 mm/page_owner_iter.c diff --git a/mm/Makefile b/mm/Makefile index e7245cb88c66..d7307b5a964c 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -115,6 +115,9 @@ obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o obj-$(CONFIG_DEBUG_RODATA_TEST) += rodata_test.o obj-$(CONFIG_DEBUG_VM_PGTABLE) += debug_vm_pgtable.o obj-$(CONFIG_PAGE_OWNER) += page_owner.o +ifdef CONFIG_BPF_SYSCALL +obj-$(CONFIG_PAGE_OWNER) += page_owner_iter.o +endif obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o obj-$(CONFIG_ZSMALLOC) += zsmalloc.o obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o diff --git a/mm/page_owner.c b/mm/page_owner.c index 8e72a85c663c..ece3b69a2579 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -14,6 +14,7 @@ #include #include "page_alloc.h" +#include "page_owner.h" /* * TODO: teach PAGE_OWNER_STACK_DEPTH (__dump_page_owner and save_stack) @@ -21,30 +22,6 @@ */ #define PAGE_OWNER_STACK_DEPTH (16) -struct page_owner { - unsigned short order; - short last_migrate_reason; - gfp_t gfp_mask; - depot_stack_handle_t handle; - depot_stack_handle_t free_handle; - u64 ts_nsec; - u64 free_ts_nsec; - char comm[TASK_COMM_LEN]; - pid_t pid; - pid_t tgid; - pid_t free_pid; - pid_t free_tgid; -}; - -/* - * Cursor and per-page result of page_owner_next_eligible(). - */ -struct page_owner_scan { - /* resume point */ - unsigned long pfn; - struct page_owner po_snap; -}; - struct stack { struct stack_record *stack_record; struct stack *next; @@ -740,7 +717,7 @@ void __dump_page_owner(const struct page *page) * must advance scan->pfn past the hit before calling again to resume * the scan. */ -static bool page_owner_next_eligible(struct page_owner_scan *scan) +bool page_owner_next_eligible(struct page_owner_scan *scan) { unsigned long pfn = scan->pfn; @@ -1221,6 +1198,11 @@ static int __init pageowner_init(void) &stack_fops); debugfs_create_file("count_threshold", 0600, dir, NULL, &threshold_fops); + +#ifdef CONFIG_BPF_SYSCALL + if (page_owner_iter_register()) + pr_warn("page_owner: failed to register bpf_iter target\n"); +#endif return 0; } late_initcall(pageowner_init) diff --git a/mm/page_owner.h b/mm/page_owner.h new file mode 100644 index 000000000000..0aa7695bec82 --- /dev/null +++ b/mm/page_owner.h @@ -0,0 +1,47 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * mm/ internal page_owner and page_owner_iter declarations + */ + +#ifndef __MM_PAGE_OWNER_H +#define __MM_PAGE_OWNER_H + +#include +#include +#include + +/* + * mm/page_owner.c + */ +struct page_owner { + unsigned short order; + short last_migrate_reason; + gfp_t gfp_mask; + depot_stack_handle_t handle; + depot_stack_handle_t free_handle; + u64 ts_nsec; + u64 free_ts_nsec; + char comm[TASK_COMM_LEN]; + pid_t pid; + pid_t tgid; + pid_t free_pid; + pid_t free_tgid; +}; + +/* + * Cursor and per-page result of page_owner_next_eligible(). + */ +struct page_owner_scan { + /* resume point */ + unsigned long pfn; + struct page_owner po_snap; +}; + +bool page_owner_next_eligible(struct page_owner_scan *scan); + +/* + * mm/page_owner_iter.c + */ +int page_owner_iter_register(void); + +#endif /* __MM_PAGE_OWNER_H */ diff --git a/mm/page_owner_iter.c b/mm/page_owner_iter.c new file mode 100644 index 000000000000..529b2c4a589a --- /dev/null +++ b/mm/page_owner_iter.c @@ -0,0 +1,118 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include + +#include "page_owner.h" + +struct bpf_iter__page_owner { + __bpf_md_ptr(struct bpf_iter_meta *, meta); + __bpf_md_ptr(struct page_owner *, po); + u64 pfn; +}; + +DEFINE_BPF_ITER_FUNC(page_owner, struct bpf_iter_meta *meta, + struct page_owner *po, u64 pfn) + +static void *page_owner_seq_start(struct seq_file *seq, loff_t *posp) +{ + struct page_owner_scan *scan = seq->private; + + if (*posp == 0) + scan->pfn = min_low_pfn; + + if (!page_owner_next_eligible(scan)) + return NULL; + return &scan->po_snap; +} + +static void *page_owner_seq_next(struct seq_file *seq, void *v, loff_t *posp) +{ + struct page_owner_scan *scan = seq->private; + + ++*posp; + scan->pfn++; + if (!page_owner_next_eligible(scan)) + return NULL; + + return &scan->po_snap; +} + +static int page_owner_prog_seq_show(struct bpf_prog *prog, + struct bpf_iter_meta *meta, void *v) +{ + struct page_owner_scan *scan = meta->seq->private; + struct bpf_iter__page_owner ctx = {}; + + ctx.meta = meta; + if (v) { + /* @po: hit-time snapshot, no RCU window needed. */ + ctx.po = &scan->po_snap; + ctx.pfn = scan->pfn; + } + + return bpf_iter_run_prog(prog, &ctx); +} + +static int page_owner_seq_show(struct seq_file *seq, void *v) +{ + struct bpf_iter_meta meta; + struct bpf_prog *prog; + + meta.seq = seq; + prog = bpf_iter_get_info(&meta, false); + if (!prog) + return 0; + + return page_owner_prog_seq_show(prog, &meta, v); +} + +static void page_owner_seq_stop(struct seq_file *seq, void *v) +{ + if (!v) { + struct bpf_iter_meta meta = { .seq = seq }; + struct bpf_prog *prog; + + prog = bpf_iter_get_info(&meta, true); + if (prog) + page_owner_prog_seq_show(prog, &meta, NULL); + } +} + +static const struct seq_operations page_owner_iter_seq_ops = { + .start = page_owner_seq_start, + .next = page_owner_seq_next, + .stop = page_owner_seq_stop, + .show = page_owner_seq_show, +}; + +static const struct bpf_iter_seq_info page_owner_iter_seq_info = { + .seq_ops = &page_owner_iter_seq_ops, + .init_seq_private = NULL, + .fini_seq_private = NULL, + .seq_priv_size = sizeof(struct page_owner_scan), +}; + +static struct bpf_iter_reg page_owner_iter_reg_info = { + .target = "page_owner", + .ctx_arg_info_size = 1, + .ctx_arg_info = { + { offsetof(struct bpf_iter__page_owner, po), + PTR_TO_BTF_ID_OR_NULL }, + }, + .seq_info = &page_owner_iter_seq_info, + .feature = BPF_ITER_RESCHED, +}; + +BTF_ID_LIST(page_owner_btf_ids) +BTF_ID(struct, page_owner) + +int page_owner_iter_register(void) +{ + page_owner_iter_reg_info.ctx_arg_info[0].btf_id = + page_owner_btf_ids[0]; + + return bpf_iter_reg_target(&page_owner_iter_reg_info); +} -- 2.20.1