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, the page 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 / { @ = count(); }' Signed-off-by: Zhen Ni --- Changes in v2: - Drop the scan->pfn++. - Fill page/po/pfn only when v is non-NULL. - Implement page_owner_seq_stop(). v1: https://lore.kernel.org/linux-mm/20261009112308.240769-3-zhen.ni@easystack.cn/ --- mm/Makefile | 3 ++ mm/page_owner.c | 33 +++--------- mm/page_owner.h | 48 +++++++++++++++++ mm/page_owner_iter.c | 124 +++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 182 insertions(+), 26 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 56c75a669a6b..617346a4ab22 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) @@ -21,31 +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 *page; - struct page_owner po_snap; -}; - struct stack { struct stack_record *stack_record; struct stack *next; @@ -741,7 +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; @@ -1196,6 +1172,11 @@ 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..fda83be69275 --- /dev/null +++ b/mm/page_owner.h @@ -0,0 +1,48 @@ +/* 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 *page; + 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..938cb42ab7d7 --- /dev/null +++ b/mm/page_owner_iter.c @@ -0,0 +1,124 @@ +// 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 *, page); + __bpf_md_ptr(struct page_owner *, po); + u64 pfn; +}; + +DEFINE_BPF_ITER_FUNC(page_owner, struct bpf_iter_meta *meta, + struct page *page, 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->page; +} + +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->page; +} + +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) { + ctx.page = (struct page *)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 = 2, + .ctx_arg_info = { + { offsetof(struct bpf_iter__page_owner, page), + PTR_TO_BTF_ID_OR_NULL }, + { offsetof(struct bpf_iter__page_owner, po), + PTR_TO_BTF_ID_OR_NULL }, + }, + .seq_info = &page_owner_iter_seq_info, +}; + +BTF_ID_LIST(page_owner_btf_ids) +BTF_ID(struct, page) +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]; + page_owner_iter_reg_info.ctx_arg_info[1].btf_id = + page_owner_btf_ids[1]; + + return bpf_iter_reg_target(&page_owner_iter_reg_info); +} -- 2.20.1