From fae7d834c43ccdb9fcecaf4d0f33145d884b3e5c Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Tue, 27 Feb 2024 19:23:31 +0000 Subject: mm: add __dump_folio() Turn __dump_page() into a wrapper around __dump_folio(). Snapshot the page & folio into a stack variable so we don't hit BUG_ON() if an allocation is freed under us and what was a folio pointer becomes a pointer to a tail page. [willy@infradead.org: fix build issue] Link: https://lkml.kernel.org/r/ZeAKCyTn_xS3O9cE@casper.infradead.org [willy@infradead.org: fix __dump_folio] Link: https://lkml.kernel.org/r/ZeJJegP8zM7S9GTy@casper.infradead.org [willy@infradead.org: fix pointer confusion] Link: https://lkml.kernel.org/r/ZeYa00ixxC4k1ot-@casper.infradead.org [akpm@linux-foundation.org: s/printk/pr_warn/] Link: https://lkml.kernel.org/r/20240227192337.757313-5-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton --- mm/debug.c | 128 +++++++++++++++++++++++++++++++++++-------------------------- 1 file changed, 73 insertions(+), 55 deletions(-) (limited to 'mm') diff --git a/mm/debug.c b/mm/debug.c index ee533a5ceb79d..12fed592c9554 100644 --- a/mm/debug.c +++ b/mm/debug.c @@ -51,84 +51,102 @@ const struct trace_print_flags vmaflag_names[] = { {0, NULL} }; -static void __dump_page(struct page *page) +static void __dump_folio(struct folio *folio, struct page *page, + unsigned long pfn, unsigned long idx) { - struct folio *folio = page_folio(page); - struct page *head = &folio->page; - struct address_space *mapping; - bool compound = PageCompound(page); - /* - * Accessing the pageblock without the zone lock. It could change to - * "isolate" again in the meantime, but since we are just dumping the - * state for debugging, it should be fine to accept a bit of - * inaccuracy here due to racing. - */ - bool page_cma = is_migrate_cma_page(page); - int mapcount; + struct address_space *mapping = folio_mapping(folio); + int mapcount = 0; char *type = ""; - if (page < head || (page >= head + MAX_ORDER_NR_PAGES)) { - /* - * Corrupt page, so we cannot call page_mapping. Instead, do a - * safe subset of the steps that page_mapping() does. Caution: - * this will be misleading for tail pages, PageSwapCache pages, - * and potentially other situations. (See the page_mapping() - * implementation for what's missing here.) - */ - unsigned long tmp = (unsigned long)page->mapping; - - if (tmp & PAGE_MAPPING_ANON) - mapping = NULL; - else - mapping = (void *)(tmp & ~PAGE_MAPPING_FLAGS); - head = page; - folio = (struct folio *)page; - compound = false; - } else { - mapping = page_mapping(page); - } - /* - * Avoid VM_BUG_ON() in page_mapcount(). - * page->_mapcount space in struct page is used by sl[aou]b pages to - * encode own info. + * page->_mapcount space in struct page is used by slab pages to + * encode own info, and we must avoid calling page_folio() again. */ - mapcount = PageSlab(head) ? 0 : page_mapcount(page); - - pr_warn("page:%p refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n", - page, page_ref_count(head), mapcount, mapping, - page_to_pgoff(page), page_to_pfn(page)); - if (compound) { - pr_warn("head:%p order:%u entire_mapcount:%d nr_pages_mapped:%d pincount:%d\n", - head, compound_order(head), + if (!folio_test_slab(folio)) { + mapcount = atomic_read(&page->_mapcount) + 1; + if (folio_test_large(folio)) + mapcount += folio_entire_mapcount(folio); + } + + pr_warn("page: refcount:%d mapcount:%d mapping:%p index:%#lx pfn:%#lx\n", + folio_ref_count(folio), mapcount, mapping, + folio->index + idx, pfn); + if (folio_test_large(folio)) { + pr_warn("head: order:%u entire_mapcount:%d nr_pages_mapped:%d pincount:%d\n", + folio_order(folio), folio_entire_mapcount(folio), folio_nr_pages_mapped(folio), atomic_read(&folio->_pincount)); } #ifdef CONFIG_MEMCG - if (head->memcg_data) - pr_warn("memcg:%lx\n", head->memcg_data); + if (folio->memcg_data) + pr_warn("memcg:%lx\n", folio->memcg_data); #endif - if (PageKsm(page)) + if (folio_test_ksm(folio)) type = "ksm "; - else if (PageAnon(page)) + else if (folio_test_anon(folio)) type = "anon "; else if (mapping) dump_mapping(mapping); BUILD_BUG_ON(ARRAY_SIZE(pageflag_names) != __NR_PAGEFLAGS + 1); - pr_warn("%sflags: %pGp%s\n", type, &head->flags, - page_cma ? " CMA" : ""); - pr_warn("page_type: %pGt\n", &head->page_type); + /* + * Accessing the pageblock without the zone lock. It could change to + * "isolate" again in the meantime, but since we are just dumping the + * state for debugging, it should be fine to accept a bit of + * inaccuracy here due to racing. + */ + pr_warn("%sflags: %pGp%s\n", type, &folio->flags, + is_migrate_cma_folio(folio, pfn) ? " CMA" : ""); + pr_warn("page_type: %pGt\n", &folio->page.page_type); print_hex_dump(KERN_WARNING, "raw: ", DUMP_PREFIX_NONE, 32, sizeof(unsigned long), page, sizeof(struct page), false); - if (head != page) + if (folio_test_large(folio)) print_hex_dump(KERN_WARNING, "head: ", DUMP_PREFIX_NONE, 32, - sizeof(unsigned long), head, - sizeof(struct page), false); + sizeof(unsigned long), folio, + 2 * sizeof(struct page), false); +} + +static void __dump_page(const struct page *page) +{ + struct folio *foliop, folio; + struct page precise; + unsigned long pfn = page_to_pfn(page); + unsigned long idx, nr_pages = 1; + int loops = 5; + +again: + memcpy(&precise, page, sizeof(*page)); + foliop = page_folio(&precise); + if (foliop == (struct folio *)&precise) { + idx = 0; + if (!folio_test_large(foliop)) + goto dump; + foliop = (struct folio *)page; + } else { + idx = folio_page_idx(foliop, page); + } + + if (idx < MAX_FOLIO_NR_PAGES) { + memcpy(&folio, foliop, 2 * sizeof(struct page)); + nr_pages = folio_nr_pages(&folio); + foliop = &folio; + } + + if (idx > nr_pages) { + if (loops-- > 0) + goto again; + pr_warn("page does not match folio\n"); + precise.compound_head &= ~1UL; + foliop = (struct folio *)&precise; + idx = 0; + } + +dump: + __dump_folio(foliop, &precise, pfn, idx); } void dump_page(struct page *page, const char *reason) -- cgit 1.2.3-korg