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) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index d45eadc..02547c8 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2066,6 +2066,13 @@ static inline long folio_nr_pages(struct folio *folio)
 #endif
 }
 
+/* Only hugetlbfs can allocate folios larger than MAX_ORDER */
+#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
+#define MAX_FOLIO_NR_PAGES     (1UL << PUD_ORDER)
+#else
+#define MAX_FOLIO_NR_PAGES     MAX_ORDER_NR_PAGES
+#endif
+
 /*
  * compound_nr() returns the number of pages in this potentially compound
  * page.  compound_nr() can be called on a tail page, and is defined to

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 633812a..c11b7cd 100644 (file)
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -76,9 +76,12 @@ extern const char * const migratetype_names[MIGRATE_TYPES];
 #ifdef CONFIG_CMA
 #  define is_migrate_cma(migratetype) unlikely((migratetype) == MIGRATE_CMA)
 #  define is_migrate_cma_page(_page) (get_pageblock_migratetype(_page) == MIGRATE_CMA)
+#  define is_migrate_cma_folio(folio, pfn)     (MIGRATE_CMA ==         \
+       get_pfnblock_flags_mask(&folio->page, pfn, MIGRATETYPE_MASK))
 #else
 #  define is_migrate_cma(migratetype) false
 #  define is_migrate_cma_page(_page) false
+#  define is_migrate_cma_folio(folio, pfn) false
 #endif
 
 static inline bool is_migrate_movable(int mt)

diff --git a/mm/debug.c b/mm/debug.c
index ee533a5..12fed59 100644 (file)
--- 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)