Move the guts of __dump_page() into a new function called
snapshot_page(). With that done, __dump_page() becomes trivial so
inline it into dump_page().
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
mm/debug.c | 53 +++++++++------------------------------------------
mm/internal.h | 2 ++
mm/util.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 61 insertions(+), 44 deletions(-)
diff --git a/mm/debug.c b/mm/debug.c
index fa3d9686034c..1ea5dacb1524 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -120,54 +120,19 @@ static void __dump_folio(const struct folio *folio, struct page *page,
2 * sizeof(struct page), false);
}
-static void __dump_page(const struct page *page)
-{
- struct folio *foliop, folio;
- struct page precise;
- unsigned long head;
- unsigned long pfn = page_to_pfn(page);
- unsigned long idx, nr_pages = 1;
- int loops = 5;
-
-again:
- memcpy(&precise, page, sizeof(*page));
- head = precise.compound_head;
- if ((head & 1) == 0) {
- foliop = (struct folio *)&precise;
- idx = 0;
- if (!folio_test_large(foliop))
- goto dump;
- foliop = (struct folio *)page;
- } else {
- foliop = (struct folio *)(head - 1);
- 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(const struct page *page, const char *reason)
{
+ struct folio stack_folio;
+ struct page stack_page;
+ const struct folio *folio;
+ unsigned long idx;
+
if (PagePoisoned(page))
pr_warn("page:%p is uninitialized and poisoned", page);
- else
- __dump_page(page);
+ else {
+ folio = snapshot_page(&stack_folio, &stack_page, &idx, page);
+ __dump_folio(folio, &stack_page, page_to_pfn(page), idx);
+ }
if (reason)
pr_warn("page dumped because: %s\n", reason);
dump_page_owner(page);
diff --git a/mm/internal.h b/mm/internal.h
index 109ef30fee11..8fdfea104068 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -856,6 +856,8 @@ static inline bool free_area_empty(struct free_area *area, int migratetype)
/* mm/util.c */
struct anon_vma *folio_anon_vma(const struct folio *folio);
+const struct folio *snapshot_page(struct folio *foliop, struct page *precise,
+ unsigned long *idxp, const struct page *unstable);
#ifdef CONFIG_MMU
void unmap_mapping_folio(struct folio *folio);
diff --git a/mm/util.c b/mm/util.c
index 682ecdb1b1c2..9f9cf3933eb1 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -1239,3 +1239,53 @@ void flush_dcache_folio(struct folio *folio)
}
EXPORT_SYMBOL(flush_dcache_folio);
#endif
+
+/*
+ * If you have an unstable reference to a page, use this to get a
+ * somewhat-consistent (potentially outdated) snapshot. The consistency
+ * is limited to the page being contained in the folio. You need to pass in
+ * a scratch folio and scratch page, probably allocated on the stack.
+ * You get back a pointer to the scratch folio you passed in, marked
+ * as const to remind you not to modify this.
+ */
+const struct folio *snapshot_page(struct folio *foliop, struct page *precise,
+ unsigned long *idxp, const struct page *unstable)
+{
+ struct folio *folio;
+ unsigned long head;
+ unsigned long idx, nr_pages = 1;
+ int loops = 5;
+
+again:
+ memcpy(precise, unstable, sizeof(struct page));
+ head = precise->compound_head;
+ /* Open-coded !PageTail because page_is_fake_head() doesn't work here */
+ if ((head & 1) == 0) {
+ folio = (struct folio *)precise;
+ *idxp = 0;
+ /* Not a tail, not a head, we have a single page */
+ if (!folio_test_large(folio))
+ goto out;
+ folio = (struct folio *)unstable;
+ } else {
+ folio = (struct folio *)(head - 1);
+ *idxp = folio_page_idx(folio, unstable);
+ }
+
+ if (idx < MAX_FOLIO_NR_PAGES || folio_test_hugetlb(folio)) {
+ memcpy(foliop, folio, sizeof(struct folio));
+ nr_pages = folio_nr_pages(foliop);
+ folio = foliop;
+ }
+
+ if (idx > nr_pages) {
+ if (loops-- > 0)
+ goto again;
+ pr_warn("page does not match folio\n");
+ precise->compound_head &= ~1UL;
+ folio = (struct folio *)precise;
+ *idxp = 0;
+ }
+out:
+ return folio;
+}
--
2.47.2
