On 2020-07-10 18:30, John Hubbard wrote:
On 2020-07-09 13:21, Matthew Wilcox (Oracle) wrote:
If we can't call page_mapping() to get the page mapping, handle the
anon/ksm/movable bits correctly.
Hi Matthew,
I see why you did this, as otherwise the new printing won't work.
Oh, and I forget to add: my only comment was just a documentation
suggestion, not critical at all, and so:
Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>
thanks,
--
John Hubbard
NVIDIA
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
mm/debug.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/mm/debug.c b/mm/debug.c
index 4f376514744d..e5de63406b59 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -70,7 +70,12 @@ void __dump_page(struct page *page, const char *reason)
if (page < head || (page >= head + MAX_ORDER_NR_PAGES)) {
/* Corrupt page, cannot call page_mapping */
It's tricky to step lightly through the debris of corrupted page
pointer here, but how about this updated comment, to replace the one-liner
above:
/*
* 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.)
*/
- mapping = page->mapping;
+ unsigned long tmp = (unsigned long)page->mapping;
+
+ if (tmp & PAGE_MAPPING_ANON)
+ mapping = NULL;
+ else
+ mapping = (void *)(tmp & ~PAGE_MAPPING_FLAGS);
head = page;
compound = false;
} else {
