The net page_pool wants to use a magic value to identify page pool pages.
The best place to put it is in the first word where it can be clearly a
non-pointer value. That means shifting dma_addr up to alias with ->index,
which means we need to find another way to indicate page_is_pfmemalloc().
Since page_pool doesn't want to set its magic value on pages which are
pfmemalloc, we can use bit 1 of compound_head to indicate that the page
came from the memory reserves.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
include/linux/mm.h | 12 +++++++-----
include/linux/mm_types.h | 7 +++----
2 files changed, 10 insertions(+), 9 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 8ba434287387..44eab3f6d5ae 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1629,10 +1629,12 @@ struct address_space *page_mapping_file(struct page *page);
static inline bool page_is_pfmemalloc(const struct page *page)
{
/*
- * Page index cannot be this large so this must be
- * a pfmemalloc page.
+ * This is not a tail page; compound_head of a head page is unused
+ * at return from the page allocator, and will be overwritten
+ * by callers who do not care whether the page came from the
+ * reserves.
*/
- return page->index == -1UL;
+ return page->compound_head & 2;
}
/*
@@ -1641,12 +1643,12 @@ static inline bool page_is_pfmemalloc(const struct page *page)
*/
static inline void set_page_pfmemalloc(struct page *page)
{
- page->index = -1UL;
+ page->compound_head = 2;
}
static inline void clear_page_pfmemalloc(struct page *page)
{
- page->index = 0;
+ page->compound_head = 0;
}
/*
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 5aacc1c10a45..39f7163dcace 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -96,10 +96,9 @@ struct page {
unsigned long private;
};
struct { /* page_pool used by netstack */
- /**
- * @dma_addr: might require a 64-bit value on
- * 32-bit architectures.
- */
+ unsigned long pp_magic;
+ unsigned long xmi;
+ unsigned long _pp_mapping_pad;
unsigned long dma_addr[2];
};
struct { /* slab, slob and slub */
--
2.30.2
