On 30/11/2022 23.07, Matthew Wilcox (Oracle) wrote:
As part of simplifying struct page, create a new netmem type which
mirrors the page_pool members in struct page.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
include/net/page_pool.h | 41 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 41 insertions(+)
diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index 813c93499f20..af6ff8c302a0 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -50,6 +50,47 @@
PP_FLAG_DMA_SYNC_DEV |\
PP_FLAG_PAGE_FRAG)
+/* page_pool used by netstack */
Can we improve the comment, making in more clear that this netmem struct
is mirroring/sharing/using part of struct page?
My proposal:
/* page_pool used by netstack mirrors/uses members in struct page */
+struct netmem {
+ unsigned long flags; /* Page flags */
+ /**
+ * @pp_magic: magic value to avoid recycling non
+ * page_pool allocated pages.
+ */
+ unsigned long pp_magic;
+ struct page_pool *pp;
+ unsigned long _pp_mapping_pad;
+ unsigned long dma_addr;
+ union {
+ /**
+ * dma_addr_upper: might require a 64-bit
+ * value on 32-bit architectures.
+ */
+ unsigned long dma_addr_upper;
+ /**
+ * For frag page support, not supported in
+ * 32-bit architectures with 64-bit DMA.
+ */
+ atomic_long_t pp_frag_count;
+ };
+ atomic_t _mapcount;
+ atomic_t _refcount;
+};
+
+#define NETMEM_MATCH(pg, nm) \
+ static_assert(offsetof(struct page, pg) == offsetof(struct netmem, nm))
+NETMEM_MATCH(flags, flags);
+NETMEM_MATCH(lru, pp_magic);
+NETMEM_MATCH(pp, pp);
+NETMEM_MATCH(mapping, _pp_mapping_pad);
+NETMEM_MATCH(dma_addr, dma_addr);
+NETMEM_MATCH(dma_addr_upper, dma_addr_upper);
+NETMEM_MATCH(pp_frag_count, pp_frag_count);
+NETMEM_MATCH(_mapcount, _mapcount);
+NETMEM_MATCH(_refcount, _refcount);
+#undef NETMEM_MATCH
+static_assert(sizeof(struct netmem) <= sizeof(struct page));
+
/*
* Fast allocation side cache array/stack
*
