Re: [PATCH v2 17/24] page_pool: Convert page_pool_return_skb_page() to use netmem

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On 06/01/2023 17.53, Matthew Wilcox wrote:
On Fri, Jan 06, 2023 at 04:49:12PM +0100, Jesper Dangaard Brouer wrote:
On 05/01/2023 22.46, Matthew Wilcox (Oracle) wrote:
This function accesses the pagepool members of struct page directly,
so it needs to become netmem.  Add page_pool_put_full_netmem() and
page_pool_recycle_netmem().

Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
---
   include/net/page_pool.h | 14 +++++++++++++-
   net/core/page_pool.c    | 13 ++++++-------
   2 files changed, 19 insertions(+), 8 deletions(-)

diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index fbb653c9f1da..126c04315929 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -464,10 +464,16 @@ static inline void page_pool_put_page(struct page_pool *pool,
   }
   /* Same as above but will try to sync the entire area pool->max_len */
+static inline void page_pool_put_full_netmem(struct page_pool *pool,
+		struct netmem *nmem, bool allow_direct)
+{
+	page_pool_put_netmem(pool, nmem, -1, allow_direct);
+}
+
   static inline void page_pool_put_full_page(struct page_pool *pool,
   					   struct page *page, bool allow_direct)
   {
-	page_pool_put_page(pool, page, -1, allow_direct);
+	page_pool_put_full_netmem(pool, page_netmem(page), allow_direct);
   }
   /* Same as above but the caller must guarantee safe context. e.g NAPI */
@@ -477,6 +483,12 @@ static inline void page_pool_recycle_direct(struct page_pool *pool,
   	page_pool_put_full_page(pool, page, true);
   }
+static inline void page_pool_recycle_netmem(struct page_pool *pool,
+					    struct netmem *nmem)
+{
+	page_pool_put_full_netmem(pool, nmem, true);
                                               ^^^^

It is not clear in what context page_pool_recycle_netmem() will be used,
but I think the 'true' (allow_direct=true) might be wrong here.

It is only in limited special cases (RX-NAPI context) we can allow
direct return to the RX-alloc-cache.

Mmm.  It's a c'n'p of the previous function:

static inline void page_pool_recycle_direct(struct page_pool *pool,
                                             struct page *page)
{
         page_pool_put_full_page(pool, page, true);
}

so perhaps it's just badly named?

Yes, I think so.

Can we name it:
 page_pool_recycle_netmem_direct

And perhaps add a comment with a warning like:
 /* Caller must guarantee safe context. e.g NAPI */

Like the page_pool_recycle_direct() function has a comment.

--Jesper





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