[PATCH bpf-next v6 1/4] xsk: Use pool->dma_pages to check for DMA

From: Kal Conley
Date: Wed Apr 12 2023 - 12:21:46 EST


Compare pool->dma_pages instead of pool->dma_pages_cnt to check for an
active DMA mapping. pool->dma_pages needs to be read anyway to access
the map so this compiles to more efficient code.

Signed-off-by: Kal Conley <kal.conley@xxxxxxxxxxx>
Acked-by: Magnus Karlsson <magnus.karlsson@xxxxxxxxx>
---
include/net/xsk_buff_pool.h | 2 +-
net/xdp/xsk_buff_pool.c | 7 ++++---
2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
index d318c769b445..a8d7b8a3688a 100644
--- a/include/net/xsk_buff_pool.h
+++ b/include/net/xsk_buff_pool.h
@@ -180,7 +180,7 @@ static inline bool xp_desc_crosses_non_contig_pg(struct xsk_buff_pool *pool,
if (likely(!cross_pg))
return false;

- return pool->dma_pages_cnt &&
+ return pool->dma_pages &&
!(pool->dma_pages[addr >> PAGE_SHIFT] & XSK_NEXT_PG_CONTIG_MASK);
}

diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index b2df1e0f8153..26f6d304451e 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -350,7 +350,7 @@ void xp_dma_unmap(struct xsk_buff_pool *pool, unsigned long attrs)
{
struct xsk_dma_map *dma_map;

- if (pool->dma_pages_cnt == 0)
+ if (!pool->dma_pages)
return;

dma_map = xp_find_dma_map(pool);
@@ -364,6 +364,7 @@ void xp_dma_unmap(struct xsk_buff_pool *pool, unsigned long attrs)

__xp_dma_unmap(dma_map, attrs);
kvfree(pool->dma_pages);
+ pool->dma_pages = NULL;
pool->dma_pages_cnt = 0;
pool->dev = NULL;
}
@@ -503,7 +504,7 @@ static struct xdp_buff_xsk *__xp_alloc(struct xsk_buff_pool *pool)
if (pool->unaligned) {
xskb = pool->free_heads[--pool->free_heads_cnt];
xp_init_xskb_addr(xskb, pool, addr);
- if (pool->dma_pages_cnt)
+ if (pool->dma_pages)
xp_init_xskb_dma(xskb, pool, pool->dma_pages, addr);
} else {
xskb = &pool->heads[xp_aligned_extract_idx(pool, addr)];
@@ -569,7 +570,7 @@ static u32 xp_alloc_new_from_fq(struct xsk_buff_pool *pool, struct xdp_buff **xd
if (pool->unaligned) {
xskb = pool->free_heads[--pool->free_heads_cnt];
xp_init_xskb_addr(xskb, pool, addr);
- if (pool->dma_pages_cnt)
+ if (pool->dma_pages)
xp_init_xskb_dma(xskb, pool, pool->dma_pages, addr);
} else {
xskb = &pool->heads[xp_aligned_extract_idx(pool, addr)];
--
2.39.2