[net-next v1 09/16] page_pool: device memory support

Mina Almasry
2023-12-08T00:53:42Z

Overload the LSB of struct page* to indicate that it's a page_pool_iov.

Refactor mm calls on struct page* into helpers, and add page_pool_iov
handling on those helpers. Modify callers of these mm APIs with calls to
these helpers instead.

In areas where struct page* is dereferenced, add a check for special
handling of page_pool_iov.

Signed-off-by: Mina Almasry <almasrymina@google.com>

---

v1:
- Disable fragmentation support for iov properly.
- fix napi_pp_put_page() path (Yunsheng).

---
include/net/page_pool/helpers.h | 78 ++++++++++++++++++++++++++++++++-
net/core/page_pool.c | 67 ++++++++++++++++++++--------
net/core/skbuff.c | 28 +++++++-----
3 files changed, 141 insertions(+), 32 deletions(-)

diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h
index 00197f14aa87..2d4e0a2c5620 100644
--- a/include/net/page_pool/helpers.h
+++ b/include/net/page_pool/helpers.h
@@ -154,6 +154,64 @@ static inline struct page_pool_iov *page_to_page_pool_iov(struct page *page)
return NULL;
}

+static inline int page_pool_page_ref_count(struct page *page)
+{
+ if (page_is_page_pool_iov(page))
+ return page_pool_iov_refcount(page_to_page_pool_iov(page));
+
+ return page_ref_count(page);
+}
+
+static inline void page_pool_page_get_many(struct page *page,
+ unsigned int count)
+{
+ if (page_is_page_pool_iov(page))
+ return page_pool_iov_get_many(page_to_page_pool_iov(page),
+ count);
+
+ return page_ref_add(page, count);
+}
+
+static inline void page_pool_page_put_many(struct page *page,
+ unsigned int count)
+{
+ if (page_is_page_pool_iov(page))
+ return page_pool_iov_put_many(page_to_page_pool_iov(page),
+ count);
+
+ if (count > 1)
+ page_ref_sub(page, count - 1);
+
+ put_page(page);
+}
+
+static inline bool page_pool_page_is_pfmemalloc(struct page *page)
+{
+ if (page_is_page_pool_iov(page))
+ return false;
+
+ return page_is_pfmemalloc(page);
+}
+
+static inline bool page_pool_page_is_pref_nid(struct page *page, int pref_nid)
+{
+ /* Assume page_pool_iov are on the preferred node without actually
+ * checking...
+ *
+ * This check is only used to check for recycling memory in the page
+ * pool's fast paths. Currently the only implementation of page_pool_iov
+ * is dmabuf device memory. It's a deliberate decision by the user to
+ * bind a certain dmabuf to a certain netdev, and the netdev rx queue
+ * would not be able to reallocate memory from another dmabuf that
+ * exists on the preferred node, so, this check doesn't make much sense
+ * in this case. Assume all page_pool_iovs can be recycled for now.
+ */
+ if (page_is_page_pool_iov(page))
+ return true;
+
+ return page_to_nid(page) == pref_nid;
+}
+
/**
* page_pool_dev_alloc_pages() - allocate a page.
* @pool: pool from which to allocate
@@ -304,6 +362,10 @@ static inline long page_pool_defrag_page(struct page *page, long nr)
{
long ret;

+ /* fragmentation support hasn't been added to ppiov yet */
+ if (WARN_ON_ONCE(page_is_page_pool_iov(page)))
+ return 0;
+
/* If nr == pp_frag_count then we have cleared all remaining
* references to the page:
* 1. 'n == 1': no need to actually overwrite it.
@@ -347,7 +409,8 @@ static inline long page_pool_defrag_page(struct page *page, long nr)
static inline bool page_pool_is_last_frag(struct page *page)
{
/* If page_pool_defrag_page() returns 0, we were the last user */
- return page_pool_defrag_page(page, 1) == 0;
+ return page_is_page_pool_iov(page) ||
+ page_pool_defrag_page(page, 1) == 0;
}

/**
@@ -434,7 +497,12 @@ static inline void page_pool_free_va(struct page_pool *pool, void *va,
*/
static inline dma_addr_t page_pool_get_dma_addr(struct page *page)
{
- dma_addr_t ret = page->dma_addr;
+ dma_addr_t ret;
+
+ if (page_is_page_pool_iov(page))
+ return page_pool_iov_dma_addr(page_to_page_pool_iov(page));
+
+ ret = page->dma_addr;

if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA)
ret <<= PAGE_SHIFT;
@@ -444,6 +512,12 @@ static inline dma_addr_t page_pool_get_dma_addr(struct page *page)

static inline bool page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
{
+ /* page_pool_iovs are mapped and their dma-addr can't be modified. */
+ if (page_is_page_pool_iov(page)) {
+ DEBUG_NET_WARN_ON_ONCE(true);
+ return false;
+ }
+
if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) {
page->dma_addr = addr >> PAGE_SHIFT;

diff --git a/net/core/page_pool.c b/net/core/page_pool.c
index 423c88564a00..f0148d66371b 100644
--- a/net/core/page_pool.c
+++ b/net/core/page_pool.c
@@ -346,7 +346,7 @@ static struct page *page_pool_refill_alloc_cache(struct page_pool *pool)
if (unlikely(!page))
break;

- if (likely(page_to_nid(page) == pref_nid)) {
+ if (likely(page_pool_page_is_pref_nid(page, pref_nid))) {
pool->alloc.cache[pool->alloc.count++] = page;
} else {
/* NUMA mismatch;
@@ -391,7 +391,15 @@ static void page_pool_dma_sync_for_device(struct page_pool *pool,
struct page *page,
unsigned int dma_sync_size)
{
- dma_addr_t dma_addr = page_pool_get_dma_addr(page);
+ dma_addr_t dma_addr;
+
+ /* page_pool_iov memory provider do not support PP_FLAG_DMA_SYNC_DEV */
+ if (page_is_page_pool_iov(page)) {
+ DEBUG_NET_WARN_ON_ONCE(true);
+ return;
+ }
+
+ dma_addr = page_pool_get_dma_addr(page);

dma_sync_size = min(dma_sync_size, pool->p.max_len);
dma_sync_single_range_for_device(pool->p.dev, dma_addr,
@@ -403,6 +411,12 @@ static bool page_pool_dma_map(struct page_pool *pool, struct page *page)
{
dma_addr_t dma;

+ if (page_is_page_pool_iov(page)) {
+ /* page_pool_iovs are already mapped */
+ DEBUG_NET_WARN_ON_ONCE(true);
+ return true;
+ }
+
/* Setup DMA mapping: use 'struct page' area for storing DMA-addr
* since dma_addr_t can be either 32 or 64 bits and does not always fit
* into page private data (i.e 32bit cpu with 64bit DMA caps)
@@ -434,22 +448,33 @@ static bool page_pool_dma_map(struct page_pool *pool, struct page *page)
static void page_pool_set_pp_info(struct page_pool *pool,
struct page *page)
{
- page->pp = pool;
- page->pp_magic |= PP_SIGNATURE;
-
- /* Ensuring all pages have been split into one fragment initially:
- * page_pool_set_pp_info() is only called once for every page when it
- * is allocated from the page allocator and page_pool_fragment_page()
- * is dirtying the same cache line as the page->pp_magic above, so
- * the overhead is negligible.
- */
- page_pool_fragment_page(page, 1);
+ if (!page_is_page_pool_iov(page)) {
+ page->pp = pool;
+ page->pp_magic |= PP_SIGNATURE;
+
+ /* Ensuring all pages have been split into one fragment
+ * initially:
+ * page_pool_set_pp_info() is only called once for every page
+ * when it is allocated from the page allocator and
+ * page_pool_fragment_page() is dirtying the same cache line as
+ * the page->pp_magic above, so * the overhead is negligible.
+ */
+ page_pool_fragment_page(page, 1);
+ } else {
+ page_to_page_pool_iov(page)->pp = pool;
+ }
+
if (pool->has_init_callback)
pool->slow.init_callback(page, pool->slow.init_arg);
}

static void page_pool_clear_pp_info(struct page *page)
{
+ if (page_is_page_pool_iov(page)) {
+ page_to_page_pool_iov(page)->pp = NULL;
+ return;
+ }
+
page->pp_magic = 0;
page->pp = NULL;
}
@@ -664,7 +689,7 @@ static bool page_pool_recycle_in_cache(struct page *page,
return false;
}

- /* Caller MUST have verified/know (page_ref_count(page) == 1) */
+ /* Caller MUST have verified/know (page_pool_page_ref_count(page) == 1) */
pool->alloc.cache[pool->alloc.count++] = page;
recycle_stat_inc(pool, cached);
return true;
@@ -689,9 +714,10 @@ __page_pool_put_page(struct page_pool *pool, struct page *page,
* refcnt == 1 means page_pool owns page, and can recycle it.
*
* page is NOT reusable when allocated when system is under
- * some pressure. (page_is_pfmemalloc)
+ * some pressure. (page_pool_page_is_pfmemalloc)
*/
- if (likely(page_ref_count(page) == 1 && !page_is_pfmemalloc(page))) {
+ if (likely(page_pool_page_ref_count(page) == 1 &&
+ !page_pool_page_is_pfmemalloc(page))) {
/* Read barrier done in page_ref_count / READ_ONCE */

if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
@@ -806,7 +832,8 @@ static struct page *page_pool_drain_frag(struct page_pool *pool,
if (likely(page_pool_defrag_page(page, drain_count)))
return NULL;

- if (page_ref_count(page) == 1 && !page_is_pfmemalloc(page)) {
+ if (page_pool_page_ref_count(page) == 1 &&
+ !page_pool_page_is_pfmemalloc(page)) {
if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
page_pool_dma_sync_for_device(pool, page, -1);

@@ -840,6 +867,10 @@ struct page *page_pool_alloc_frag(struct page_pool *pool,
if (WARN_ON(size > max_size))
return NULL;

+ /* page_pool_iov's don't currently support fragmentation */
+ if (WARN_ON_ONCE(pool->mp_ops == &dmabuf_devmem_ops))
+ return NULL;
+
size = ALIGN(size, dma_get_cache_alignment());
*offset = pool->frag_offset;

@@ -882,9 +913,9 @@ static void page_pool_empty_ring(struct page_pool *pool)
/* Empty recycle ring */
while ((page = ptr_ring_consume_bh(&pool->ring))) {
/* Verify the refcnt invariant of cached pages */
- if (!(page_ref_count(page) == 1))
+ if (!(page_pool_page_ref_count(page) == 1))
pr_crit("%s() page_pool refcnt %d violation\n",
- __func__, page_ref_count(page));
+ __func__, page_pool_page_ref_count(page));

page_pool_return_page(pool, page);
}
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index b157efea5dea..07f802f1adf1 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -896,19 +896,23 @@ bool napi_pp_put_page(struct page *page, bool napi_safe)
bool allow_direct = false;
struct page_pool *pp;

- page = compound_head(page);
-
- /* page->pp_magic is OR'ed with PP_SIGNATURE after the allocation
- * in order to preserve any existing bits, such as bit 0 for the
- * head page of compound page and bit 1 for pfmemalloc page, so
- * mask those bits for freeing side when doing below checking,
- * and page_is_pfmemalloc() is checked in __page_pool_put_page()
- * to avoid recycling the pfmemalloc page.
- */
- if (unlikely((page->pp_magic & ~0x3UL) != PP_SIGNATURE))
- return false;
+ if (!page_is_page_pool_iov(page)) {
+ page = compound_head(page);
+
+ /* page->pp_magic is OR'ed with PP_SIGNATURE after the allocation
+ * in order to preserve any existing bits, such as bit 0 for the
+ * head page of compound page and bit 1 for pfmemalloc page, so
+ * mask those bits for freeing side when doing below checking,
+ * and page_is_pfmemalloc() is checked in __page_pool_put_page()
+ * to avoid recycling the pfmemalloc page.
+ */
+ if (unlikely((page->pp_magic & ~0x3UL) != PP_SIGNATURE))
+ return false;

- pp = page->pp;
+ pp = page->pp;
+ } else {
+ pp = page_to_page_pool_iov(page)->pp;
+ }

/* Allow direct recycle if we have reasons to believe that we are
* in the same context as the consumer would run, so there's
--
2.43.0.472.g3155946c3a-goog