Convert netmem to be a union of struct page and struct netmem. Overload the LSB of struct netmem* to indicate that it's a net_iov, otherwise it's a page.
Currently these entries in struct page are rented by the page_pool and used exclusively by the net stack:
struct { unsigned long pp_magic; struct page_pool *pp; unsigned long _pp_mapping_pad; unsigned long dma_addr; atomic_long_t pp_ref_count; };
Mirror these (and only these) entries into struct net_iov and implement netmem helpers that can access these common fields regardless of whether the underlying type is page or net_iov.
Implement checks for net_iov in netmem helpers which delegate to mm APIs, to ensure net_iov are never passed to the mm stack.
Signed-off-by: Mina Almasry almasrymina@google.com
---
RFCv5: - Use netmem instead of page* with LSB set. - Use pp_ref_count for refcounting net_iov. - Removed many of the custom checks for netmem.
v1: - Disable fragmentation support for iov properly. - fix napi_pp_put_page() path (Yunsheng). - Use pp_frag_count for devmem refcounting.
--- include/net/netmem.h | 145 ++++++++++++++++++++++++++++++-- include/net/page_pool/helpers.h | 25 +++--- net/core/page_pool.c | 26 +++--- net/core/skbuff.c | 9 +- 4 files changed, 164 insertions(+), 41 deletions(-)
diff --git a/include/net/netmem.h b/include/net/netmem.h index 31f338f19da0..7557aecc0f78 100644 --- a/include/net/netmem.h +++ b/include/net/netmem.h @@ -12,11 +12,47 @@
/* net_iov */
+DECLARE_STATIC_KEY_FALSE(page_pool_mem_providers); + +/* We overload the LSB of the struct page pointer to indicate whether it's + * a page or net_iov. + */ +#define NET_IOV 0x01UL + struct net_iov { + unsigned long __unused_padding; + unsigned long pp_magic; + struct page_pool *pp; struct dmabuf_genpool_chunk_owner *owner; unsigned long dma_addr; + atomic_long_t pp_ref_count; };
+/* These fields in struct page are used by the page_pool and net stack: + * + * struct { + * unsigned long pp_magic; + * struct page_pool *pp; + * unsigned long _pp_mapping_pad; + * unsigned long dma_addr; + * atomic_long_t pp_ref_count; + * }; + * + * We mirror the page_pool fields here so the page_pool can access these fields + * without worrying whether the underlying fields belong to a page or net_iov. + * + * The non-net stack fields of struct page are private to the mm stack and must + * never be mirrored to net_iov. + */ +#define NET_IOV_ASSERT_OFFSET(pg, iov) \ + static_assert(offsetof(struct page, pg) == \ + offsetof(struct net_iov, iov)) +NET_IOV_ASSERT_OFFSET(pp_magic, pp_magic); +NET_IOV_ASSERT_OFFSET(pp, pp); +NET_IOV_ASSERT_OFFSET(dma_addr, dma_addr); +NET_IOV_ASSERT_OFFSET(pp_ref_count, pp_ref_count); +#undef NET_IOV_ASSERT_OFFSET + static inline struct dmabuf_genpool_chunk_owner * net_iov_owner(const struct net_iov *niov) { @@ -47,19 +83,25 @@ net_iov_binding(const struct net_iov *niov) struct netmem { union { struct page page; - - /* Stub to prevent compiler implicitly converting from page* - * to netmem_t* and vice versa. - * - * Other memory type(s) net stack would like to support - * can be added to this union. - */ - void *addr; + struct net_iov niov; }; };
+static inline bool netmem_is_net_iov(const struct netmem *netmem) +{ +#ifdef CONFIG_PAGE_POOL + return static_branch_unlikely(&page_pool_mem_providers) && + (unsigned long)netmem & NET_IOV; +#else + return false; +#endif +} + static inline struct page *netmem_to_page(struct netmem *netmem) { + if (WARN_ON_ONCE(netmem_is_net_iov(netmem))) + return NULL; + return &netmem->page; }
@@ -70,17 +112,104 @@ static inline struct netmem *page_to_netmem(struct page *page)
static inline int netmem_ref_count(struct netmem *netmem) { + /* The non-pp refcount of netmem is always 1. On netmem, we only support + * pp refcounting. + */ + if (netmem_is_net_iov(netmem)) + return 1; + return page_ref_count(netmem_to_page(netmem)); }
static inline unsigned long netmem_to_pfn(struct netmem *netmem) { + if (netmem_is_net_iov(netmem)) + return 0; + return page_to_pfn(netmem_to_page(netmem)); }
+static inline struct net_iov *__netmem_clear_lsb(struct netmem *netmem) +{ + return (struct net_iov *)((unsigned long)netmem & ~NET_IOV); +} + +static inline unsigned long netmem_get_pp_magic(struct netmem *netmem) +{ + return __netmem_clear_lsb(netmem)->pp_magic; +} + +static inline void netmem_or_pp_magic(struct netmem *netmem, + unsigned long pp_magic) +{ + __netmem_clear_lsb(netmem)->pp_magic |= pp_magic; +} + +static inline void netmem_clear_pp_magic(struct netmem *netmem) +{ + __netmem_clear_lsb(netmem)->pp_magic = 0; +} + +static inline struct page_pool *netmem_get_pp(struct netmem *netmem) +{ + return __netmem_clear_lsb(netmem)->pp; +} + +static inline void netmem_set_pp(struct netmem *netmem, struct page_pool *pool) +{ + __netmem_clear_lsb(netmem)->pp = pool; +} + +static inline unsigned long netmem_get_dma_addr(struct netmem *netmem) +{ + return __netmem_clear_lsb(netmem)->dma_addr; +} + +static inline void netmem_set_dma_addr(struct netmem *netmem, + unsigned long dma_addr) +{ + __netmem_clear_lsb(netmem)->dma_addr = dma_addr; +} + +static inline atomic_long_t *netmem_get_pp_ref_count_ref(struct netmem *netmem) +{ + return &__netmem_clear_lsb(netmem)->pp_ref_count; +} + +static inline bool netmem_is_pref_nid(struct netmem *netmem, int pref_nid) +{ + /* Assume net_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 net_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 net_iovs can be recycled for now. + */ + if (netmem_is_net_iov(netmem)) + return true; + + return page_to_nid(netmem_to_page(netmem)) == pref_nid; +} + static inline struct netmem *netmem_compound_head(struct netmem *netmem) { + /* niov are never compounded */ + if (netmem_is_net_iov(netmem)) + return netmem; + return page_to_netmem(compound_head(netmem_to_page(netmem))); }
+static inline void *netmem_address(struct netmem *netmem) +{ + if (netmem_is_net_iov(netmem)) + return NULL; + + return page_address(netmem_to_page(netmem)); +} + #endif /* _NET_NETMEM_H */ diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h index c71969279284..8827518379a8 100644 --- a/include/net/page_pool/helpers.h +++ b/include/net/page_pool/helpers.h @@ -215,7 +215,7 @@ inline enum dma_data_direction page_pool_get_dma_dir(struct page_pool *pool)
static inline void page_pool_fragment_netmem(struct netmem *netmem, long nr) { - atomic_long_set(&netmem_to_page(netmem)->pp_ref_count, nr); + atomic_long_set(netmem_get_pp_ref_count_ref(netmem), nr); }
/** @@ -243,7 +243,7 @@ static inline void page_pool_fragment_page(struct page *page, long nr)
static inline long page_pool_unref_netmem(struct netmem *netmem, long nr) { - struct page *page = netmem_to_page(netmem); + atomic_long_t *pp_ref_count = netmem_get_pp_ref_count_ref(netmem); long ret;
/* If nr == pp_ref_count then we have cleared all remaining @@ -260,19 +260,19 @@ static inline long page_pool_unref_netmem(struct netmem *netmem, long nr) * initially, and only overwrite it when the page is partitioned into * more than one piece. */ - if (atomic_long_read(&page->pp_ref_count) == nr) { + if (atomic_long_read(pp_ref_count) == nr) { /* As we have ensured nr is always one for constant case using * the BUILD_BUG_ON(), only need to handle the non-constant case * here for pp_ref_count draining, which is a rare case. */ BUILD_BUG_ON(__builtin_constant_p(nr) && nr != 1); if (!__builtin_constant_p(nr)) - atomic_long_set(&page->pp_ref_count, 1); + atomic_long_set(pp_ref_count, 1);
return 0; }
- ret = atomic_long_sub_return(nr, &page->pp_ref_count); + ret = atomic_long_sub_return(nr, pp_ref_count); WARN_ON(ret < 0);
/* We are the last user here too, reset pp_ref_count back to 1 to @@ -281,7 +281,7 @@ static inline long page_pool_unref_netmem(struct netmem *netmem, long nr) * page_pool_unref_page() currently. */ if (unlikely(!ret)) - atomic_long_set(&page->pp_ref_count, 1); + atomic_long_set(pp_ref_count, 1);
return ret; } @@ -391,9 +391,7 @@ static inline void page_pool_free_va(struct page_pool *pool, void *va,
static inline dma_addr_t page_pool_get_dma_addr_netmem(struct netmem *netmem) { - struct page *page = netmem_to_page(netmem); - - dma_addr_t ret = page->dma_addr; + dma_addr_t ret = netmem_get_dma_addr(netmem);
if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) ret <<= PAGE_SHIFT; @@ -416,18 +414,17 @@ static inline dma_addr_t page_pool_get_dma_addr(struct page *page) static inline bool page_pool_set_dma_addr_netmem(struct netmem *netmem, dma_addr_t addr) { - struct page *page = netmem_to_page(netmem); - if (PAGE_POOL_32BIT_ARCH_WITH_64BIT_DMA) { - page->dma_addr = addr >> PAGE_SHIFT; + netmem_set_dma_addr(netmem, addr >> PAGE_SHIFT);
/* We assume page alignment to shave off bottom bits, * if this "compression" doesn't work we need to drop. */ - return addr != (dma_addr_t)page->dma_addr << PAGE_SHIFT; + return addr != (dma_addr_t)netmem_get_dma_addr(netmem) + << PAGE_SHIFT; }
- page->dma_addr = addr; + netmem_set_dma_addr(netmem, addr); return false; }
diff --git a/net/core/page_pool.c b/net/core/page_pool.c index 965a7bc0a407..173158a3dd61 100644 --- a/net/core/page_pool.c +++ b/net/core/page_pool.c @@ -25,7 +25,7 @@
#include "page_pool_priv.h"
-static DEFINE_STATIC_KEY_FALSE(page_pool_mem_providers); +DEFINE_STATIC_KEY_FALSE(page_pool_mem_providers);
#define DEFER_TIME (msecs_to_jiffies(1000)) #define DEFER_WARN_INTERVAL (60 * HZ) @@ -334,7 +334,7 @@ page_pool_refill_alloc_cache(struct page_pool *pool) if (unlikely(!netmem)) break;
- if (likely(page_to_nid(netmem_to_page(netmem)) == pref_nid)) { + if (likely(netmem_is_pref_nid(netmem, pref_nid))) { pool->alloc.cache[pool->alloc.count++] = netmem; } else { /* NUMA mismatch; @@ -421,10 +421,8 @@ static bool page_pool_dma_map(struct page_pool *pool, struct netmem *netmem)
static void page_pool_set_pp_info(struct page_pool *pool, struct netmem *netmem) { - struct page *page = netmem_to_page(netmem); - - page->pp = pool; - page->pp_magic |= PP_SIGNATURE; + netmem_set_pp(netmem, pool); + netmem_or_pp_magic(netmem, 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 @@ -439,10 +437,8 @@ static void page_pool_set_pp_info(struct page_pool *pool, struct netmem *netmem)
static void page_pool_clear_pp_info(struct netmem *netmem) { - struct page *page = netmem_to_page(netmem); - - page->pp_magic = 0; - page->pp = NULL; + netmem_clear_pp_magic(netmem); + netmem_set_pp(netmem, NULL); }
static struct page *__page_pool_alloc_page_order(struct page_pool *pool, @@ -670,8 +666,9 @@ static bool page_pool_recycle_in_cache(struct netmem *netmem,
static bool __page_pool_page_can_be_recycled(struct netmem *netmem) { - return page_ref_count(netmem_to_page(netmem)) == 1 && - !page_is_pfmemalloc(netmem_to_page(netmem)); + return netmem_is_net_iov(netmem) || + (page_ref_count(netmem_to_page(netmem)) == 1 && + !page_is_pfmemalloc(netmem_to_page(netmem))); }
/* If the page refcnt == 1, this will try to recycle the page. @@ -693,7 +690,7 @@ __page_pool_put_page(struct page_pool *pool, struct netmem *netmem, * 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_pool_page_can_be_recycled(netmem))) { /* Read barrier done in page_ref_count / READ_ONCE */ @@ -709,6 +706,7 @@ __page_pool_put_page(struct page_pool *pool, struct netmem *netmem, /* Page found as candidate for recycling */ return netmem; } + /* Fallback/non-XDP mode: API user have elevated refcnt. * * Many drivers split up the page into fragments, and some @@ -906,7 +904,7 @@ static void page_pool_empty_ring(struct page_pool *pool) /* Empty recycle ring */ while ((netmem = ptr_ring_consume_bh(&pool->ring))) { /* Verify the refcnt invariant of cached pages */ - if (!(page_ref_count(netmem_to_page(netmem)) == 1)) + if (!(netmem_ref_count(netmem) == 1)) pr_crit("%s() page_pool refcnt %d violation\n", __func__, netmem_ref_count(netmem));
diff --git a/net/core/skbuff.c b/net/core/skbuff.c index ab86799b7fe4..96f85543f1dc 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -901,11 +901,10 @@ static void skb_clone_fraglist(struct sk_buff *skb) #if IS_ENABLED(CONFIG_PAGE_POOL) bool napi_pp_put_page(struct netmem *netmem, bool napi_safe) { - struct page *page = netmem_to_page(netmem); bool allow_direct = false; struct page_pool *pp;
- page = compound_head(page); + netmem = netmem_compound_head(netmem);
/* 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 @@ -914,10 +913,10 @@ bool napi_pp_put_page(struct netmem *netmem, bool napi_safe) * 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)) + if (unlikely((netmem_get_pp_magic(netmem) & ~0x3UL) != PP_SIGNATURE)) return false;
- pp = page->pp; + pp = netmem_get_pp(netmem);
/* Allow direct recycle if we have reasons to believe that we are * in the same context as the consumer would run, so there's @@ -937,7 +936,7 @@ bool napi_pp_put_page(struct netmem *netmem, bool napi_safe) * The page will be returned to the pool here regardless of the * 'flipped' fragment being in use or not. */ - page_pool_put_full_netmem(pp, page_to_netmem(page), allow_direct); + page_pool_put_full_netmem(pp, netmem, allow_direct);
return true; }