/* SPDX-License-Identifier: GPL-2.0
 *
 * page_pool.h
 *      Author: Jesper Dangaard Brouer <netoptimizer@brouer.com>
 *      Copyright (C) 2016 Red Hat, Inc.
 */

/**
 * DOC: page_pool allocator
 *
 * This page_pool allocator is optimized for the XDP mode that
 * uses one-frame-per-page, but have fallbacks that act like the
 * regular page allocator APIs.
 *
 * Basic use involve replacing alloc_pages() calls with the
 * page_pool_alloc_pages() call.  Drivers should likely use
 * page_pool_dev_alloc_pages() replacing dev_alloc_pages().
 *
 * API keeps track of in-flight pages, in-order to let API user know
 * when it is safe to dealloactor page_pool object.  Thus, API users
 * must make sure to call page_pool_release_page() when a page is
 * "leaving" the page_pool.  Or call page_pool_put_page() where
 * appropiate.  For maintaining correct accounting.
 *
 * API user must only call page_pool_put_page() once on a page, as it
 * will either recycle the page, or in case of elevated refcnt, it
 * will release the DMA mapping and in-flight state accounting.  We
 * hope to lift this requirement in the future.
 */
#ifndef _NET_PAGE_POOL_H
#define _NET_PAGE_POOL_H

#include <linux/mm.h> /* Needed by ptr_ring */
#include <linux/ptr_ring.h>
#include <linux/dma-direction.h>

#define PP_FLAG_DMA_MAP         BIT(0) /* Should page_pool do the DMA
                                        * map/unmap
                                        */
#define PP_FLAG_DMA_SYNC_DEV    BIT(1) /* If set all pages that the driver gets
                                        * from page_pool will be
                                        * DMA-synced-for-device according to
                                        * the length provided by the device
                                        * driver.
                                        * Please note DMA-sync-for-CPU is still
                                        * device driver responsibility
                                        */
#define PP_FLAG_PAGE_FRAG       BIT(2) /* for page frag feature */
#define PP_FLAG_ALL             (PP_FLAG_DMA_MAP |\
                                 PP_FLAG_DMA_SYNC_DEV |\
                                 PP_FLAG_PAGE_FRAG)

/*
 * Fast allocation side cache array/stack
 *
 * The cache size and refill watermark is related to the network
 * use-case.  The NAPI budget is 64 packets.  After a NAPI poll the RX
 * ring is usually refilled and the max consumed elements will be 64,
 * thus a natural max size of objects needed in the cache.
 *
 * Keeping room for more objects, is due to XDP_DROP use-case.  As
 * XDP_DROP allows the opportunity to recycle objects directly into
 * this array, as it shares the same softirq/NAPI protection.  If
 * cache is already full (or partly full) then the XDP_DROP recycles
 * would have to take a slower code path.
 */
#define PP_ALLOC_CACHE_SIZE     128
#define PP_ALLOC_CACHE_REFILL   64
struct pp_alloc_cache {
        u32 count;
        struct page *cache[PP_ALLOC_CACHE_SIZE];
};

struct page_pool_params {
        unsigned int    flags;
        unsigned int    order;
        unsigned int    pool_size;
        int             nid;  /* Numa node id to allocate from pages from */
        struct device   *dev; /* device, for DMA pre-mapping purposes */
        enum dma_data_direction dma_dir; /* DMA mapping direction */
        unsigned int    max_len; /* max DMA sync memory size */
        unsigned int    offset;  /* DMA addr offset */
};

struct page_pool {
        struct page_pool_params p;

        struct delayed_work release_dw;
        void (*disconnect)(void *);
        unsigned long defer_start;
        unsigned long defer_warn;

        u32 pages_state_hold_cnt;
        unsigned int frag_offset;
        struct page *frag_page;
        long frag_users;

        /*
         * Data structure for allocation side
         *
         * Drivers allocation side usually already perform some kind
         * of resource protection.  Piggyback on this protection, and
         * require driver to protect allocation side.
         *
         * For NIC drivers this means, allocate a page_pool per
         * RX-queue. As the RX-queue is already protected by
         * Softirq/BH scheduling and napi_schedule. NAPI schedule
         * guarantee that a single napi_struct will only be scheduled
         * on a single CPU (see napi_schedule).
         */
        struct pp_alloc_cache alloc ____cacheline_aligned_in_smp;

        /* Data structure for storing recycled pages.
         *
         * Returning/freeing pages is more complicated synchronization
         * wise, because free's can happen on remote CPUs, with no
         * association with allocation resource.
         *
         * Use ptr_ring, as it separates consumer and producer
         * effeciently, it a way that doesn't bounce cache-lines.
         *
         * TODO: Implement bulk return pages into this structure.
         */
        struct ptr_ring ring;

        atomic_t pages_state_release_cnt;

        /* A page_pool is strictly tied to a single RX-queue being
         * protected by NAPI, due to above pp_alloc_cache. This
         * refcnt serves purpose is to simplify drivers error handling.
         */
        refcount_t user_cnt;

        u64 destroy_cnt;
};

struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp);

static inline struct page *page_pool_dev_alloc_pages(struct page_pool *pool)
{
        gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);

        return page_pool_alloc_pages(pool, gfp);
}

struct page *page_pool_alloc_frag(struct page_pool *pool, unsigned int *offset,
                                  unsigned int size, gfp_t gfp);

static inline struct page *page_pool_dev_alloc_frag(struct page_pool *pool,
                                                    unsigned int *offset,
                                                    unsigned int size)
{
        gfp_t gfp = (GFP_ATOMIC | __GFP_NOWARN);

        return page_pool_alloc_frag(pool, offset, size, gfp);
}

/* get the stored dma direction. A driver might decide to treat this locally and
 * avoid the extra cache line from page_pool to determine the direction
 */
static
inline enum dma_data_direction page_pool_get_dma_dir(struct page_pool *pool)
{
        return pool->p.dma_dir;
}

bool page_pool_return_skb_page(struct page *page);

struct page_pool *page_pool_create(const struct page_pool_params *params);

#ifdef CONFIG_PAGE_POOL
void page_pool_destroy(struct page_pool *pool);
void page_pool_use_xdp_mem(struct page_pool *pool, void (*disconnect)(void *));
void page_pool_release_page(struct page_pool *pool, struct page *page);
void page_pool_put_page_bulk(struct page_pool *pool, void **data,
                             int count);
#else
static inline void page_pool_destroy(struct page_pool *pool)
{
}

static inline void page_pool_use_xdp_mem(struct page_pool *pool,
                                         void (*disconnect)(void *))
{
}
static inline void page_pool_release_page(struct page_pool *pool,
                                          struct page *page)
{
}

static inline void page_pool_put_page_bulk(struct page_pool *pool, void **data,
                                           int count)
{
}
#endif

void page_pool_put_page(struct page_pool *pool, struct page *page,
                        unsigned int dma_sync_size, bool allow_direct);

/* Same as above but will try to sync the entire area pool->max_len */
static inline void page_pool_put_full_page(struct page_pool *pool,
                                           struct page *page, bool allow_direct)
{
        /* When page_pool isn't compiled-in, net/core/xdp.c doesn't
         * allow registering MEM_TYPE_PAGE_POOL, but shield linker.
         */
#ifdef CONFIG_PAGE_POOL
        page_pool_put_page(pool, page, -1, allow_direct);
#endif
}

/* Same as above but the caller must guarantee safe context. e.g NAPI */
static inline void page_pool_recycle_direct(struct page_pool *pool,
                                            struct page *page)
{
        page_pool_put_full_page(pool, page, true);
}

#define PAGE_POOL_DMA_USE_PP_FRAG_COUNT \
                (sizeof(dma_addr_t) > sizeof(unsigned long))

static inline dma_addr_t page_pool_get_dma_addr(struct page *page)
{
        dma_addr_t ret = page->dma_addr;

        if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT)
                ret |= (dma_addr_t)page->dma_addr_upper << 16 << 16;

        return ret;
}

static inline void page_pool_set_dma_addr(struct page *page, dma_addr_t addr)
{
        page->dma_addr = addr;
        if (PAGE_POOL_DMA_USE_PP_FRAG_COUNT)
                page->dma_addr_upper = upper_32_bits(addr);
}

static inline void page_pool_set_frag_count(struct page *page, long nr)
{
        atomic_long_set(&page->pp_frag_count, nr);
}

static inline long page_pool_atomic_sub_frag_count_return(struct page *page,
                                                          long nr)
{
        long ret;

        /* As suggested by Alexander, atomic_long_read() may cover up the
         * reference count errors, so avoid calling atomic_long_read() in
         * the cases of freeing or draining the page_frags, where we would
         * not expect it to match or that are slowpath anyway.
         */
        if (__builtin_constant_p(nr) &&
            atomic_long_read(&page->pp_frag_count) == nr)
                return 0;

        ret = atomic_long_sub_return(nr, &page->pp_frag_count);
        WARN_ON(ret < 0);
        return ret;
}

static inline bool is_page_pool_compiled_in(void)
{
#ifdef CONFIG_PAGE_POOL
        return true;
#else
        return false;
#endif
}

static inline bool page_pool_put(struct page_pool *pool)
{
        return refcount_dec_and_test(&pool->user_cnt);
}

/* Caller must provide appropriate safe context, e.g. NAPI. */
void page_pool_update_nid(struct page_pool *pool, int new_nid);
static inline void page_pool_nid_changed(struct page_pool *pool, int new_nid)
{
        if (unlikely(pool->p.nid != new_nid))
                page_pool_update_nid(pool, new_nid);
}

static inline void page_pool_ring_lock(struct page_pool *pool)
        __acquires(&pool->ring.producer_lock)
{
        if (in_serving_softirq())
                spin_lock(&pool->ring.producer_lock);
        else
                spin_lock_bh(&pool->ring.producer_lock);
}

static inline void page_pool_ring_unlock(struct page_pool *pool)
        __releases(&pool->ring.producer_lock)
{
        if (in_serving_softirq())
                spin_unlock(&pool->ring.producer_lock);
        else
                spin_unlock_bh(&pool->ring.producer_lock);
}

#endif /* _NET_PAGE_POOL_H */