/* SPDX-License-Identifier: GPL-2.0
 *
 * page_pool.h
 *    Author:    Jesper Dangaard Brouer <[email protected]>
 *    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 */
    struct napi_struct *napi; /* Sole consumer of pages, otherwise NULL */
    enum dma_data_direction dma_dir; /* DMA mapping direction */
    unsigned int    max_len; /* max DMA sync memory size */
    unsigned int    offset;  /* DMA addr offset */
    void (*init_callback)(struct page *page, void *arg);
    void *init_arg;
};

#ifdef CONFIG_PAGE_POOL_STATS
struct page_pool_alloc_stats {
    u64 fast; /* fast path allocations */
    u64 slow; /* slow-path order 0 allocations */
    u64 slow_high_order; /* slow-path high order allocations */
    u64 empty; /* failed refills due to empty ptr ring, forcing
            * slow path allocation
            */
    u64 refill; /* allocations via successful refill */
    u64 waive;  /* failed refills due to numa zone mismatch */
};

struct page_pool_recycle_stats {
    u64 cached;    /* recycling placed page in the cache. */
    u64 cache_full; /* cache was full */
    u64 ring;    /* recycling placed page back into ptr ring */
    u64 ring_full;    /* page was released from page-pool because
             * PTR ring was full.
             */
    u64 released_refcnt; /* page released because of elevated
                  * refcnt
                  */
};

/* This struct wraps the above stats structs so users of the
 * page_pool_get_stats API can pass a single argument when requesting the
 * stats for the page pool.
 */
struct page_pool_stats {
    struct page_pool_alloc_stats alloc_stats;
    struct page_pool_recycle_stats recycle_stats;
};

int page_pool_ethtool_stats_get_count(void);
u8 *page_pool_ethtool_stats_get_strings(u8 *data);
u64 *page_pool_ethtool_stats_get(u64 *data, void *stats);

/*
 * Drivers that wish to harvest page pool stats and report them to users
 * (perhaps via ethtool, debugfs, or another mechanism) can allocate a
 * struct page_pool_stats call page_pool_get_stats to get stats for the specified pool.
 */
bool page_pool_get_stats(struct page_pool *pool,
             struct page_pool_stats *stats);
#else

static inline int page_pool_ethtool_stats_get_count(void)
{
    return 0;
}

static inline u8 *page_pool_ethtool_stats_get_strings(u8 *data)
{
    return data;
}

static inline u64 *page_pool_ethtool_stats_get(u64 *data, void *stats)
{
    return data;
}

#endif

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;

#ifdef CONFIG_PAGE_POOL_STATS
    /* these stats are incremented while in softirq context */
    struct page_pool_alloc_stats alloc_stats;
#endif
    u32 xdp_mem_id;

    /*
     * 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;

#ifdef CONFIG_PAGE_POOL_STATS
    /* recycle stats are per-cpu to avoid locking */
    struct page_pool_recycle_stats __percpu *recycle_stats;
#endif
    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, bool napi_safe);

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

struct xdp_mem_info;

#ifdef CONFIG_PAGE_POOL
void page_pool_unlink_napi(struct page_pool *pool);
void page_pool_destroy(struct page_pool *pool);
void page_pool_use_xdp_mem(struct page_pool *pool, void (*disconnect)(void *),
               struct xdp_mem_info *mem);
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_unlink_napi(struct page_pool *pool)
{
}

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 *),
                     struct xdp_mem_info *mem)
{
}
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_defragged_page(struct page_pool *pool, struct page *page,
                  unsigned int dma_sync_size,
                  bool allow_direct);

/* pp_frag_count represents the number of writers who can update the page
 * either by updating skb->data or via DMA mappings for the device.
 * We can't rely on the page refcnt for that as we don't know who might be
 * holding page references and we can't reliably destroy or sync DMA mappings
 * of the fragments.
 *
 * When pp_frag_count reaches 0 we can either recycle the page if the page
 * refcnt is 1 or return it back to the memory allocator and destroy any
 * mappings we have.
 */
static inline void page_pool_fragment_page(struct page *page, long nr)
{
    atomic_long_set(&page->pp_frag_count, nr);
}

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

    /* If nr == pp_frag_count then we have cleared all remaining
     * references to the page. No need to actually overwrite it, instead
     * we can leave this to be overwritten by the calling function.
     *
     * The main advantage to doing this is that an atomic_read is
     * generally a much cheaper operation than an atomic update,
     * especially when dealing with a page that may be partitioned
     * into only 2 or 3 pieces.
     */
    if (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 page_pool_is_last_frag(struct page_pool *pool,
                      struct page *page)
{
    /* If fragments aren't enabled or count is 0 we were the last user */
    return !(pool->p.flags & PP_FLAG_PAGE_FRAG) ||
           (page_pool_defrag_page(page, 1) == 0);
}

static inline void page_pool_put_page(struct page_pool *pool,
                      struct page *page,
                      unsigned int dma_sync_size,
                      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
    if (!page_pool_is_last_frag(pool, page))
        return;

    page_pool_put_defragged_page(pool, page, dma_sync_size, allow_direct);
#endif
}

/* 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)
{
    page_pool_put_page(pool, page, -1, allow_direct);
}

/* 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 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);
}

#endif /* _NET_PAGE_POOL_H */