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

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/device.h>

#include <net/page_pool.h>
#include <net/xdp.h>

#include <linux/dma-direction.h>
#include <linux/dma-mapping.h>
#include <linux/page-flags.h>
#include <linux/mm.h> /* for __put_page() */

#include <trace/events/page_pool.h>

#define DEFER_TIME (msecs_to_jiffies(1000))
#define DEFER_WARN_INTERVAL (60 * HZ)

static int page_pool_init(struct page_pool *pool,
                          const struct page_pool_params *params)
{
        unsigned int ring_qsize = 1024; /* Default */

        memcpy(&pool->p, params, sizeof(pool->p));

        /* Validate only known flags were used */
        if (pool->p.flags & ~(PP_FLAG_ALL))
                return -EINVAL;

        if (pool->p.pool_size)
                ring_qsize = pool->p.pool_size;

        /* Sanity limit mem that can be pinned down */
        if (ring_qsize > 32768)
                return -E2BIG;

        /* DMA direction is either DMA_FROM_DEVICE or DMA_BIDIRECTIONAL.
         * DMA_BIDIRECTIONAL is for allowing page used for DMA sending,
         * which is the XDP_TX use-case.
         */
        if (pool->p.flags & PP_FLAG_DMA_MAP) {
                if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
                    (pool->p.dma_dir != DMA_BIDIRECTIONAL))
                        return -EINVAL;
        }

        if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV) {
                /* In order to request DMA-sync-for-device the page
                 * needs to be mapped
                 */
                if (!(pool->p.flags & PP_FLAG_DMA_MAP))
                        return -EINVAL;

                if (!pool->p.max_len)
                        return -EINVAL;

                /* pool->p.offset has to be set according to the address
                 * offset used by the DMA engine to start copying rx data
                 */
        }

        if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0)
                return -ENOMEM;

        atomic_set(&pool->pages_state_release_cnt, 0);

        /* Driver calling page_pool_create() also call page_pool_destroy() */
        refcount_set(&pool->user_cnt, 1);

        if (pool->p.flags & PP_FLAG_DMA_MAP)
                get_device(pool->p.dev);

        return 0;
}

struct page_pool *page_pool_create(const struct page_pool_params *params)
{
        struct page_pool *pool;
        int err;

        pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, params->nid);
        if (!pool)
                return ERR_PTR(-ENOMEM);

        err = page_pool_init(pool, params);
        if (err < 0) {
                pr_warn("%s() gave up with errno %d\n", __func__, err);
                kfree(pool);
                return ERR_PTR(err);
        }

        return pool;
}
EXPORT_SYMBOL(page_pool_create);

static void page_pool_return_page(struct page_pool *pool, struct page *page);

noinline
static struct page *page_pool_refill_alloc_cache(struct page_pool *pool)
{
        struct ptr_ring *r = &pool->ring;
        struct page *page;
        int pref_nid; /* preferred NUMA node */

        /* Quicker fallback, avoid locks when ring is empty */
        if (__ptr_ring_empty(r))
                return NULL;

        /* Softirq guarantee CPU and thus NUMA node is stable. This,
         * assumes CPU refilling driver RX-ring will also run RX-NAPI.
         */
#ifdef CONFIG_NUMA
        pref_nid = (pool->p.nid == NUMA_NO_NODE) ? numa_mem_id() : pool->p.nid;
#else
        /* Ignore pool->p.nid setting if !CONFIG_NUMA, helps compiler */
        pref_nid = numa_mem_id(); /* will be zero like page_to_nid() */
#endif

        /* Slower-path: Get pages from locked ring queue */
        spin_lock(&r->consumer_lock);

        /* Refill alloc array, but only if NUMA match */
        do {
                page = __ptr_ring_consume(r);
                if (unlikely(!page))
                        break;

                if (likely(page_to_nid(page) == pref_nid)) {
                        pool->alloc.cache[pool->alloc.count++] = page;
                } else {
                        /* NUMA mismatch;
                         * (1) release 1 page to page-allocator and
                         * (2) break out to fallthrough to alloc_pages_node.
                         * This limit stress on page buddy alloactor.
                         */
                        page_pool_return_page(pool, page);
                        page = NULL;
                        break;
                }
        } while (pool->alloc.count < PP_ALLOC_CACHE_REFILL);

        /* Return last page */
        if (likely(pool->alloc.count > 0))
                page = pool->alloc.cache[--pool->alloc.count];

        spin_unlock(&r->consumer_lock);
        return page;
}

/* fast path */
static struct page *__page_pool_get_cached(struct page_pool *pool)
{
        struct page *page;

        /* Caller MUST guarantee safe non-concurrent access, e.g. softirq */
        if (likely(pool->alloc.count)) {
                /* Fast-path */
                page = pool->alloc.cache[--pool->alloc.count];
        } else {
                page = page_pool_refill_alloc_cache(pool);
        }

        return page;
}

static void page_pool_dma_sync_for_device(struct page_pool *pool,
                                          struct page *page,
                                          unsigned int dma_sync_size)
{
        dma_sync_size = min(dma_sync_size, pool->p.max_len);
        dma_sync_single_range_for_device(pool->p.dev, page->dma_addr,
                                         pool->p.offset, dma_sync_size,
                                         pool->p.dma_dir);
}

/* slow path */
noinline
static struct page *__page_pool_alloc_pages_slow(struct page_pool *pool,
                                                 gfp_t _gfp)
{
        struct page *page;
        gfp_t gfp = _gfp;
        dma_addr_t dma;

        /* We could always set __GFP_COMP, and avoid this branch, as
         * prep_new_page() can handle order-0 with __GFP_COMP.
         */
        if (pool->p.order)
                gfp |= __GFP_COMP;

        /* FUTURE development:
         *
         * Current slow-path essentially falls back to single page
         * allocations, which doesn't improve performance.  This code
         * need bulk allocation support from the page allocator code.
         */

        /* Cache was empty, do real allocation */
#ifdef CONFIG_NUMA
        page = alloc_pages_node(pool->p.nid, gfp, pool->p.order);
#else
        page = alloc_pages(gfp, pool->p.order);
#endif
        if (!page)
                return NULL;

        if (!(pool->p.flags & PP_FLAG_DMA_MAP))
                goto skip_dma_map;

        /* 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)
         * This mapping is kept for lifetime of page, until leaving pool.
         */
        dma = dma_map_page_attrs(pool->p.dev, page, 0,
                                 (PAGE_SIZE << pool->p.order),
                                 pool->p.dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
        if (dma_mapping_error(pool->p.dev, dma)) {
                put_page(page);
                return NULL;
        }
        page->dma_addr = dma;

        if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
                page_pool_dma_sync_for_device(pool, page, pool->p.max_len);

skip_dma_map:
        /* Track how many pages are held 'in-flight' */
        pool->pages_state_hold_cnt++;

        trace_page_pool_state_hold(pool, page, pool->pages_state_hold_cnt);

        /* When page just alloc'ed is should/must have refcnt 1. */
        return page;
}

/* For using page_pool replace: alloc_pages() API calls, but provide
 * synchronization guarantee for allocation side.
 */
struct page *page_pool_alloc_pages(struct page_pool *pool, gfp_t gfp)
{
        struct page *page;

        /* Fast-path: Get a page from cache */
        page = __page_pool_get_cached(pool);
        if (page)
                return page;

        /* Slow-path: cache empty, do real allocation */
        page = __page_pool_alloc_pages_slow(pool, gfp);
        return page;
}
EXPORT_SYMBOL(page_pool_alloc_pages);

/* Calculate distance between two u32 values, valid if distance is below 2^(31)
 *  https://en.wikipedia.org/wiki/Serial_number_arithmetic#General_Solution
 */
#define _distance(a, b) (s32)((a) - (b))

static s32 page_pool_inflight(struct page_pool *pool)
{
        u32 release_cnt = atomic_read(&pool->pages_state_release_cnt);
        u32 hold_cnt = READ_ONCE(pool->pages_state_hold_cnt);
        s32 inflight;

        inflight = _distance(hold_cnt, release_cnt);

        trace_page_pool_release(pool, inflight, hold_cnt, release_cnt);
        WARN(inflight < 0, "Negative(%d) inflight packet-pages", inflight);

        return inflight;
}

/* Disconnects a page (from a page_pool).  API users can have a need
 * to disconnect a page (from a page_pool), to allow it to be used as
 * a regular page (that will eventually be returned to the normal
 * page-allocator via put_page).
 */
void page_pool_release_page(struct page_pool *pool, struct page *page)
{
        dma_addr_t dma;
        int count;

        if (!(pool->p.flags & PP_FLAG_DMA_MAP))
                /* Always account for inflight pages, even if we didn't
                 * map them
                 */
                goto skip_dma_unmap;

        dma = page->dma_addr;

        /* When page is unmapped, it cannot be returned our pool */
        dma_unmap_page_attrs(pool->p.dev, dma,
                             PAGE_SIZE << pool->p.order, pool->p.dma_dir,
                             DMA_ATTR_SKIP_CPU_SYNC);
        page->dma_addr = 0;
skip_dma_unmap:
        /* This may be the last page returned, releasing the pool, so
         * it is not safe to reference pool afterwards.
         */
        count = atomic_inc_return(&pool->pages_state_release_cnt);
        trace_page_pool_state_release(pool, page, count);
}
EXPORT_SYMBOL(page_pool_release_page);

/* Return a page to the page allocator, cleaning up our state */
static void page_pool_return_page(struct page_pool *pool, struct page *page)
{
        page_pool_release_page(pool, page);

        put_page(page);
        /* An optimization would be to call __free_pages(page, pool->p.order)
         * knowing page is not part of page-cache (thus avoiding a
         * __page_cache_release() call).
         */
}

static bool page_pool_recycle_in_ring(struct page_pool *pool, struct page *page)
{
        int ret;
        /* BH protection not needed if current is serving softirq */
        if (in_serving_softirq())
                ret = ptr_ring_produce(&pool->ring, page);
        else
                ret = ptr_ring_produce_bh(&pool->ring, page);

        return (ret == 0) ? true : false;
}

/* Only allow direct recycling in special circumstances, into the
 * alloc side cache.  E.g. during RX-NAPI processing for XDP_DROP use-case.
 *
 * Caller must provide appropriate safe context.
 */
static bool page_pool_recycle_in_cache(struct page *page,
                                       struct page_pool *pool)
{
        if (unlikely(pool->alloc.count == PP_ALLOC_CACHE_SIZE))
                return false;

        /* Caller MUST have verified/know (page_ref_count(page) == 1) */
        pool->alloc.cache[pool->alloc.count++] = page;
        return true;
}

/* If the page refcnt == 1, this will try to recycle the page.
 * if PP_FLAG_DMA_SYNC_DEV is set, we'll try to sync the DMA area for
 * the configured size min(dma_sync_size, pool->max_len).
 * If the page refcnt != 1, then the page will be returned to memory
 * subsystem.
 */
static __always_inline struct page *
__page_pool_put_page(struct page_pool *pool, struct page *page,
                     unsigned int dma_sync_size, bool allow_direct)
{
        /* This allocator is optimized for the XDP mode that uses
         * one-frame-per-page, but have fallbacks that act like the
         * regular page allocator APIs.
         *
         * 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)
         */
        if (likely(page_ref_count(page) == 1 && !page_is_pfmemalloc(page))) {
                /* Read barrier done in page_ref_count / READ_ONCE */

                if (pool->p.flags & PP_FLAG_DMA_SYNC_DEV)
                        page_pool_dma_sync_for_device(pool, page,
                                                      dma_sync_size);

                if (allow_direct && in_serving_softirq() &&
                    page_pool_recycle_in_cache(page, pool))
                        return NULL;

                /* Page found as candidate for recycling */
                return page;
        }
        /* Fallback/non-XDP mode: API user have elevated refcnt.
         *
         * Many drivers split up the page into fragments, and some
         * want to keep doing this to save memory and do refcnt based
         * recycling. Support this use case too, to ease drivers
         * switching between XDP/non-XDP.
         *
         * In-case page_pool maintains the DMA mapping, API user must
         * call page_pool_put_page once.  In this elevated refcnt
         * case, the DMA is unmapped/released, as driver is likely
         * doing refcnt based recycle tricks, meaning another process
         * will be invoking put_page.
         */
        /* Do not replace this with page_pool_return_page() */
        page_pool_release_page(pool, page);
        put_page(page);

        return NULL;
}

void page_pool_put_page(struct page_pool *pool, struct page *page,
                        unsigned int dma_sync_size, bool allow_direct)
{
        page = __page_pool_put_page(pool, page, dma_sync_size, allow_direct);
        if (page && !page_pool_recycle_in_ring(pool, page)) {
                /* Cache full, fallback to free pages */
                page_pool_return_page(pool, page);
        }
}
EXPORT_SYMBOL(page_pool_put_page);

/* Caller must not use data area after call, as this function overwrites it */
void page_pool_put_page_bulk(struct page_pool *pool, void **data,
                             int count)
{
        int i, bulk_len = 0;

        for (i = 0; i < count; i++) {
                struct page *page = virt_to_head_page(data[i]);

                page = __page_pool_put_page(pool, page, -1, false);
                /* Approved for bulk recycling in ptr_ring cache */
                if (page)
                        data[bulk_len++] = page;
        }

        if (unlikely(!bulk_len))
                return;

        /* Bulk producer into ptr_ring page_pool cache */
        page_pool_ring_lock(pool);
        for (i = 0; i < bulk_len; i++) {
                if (__ptr_ring_produce(&pool->ring, data[i]))
                        break; /* ring full */
        }
        page_pool_ring_unlock(pool);

        /* Hopefully all pages was return into ptr_ring */
        if (likely(i == bulk_len))
                return;

        /* ptr_ring cache full, free remaining pages outside producer lock
         * since put_page() with refcnt == 1 can be an expensive operation
         */
        for (; i < bulk_len; i++)
                page_pool_return_page(pool, data[i]);
}
EXPORT_SYMBOL(page_pool_put_page_bulk);

static void page_pool_empty_ring(struct page_pool *pool)
{
        struct page *page;

        /* Empty recycle ring */
        while ((page = ptr_ring_consume_bh(&pool->ring))) {
                /* Verify the refcnt invariant of cached pages */
                if (!(page_ref_count(page) == 1))
                        pr_crit("%s() page_pool refcnt %d violation\n",
                                __func__, page_ref_count(page));

                page_pool_return_page(pool, page);
        }
}

static void page_pool_free(struct page_pool *pool)
{
        if (pool->disconnect)
                pool->disconnect(pool);

        ptr_ring_cleanup(&pool->ring, NULL);

        if (pool->p.flags & PP_FLAG_DMA_MAP)
                put_device(pool->p.dev);

        kfree(pool);
}

static void page_pool_empty_alloc_cache_once(struct page_pool *pool)
{
        struct page *page;

        if (pool->destroy_cnt)
                return;

        /* Empty alloc cache, assume caller made sure this is
         * no-longer in use, and page_pool_alloc_pages() cannot be
         * call concurrently.
         */
        while (pool->alloc.count) {
                page = pool->alloc.cache[--pool->alloc.count];
                page_pool_return_page(pool, page);
        }
}

static void page_pool_scrub(struct page_pool *pool)
{
        page_pool_empty_alloc_cache_once(pool);
        pool->destroy_cnt++;

        /* No more consumers should exist, but producers could still
         * be in-flight.
         */
        page_pool_empty_ring(pool);
}

static int page_pool_release(struct page_pool *pool)
{
        int inflight;

        page_pool_scrub(pool);
        inflight = page_pool_inflight(pool);
        if (!inflight)
                page_pool_free(pool);

        return inflight;
}

static void page_pool_release_retry(struct work_struct *wq)
{
        struct delayed_work *dwq = to_delayed_work(wq);
        struct page_pool *pool = container_of(dwq, typeof(*pool), release_dw);
        int inflight;

        inflight = page_pool_release(pool);
        if (!inflight)
                return;

        /* Periodic warning */
        if (time_after_eq(jiffies, pool->defer_warn)) {
                int sec = (s32)((u32)jiffies - (u32)pool->defer_start) / HZ;

                pr_warn("%s() stalled pool shutdown %d inflight %d sec\n",
                        __func__, inflight, sec);
                pool->defer_warn = jiffies + DEFER_WARN_INTERVAL;
        }

        /* Still not ready to be disconnected, retry later */
        schedule_delayed_work(&pool->release_dw, DEFER_TIME);
}

void page_pool_use_xdp_mem(struct page_pool *pool, void (*disconnect)(void *))
{
        refcount_inc(&pool->user_cnt);
        pool->disconnect = disconnect;
}

void page_pool_destroy(struct page_pool *pool)
{
        if (!pool)
                return;

        if (!page_pool_put(pool))
                return;

        if (!page_pool_release(pool))
                return;

        pool->defer_start = jiffies;
        pool->defer_warn  = jiffies + DEFER_WARN_INTERVAL;

        INIT_DELAYED_WORK(&pool->release_dw, page_pool_release_retry);
        schedule_delayed_work(&pool->release_dw, DEFER_TIME);
}
EXPORT_SYMBOL(page_pool_destroy);

/* Caller must provide appropriate safe context, e.g. NAPI. */
void page_pool_update_nid(struct page_pool *pool, int new_nid)
{
        struct page *page;

        trace_page_pool_update_nid(pool, new_nid);
        pool->p.nid = new_nid;

        /* Flush pool alloc cache, as refill will check NUMA node */
        while (pool->alloc.count) {
                page = pool->alloc.cache[--pool->alloc.count];
                page_pool_return_page(pool, page);
        }
}
EXPORT_SYMBOL(page_pool_update_nid);