[linux-block.git] / net / core / page_pool.c

/* 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 <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.dma_dir != DMA_FROM_DEVICE) &&
	    (pool->p.dma_dir != DMA_BIDIRECTIONAL))
		return -EINVAL;

	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);

/* fast path */
static struct page *__page_pool_get_cached(struct page_pool *pool)
{
	struct ptr_ring *r = &pool->ring;
	bool refill = false;
	struct page *page;

	/* Test for safe-context, caller should provide this guarantee */
	if (likely(in_serving_softirq())) {
		if (likely(pool->alloc.count)) {
			/* Fast-path */
			page = pool->alloc.cache[--pool->alloc.count];
			return page;
		}
		refill = true;
	}

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

	/* Slow-path: Get page from locked ring queue,
	 * refill alloc array if requested.
	 */
	spin_lock(&r->consumer_lock);
	page = __ptr_ring_consume(r);
	if (refill)
		pool->alloc.count = __ptr_ring_consume_batched(r,
							pool->alloc.cache,
							PP_ALLOC_CACHE_REFILL);
	spin_unlock(&r->consumer_lock);
	return page;
}

/* 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 */
	page = alloc_pages_node(pool->p.nid, gfp, pool->p.order);
	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;

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

	return inflight;
}

/* Cleanup page_pool state from page */
static void __page_pool_clean_page(struct page_pool *pool,
				   struct page *page)
{
	dma_addr_t dma;
	int count;

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

	dma = page->dma_addr;
	/* DMA unmap */
	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);
}

/* unmap the page and clean our state */
void page_pool_unmap_page(struct page_pool *pool, struct page *page)
{
	/* When page is unmapped, this implies page will not be
	 * returned to page_pool.
	 */
	__page_pool_clean_page(pool, page);
}
EXPORT_SYMBOL(page_pool_unmap_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_clean_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_into_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_direct(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;
}

void __page_pool_put_page(struct page_pool *pool,
			  struct page *page, 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.
	 */
	if (likely(page_ref_count(page) == 1)) {
		/* Read barrier done in page_ref_count / READ_ONCE */

		if (allow_direct && in_serving_softirq())
			if (__page_pool_recycle_direct(page, pool))
				return;

		if (!__page_pool_recycle_into_ring(pool, page)) {
			/* Cache full, fallback to free pages */
			__page_pool_return_page(pool, page);
		}
		return;
	}
	/* 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.
	 */
	__page_pool_clean_page(pool, page);
	put_page(page);
}
EXPORT_SYMBOL(__page_pool_put_page);

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_scrub(struct page_pool *pool)
{
	struct page *page;

	/* 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);
	}

	/* 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);
Commit	Line	Data
ff7d6b27 JDB	1	/* SPDX-License-Identifier: GPL-2.0
	2	*
	3	* page_pool.c
	4	* Author: Jesper Dangaard Brouer <netoptimizer@brouer.com>
	5	* Copyright (C) 2016 Red Hat, Inc.
	6	*/
32c28f7e	7
ff7d6b27 JDB	8	#include <linux/types.h>
	9	#include <linux/kernel.h>
	10	#include <linux/slab.h>
f71fec47	11	#include <linux/device.h>
ff7d6b27 JDB	12
	13	#include <net/page_pool.h>
	14	#include <linux/dma-direction.h>
	15	#include <linux/dma-mapping.h>
	16	#include <linux/page-flags.h>
	17	#include <linux/mm.h> /* for __put_page() */
	18
32c28f7e JDB	19	#include <trace/events/page_pool.h>
32c28f7e JDB	20
c3f812ce JL	21	#define DEFER_TIME (msecs_to_jiffies(1000))
	22	#define DEFER_WARN_INTERVAL (60 * HZ)
	23
ff7d6b27 JDB	24	static int page_pool_init(struct page_pool *pool,
	25	const struct page_pool_params *params)
	26	{
	27	unsigned int ring_qsize = 1024; /* Default */
	28
	29	memcpy(&pool->p, params, sizeof(pool->p));
	30
	31	/* Validate only known flags were used */
	32	if (pool->p.flags & ~(PP_FLAG_ALL))
	33	return -EINVAL;
	34
	35	if (pool->p.pool_size)
	36	ring_qsize = pool->p.pool_size;
	37
	38	/* Sanity limit mem that can be pinned down */
	39	if (ring_qsize > 32768)
	40	return -E2BIG;
	41
	42	/* DMA direction is either DMA_FROM_DEVICE or DMA_BIDIRECTIONAL.
	43	* DMA_BIDIRECTIONAL is for allowing page used for DMA sending,
	44	* which is the XDP_TX use-case.
	45	*/
	46	if ((pool->p.dma_dir != DMA_FROM_DEVICE) &&
	47	(pool->p.dma_dir != DMA_BIDIRECTIONAL))
	48	return -EINVAL;
	49
	50	if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0)
	51	return -ENOMEM;
	52
99c07c43 JDB	53	atomic_set(&pool->pages_state_release_cnt, 0);
99c07c43 JDB	54
1da4bbef IK	55	/* Driver calling page_pool_create() also call page_pool_destroy() */
	56	refcount_set(&pool->user_cnt, 1);
	57
f71fec47 JDB	58	if (pool->p.flags & PP_FLAG_DMA_MAP)
	59	get_device(pool->p.dev);
	60
ff7d6b27 JDB	61	return 0;
	62	}
	63
	64	struct page_pool page_pool_create(const struct page_pool_params params)
	65	{
	66	struct page_pool *pool;
873343e7	67	int err;
ff7d6b27 JDB	68
	69	pool = kzalloc_node(sizeof(*pool), GFP_KERNEL, params->nid);
	70	if (!pool)
	71	return ERR_PTR(-ENOMEM);
	72
	73	err = page_pool_init(pool, params);
	74	if (err < 0) {
	75	pr_warn("%s() gave up with errno %d\n", __func__, err);
	76	kfree(pool);
	77	return ERR_PTR(err);
	78	}
1da4bbef	79
ff7d6b27 JDB	80	return pool;
	81	}
	82	EXPORT_SYMBOL(page_pool_create);
	83
	84	/* fast path */
	85	static struct page __page_pool_get_cached(struct page_pool pool)
	86	{
	87	struct ptr_ring *r = &pool->ring;
8d73f8f2	88	bool refill = false;
ff7d6b27 JDB	89	struct page *page;
ff7d6b27 JDB	90
ff7d6b27 JDB	91	/* Test for safe-context, caller should provide this guarantee */
	92	if (likely(in_serving_softirq())) {
	93	if (likely(pool->alloc.count)) {
	94	/* Fast-path */
	95	page = pool->alloc.cache[--pool->alloc.count];
	96	return page;
	97	}
8d73f8f2	98	refill = true;
ff7d6b27 JDB	99	}
ff7d6b27 JDB	100
8d73f8f2 JL	101	/* Quicker fallback, avoid locks when ring is empty */
	102	if (__ptr_ring_empty(r))
	103	return NULL;
	104
	105	/* Slow-path: Get page from locked ring queue,
	106	* refill alloc array if requested.
	107	*/
	108	spin_lock(&r->consumer_lock);
	109	page = __ptr_ring_consume(r);
	110	if (refill)
	111	pool->alloc.count = __ptr_ring_consume_batched(r,
	112	pool->alloc.cache,
	113	PP_ALLOC_CACHE_REFILL);
	114	spin_unlock(&r->consumer_lock);
ff7d6b27 JDB	115	return page;
	116	}
	117
	118	/* slow path */
	119	noinline
	120	static struct page __page_pool_alloc_pages_slow(struct page_pool pool,
	121	gfp_t _gfp)
	122	{
	123	struct page *page;
	124	gfp_t gfp = _gfp;
	125	dma_addr_t dma;
	126
	127	/* We could always set __GFP_COMP, and avoid this branch, as
	128	* prep_new_page() can handle order-0 with __GFP_COMP.
	129	*/
	130	if (pool->p.order)
	131	gfp \|= __GFP_COMP;
	132
	133	/* FUTURE development:
	134	*
	135	* Current slow-path essentially falls back to single page
	136	* allocations, which doesn't improve performance. This code
	137	* need bulk allocation support from the page allocator code.
	138	*/
	139
	140	/* Cache was empty, do real allocation */
	141	page = alloc_pages_node(pool->p.nid, gfp, pool->p.order);
	142	if (!page)
	143	return NULL;
	144
	145	if (!(pool->p.flags & PP_FLAG_DMA_MAP))
	146	goto skip_dma_map;
	147
1567b85e IA	148	/* Setup DMA mapping: use 'struct page' area for storing DMA-addr
	149	* since dma_addr_t can be either 32 or 64 bits and does not always fit
	150	* into page private data (i.e 32bit cpu with 64bit DMA caps)
ff7d6b27 JDB	151	* This mapping is kept for lifetime of page, until leaving pool.
ff7d6b27 JDB	152	*/
13f16d9d JDB	153	dma = dma_map_page_attrs(pool->p.dev, page, 0,
	154	(PAGE_SIZE << pool->p.order),
	155	pool->p.dma_dir, DMA_ATTR_SKIP_CPU_SYNC);
ff7d6b27 JDB	156	if (dma_mapping_error(pool->p.dev, dma)) {
	157	put_page(page);
	158	return NULL;
	159	}
1567b85e	160	page->dma_addr = dma;
ff7d6b27 JDB	161
ff7d6b27 JDB	162	skip_dma_map:
99c07c43 JDB	163	/* Track how many pages are held 'in-flight' */
	164	pool->pages_state_hold_cnt++;
	165
32c28f7e JDB	166	trace_page_pool_state_hold(pool, page, pool->pages_state_hold_cnt);
32c28f7e JDB	167
ff7d6b27 JDB	168	/* When page just alloc'ed is should/must have refcnt 1. */
	169	return page;
	170	}
	171
	172	/* For using page_pool replace: alloc_pages() API calls, but provide
	173	* synchronization guarantee for allocation side.
	174	*/
	175	struct page page_pool_alloc_pages(struct page_pool pool, gfp_t gfp)
	176	{
	177	struct page *page;
	178
	179	/* Fast-path: Get a page from cache */
	180	page = __page_pool_get_cached(pool);
	181	if (page)
	182	return page;
	183
	184	/* Slow-path: cache empty, do real allocation */
	185	page = __page_pool_alloc_pages_slow(pool, gfp);
	186	return page;
	187	}
	188	EXPORT_SYMBOL(page_pool_alloc_pages);
	189
99c07c43 JDB	190	/* Calculate distance between two u32 values, valid if distance is below 2^(31)
	191	* https://en.wikipedia.org/wiki/Serial_number_arithmetic#General_Solution
	192	*/
	193	#define _distance(a, b) (s32)((a) - (b))
	194
	195	static s32 page_pool_inflight(struct page_pool *pool)
	196	{
	197	u32 release_cnt = atomic_read(&pool->pages_state_release_cnt);
	198	u32 hold_cnt = READ_ONCE(pool->pages_state_hold_cnt);
c3f812ce	199	s32 inflight;
99c07c43	200
c3f812ce	201	inflight = _distance(hold_cnt, release_cnt);
99c07c43	202
c3f812ce	203	trace_page_pool_inflight(pool, inflight, hold_cnt, release_cnt);
99c07c43 JDB	204	WARN(inflight < 0, "Negative(%d) inflight packet-pages", inflight);
99c07c43 JDB	205
c3f812ce	206	return inflight;
99c07c43 JDB	207	}
99c07c43 JDB	208
ff7d6b27 JDB	209	/* Cleanup page_pool state from page */
	210	static void __page_pool_clean_page(struct page_pool *pool,
	211	struct page *page)
	212	{
1567b85e	213	dma_addr_t dma;
c3f812ce	214	int count;
1567b85e	215
ff7d6b27	216	if (!(pool->p.flags & PP_FLAG_DMA_MAP))
99c07c43	217	goto skip_dma_unmap;
ff7d6b27	218
1567b85e	219	dma = page->dma_addr;
ff7d6b27	220	/* DMA unmap */
13f16d9d JDB	221	dma_unmap_page_attrs(pool->p.dev, dma,
	222	PAGE_SIZE << pool->p.order, pool->p.dma_dir,
	223	DMA_ATTR_SKIP_CPU_SYNC);
1567b85e	224	page->dma_addr = 0;
99c07c43	225	skip_dma_unmap:
c3f812ce JL	226	/* This may be the last page returned, releasing the pool, so
	227	* it is not safe to reference pool afterwards.
	228	*/
	229	count = atomic_inc_return(&pool->pages_state_release_cnt);
	230	trace_page_pool_state_release(pool, page, count);
ff7d6b27 JDB	231	}
ff7d6b27 JDB	232
a25d50bf IA	233	/* unmap the page and clean our state */
	234	void page_pool_unmap_page(struct page_pool pool, struct page page)
	235	{
99c07c43 JDB	236	/* When page is unmapped, this implies page will not be
	237	* returned to page_pool.
	238	*/
a25d50bf IA	239	__page_pool_clean_page(pool, page);
	240	}
	241	EXPORT_SYMBOL(page_pool_unmap_page);
	242
ff7d6b27 JDB	243	/* Return a page to the page allocator, cleaning up our state */
	244	static void __page_pool_return_page(struct page_pool pool, struct page page)
	245	{
	246	__page_pool_clean_page(pool, page);
99c07c43	247
ff7d6b27 JDB	248	put_page(page);
	249	/* An optimization would be to call __free_pages(page, pool->p.order)
	250	* knowing page is not part of page-cache (thus avoiding a
	251	* __page_cache_release() call).
	252	*/
	253	}
	254
	255	static bool __page_pool_recycle_into_ring(struct page_pool *pool,
	256	struct page *page)
	257	{
	258	int ret;
	259	/* BH protection not needed if current is serving softirq */
	260	if (in_serving_softirq())
	261	ret = ptr_ring_produce(&pool->ring, page);
	262	else
	263	ret = ptr_ring_produce_bh(&pool->ring, page);
	264
	265	return (ret == 0) ? true : false;
	266	}
	267
	268	/* Only allow direct recycling in special circumstances, into the
	269	* alloc side cache. E.g. during RX-NAPI processing for XDP_DROP use-case.
	270	*
	271	* Caller must provide appropriate safe context.
	272	*/
	273	static bool __page_pool_recycle_direct(struct page *page,
	274	struct page_pool *pool)
	275	{
	276	if (unlikely(pool->alloc.count == PP_ALLOC_CACHE_SIZE))
	277	return false;
	278
	279	/* Caller MUST have verified/know (page_ref_count(page) == 1) */
	280	pool->alloc.cache[pool->alloc.count++] = page;
	281	return true;
	282	}
	283
	284	void __page_pool_put_page(struct page_pool *pool,
	285	struct page *page, bool allow_direct)
	286	{
	287	/* This allocator is optimized for the XDP mode that uses
	288	* one-frame-per-page, but have fallbacks that act like the
	289	* regular page allocator APIs.
	290	*
	291	* refcnt == 1 means page_pool owns page, and can recycle it.
	292	*/
	293	if (likely(page_ref_count(page) == 1)) {
	294	/* Read barrier done in page_ref_count / READ_ONCE */
	295
	296	if (allow_direct && in_serving_softirq())
	297	if (__page_pool_recycle_direct(page, pool))
	298	return;
	299
	300	if (!__page_pool_recycle_into_ring(pool, page)) {
	301	/* Cache full, fallback to free pages */
	302	__page_pool_return_page(pool, page);
	303	}
	304	return;
	305	}
	306	/* Fallback/non-XDP mode: API user have elevated refcnt.
	307	*
	308	* Many drivers split up the page into fragments, and some
	309	* want to keep doing this to save memory and do refcnt based
	310	* recycling. Support this use case too, to ease drivers
	311	* switching between XDP/non-XDP.
312	*
313	* In-case page_pool maintains the DMA mapping, API user must
314	* call page_pool_put_page once. In this elevated refcnt
315	* case, the DMA is unmapped/released, as driver is likely
316	* doing refcnt based recycle tricks, meaning another process
317	* will be invoking put_page.
318	*/
319	__page_pool_clean_page(pool, page);
320	put_page(page);
321	}
322	EXPORT_SYMBOL(__page_pool_put_page);
323
324	static void __page_pool_empty_ring(struct page_pool *pool)
325	{
326	struct page *page;
327
328	/* Empty recycle ring */
4905bd9a	329	while ((page = ptr_ring_consume_bh(&pool->ring))) {
ff7d6b27 JDB	330	/* Verify the refcnt invariant of cached pages */
	331	if (!(page_ref_count(page) == 1))
	332	pr_crit("%s() page_pool refcnt %d violation\n",
	333	__func__, page_ref_count(page));
	334
	335	__page_pool_return_page(pool, page);
	336	}
	337	}
	338
c3f812ce	339	static void page_pool_free(struct page_pool *pool)
d956a048	340	{
c3f812ce JL	341	if (pool->disconnect)
c3f812ce JL	342	pool->disconnect(pool);
e54cfd7e JDB	343
e54cfd7e JDB	344	ptr_ring_cleanup(&pool->ring, NULL);
f71fec47 JDB	345
	346	if (pool->p.flags & PP_FLAG_DMA_MAP)
	347	put_device(pool->p.dev);
	348
e54cfd7e JDB	349	kfree(pool);
e54cfd7e JDB	350	}
e54cfd7e	351
c3f812ce	352	static void page_pool_scrub(struct page_pool *pool)
ff7d6b27 JDB	353	{
	354	struct page *page;
	355
	356	/* Empty alloc cache, assume caller made sure this is
	357	* no-longer in use, and page_pool_alloc_pages() cannot be
	358	* call concurrently.
	359	*/
	360	while (pool->alloc.count) {
	361	page = pool->alloc.cache[--pool->alloc.count];
	362	__page_pool_return_page(pool, page);
	363	}
	364
	365	/* No more consumers should exist, but producers could still
	366	* be in-flight.
	367	*/
	368	__page_pool_empty_ring(pool);
c3f812ce JL	369	}
	370
	371	static int page_pool_release(struct page_pool *pool)
	372	{
	373	int inflight;
	374
	375	page_pool_scrub(pool);
	376	inflight = page_pool_inflight(pool);
	377	if (!inflight)
	378	page_pool_free(pool);
	379
	380	return inflight;
	381	}
	382
	383	static void page_pool_release_retry(struct work_struct *wq)
	384	{
	385	struct delayed_work *dwq = to_delayed_work(wq);
	386	struct page_pool pool = container_of(dwq, typeof(pool), release_dw);
	387	int inflight;
	388
	389	inflight = page_pool_release(pool);
	390	if (!inflight)
	391	return;
	392
	393	/* Periodic warning */
	394	if (time_after_eq(jiffies, pool->defer_warn)) {
	395	int sec = (s32)((u32)jiffies - (u32)pool->defer_start) / HZ;
	396
	397	pr_warn("%s() stalled pool shutdown %d inflight %d sec\n",
	398	__func__, inflight, sec);
	399	pool->defer_warn = jiffies + DEFER_WARN_INTERVAL;
	400	}
	401
	402	/* Still not ready to be disconnected, retry later */
	403	schedule_delayed_work(&pool->release_dw, DEFER_TIME);
	404	}
	405
	406	void page_pool_use_xdp_mem(struct page_pool pool, void (disconnect)(void *))
	407	{
	408	refcount_inc(&pool->user_cnt);
	409	pool->disconnect = disconnect;
	410	}
	411
	412	void page_pool_destroy(struct page_pool *pool)
	413	{
	414	if (!pool)
	415	return;
	416
	417	if (!page_pool_put(pool))
	418	return;
	419
	420	if (!page_pool_release(pool))
	421	return;
	422
	423	pool->defer_start = jiffies;
	424	pool->defer_warn = jiffies + DEFER_WARN_INTERVAL;
ff7d6b27	425
c3f812ce JL	426	INIT_DELAYED_WORK(&pool->release_dw, page_pool_release_retry);
c3f812ce JL	427	schedule_delayed_work(&pool->release_dw, DEFER_TIME);
ff7d6b27	428	}
c3f812ce	429	EXPORT_SYMBOL(page_pool_destroy);