/* 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>
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 = 0;
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;
struct page *page;
/* Quicker fallback, avoid locks when ring is empty */
if (__ptr_ring_empty(r))
return NULL;
/* 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;
}
/* Slower-path: Alloc array empty, time to refill
*
* Open-coded bulk ptr_ring consumer.
*
* Discussion: the ring consumer lock is not really
* needed due to the softirq/NAPI protection, but
* later need the ability to reclaim pages on the
* ring. Thus, keeping the locks.
*/
spin_lock(&r->consumer_lock);
while ((page = __ptr_ring_consume(r))) {
if (pool->alloc.count == PP_ALLOC_CACHE_REFILL)
break;
pool->alloc.cache[pool->alloc.count++] = page;
}
spin_unlock(&r->consumer_lock);
return page;
}
/* Slow-path: Get page from locked ring queue */
page = ptr_ring_consume(&pool->ring);
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 distance;
distance = _distance(hold_cnt, release_cnt);
trace_page_pool_inflight(pool, distance, hold_cnt, release_cnt);
return distance;
}
static bool __page_pool_safe_to_destroy(struct page_pool *pool)
{
s32 inflight = page_pool_inflight(pool);
/* The distance should not be able to become negative */
WARN(inflight < 0, "Negative(%d) inflight packet-pages", inflight);
return (inflight == 0);
}
/* Cleanup page_pool state from page */
static void __page_pool_clean_page(struct page_pool *pool,
struct page *page)
{
dma_addr_t dma;
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:
atomic_inc(&pool->pages_state_release_cnt);
trace_page_pool_state_release(pool, page,
atomic_read(&pool->pages_state_release_cnt));
}
/* 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 __warn_in_flight(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 distance;
distance = _distance(hold_cnt, release_cnt);
/* Drivers should fix this, but only problematic when DMA is used */
WARN(1, "Still in-flight pages:%d hold:%u released:%u",
distance, hold_cnt, release_cnt);
}
void __page_pool_free(struct page_pool *pool)
{
/* Only last user actually free/release resources */
if (!page_pool_put(pool))
return;
WARN(pool->alloc.count, "API usage violation");
WARN(!ptr_ring_empty(&pool->ring), "ptr_ring is not empty");
/* Can happen due to forced shutdown */
if (!__page_pool_safe_to_destroy(pool))
__warn_in_flight(pool);
ptr_ring_cleanup(&pool->ring, NULL);
if (pool->p.flags & PP_FLAG_DMA_MAP)
put_device(pool->p.dev);
kfree(pool);
}
EXPORT_SYMBOL(__page_pool_free);
/* Request to shutdown: release pages cached by page_pool, and check
* for in-flight pages
*/
bool __page_pool_request_shutdown(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);
return __page_pool_safe_to_destroy(pool);
}
EXPORT_SYMBOL(__page_pool_request_shutdown);
