diff options
Diffstat (limited to 'include/net')
-rw-r--r-- | include/net/page_pool/helpers.h | 47 |
1 files changed, 34 insertions, 13 deletions
diff --git a/include/net/page_pool/helpers.h b/include/net/page_pool/helpers.h index 8f64adf86f5b..759489c037c7 100644 --- a/include/net/page_pool/helpers.h +++ b/include/net/page_pool/helpers.h @@ -115,28 +115,49 @@ 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. + * references to the page: + * 1. 'n == 1': no need to actually overwrite it. + * 2. 'n != 1': overwrite it with one, which is the rare case + * for pp_frag_count draining. * - * 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. + * The main advantage to doing this is that not only we avoid a atomic + * update, as 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; but also unify the pp_frag_count + * handling by ensuring all pages have partitioned into only 1 piece + * initially, and only overwrite it when the page is partitioned into + * more than one piece. */ - if (atomic_long_read(&page->pp_frag_count) == nr) + if (atomic_long_read(&page->pp_frag_count) == nr) { + /* As we have ensured nr is always one for constant case using + * the BUILD_BUG_ON(), only need to handle the non-constant case + * here for pp_frag_count draining, which is a rare case. + */ + BUILD_BUG_ON(__builtin_constant_p(nr) && nr != 1); + if (!__builtin_constant_p(nr)) + atomic_long_set(&page->pp_frag_count, 1); + return 0; + } ret = atomic_long_sub_return(nr, &page->pp_frag_count); WARN_ON(ret < 0); + + /* We are the last user here too, reset pp_frag_count back to 1 to + * ensure all pages have been partitioned into 1 piece initially, + * this should be the rare case when the last two fragment users call + * page_pool_defrag_page() currently. + */ + if (unlikely(!ret)) + atomic_long_set(&page->pp_frag_count, 1); + return ret; } -static inline bool page_pool_is_last_frag(struct page_pool *pool, - struct page *page) +static inline bool page_pool_is_last_frag(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); + /* If page_pool_defrag_page() returns 0, we were the last user */ + return page_pool_defrag_page(page, 1) == 0; } /** @@ -161,7 +182,7 @@ static inline void page_pool_put_page(struct page_pool *pool, * allow registering MEM_TYPE_PAGE_POOL, but shield linker. */ #ifdef CONFIG_PAGE_POOL - if (!page_pool_is_last_frag(pool, page)) + if (!page_pool_is_last_frag(page)) return; page_pool_put_defragged_page(pool, page, dma_sync_size, allow_direct); |