From nobody Fri Dec 19 16:46:32 2025 Received: from szxga04-in.huawei.com (szxga04-in.huawei.com [45.249.212.190]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3B403194124; Mon, 26 Aug 2024 12:46:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.190 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724676400; cv=none; b=frEPqVKJZzINGQoew4J7pKVS8Q/+0JL6d+oiMyuWx8bmsQVQr2DpvMcplScaAaRarnBwoQ19HLXBmSj2XGmzwih0czuWukscALfqPhqA2zsYdcWw7w2PdRoVJYAbQmt63zFNHlHzJWtKPMHZ8+Gjf28zaWsC6tzL8oX1/kl9OIU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724676400; c=relaxed/simple; bh=cDk3Axvfijb1LblY5Ie0+lSzdCgFfeGH1pHhnML9ks0=; h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=mT4oUX91xr/wGytbv9mq7TPtrymnC50szEjpplWsPWBlw6mke48YYRnqdLb6zCstADgQ7Ub+tfUIvtkjlvKpcttKw+mJvB80u0kkl2nPT03I3g+s3nfHS0Bm++I2Ib9wL3EX5SIEStjQI+yJ6b0zik02qHvZhoTnnu7YdlxD1iw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.190 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.234]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4Wsr0D6wbSz20mjC; Mon, 26 Aug 2024 20:41:48 +0800 (CST) Received: from dggpemf200006.china.huawei.com (unknown [7.185.36.61]) by mail.maildlp.com (Postfix) with ESMTPS id 35F701402E1; Mon, 26 Aug 2024 20:46:36 +0800 (CST) Received: from localhost.localdomain (10.90.30.45) by dggpemf200006.china.huawei.com (7.185.36.61) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Mon, 26 Aug 2024 20:46:35 +0800 From: Yunsheng Lin To: , , CC: , , Yunsheng Lin , Alexander Duyck , Jonathan Corbet , Andrew Morton , , Subject: [PATCH net-next v15 12/13] mm: page_frag: update documentation for page_frag Date: Mon, 26 Aug 2024 20:40:19 +0800 Message-ID: <20240826124021.2635705-13-linyunsheng@huawei.com> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20240826124021.2635705-1-linyunsheng@huawei.com> References: <20240826124021.2635705-1-linyunsheng@huawei.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpemf200006.china.huawei.com (7.185.36.61) Content-Type: text/plain; charset="utf-8" Update documentation about design, implementation and API usages for page_frag. CC: Alexander Duyck Signed-off-by: Yunsheng Lin --- Documentation/mm/page_frags.rst | 173 +++++++++++++++++++++- include/linux/page_frag_cache.h | 251 ++++++++++++++++++++++++++++++++ mm/page_frag_cache.c | 12 +- 3 files changed, 433 insertions(+), 3 deletions(-) diff --git a/Documentation/mm/page_frags.rst b/Documentation/mm/page_frags.= rst index 503ca6cdb804..d80f44cb471e 100644 --- a/Documentation/mm/page_frags.rst +++ b/Documentation/mm/page_frags.rst @@ -1,3 +1,5 @@ +.. SPDX-License-Identifier: GPL-2.0 + =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D Page fragments =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D @@ -40,4 +42,173 @@ page via a single call. The advantage to doing this is= that it allows for cleaning up the multiple references that were added to a page in order to avoid calling get_page per allocation. =20 -Alexander Duyck, Nov 29, 2016. + +Architecture overview +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +.. code-block:: none + + +----------------------+ + | page_frag API caller | + +----------------------+ + | + | + v + +------------------------------------------------------------------+ + | request page fragment | + +------------------------------------------------------------------+ + | | | + | | | + | Cache not enough | + | | | + | +-----------------+ | + | | reuse old cache |--Usable-->| + | +-----------------+ | + | | | + | Not usable | + | | | + | v | + Cache empty +-----------------+ | + | | drain old cache | | + | +-----------------+ | + | | | + v_________________________________v | + | | + | | + _________________v_______________ | + | | Cache is enou= gh + | | | + PAGE_SIZE < PAGE_FRAG_CACHE_MAX_SIZE | | + | | | + | PAGE_SIZE >=3D PAGE_FRAG_CACHE_MAX_SIZE | + v | | + +----------------------------------+ | | + | refill cache with order > 0 page | | | + +----------------------------------+ | | + | | | | + | | | | + | Refill failed | | + | | | | + | v v | + | +------------------------------------+ | + | | refill cache with order 0 page | | + | +----------------------------------=3D-+ | + | | | + Refill succeed | | + | Refill succeed | + | | | + v v v + +------------------------------------------------------------------+ + | allocate fragment from cache | + +------------------------------------------------------------------+ + +API interface +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D +As the design and implementation of page_frag API implies, the allocation = side +does not allow concurrent calling. Instead it is assumed that the caller m= ust +ensure there is not concurrent alloc calling to the same page_frag_cache +instance by using its own lock or rely on some lockless guarantee like NAPI +softirq. + +Depending on different aligning requirement, the page_frag API caller may = call +page_frag_*_align*() to ensure the returned virtual address or offset of t= he +page is aligned according to the 'align/alignment' parameter. Note the siz= e of +the allocated fragment is not aligned, the caller needs to provide an alig= ned +fragsz if there is an alignment requirement for the size of the fragment. + +Depending on different use cases, callers expecting to deal with va, page = or +both va and page for them may call page_frag_alloc, page_frag_refill, or +page_frag_alloc_refill API accordingly. + +There is also a use case that needs minimum memory in order for forward pr= ogress, +but more performant if more memory is available. Using page_frag_*_prepare= () and +page_frag_commit*() related API, the caller requests the minimum memory it= needs +and the prepare API will return the maximum size of the fragment returned.= The +caller needs to either call the commit API to report how much memory it ac= tually +uses, or not do so if deciding to not use any memory. + +.. kernel-doc:: include/linux/page_frag_cache.h + :identifiers: page_frag_cache_init page_frag_cache_is_pfmemalloc + page_frag_cache_page_offset __page_frag_alloc_align + page_frag_alloc_align page_frag_alloc + __page_frag_refill_align page_frag_refill_align + page_frag_refill __page_frag_refill_prepare_align + page_frag_refill_prepare_align page_frag_refill_prepare + __page_frag_alloc_refill_prepare_align + page_frag_alloc_refill_prepare_align + page_frag_alloc_refill_prepare + __page_frag_alloc_refill_probe_align + page_frag_alloc_refill_probe page_frag_refill_probe + page_frag_commit page_frag_commit_noref + page_frag_alloc_abort + +.. kernel-doc:: mm/page_frag_cache.c + :identifiers: page_frag_cache_drain page_frag_free + +Coding examples +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +Init & Drain API +---------------- + +.. code-block:: c + + page_frag_cache_init(nc); + ... + page_frag_cache_drain(nc); + + +Alloc & Free API +---------------- + +.. code-block:: c + + void *va; + + va =3D page_frag_alloc_align(nc, size, gfp, align); + if (!va) + goto do_error; + + err =3D do_something(va, size); + if (err) { + page_frag_free(va); + goto do_error; + } + +Prepare & Commit API +-------------------- + +.. code-block:: c + + struct page_frag page_frag, *pfrag; + bool merge =3D true; + void *va; + + pfrag =3D &page_frag; + va =3D page_frag_alloc_refill_prepare(nc, 32U, pfrag, GFP_KERNEL); + if (!va) + goto wait_for_space; + + copy =3D min_t(unsigned int, copy, pfrag->size); + if (!skb_can_coalesce(skb, i, pfrag->page, pfrag->offset)) { + if (i >=3D max_skb_frags) + goto new_segment; + + merge =3D false; + } + + copy =3D mem_schedule(copy); + if (!copy) + goto wait_for_space; + + err =3D copy_from_iter_full_nocache(va, copy, iter); + if (err) + goto do_error; + + if (merge) { + skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy); + page_frag_commit_noref(nc, pfrag, copy); + } else { + skb_fill_page_desc(skb, i, pfrag->page, pfrag->offset, copy); + page_frag_commit(nc, pfrag, copy); + } diff --git a/include/linux/page_frag_cache.h b/include/linux/page_frag_cach= e.h index 9d2a7dd39d64..01a0d7db3ac0 100644 --- a/include/linux/page_frag_cache.h +++ b/include/linux/page_frag_cache.h @@ -59,11 +59,28 @@ static inline struct page *page_frag_encoded_page_ptr(u= nsigned long encoded_page return virt_to_page((void *)encoded_page); } =20 +/** + * page_frag_cache_init() - Init page_frag cache. + * @nc: page_frag cache from which to init + * + * Inline helper to init the page_frag cache. + */ static inline void page_frag_cache_init(struct page_frag_cache *nc) { nc->encoded_page =3D 0; } =20 +/** + * page_frag_cache_is_pfmemalloc() - Check for pfmemalloc. + * @nc: page_frag cache from which to check + * + * Used to check if the current page in page_frag cache is pfmemalloc'ed. + * It has the same calling context expectation as the alloc API. + * + * Return: + * true if the current page in page_frag cache is pfmemalloc'ed, otherwise + * return false. + */ static inline bool page_frag_cache_is_pfmemalloc(struct page_frag_cache *n= c) { return page_frag_encoded_page_pfmemalloc(nc->encoded_page); @@ -74,6 +91,16 @@ static inline unsigned int page_frag_cache_page_size(uns= igned long encoded_page) return PAGE_SIZE << page_frag_encoded_page_order(encoded_page); } =20 +/** + * page_frag_cache_page_offset() - Return the current page fragment's offs= et. + * @nc: page_frag cache from which to check + * + * The API is only used in net/sched/em_meta.c for historical reason, do n= ot use + * it for new caller unless there is a strong reason. + * + * Return: + * the offset of the current page fragment in the page_frag cache. + */ static inline unsigned int page_frag_cache_page_offset(const struct page_f= rag_cache *nc) { return nc->offset; @@ -115,6 +142,19 @@ static inline void __page_frag_cache_commit(struct pag= e_frag_cache *nc, nc->offset =3D pfrag->offset + used_sz; } =20 +/** + * __page_frag_alloc_align() - Alloc a page fragment with aligning + * requirement. + * @nc: page_frag cache from which to allocate + * @fragsz: the requested fragment size + * @gfp_mask: the allocation gfp to use when cache need to be refilled + * @align_mask: the requested aligning requirement for the 'va' + * + * Alloc a page fragment from page_frag cache with aligning requirement. + * + * Return: + * Virtual address of the page fragment, otherwise return NULL. + */ static inline void *__page_frag_alloc_align(struct page_frag_cache *nc, un= signed int fragsz, gfp_t gfp_mask, unsigned int align_mask) { @@ -130,6 +170,19 @@ static inline void *__page_frag_alloc_align(struct pag= e_frag_cache *nc, unsigned return va; } =20 +/** + * page_frag_alloc_align() - Alloc a page fragment with aligning requireme= nt. + * @nc: page_frag cache from which to allocate + * @fragsz: the requested fragment size + * @gfp_mask: the allocation gfp to use when cache needs to be refilled + * @align: the requested aligning requirement for the fragment + * + * WARN_ON_ONCE() checking for @align before allocing a page fragment from + * page_frag cache with aligning requirement. + * + * Return: + * virtual address of the page fragment, otherwise return NULL. + */ static inline void *page_frag_alloc_align(struct page_frag_cache *nc, unsigned int fragsz, gfp_t gfp_mask, unsigned int align) @@ -138,12 +191,36 @@ static inline void *page_frag_alloc_align(struct page= _frag_cache *nc, return __page_frag_alloc_align(nc, fragsz, gfp_mask, -align); } =20 +/** + * page_frag_alloc() - Alloc a page fragment. + * @nc: page_frag cache from which to allocate + * @fragsz: the requested fragment size + * @gfp_mask: the allocation gfp to use when cache need to be refilled + * + * Alloc a page fragment from page_frag cache. + * + * Return: + * virtual address of the page fragment, otherwise return NULL. + */ static inline void *page_frag_alloc(struct page_frag_cache *nc, unsigned int fragsz, gfp_t gfp_mask) { return __page_frag_alloc_align(nc, fragsz, gfp_mask, ~0u); } =20 +/** + * __page_frag_refill_align() - Refill a page_frag with aligning requireme= nt. + * @nc: page_frag cache from which to refill + * @fragsz: the requested fragment size + * @pfrag: the page_frag to be refilled. + * @gfp_mask: the allocation gfp to use when cache need to be refilled + * @align_mask: the requested aligning requirement for the fragment + * + * Refill a page_frag from page_frag cache with aligning requirement. + * + * Return: + * True if refill succeeds, otherwise return false. + */ static inline bool __page_frag_refill_align(struct page_frag_cache *nc, un= signed int fragsz, struct page_frag *pfrag, gfp_t gfp_mask, unsigned int align_mask) @@ -155,6 +232,20 @@ static inline bool __page_frag_refill_align(struct pag= e_frag_cache *nc, unsigned return true; } =20 +/** + * page_frag_refill_align() - Refill a page_frag with aligning requirement. + * @nc: page_frag cache from which to refill + * @fragsz: the requested fragment size + * @pfrag: the page_frag to be refilled. + * @gfp_mask: the allocation gfp to use when cache needs to be refilled + * @align: the requested aligning requirement for the fragment + * + * WARN_ON_ONCE() checking for @align before refilling a page_frag from + * page_frag cache with aligning requirement. + * + * Return: + * True if refill succeeds, otherwise return false. + */ static inline bool page_frag_refill_align(struct page_frag_cache *nc, unsi= gned int fragsz, struct page_frag *pfrag, gfp_t gfp_mask, unsigned int align) @@ -163,12 +254,38 @@ static inline bool page_frag_refill_align(struct page= _frag_cache *nc, unsigned i return __page_frag_refill_align(nc, fragsz, pfrag, gfp_mask, -align); } =20 +/** + * page_frag_refill() - Refill a page_frag. + * @nc: page_frag cache from which to refill + * @fragsz: the requested fragment size + * @pfrag: the page_frag to be refilled. + * @gfp_mask: the allocation gfp to use when cache need to be refilled + * + * Refill a page_frag from page_frag cache. + * + * Return: + * True if refill succeeds, otherwise return false. + */ static inline bool page_frag_refill(struct page_frag_cache *nc, unsigned i= nt fragsz, struct page_frag *pfrag, gfp_t gfp_mask) { return __page_frag_refill_align(nc, fragsz, pfrag, gfp_mask, ~0u); } =20 +/** + * __page_frag_refill_prepare_align() - Prepare refilling a page_frag with= aligning + * requirement. + * @nc: page_frag cache from which to refill + * @fragsz: the requested fragment size + * @pfrag: the page_frag to be refilled. + * @gfp_mask: the allocation gfp to use when cache need to be refilled + * @align_mask: the requested aligning requirement for the fragment + * + * Prepare refill a page_frag from page_frag cache with aligning requireme= nt. + * + * Return: + * True if prepare refilling succeeds, otherwise return false. + */ static inline bool __page_frag_refill_prepare_align(struct page_frag_cache= *nc, unsigned int fragsz, struct page_frag *pfrag, @@ -178,6 +295,21 @@ static inline bool __page_frag_refill_prepare_align(st= ruct page_frag_cache *nc, return !!__page_frag_cache_prepare(nc, fragsz, pfrag, gfp_mask, align_mas= k); } =20 +/** + * page_frag_refill_prepare_align() - Prepare refilling a page_frag with a= ligning + * requirement. + * @nc: page_frag cache from which to refill + * @fragsz: the requested fragment size + * @pfrag: the page_frag to be refilled. + * @gfp_mask: the allocation gfp to use when cache needs to be refilled + * @align: the requested aligning requirement for the fragment + * + * WARN_ON_ONCE() checking for @align before prepare refilling a page_frag= from + * page_frag cache with aligning requirement. + * + * Return: + * True if prepare refilling succeeds, otherwise return false. + */ static inline bool page_frag_refill_prepare_align(struct page_frag_cache *= nc, unsigned int fragsz, struct page_frag *pfrag, @@ -188,6 +320,18 @@ static inline bool page_frag_refill_prepare_align(stru= ct page_frag_cache *nc, return __page_frag_refill_prepare_align(nc, fragsz, pfrag, gfp_mask, -ali= gn); } =20 +/** + * page_frag_refill_prepare() - Prepare refilling a page_frag. + * @nc: page_frag cache from which to refill + * @fragsz: the requested fragment size + * @pfrag: the page_frag to be refilled. + * @gfp_mask: the allocation gfp to use when cache need to be refilled + * + * Prepare refilling a page_frag from page_frag cache. + * + * Return: + * True if refill succeeds, otherwise return false. + */ static inline bool page_frag_refill_prepare(struct page_frag_cache *nc, unsigned int fragsz, struct page_frag *pfrag, @@ -196,6 +340,20 @@ static inline bool page_frag_refill_prepare(struct pag= e_frag_cache *nc, return __page_frag_refill_prepare_align(nc, fragsz, pfrag, gfp_mask, ~0u); } =20 +/** + * __page_frag_alloc_refill_prepare_align() - Prepare allocing a fragment = and + * refilling a page_frag with aligning requirement. + * @nc: page_frag cache from which to allocate and refill + * @fragsz: the requested fragment size + * @pfrag: the page_frag to be refilled. + * @gfp_mask: the allocation gfp to use when cache need to be refilled + * @align_mask: the requested aligning requirement for the fragment. + * + * Prepare allocing a fragment and refilling a page_frag from page_frag ca= che. + * + * Return: + * virtual address of the page fragment, otherwise return NULL. + */ static inline void *__page_frag_alloc_refill_prepare_align(struct page_fra= g_cache *nc, unsigned int fragsz, struct page_frag *pfrag, @@ -205,6 +363,21 @@ static inline void *__page_frag_alloc_refill_prepare_a= lign(struct page_frag_cach return __page_frag_cache_prepare(nc, fragsz, pfrag, gfp_mask, align_mask); } =20 +/** + * page_frag_alloc_refill_prepare_align() - Prepare allocing a fragment and + * refilling a page_frag with aligning requirement. + * @nc: page_frag cache from which to allocate and refill + * @fragsz: the requested fragment size + * @pfrag: the page_frag to be refilled. + * @gfp_mask: the allocation gfp to use when cache need to be refilled + * @align: the requested aligning requirement for the fragment. + * + * WARN_ON_ONCE() checking for @align before prepare allocing a fragment a= nd + * refilling a page_frag from page_frag cache. + * + * Return: + * virtual address of the page fragment, otherwise return NULL. + */ static inline void *page_frag_alloc_refill_prepare_align(struct page_frag_= cache *nc, unsigned int fragsz, struct page_frag *pfrag, @@ -215,6 +388,19 @@ static inline void *page_frag_alloc_refill_prepare_ali= gn(struct page_frag_cache return __page_frag_alloc_refill_prepare_align(nc, fragsz, pfrag, gfp_mask= , -align); } =20 +/** + * page_frag_alloc_refill_prepare() - Prepare allocing a fragment and refi= lling + * a page_frag. + * @nc: page_frag cache from which to allocate and refill + * @fragsz: the requested fragment size + * @pfrag: the page_frag to be refilled. + * @gfp_mask: the allocation gfp to use when cache need to be refilled + * + * Prepare allocing a fragment and refilling a page_frag from page_frag ca= che. + * + * Return: + * virtual address of the page fragment, otherwise return NULL. + */ static inline void *page_frag_alloc_refill_prepare(struct page_frag_cache = *nc, unsigned int fragsz, struct page_frag *pfrag, @@ -223,6 +409,20 @@ static inline void *page_frag_alloc_refill_prepare(str= uct page_frag_cache *nc, return __page_frag_alloc_refill_prepare_align(nc, fragsz, pfrag, gfp_mask= , ~0u); } =20 +/** + * __page_frag_alloc_refill_probe_align() - Probe allocing a fragment and = refilling + * a page_frag with aligning requirement. + * @nc: page_frag cache from which to allocate and refill + * @fragsz: the requested fragment size + * @pfrag: the page_frag to be refilled. + * @align_mask: the requested aligning requirement for the fragment. + * + * Probe allocing a fragment and refilling a page_frag from page_frag cach= e with + * aligning requirement. + * + * Return: + * virtual address of the page fragment, otherwise return NULL. + */ static inline void *__page_frag_alloc_refill_probe_align(struct page_frag_= cache *nc, unsigned int fragsz, struct page_frag *pfrag, @@ -243,6 +443,18 @@ static inline void *__page_frag_alloc_refill_probe_ali= gn(struct page_frag_cache return page_frag_encoded_page_address(encoded_page) + offset; } =20 +/** + * page_frag_alloc_refill_probe() - Probe allocing a fragment and refilling + * a page_frag. + * @nc: page_frag cache from which to allocate and refill + * @fragsz: the requested fragment size + * @pfrag: the page_frag to be refilled + * + * Probe allocing a fragment and refilling a page_frag from page_frag cach= e. + * + * Return: + * virtual address of the page fragment, otherwise return NULL. + */ static inline void *page_frag_alloc_refill_probe(struct page_frag_cache *n= c, unsigned int fragsz, struct page_frag *pfrag) @@ -250,6 +462,17 @@ static inline void *page_frag_alloc_refill_probe(struc= t page_frag_cache *nc, return __page_frag_alloc_refill_probe_align(nc, fragsz, pfrag, ~0u); } =20 +/** + * page_frag_refill_probe() - Probe refilling a page_frag. + * @nc: page_frag cache from which to refill + * @fragsz: the requested fragment size + * @pfrag: the page_frag to be refilled + * + * Probe refilling a page_frag from page_frag cache. + * + * Return: + * True if refill succeeds, otherwise return false. + */ static inline bool page_frag_refill_probe(struct page_frag_cache *nc, unsigned int fragsz, struct page_frag *pfrag) @@ -257,18 +480,46 @@ static inline bool page_frag_refill_probe(struct page= _frag_cache *nc, return !!page_frag_alloc_refill_probe(nc, fragsz, pfrag); } =20 +/** + * page_frag_commit - Commit allocing a page fragment. + * @nc: page_frag cache from which to commit + * @pfrag: the page_frag to be committed + * @used_sz: size of the page fragment has been used + * + * Commit the actual used size for the allocation that was either prepared + * or probed. + */ static inline void page_frag_commit(struct page_frag_cache *nc, struct pag= e_frag *pfrag, unsigned int used_sz) { __page_frag_cache_commit(nc, pfrag, true, used_sz); } =20 +/** + * page_frag_commit_noref - Commit allocing a page fragment without taking + * page refcount. + * @nc: page_frag cache from which to commit + * @pfrag: the page_frag to be committed + * @used_sz: size of the page fragment has been used + * + * Commit the alloc preparing or probing by passing the actual used size, = but + * not taking refcount. Mostly used for fragmemt coalescing case when the + * current fragment can share the same refcount with previous fragment. + */ static inline void page_frag_commit_noref(struct page_frag_cache *nc, struct page_frag *pfrag, unsigned int used_sz) { __page_frag_cache_commit(nc, pfrag, false, used_sz); } =20 +/** + * page_frag_alloc_abort - Abort the page fragment allocation. + * @nc: page_frag cache to which the page fragment is aborted back + * @fragsz: size of the page fragment to be aborted + * + * It is expected to be called from the same context as the alloc API. + * Mostly used for error handling cases where the fragment is no longer ne= eded. + */ static inline void page_frag_alloc_abort(struct page_frag_cache *nc, unsig= ned int fragsz) { VM_BUG_ON(fragsz > nc->offset); diff --git a/mm/page_frag_cache.c b/mm/page_frag_cache.c index e0ad3de11249..48e3aeb86942 100644 --- a/mm/page_frag_cache.c +++ b/mm/page_frag_cache.c @@ -47,6 +47,10 @@ static struct page *__page_frag_cache_refill(struct page= _frag_cache *nc, return page; } =20 +/** + * page_frag_cache_drain - Drain the current page from page_frag cache. + * @nc: page_frag cache from which to drain + */ void page_frag_cache_drain(struct page_frag_cache *nc) { if (!nc->encoded_page) @@ -137,8 +141,12 @@ void *__page_frag_cache_prepare(struct page_frag_cache= *nc, unsigned int fragsz, } EXPORT_SYMBOL(__page_frag_cache_prepare); =20 -/* - * Frees a page fragment allocated out of either a compound or order 0 pag= e. +/** + * page_frag_free - Free a page fragment. + * @addr: va of page fragment to be freed + * + * Free a page fragment allocated out of either a compound or order 0 page= by + * virtual address. */ void page_frag_free(void *addr) { --=20 2.33.0