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Thu, 14 Nov 2024 20:22:47 +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; Thu, 14 Nov 2024 20:22:47 +0800 From: Yunsheng Lin To: , , CC: , , Yunsheng Lin , Alexander Duyck , Andrew Morton , Linux-MM , Jonathan Corbet , Subject: [PATCH net-next v1 04/10] mm: page_frag: introduce page_frag_alloc_abort() related API Date: Thu, 14 Nov 2024 20:15:59 +0800 Message-ID: <20241114121606.3434517-5-linyunsheng@huawei.com> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20241114121606.3434517-1-linyunsheng@huawei.com> References: <20241114121606.3434517-1-linyunsheng@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.90.30.45] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemf200006.china.huawei.com (7.185.36.61) X-Stat-Signature: 7mom3knn6z4tbdx3hkasd794ycxitfn1 X-Rspam-User: X-Rspamd-Queue-Id: CE36EC0025 X-Rspamd-Server: rspam02 X-HE-Tag: 1731586915-376454 X-HE-Meta: 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 ZWTbECt5 ycqkgj64nz1ogUuVm5obcszPLIJS12ZKv9VqBnwL0g0ZY+feSpctfEG9t+oMLCcNg7WHYk1XMoyv3bAjw8LsdBdDpb8UChYst7smqsjeO3o/YnxEGLDVUz3iyOFxhlLToOMUNaQA0eRz/JtD9pvjpYDdD9RnzcrTHZaAZxncfLPMrHo/3i4mwoTKe1FT8KqKA3F9qDYaT16Jaq3aeUe+cqVQdPCiGyUuYl8UgVq+K2KjXJq+9BpCcRBgLdtHRTCvTJsgPMfgmoq9GQn3MiZa3E8/P0sfSmhOxB/w7cwUXL/huEouX0xtkaAd956pWhsGS02dwj0o9dyZJWcfMEhYTulchO0xRTbGlQkGAjhtaTF+W3SZrRipWtWlDbQV4pTX/LjSKotbV1ZzkjLj7RTviLpSDKQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: For some case as tun_build_skb() without the needing of using complicated prepare & commit API, add the abort API to abort the operation of page_frag_alloc_*() related API for error handling knowing that no one else is taking extra reference to the just allocated fragment, and add abort_ref API to only abort the reference counting of the allocated fragment if it is already referenced by someone else. CC: Alexander Duyck CC: Andrew Morton CC: Linux-MM Signed-off-by: Yunsheng Lin --- Documentation/mm/page_frags.rst | 7 +++++-- include/linux/page_frag_cache.h | 20 ++++++++++++++++++++ mm/page_frag_cache.c | 21 +++++++++++++++++++++ 3 files changed, 46 insertions(+), 2 deletions(-) diff --git a/Documentation/mm/page_frags.rst b/Documentation/mm/page_frags.rst index 34e654c2956e..339e641beb53 100644 --- a/Documentation/mm/page_frags.rst +++ b/Documentation/mm/page_frags.rst @@ -114,9 +114,10 @@ fragsz if there is an alignment requirement for the size of the fragment. .. kernel-doc:: include/linux/page_frag_cache.h :identifiers: page_frag_cache_init page_frag_cache_is_pfmemalloc __page_frag_alloc_align page_frag_alloc_align page_frag_alloc + page_frag_alloc_abort .. kernel-doc:: mm/page_frag_cache.c - :identifiers: page_frag_cache_drain page_frag_free + :identifiers: page_frag_cache_drain page_frag_free page_frag_alloc_abort_ref Coding examples =============== @@ -143,8 +144,10 @@ Allocation & freeing API goto do_error; err = do_something(va, size); - if (err) + if (err) { + page_frag_alloc_abort(nc, va, size); goto do_error; + } ... diff --git a/include/linux/page_frag_cache.h b/include/linux/page_frag_cache.h index a2b1127e8ac8..c3347c97522c 100644 --- a/include/linux/page_frag_cache.h +++ b/include/linux/page_frag_cache.h @@ -141,5 +141,25 @@ static inline void *page_frag_alloc(struct page_frag_cache *nc, } void page_frag_free(void *addr); +void page_frag_alloc_abort_ref(struct page_frag_cache *nc, void *va, + unsigned int fragsz); + +/** + * page_frag_alloc_abort - Abort the page fragment allocation. + * @nc: page_frag cache to which the page fragment is aborted back + * @va: virtual address of page fragment to be aborted + * @fragsz: size of the page fragment to be aborted + * + * It is expected to be called from the same context as the allocation API. + * Mostly used for error handling cases to abort the fragment allocation knowing + * that no one else is taking extra reference to the just aborted fragment, so + * that the aborted fragment can be reused. + */ +static inline void page_frag_alloc_abort(struct page_frag_cache *nc, void *va, + unsigned int fragsz) +{ + page_frag_alloc_abort_ref(nc, va, fragsz); + nc->offset -= fragsz; +} #endif diff --git a/mm/page_frag_cache.c b/mm/page_frag_cache.c index d014130fb893..8c3cfdbe8c2b 100644 --- a/mm/page_frag_cache.c +++ b/mm/page_frag_cache.c @@ -201,3 +201,24 @@ void page_frag_free(void *addr) free_unref_page(page, compound_order(page)); } EXPORT_SYMBOL(page_frag_free); + +/** + * page_frag_alloc_abort_ref - Abort the reference of allocated fragment. + * @nc: page_frag cache to which the page fragment is aborted back + * @va: virtual address of page fragment to be aborted + * @fragsz: size of the page fragment to be aborted + * + * It is expected to be called from the same context as the allocation API. + * Mostly used for error handling cases to abort the reference of allocated + * fragment if the fragment has been referenced for other usages, to avoid the + * atomic operation of page_frag_free() API. + */ +void page_frag_alloc_abort_ref(struct page_frag_cache *nc, void *va, + unsigned int fragsz) +{ + VM_BUG_ON(va + fragsz != + encoded_page_decode_virt(nc->encoded_page) + nc->offset); + + nc->pagecnt_bias++; +} +EXPORT_SYMBOL(page_frag_alloc_abort_ref);