From patchwork Tue Dec 15 00:20:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pavel Begunkov X-Patchwork-Id: 11973461 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1DAF2C4361B for ; Tue, 15 Dec 2020 00:27:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DAE0422209 for ; Tue, 15 Dec 2020 00:27:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728468AbgLOAZg (ORCPT ); Mon, 14 Dec 2020 19:25:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53546 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728755AbgLOAZY (ORCPT ); Mon, 14 Dec 2020 19:25:24 -0500 Received: from mail-wr1-x441.google.com (mail-wr1-x441.google.com [IPv6:2a00:1450:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C80DFC061282; Mon, 14 Dec 2020 16:24:11 -0800 (PST) Received: by mail-wr1-x441.google.com with SMTP id y17so18129652wrr.10; Mon, 14 Dec 2020 16:24:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=atVGnGnKX0+QWRcHgwbeiUpqoMrtsuGF8OD/ap3yMV0=; b=u+zjC4RjWtSd1EVEtSggrw5x/fzyJXtB05ocK2DmCyHbvHdbAjSYxqLG/aQQ/1SN7+ v8zcHxWf3G+8vVngFW8HMhPd4JY2HkvboHm3n5Pb04oWacCx+zManfJ+/QEd3911HPgi 5VgZYb+6nxuhmIlsEbRI8AUA0I1FGrZZlsVfA5jTjyqLOp/nV2w29yuWXPkRlUcJWDpP 4d7OeUsozBCiZNZFfhlcizeVjluwsy8qgAwJf3Y/uJOLfdRI7DjoIRBGKd2S+0Yv9ddS nhAy6A+Ovk//nWdeGQ/vYQc5ldTzOEXOsG45nqJlWDD4IABVlHzYKw6sdiv00OUaDbOo oTlg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=atVGnGnKX0+QWRcHgwbeiUpqoMrtsuGF8OD/ap3yMV0=; b=P4b0RQrWgJOlf89pTppOa6bd58Ig4/i9gNEELgnL2ndcqrypiHf62srVG6cEhD0rzB tgHUAVsUeEt2YikzzToYTAxO0J4utwCDVNcu09m/lLYrLiz0wi3KDSmxMM9yv39qdvlC o4S7hEJPsPmbGX2QO0Je2zPCZKcQ+fU6MSnOiNPLUimpSxrj6CW2Xc2faqhkCTuDRVXh f7/aeHLyWr7VwTbLuNJ9seutqYaT5hsYxG6M3XpqWcSBnisP7BNimczqSwk6EIPPDZEC VrROe5dakfiEjFNDa53iNcccrC0tdET9jCsgG3i+2UXvCRXqXSMxfDj09HtgxBdRJD8r g3Tg== X-Gm-Message-State: AOAM53262akUQov4R5/c2dtwtkg7s5/8CtK1FGeG2oTHR2USIeFcbz1e 9bg2Qd0Dphtlp8ggyxGjHbERX3tQdCAOBeID X-Google-Smtp-Source: ABdhPJzD6TNgMT/l5rfeMAyPUUuqa5EHPZa+zhYb6kKMMDi0EGqLG8qd52Qk85eB5WU9zWrxCo1MOg== X-Received: by 2002:adf:f18a:: with SMTP id h10mr33264191wro.244.1607991850205; Mon, 14 Dec 2020 16:24:10 -0800 (PST) Received: from localhost.localdomain ([85.255.232.163]) by smtp.gmail.com with ESMTPSA id b19sm5362012wmj.37.2020.12.14.16.24.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Dec 2020 16:24:09 -0800 (PST) From: Pavel Begunkov To: linux-block@vger.kernel.org Cc: Jens Axboe , Christoph Hellwig , Matthew Wilcox , Ming Lei , Johannes Weiner , Alexander Viro , "Darrick J . Wong" , "Martin K . Petersen" , Jonathan Corbet , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org, target-devel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-doc@vger.kernel.org Subject: [PATCH v1 6/6] block/iomap: don't copy bvec for direct IO Date: Tue, 15 Dec 2020 00:20:25 +0000 Message-Id: <498b34d746627e874740d8315b2924880c46dbc3.1607976425.git.asml.silence@gmail.com> X-Mailer: git-send-email 2.24.0 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org The block layer spends quite a while in blkdev_direct_IO() to copy and initialise bio's bvec. However, if we've already got a bvec in the input iterator it might be reused in some cases, i.e. when new ITER_BVEC_FLAG_FIXED flag is set. Simple tests show considerable performance boost, and it also reduces memory footprint. Suggested-by: Matthew Wilcox Signed-off-by: Pavel Begunkov --- Documentation/filesystems/porting.rst | 9 ++++ block/bio.c | 64 +++++++++++---------------- include/linux/bio.h | 3 ++ 3 files changed, 38 insertions(+), 38 deletions(-) diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst index 867036aa90b8..47a622879952 100644 --- a/Documentation/filesystems/porting.rst +++ b/Documentation/filesystems/porting.rst @@ -865,3 +865,12 @@ no matter what. Everything is handled by the caller. clone_private_mount() returns a longterm mount now, so the proper destructor of its result is kern_unmount() or kern_unmount_array(). + +--- + +**mandatory** + +For bvec based itererators bio_iov_iter_get_pages() now doesn't copy bvecs but +uses the one provided. Anyone issuing kiocb-I/O should ensure that the bvec and +page references stay until I/O has completed, i.e. until ->ki_complete() has +been called or returned with non -EIOCBQUEUED code. diff --git a/block/bio.c b/block/bio.c index 3192358c411f..f8229be24562 100644 --- a/block/bio.c +++ b/block/bio.c @@ -960,25 +960,16 @@ void bio_release_pages(struct bio *bio, bool mark_dirty) } EXPORT_SYMBOL_GPL(bio_release_pages); -static int __bio_iov_bvec_add_pages(struct bio *bio, struct iov_iter *iter) +static int bio_iov_bvec_set(struct bio *bio, struct iov_iter *iter) { - const struct bio_vec *bv = iter->bvec; - struct page *page = bv->bv_page; - bool same_page = false; - unsigned int off, len; - - if (WARN_ON_ONCE(iter->iov_offset > bv->bv_len)) - return -EINVAL; - - len = min_t(size_t, bv->bv_len - iter->iov_offset, iter->count); - off = bv->bv_offset + iter->iov_offset; - - if (!__bio_try_merge_page(bio, page, len, off, &same_page)) { - if (bio_full(bio, len)) - return -EINVAL; - bio_add_page_noaccount(bio, page, len, off); - } - iov_iter_advance(iter, len); + WARN_ON_ONCE(BVEC_POOL_IDX(bio) != 0); + bio->bi_vcnt = iter->nr_segs; + bio->bi_max_vecs = iter->nr_segs; + bio->bi_io_vec = (struct bio_vec *)iter->bvec; + bio->bi_iter.bi_bvec_done = iter->iov_offset; + bio->bi_iter.bi_size = iter->count; + + iov_iter_advance(iter, iter->count); return 0; } @@ -1092,12 +1083,13 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter) * This takes either an iterator pointing to user memory, or one pointing to * kernel pages (BVEC iterator). If we're adding user pages, we pin them and * map them into the kernel. On IO completion, the caller should put those - * pages. If we're adding kernel pages, and the caller told us it's safe to - * do so, we just have to add the pages to the bio directly. We don't grab an - * extra reference to those pages (the user should already have that), and we - * don't put the page on IO completion. The caller needs to check if the bio is - * flagged BIO_NO_PAGE_REF on IO completion. If it isn't, then pages should be - * released. + * pages. If we're adding kernel pages, it doesn't take extra page references + * and reuses the provided bvec, so the caller must ensure that the bvec isn't + * freed and page references remain to be taken until I/O has completed. If + * the I/O is completed asynchronously, the bvec must not be freed before + * ->ki_complete() has been called. The caller needs to check if the bio is + * flagged BIO_NO_PAGE_REF on IO completion. If it isn't, then pages should + * be released. * * The function tries, but does not guarantee, to pin as many pages as * fit into the bio, or are requested in @iter, whatever is smaller. If @@ -1109,27 +1101,23 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter) */ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) { - const bool is_bvec = iov_iter_is_bvec(iter); int ret; - if (WARN_ON_ONCE(bio->bi_vcnt)) - return -EINVAL; + if (iov_iter_is_bvec(iter)) { + if (WARN_ON_ONCE(bio_op(bio) == REQ_OP_ZONE_APPEND)) + return -EINVAL; + bio_iov_bvec_set(bio, iter); + bio_set_flag(bio, BIO_NO_PAGE_REF); + return 0; + } do { - if (bio_op(bio) == REQ_OP_ZONE_APPEND) { - if (WARN_ON_ONCE(is_bvec)) - return -EINVAL; + if (bio_op(bio) == REQ_OP_ZONE_APPEND) ret = __bio_iov_append_get_pages(bio, iter); - } else { - if (is_bvec) - ret = __bio_iov_bvec_add_pages(bio, iter); - else - ret = __bio_iov_iter_get_pages(bio, iter); - } + else + ret = __bio_iov_iter_get_pages(bio, iter); } while (!ret && iov_iter_count(iter) && !bio_full(bio, 0)); - if (is_bvec) - bio_set_flag(bio, BIO_NO_PAGE_REF); return bio->bi_vcnt ? 0 : ret; } EXPORT_SYMBOL_GPL(bio_iov_iter_get_pages); diff --git a/include/linux/bio.h b/include/linux/bio.h index 2a9f3f0bbe0a..337f4280b639 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -444,6 +444,9 @@ static inline void bio_wouldblock_error(struct bio *bio) static inline int bio_iov_vecs_to_alloc(struct iov_iter *iter, int max_segs) { + /* reuse iter->bvec */ + if (iov_iter_is_bvec(iter)) + return 0; return iov_iter_npages(iter, max_segs); }