Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:48186 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726457AbeKZNLi (ORCPT ); Mon, 26 Nov 2018 08:11:38 -0500 From: Ming Lei To: Jens Axboe Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Theodore Ts'o , Omar Sandoval , Sagi Grimberg , Dave Chinner , Kent Overstreet , Mike Snitzer , dm-devel@redhat.com, Alexander Viro , linux-fsdevel@vger.kernel.org, Shaohua Li , linux-raid@vger.kernel.org, David Sterba , linux-btrfs@vger.kernel.org, "Darrick J . Wong" , linux-xfs@vger.kernel.org, Gao Xiang , Christoph Hellwig , linux-ext4@vger.kernel.org, Coly Li , linux-bcache@vger.kernel.org, Boaz Harrosh , Bob Peterson , cluster-devel@redhat.com, Ming Lei Subject: [PATCH V12 07/20] block: introduce multi-page bvec helpers Date: Mon, 26 Nov 2018 10:17:07 +0800 Message-Id: <20181126021720.19471-8-ming.lei@redhat.com> In-Reply-To: <20181126021720.19471-1-ming.lei@redhat.com> References: <20181126021720.19471-1-ming.lei@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: This patch introduces helpers of 'bvec_iter_*' for multi-page bvec support. The introduced helpers treate one bvec as real multi-page segment, which may include more than one pages. The existed helpers of bvec_iter_* are interfaces for supporting current bvec iterator which is thought as single-page by drivers, fs, dm and etc. These introduced helpers will build single-page bvec in flight, so this way won't break current bio/bvec users, which needn't any change. Follows some multi-page bvec background: - bvecs stored in bio->bi_io_vec is always multi-page style - bvec(struct bio_vec) represents one physically contiguous I/O buffer, now the buffer may include more than one page after multi-page bvec is supported, and all these pages represented by one bvec is physically contiguous. Before multi-page bvec support, at most one page is included in one bvec, we call it single-page bvec. - .bv_page of the bvec points to the 1st page in the multi-page bvec - .bv_offset of the bvec is the offset of the buffer in the bvec The effect on the current drivers/filesystem/dm/bcache/...: - almost everyone supposes that one bvec only includes one single page, so we keep the sp interface not changed, for example, bio_for_each_segment() still returns single-page bvec - bio_for_each_segment_all() will return single-page bvec too - during iterating, iterator variable(struct bvec_iter) is always updated in multi-page bvec style, and bvec_iter_advance() is kept not changed - returned(copied) single-page bvec is built in flight by bvec helpers from the stored multi-page bvec Reviewed-by: Omar Sandoval Signed-off-by: Ming Lei --- include/linux/bvec.h | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-) diff --git a/include/linux/bvec.h b/include/linux/bvec.h index 716a87b26a6a..babc6316c117 100644 --- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -23,6 +23,7 @@ #include #include #include +#include /* * was unsigned short, but we might as well be ready for > 64kB I/O pages @@ -50,16 +51,32 @@ struct bvec_iter { */ #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx]) -#define segment_iter_page(bvec, iter) \ +/* multi-page (segment) helpers */ +#define bvec_iter_page(bvec, iter) \ (__bvec_iter_bvec((bvec), (iter))->bv_page) -#define segment_iter_len(bvec, iter) \ +#define bvec_iter_len(bvec, iter) \ min((iter).bi_size, \ __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done) -#define segment_iter_offset(bvec, iter) \ +#define bvec_iter_offset(bvec, iter) \ (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done) +#define bvec_iter_page_idx(bvec, iter) \ + (bvec_iter_offset((bvec), (iter)) / PAGE_SIZE) + +/* For building single-page bvec(segment) in flight */ + #define segment_iter_offset(bvec, iter) \ + (bvec_iter_offset((bvec), (iter)) % PAGE_SIZE) + +#define segment_iter_len(bvec, iter) \ + min_t(unsigned, bvec_iter_len((bvec), (iter)), \ + PAGE_SIZE - segment_iter_offset((bvec), (iter))) + +#define segment_iter_page(bvec, iter) \ + nth_page(bvec_iter_page((bvec), (iter)), \ + bvec_iter_page_idx((bvec), (iter))) + #define segment_iter_bvec(bvec, iter) \ ((struct bio_vec) { \ .bv_page = segment_iter_page((bvec), (iter)), \ @@ -67,8 +84,6 @@ struct bvec_iter { .bv_offset = segment_iter_offset((bvec), (iter)), \ }) -#define bvec_iter_len segment_iter_len - static inline bool bvec_iter_advance(const struct bio_vec *bv, struct bvec_iter *iter, unsigned bytes) { -- 2.9.5