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Date: Fri, 15 Feb 2019 19:13:10 +0800 From: Ming Lei <ming.lei@...hat.com> To: Jens Axboe <axboe@...nel.dk> Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, Theodore Ts'o <tytso@....edu>, Omar Sandoval <osandov@...com>, Sagi Grimberg <sagi@...mberg.me>, Dave Chinner <dchinner@...hat.com>, Kent Overstreet <kent.overstreet@...il.com>, Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com, Alexander Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org, linux-raid@...r.kernel.org, David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org, "Darrick J . Wong" <darrick.wong@...cle.com>, linux-xfs@...r.kernel.org, Gao Xiang <gaoxiang25@...wei.com>, Christoph Hellwig <hch@....de>, linux-ext4@...r.kernel.org, Coly Li <colyli@...e.de>, linux-bcache@...r.kernel.org, Boaz Harrosh <ooo@...ctrozaur.com>, Bob Peterson <rpeterso@...hat.com>, cluster-devel@...hat.com, Ming Lei <ming.lei@...hat.com> Subject: [PATCH V15 04/18] block: introduce multi-page bvec helpers This patch introduces helpers of 'mp_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: Christoph Hellwig <hch@....de> Reviewed-by: Omar Sandoval <osandov@...com> Signed-off-by: Ming Lei <ming.lei@...hat.com> --- include/linux/bvec.h | 30 +++++++++++++++++++++++++++--- 1 file changed, 27 insertions(+), 3 deletions(-) diff --git a/include/linux/bvec.h b/include/linux/bvec.h index ba0ae40e77c9..0ae729b1c9fe 100644 --- a/include/linux/bvec.h +++ b/include/linux/bvec.h @@ -23,6 +23,7 @@ #include <linux/kernel.h> #include <linux/bug.h> #include <linux/errno.h> +#include <linux/mm.h> /* * was unsigned short, but we might as well be ready for > 64kB I/O pages @@ -50,16 +51,39 @@ struct bvec_iter { */ #define __bvec_iter_bvec(bvec, iter) (&(bvec)[(iter).bi_idx]) -#define bvec_iter_page(bvec, iter) \ +/* multi-page (mp_bvec) helpers */ +#define mp_bvec_iter_page(bvec, iter) \ (__bvec_iter_bvec((bvec), (iter))->bv_page) -#define bvec_iter_len(bvec, iter) \ +#define mp_bvec_iter_len(bvec, iter) \ min((iter).bi_size, \ __bvec_iter_bvec((bvec), (iter))->bv_len - (iter).bi_bvec_done) -#define bvec_iter_offset(bvec, iter) \ +#define mp_bvec_iter_offset(bvec, iter) \ (__bvec_iter_bvec((bvec), (iter))->bv_offset + (iter).bi_bvec_done) +#define mp_bvec_iter_page_idx(bvec, iter) \ + (mp_bvec_iter_offset((bvec), (iter)) / PAGE_SIZE) + +#define mp_bvec_iter_bvec(bvec, iter) \ +((struct bio_vec) { \ + .bv_page = mp_bvec_iter_page((bvec), (iter)), \ + .bv_len = mp_bvec_iter_len((bvec), (iter)), \ + .bv_offset = mp_bvec_iter_offset((bvec), (iter)), \ +}) + +/* For building single-page bvec in flight */ + #define bvec_iter_offset(bvec, iter) \ + (mp_bvec_iter_offset((bvec), (iter)) % PAGE_SIZE) + +#define bvec_iter_len(bvec, iter) \ + min_t(unsigned, mp_bvec_iter_len((bvec), (iter)), \ + PAGE_SIZE - bvec_iter_offset((bvec), (iter))) + +#define bvec_iter_page(bvec, iter) \ + nth_page(mp_bvec_iter_page((bvec), (iter)), \ + mp_bvec_iter_page_idx((bvec), (iter))) + #define bvec_iter_bvec(bvec, iter) \ ((struct bio_vec) { \ .bv_page = bvec_iter_page((bvec), (iter)), \ -- 2.9.5
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