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From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, Theodore Ts'o <tytso@mit.edu>,
	Omar Sandoval <osandov@fb.com>, Sagi Grimberg <sagi@grimberg.me>,
	Dave Chinner <dchinner@redhat.com>,
	Kent Overstreet <kent.overstreet@gmail.com>,
	Mike Snitzer <snitzer@redhat.com>,
	dm-devel@redhat.com, Alexander Viro <viro@zeniv.linux.org.uk>,
	linux-fsdevel@vger.kernel.org, linux-raid@vger.kernel.org,
	David Sterba <dsterba@suse.com>,
	linux-btrfs@vger.kernel.org,
	"Darrick J . Wong" <darrick.wong@oracle.com>,
	linux-xfs@vger.kernel.org, Gao Xiang <gaoxiang25@huawei.com>,
	Christoph Hellwig <hch@lst.de>,
	linux-ext4@vger.kernel.org, Coly Li <colyli@suse.de>,
	linux-bcache@vger.kernel.org, Boaz Harrosh <ooo@electrozaur.com>,
	Bob Peterson <rpeterso@redhat.com>,
	cluster-devel@redhat.com, Ming Lei <ming.lei@redhat.com>
Subject: [PATCH V14 04/18] block: introduce multi-page bvec helpers
Date: Mon, 21 Jan 2019 16:17:51 +0800
Message-ID: <20190121081805.32727-5-ming.lei@redhat.com> (raw)
In-Reply-To: <20190121081805.32727-1-ming.lei@redhat.com>

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@lst.de>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Ming Lei <ming.lei@redhat.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


  parent reply index

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-21  8:17 [PATCH V14 00/18] block: support multi-page bvec Ming Lei
2019-01-21  8:17 ` [PATCH V14 01/18] btrfs: look at bi_size for repair decisions Ming Lei
2019-01-21  8:17 ` [PATCH V14 02/18] block: don't use bio->bi_vcnt to figure out segment number Ming Lei
2019-01-21  8:17 ` [PATCH V14 03/18] block: remove bvec_iter_rewind() Ming Lei
2019-01-21  8:17 ` Ming Lei [this message]
2019-01-21  8:17 ` [PATCH V14 05/18] block: introduce bio_for_each_mp_bvec() and rq_for_each_mp_bvec() Ming Lei
2019-01-21  8:17 ` [PATCH V14 06/18] block: use bio_for_each_mp_bvec() to compute multi-page bvec count Ming Lei
2019-01-21  8:17 ` [PATCH V14 07/18] block: use bio_for_each_mp_bvec() to map sg Ming Lei
2019-01-21  8:17 ` [PATCH V14 08/18] block: introduce mp_bvec_last_segment() Ming Lei
2019-01-21  8:17 ` [PATCH V14 09/18] fs/buffer.c: use bvec iterator to truncate the bio Ming Lei
2019-01-21  8:17 ` [PATCH V14 10/18] btrfs: use mp_bvec_last_segment to get bio's last page Ming Lei
2019-01-21  8:17 ` [PATCH V14 11/18] block: loop: pass multi-page bvec to iov_iter Ming Lei
2019-01-21  8:17 ` [PATCH V14 12/18] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages() Ming Lei
2019-01-21  8:18 ` [PATCH V14 13/18] block: allow bio_for_each_segment_all() to iterate over multi-page bvec Ming Lei
2019-01-21  8:18 ` [PATCH V14 14/18] block: enable multipage bvecs Ming Lei
2019-01-21  8:18 ` [PATCH V14 15/18] block: always define BIO_MAX_PAGES as 256 Ming Lei
2019-01-21  8:18 ` [PATCH V14 16/18] block: document usage of bio iterator helpers Ming Lei
2019-01-21  8:18 ` [PATCH V14 17/18] block: kill QUEUE_FLAG_NO_SG_MERGE Ming Lei
2019-01-21  8:18 ` [PATCH V14 18/18] block: kill BLK_MQ_F_SG_MERGE Ming Lei
2019-01-21  8:22 ` [PATCH V14 00/18] block: support multi-page bvec Christoph Hellwig
2019-01-21  8:37   ` Ming Lei
2019-01-21  8:38     ` Christoph Hellwig
2019-01-21  8:40       ` Ming Lei
2019-01-21  9:43 ` Sagi Grimberg
2019-01-22  2:01   ` Ming Lei

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