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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 V13 17/19] block: document usage of bio iterator helpers
Date: Fri, 11 Jan 2019 19:01:25 +0800	[thread overview]
Message-ID: <20190111110127.21664-18-ming.lei@redhat.com> (raw)
In-Reply-To: <20190111110127.21664-1-ming.lei@redhat.com>

Now multi-page bvec is supported, some helpers may return page by
page, meantime some may return segment by segment, this patch
documents the usage.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 Documentation/block/biovecs.txt | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/Documentation/block/biovecs.txt b/Documentation/block/biovecs.txt
index 25689584e6e0..ce6eccaf5df7 100644
--- a/Documentation/block/biovecs.txt
+++ b/Documentation/block/biovecs.txt
@@ -117,3 +117,28 @@ Other implications:
    size limitations and the limitations of the underlying devices. Thus
    there's no need to define ->merge_bvec_fn() callbacks for individual block
    drivers.
+
+Usage of helpers:
+=================
+
+* The following helpers whose names have the suffix of "_all" can only be used
+on non-BIO_CLONED bio. They are usually used by filesystem code. Drivers
+shouldn't use them because the bio may have been split before it reached the
+driver.
+
+	bio_for_each_segment_all()
+	bio_first_bvec_all()
+	bio_first_page_all()
+	bio_last_bvec_all()
+
+* The following helpers iterate over single-page segment. The passed 'struct
+bio_vec' will contain a single-page IO vector during the iteration
+
+	bio_for_each_segment()
+	bio_for_each_segment_all()
+
+* The following helpers iterate over multi-page bvec. The passed 'struct
+bio_vec' will contain a multi-page IO vector during the iteration
+
+	bio_for_each_bvec()
+	rq_for_each_bvec()
-- 
2.9.5


  parent reply	other threads:[~2019-01-11 11:07 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-11 11:01 [PATCH V13 00/19] block: support multi-page bvec Ming Lei
2019-01-11 11:01 ` [PATCH V13 01/19] btrfs: look at bi_size for repair decisions Ming Lei
2019-01-11 11:01 ` [PATCH V13 02/19] block: don't use bio->bi_vcnt to figure out segment number Ming Lei
2019-01-11 11:01 ` [PATCH V13 03/19] block: remove bvec_iter_rewind() Ming Lei
2019-01-11 11:01 ` [PATCH V13 04/19] block: rename bvec helpers Ming Lei
2019-01-11 11:01 ` [PATCH V13 05/19] block: introduce multi-page " Ming Lei
2019-01-11 11:01 ` [PATCH V13 06/19] block: introduce bio_for_each_bvec() and rq_for_each_bvec() Ming Lei
2019-01-11 11:01 ` [PATCH V13 07/19] block: use bio_for_each_bvec() to compute multi-page bvec count Ming Lei
2019-01-11 11:01 ` [PATCH V13 08/19] block: use bio_for_each_bvec() to map sg Ming Lei
2019-01-11 11:01 ` [PATCH V13 09/19] block: introduce bvec_last_segment() Ming Lei
2019-01-11 11:01 ` [PATCH V13 10/19] fs/buffer.c: use bvec iterator to truncate the bio Ming Lei
2019-01-11 11:01 ` [PATCH V13 11/19] btrfs: use bvec_last_segment to get bio's last page Ming Lei
2019-01-11 11:01 ` [PATCH V13 12/19] block: loop: pass multi-page bvec to iov_iter Ming Lei
2019-01-11 11:01 ` [PATCH V13 13/19] bcache: avoid to use bio_for_each_segment_all() in bch_bio_alloc_pages() Ming Lei
2019-01-11 11:01 ` [PATCH V13 14/19] block: allow bio_for_each_segment_all() to iterate over multi-page bvec Ming Lei
2019-01-11 11:01 ` [PATCH V13 15/19] block: enable multipage bvecs Ming Lei
2019-01-11 11:01 ` [PATCH V13 16/19] block: always define BIO_MAX_PAGES as 256 Ming Lei
2019-01-11 11:01 ` Ming Lei [this message]
2019-01-11 11:01 ` [PATCH V13 18/19] block: kill QUEUE_FLAG_NO_SG_MERGE Ming Lei
2019-01-11 11:01 ` [PATCH V13 19/19] block: kill BLK_MQ_F_SG_MERGE Ming Lei
2019-01-15  3:44 ` [PATCH V13 00/19] block: support multi-page bvec Jens Axboe

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