[PATCH V15 16/18] block: document usage of bio iterator helpers
From: Ming Lei <hidden>
Date: 2019-02-15 11:17:57
Also in:
dm-devel, linux-bcache, linux-block, linux-btrfs, linux-ext4, linux-fsdevel, linux-mm, linux-xfs, lkml
Subsystem:
block layer, documentation, the rest · Maintainers:
Jens Axboe, Jonathan Corbet, Linus Torvalds
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 <redacted> Signed-off-by: Ming Lei <redacted> --- 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