Commit ac4fa1d1 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe

block: document usage of bio iterator helpers

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: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 68614289
...@@ -117,3 +117,28 @@ Other implications: ...@@ -117,3 +117,28 @@ Other implications:
size limitations and the limitations of the underlying devices. Thus size limitations and the limitations of the underlying devices. Thus
there's no need to define ->merge_bvec_fn() callbacks for individual block there's no need to define ->merge_bvec_fn() callbacks for individual block
drivers. 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()
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment