On 21.11.18 г. 5:23 ч., Ming Lei wrote: > 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. > > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> > --- > Documentation/block/biovecs.txt | 24 ++++++++++++++++++++++++ > 1 file changed, 24 insertions(+) > > diff --git a/Documentation/block/biovecs.txt b/Documentation/block/biovecs.txt > index 25689584e6e0..bb008f7afb05 100644 > --- a/Documentation/block/biovecs.txt > +++ b/Documentation/block/biovecs.txt > @@ -117,3 +117,27 @@ 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 bvecs. 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 single-page bvecs. The passed 'struct > +bio_vec' will contain a single-page IO vector during the iteration > + > + bio_for_each_bvec() Just put this helper right below the above 2, no need to repeat the explanation. Also I'd suggest introducing another catch-all sentence "All other helpers are assumed to iterate multipage bio vecs" and perhaps give an example with 1-2 helpers. >
