diff mbox series

[V11,17/19] block: document usage of bio iterator helpers

Message ID 20181121032327.8434-18-ming.lei@redhat.com (mailing list archive)
State New, archived
Headers show
Series block: support multi-page bvec | expand

Commit Message

Ming Lei Nov. 21, 2018, 3:23 a.m. UTC
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@redhat.com>
---
 Documentation/block/biovecs.txt | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

Comments

Nikolay Borisov Nov. 21, 2018, 7:45 a.m. UTC | #1
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@redhat.com>
> ---
>  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.

>
Christoph Hellwig Nov. 21, 2018, 2:34 p.m. UTC | #2
On Wed, Nov 21, 2018 at 09:45:25AM +0200, Nikolay Borisov wrote:
> > +	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.

Well, I think the second explanation is wrong - bio_for_each_bvec
iterates over the whole bvecs, not just single page.
diff mbox series

Patch

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()