[v10,01/41] block: add bio_add_zone_append_page

Commit Message

Naohiro Aota Nov. 10, 2020, 11:26 a.m. UTC

From: Johannes Thumshirn <[e-mail]>

Add bio_add_zone_append_page(), a wrapper around bio_add_hw_page() which
is intended to be used by file systems that directly add pages to a bio
instead of using bio_iov_iter_get_pages().

Cc: Jens Axboe <[e-mail]>
Signed-off-by: Johannes Thumshirn <[e-mail]>
---
 block/bio.c         | 38 ++++++++++++++++++++++++++++++++++++++
 include/linux/bio.h |  2 ++
 2 files changed, 40 insertions(+)

Comments

Christoph Hellwig Nov. 10, 2020, 5:20 p.m. UTC | #1

> +int bio_add_zone_append_page(struct bio *bio, struct page *page,
> +			     unsigned int len, unsigned int offset)
> +{
> +	struct request_queue *q;
> +	bool same_page = false;
> +
> +	if (WARN_ON_ONCE(bio_op(bio) != REQ_OP_ZONE_APPEND))
> +		return 0;
> +
> +	if (WARN_ON_ONCE(!bio->bi_disk))
> +		return 0;

Do we need this check?  I'd rather just initialize q at declaration time
and let the NULL pointer deref be the obvious sign for a grave
programming error..

Except for that the patch looks good to me:

Reviewed-by: Christoph Hellwig <[e-mail]>

Johannes Thumshirn Nov. 11, 2020, 7:20 a.m. UTC | #2

On 10/11/2020 18:20, Christoph Hellwig wrote:
> Do we need this check?  I'd rather just initialize q at declaration time
> and let the NULL pointer deref be the obvious sign for a grave
> programming error..

I wanted to be a bit more gentle, but I don't mind the other way around
as well.

Patch

diff --git a/block/bio.c b/block/bio.c
index 58d765400226..c8943201c26c 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -853,6 +853,44 @@  int bio_add_pc_page(struct request_queue *q, struct bio *bio,
 }
 EXPORT_SYMBOL(bio_add_pc_page);
 
+/**
+ * bio_add_zone_append_page - attempt to add page to zone-append bio
+ * @bio: destination bio
+ * @page: page to add
+ * @len: vec entry length
+ * @offset: vec entry offset
+ *
+ * Attempt to add a page to the bio_vec maplist of a bio that will be submitted
+ * for a zone-append request. This can fail for a number of reasons, such as the
+ * bio being full or the target block device is not a zoned block device or
+ * other limitations of the target block device. The target block device must
+ * allow bio's up to PAGE_SIZE, so it is always possible to add a single page
+ * to an empty bio.
+ *
+ * Returns: number of bytes added to the bio, or 0 in case of a failure.
+ */
+int bio_add_zone_append_page(struct bio *bio, struct page *page,
+			     unsigned int len, unsigned int offset)
+{
+	struct request_queue *q;
+	bool same_page = false;
+
+	if (WARN_ON_ONCE(bio_op(bio) != REQ_OP_ZONE_APPEND))
+		return 0;
+
+	if (WARN_ON_ONCE(!bio->bi_disk))
+		return 0;
+
+	q = bio->bi_disk->queue;
+
+	if (WARN_ON_ONCE(!blk_queue_is_zoned(q)))
+		return 0;
+
+	return bio_add_hw_page(q, bio, page, len, offset,
+			       queue_max_zone_append_sectors(q), &same_page);
+}
+EXPORT_SYMBOL_GPL(bio_add_zone_append_page);
+
 /**
  * __bio_try_merge_page - try appending data to an existing bvec.
  * @bio: destination bio
diff --git a/include/linux/bio.h b/include/linux/bio.h
index c6d765382926..7ef300cb4e9a 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -442,6 +442,8 @@  void bio_chain(struct bio *, struct bio *);
 extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
 extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
 			   unsigned int, unsigned int);
+int bio_add_zone_append_page(struct bio *bio, struct page *page,
+			     unsigned int len, unsigned int offset);
 bool __bio_try_merge_page(struct bio *bio, struct page *page,
 		unsigned int len, unsigned int off, bool *same_page);
 void __bio_add_page(struct bio *bio, struct page *page,