Re: [PATCH 01/33] block: add a lower-level bio_add_page interface

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/bio.c         | 87 ++++++++++++++++++++++++++++++---------------
 include/linux/bio.h |  9 +++++
 2 files changed, 67 insertions(+), 29 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index 53e0f0a1ed94..6ceba6adbf42 100644
--- a/block/bio.c
+++ b/block/bio.c

@@ -773,7 +773,7 @@ int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page
                        return 0;
        }

-       if (bio->bi_vcnt >= bio->bi_max_vecs)
+       if (bio_full(bio))
                return 0;

        /*

@@ -820,6 +820,59 @@ int bio_add_pc_page(struct request_queue *q, struct bio *bio, struct page
 }
 EXPORT_SYMBOL(bio_add_pc_page);

+/**
+ * __bio_try_merge_page - try adding data to an existing bvec
+ * @bio: destination bio
+ * @page: page to add
+ * @len: length of the range to add
+ * @off: offset into @page
+ *
+ * Try adding the data described at @page + @offset to the last bvec of @bio.
+ * Return %true on success or %false on failure.  This can happen frequently
+ * for file systems with a block size smaller than the page size.
+ */
+bool __bio_try_merge_page(struct bio *bio, struct page *page,
+               unsigned int len, unsigned int off)
+{
+       if (bio->bi_vcnt > 0) {
+               struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt - 1];
+
+               if (page == bv->bv_page && off == bv->bv_offset + bv->bv_len) {
+                       bv->bv_len += len;
+                       bio->bi_iter.bi_size += len;
+                       return true;
+               }
+       }
+       return false;
+}
+EXPORT_SYMBOL_GPL(__bio_try_merge_page);
+
+/**
+ * __bio_add_page - add page to a bio in a new segment
+ * @bio: destination bio
+ * @page: page to add
+ * @len: length of the range to add
+ * @off: offset into @page
+ *
+ * Add the data at @page + @offset to @bio as a new bvec.  The caller must
+ * ensure that @bio has space for another bvec.
+ */
+void __bio_add_page(struct bio *bio, struct page *page,
+               unsigned int len, unsigned int off)
+{
+       struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt];
+
+       WARN_ON_ONCE(bio_full(bio));
+
+       bv->bv_page = page;
+       bv->bv_offset = off;
+       bv->bv_len = len;
+
+       bio->bi_iter.bi_size += len;
+       bio->bi_vcnt++;
+}
+EXPORT_SYMBOL_GPL(__bio_add_page);