[PATCH V4 22/45] block: introduce segment_last_page()

Ming Lei
2017-12-18T12:28:54Z

BTRFS and guard_bio_eod() need to get the last page from one segment, so
introduce this helper to make them happy.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
include/linux/bvec.h | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)

diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 84c395feed49..217afcd83a15 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -219,4 +219,26 @@ static inline bool bvec_iter_seg_advance(const struct bio_vec *bv,
.bi_bvec_done = 0, \
}

+/* get the last page from the multipage bvec and store it in @pg */
+static inline void segment_last_page(const struct bio_vec *seg,
+ struct bio_vec *pg)
+{
+ unsigned total = seg->bv_offset + seg->bv_len;
+ unsigned last_page = total / PAGE_SIZE;
+
+ if (last_page * PAGE_SIZE == total)
+ last_page--;
+
+ pg->bv_page = nth_page(seg->bv_page, last_page);
+
+ /* the whole segment is inside the last page */
+ if (seg->bv_offset >= last_page * PAGE_SIZE) {
+ pg->bv_offset = seg->bv_offset % PAGE_SIZE;
+ pg->bv_len = seg->bv_len;
+ } else {
+ pg->bv_offset = 0;
+ pg->bv_len = total - last_page * PAGE_SIZE;
+ }
+}
+
#endif /* __LINUX_BVEC_ITER_H */
--
2.9.5