[PATCH V6 08/30] block: introduce chunk_last_segment()

Ming Lei
2018-06-09T12:29:52Z

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

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
include/linux/bvec.h | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 9e082d023392..aac75d87d884 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -219,4 +219,29 @@ static inline bool bvec_iter_chunk_advance(const struct bio_vec *bv,
.bi_bvec_done = 0, \
}

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