Helper function to find the sector offset in a bio given bvec index
and page offset.
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
---
fs/bio.c | 34 ++++++++++++++++++++++++++++++++++
include/linux/bio.h | 1 +
2 files changed, 35 insertions(+), 0 deletions(-)
diff --git a/fs/bio.c b/fs/bio.c
index e56e768..55ee2fd 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -1300,6 +1300,40 @@ struct bio_pair *bio_split(struct bio *bi, mempool_t *pool, int first_sectors)
return bp;
}
+/**
+ * bio_sector_offset - Find hardware sector offset in bio
+ * @bio: bio to inspect
+ * @index: bio_vec index
+ * @offset: offset in bv_page
+ *
+ * Return the number of hardware sectors between beginning of bio
+ * and an end point indicated by a bio_vec index and an offset
+ * within that vector's page.
+ */
+sector_t bio_sector_offset(struct bio *bio, unsigned short index,
+ unsigned int offset)
+{
+ struct bio_vec *bv;
+ unsigned int sector_sz = bio->bi_bdev->bd_disk->queue->hardsect_size;
+ sector_t sectors;
+ int i;
+
+ sectors = 0;
+
+ BUG_ON(index >= bio->bi_vcnt);
+
+ bio_for_each_segment(bv, bio, i) {
+ if (i == index) {
+ if (offset > bv->bv_offset)
+ sectors += (offset - bv->bv_offset) / sector_sz;
+ return sectors;
+ }
+
+ sectors += bv->bv_len / sector_sz;
+ }
+
+ BUG();
+}
/*
* create memory pools for biovec's in a bio_set.
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 6aba97d..386a1df 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -327,6 +327,7 @@ 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);
extern int bio_get_nr_vecs(struct block_device *);
+extern sector_t bio_sector_offset(struct bio *, unsigned short, unsigned int);
extern struct bio *bio_map_user(struct request_queue *, struct block_device *,
unsigned long, unsigned int, int, gfp_t);
struct sg_iovec;
--
1.6.0.2
--
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