Some ->bi_end_io handlers (for example: pi_verify or decrypt handlers)
need to know original data vector, but after bio traverse io-stack it may
be advanced, splited and relocated many times so it is hard to guess
original iterator. Let's add 'bi_done' conter which accounts number
of bytes iterator was advanced during it's evolution. Later end_io handler
may easily restore original iterator by rewinding iterator to
iter->bi_done.
Note: this change makes sizeof (struct bvec_iter) multiple to 8
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
---
include/linux/bio.h | 21 +++++++++++++++++++--
include/linux/bvec.h | 27 +++++++++++++++++++++++++++
2 files changed, 46 insertions(+), 2 deletions(-)
diff --git a/include/linux/bio.h b/include/linux/bio.h
index 643ecba..ab812a0 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -166,9 +166,10 @@ static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
{
iter->bi_sector += bytes >> 9;
- if (bio_no_advance_iter(bio))
+ if (bio_no_advance_iter(bio)) {
iter->bi_size -= bytes;
- else {
+ iter->bi_done += bytes;
+ } else {
int err;
err = bvec_iter_advance(bio->bi_io_vec, iter, bytes);
@@ -176,6 +177,22 @@ static inline void bio_advance_iter(struct bio *bio, struct bvec_iter *iter,
}
}
+static inline int bio_rewind_iter(struct bio *bio, struct bvec_iter *iter,
+ unsigned int bytes)
+{
+ int err = 0;
+
+ iter->bi_sector -= bytes >> 9;
+
+ if (bio_no_advance_iter(bio)) {
+ iter->bi_size += bytes;
+ iter->bi_done -= bytes;
+ } else {
+ err = bvec_iter_rewind(bio->bi_io_vec, iter, bytes);
+ }
+ return err;
+}
+
#define __bio_for_each_segment(bvl, bio, iter, start) \
for (iter = (start); \
(iter).bi_size && \
diff --git a/include/linux/bvec.h b/include/linux/bvec.h
index 984a7a8..8cfe4d6 100644
--- a/include/linux/bvec.h
+++ b/include/linux/bvec.h
@@ -40,6 +40,8 @@ struct bvec_iter {
unsigned int bi_idx; /* current index into bvl_vec */
+ unsigned int bi_done; /* number of bytes completed */
+
unsigned int bi_bvec_done; /* number of bytes completed in
current bvec */
};
@@ -84,6 +86,7 @@ static inline int bvec_iter_advance(const struct bio_vec *bv,
bytes -= len;
iter->bi_size -= len;
iter->bi_bvec_done += len;
+ iter->bi_done += len;
if (iter->bi_bvec_done == __bvec_iter_bvec(bv, *iter)->bv_len) {
iter->bi_bvec_done = 0;
@@ -93,6 +96,30 @@ static inline int bvec_iter_advance(const struct bio_vec *bv,
return 0;
}
+static inline int bvec_iter_rewind(const struct bio_vec *bv,
+ struct bvec_iter *iter,
+ unsigned int bytes)
+{
+ while (bytes) {
+ unsigned len = min(bytes, iter->bi_bvec_done);
+
+ if (iter->bi_bvec_done == 0) {
+ if (WARN_ONCE(iter->bi_idx == 0,
+ "Attempted to rewind iter beyond "
+ "bvec's boundaries\n")) {
+ return -EINVAL;
+ }
+ iter->bi_idx--;
+ iter->bi_bvec_done = __bvec_iter_bvec(bv, *iter)->bv_len;
+ continue;
+ }
+ bytes -= len;
+ iter->bi_size += len;
+ iter->bi_bvec_done -= len;
+ }
+ return 0;
+}
+
#define for_each_bvec(bvl, bio_vec, iter, start) \
for (iter = (start); \
(iter).bi_size && \
--
2.9.3
