Re: [Cluster-devel] [PATCH V11 10/19] block: loop: pass multi-page bvec to iov_iter

2018-11-21 Thread Christoph Hellwig
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 1ad6eafc43f2..a281b6737b61 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -805,6 +805,10 @@ struct req_iterator {
>   __rq_for_each_bio(_iter.bio, _rq)   \
>   bio_for_each_segment(bvl, _iter.bio, _iter.iter)
>  
> +#define rq_for_each_bvec(bvl, _rq, _iter)\
> + __rq_for_each_bio(_iter.bio, _rq)   \
> + bio_for_each_bvec(bvl, _iter.bio, _iter.iter)
> +

I think this should go into the patch adding bio_for_each_bvec and
friends.

Otherwise looks fine:

Reviewed-by: Christoph Hellwig 



[Cluster-devel] [PATCH V11 10/19] block: loop: pass multi-page bvec to iov_iter

2018-11-20 Thread Ming Lei
iov_iter is implemented on bvec itererator helpers, so it is safe to pass
multi-page bvec to it, and this way is much more efficient than passing one
page in each bvec.

Signed-off-by: Ming Lei 
---
 drivers/block/loop.c   | 20 ++--
 include/linux/blkdev.h |  4 
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 176ab1f28eca..e3683211f12d 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -510,21 +510,22 @@ static int lo_rw_aio(struct loop_device *lo, struct 
loop_cmd *cmd,
 loff_t pos, bool rw)
 {
struct iov_iter iter;
+   struct req_iterator rq_iter;
struct bio_vec *bvec;
struct request *rq = blk_mq_rq_from_pdu(cmd);
struct bio *bio = rq->bio;
struct file *file = lo->lo_backing_file;
+   struct bio_vec tmp;
unsigned int offset;
-   int segments = 0;
+   int nr_bvec = 0;
int ret;
 
+   rq_for_each_bvec(tmp, rq, rq_iter)
+   nr_bvec++;
+
if (rq->bio != rq->biotail) {
-   struct req_iterator iter;
-   struct bio_vec tmp;
 
-   __rq_for_each_bio(bio, rq)
-   segments += bio_segments(bio);
-   bvec = kmalloc_array(segments, sizeof(struct bio_vec),
+   bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec),
 GFP_NOIO);
if (!bvec)
return -EIO;
@@ -533,10 +534,10 @@ static int lo_rw_aio(struct loop_device *lo, struct 
loop_cmd *cmd,
/*
 * The bios of the request may be started from the middle of
 * the 'bvec' because of bio splitting, so we can't directly
-* copy bio->bi_iov_vec to new bvec. The rq_for_each_segment
+* copy bio->bi_iov_vec to new bvec. The rq_for_each_bvec
 * API will take care of all details for us.
 */
-   rq_for_each_segment(tmp, rq, iter) {
+   rq_for_each_bvec(tmp, rq, rq_iter) {
*bvec = tmp;
bvec++;
}
@@ -550,11 +551,10 @@ static int lo_rw_aio(struct loop_device *lo, struct 
loop_cmd *cmd,
 */
offset = bio->bi_iter.bi_bvec_done;
bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
-   segments = bio_segments(bio);
}
atomic_set(>ref, 2);
 
-   iov_iter_bvec(, rw, bvec, segments, blk_rq_bytes(rq));
+   iov_iter_bvec(, rw, bvec, nr_bvec, blk_rq_bytes(rq));
iter.iov_offset = offset;
 
cmd->iocb.ki_pos = pos;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 1ad6eafc43f2..a281b6737b61 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -805,6 +805,10 @@ struct req_iterator {
__rq_for_each_bio(_iter.bio, _rq)   \
bio_for_each_segment(bvl, _iter.bio, _iter.iter)
 
+#define rq_for_each_bvec(bvl, _rq, _iter)  \
+   __rq_for_each_bio(_iter.bio, _rq)   \
+   bio_for_each_bvec(bvl, _iter.bio, _iter.iter)
+
 #define rq_iter_last(bvec, _iter)  \
(_iter.bio->bi_next == NULL &&  \
 bio_iter_last(bvec, _iter.iter))
-- 
2.9.5