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block: loop: pass multi-page bvec to iov_iter 

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.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2019-02-15 19:13:17 +08:00 committed by Jens Axboe
parent c3a7ce7380
commit 86af5952a8
1 changed files with 11 additions and 11 deletions
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22
drivers/block/loop.c
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@ -511,21 +511,22 @@ 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;
if (rq->bio != rq->biotail) {
struct req_iterator iter;
struct bio_vec tmp;
rq_for_each_bvec(tmp, rq, rq_iter)
nr_bvec++;
__rq_for_each_bio(bio, rq)
segments += bio_segments(bio);
bvec = kmalloc_array(segments, sizeof(struct bio_vec),
if (rq->bio != rq->biotail) {
bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec),
GFP_NOIO);
if (!bvec)
return -EIO;
@ -534,10 +535,10 @@ 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++;
}
@ -551,11 +552,10 @@ 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(&cmd->ref, 2);
iov_iter_bvec(&iter, rw, bvec, segments, blk_rq_bytes(rq));
iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));
iter.iov_offset = offset;
cmd->iocb.ki_pos = pos;