[PATCH 09/23] loop: zero-fill bio on the submitting cpu

Christoph Hellwig
2017-04-20T14:03:02Z

In thruth I've just audited which blk-mq drivers don't currently have a
complete callback, but I think this change is at least borderline useful.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
---
drivers/block/loop.c | 30 ++++++++++++++----------------
drivers/block/loop.h | 1 +
2 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 3081d83d2ea3..86351b3f7350 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -445,32 +445,27 @@ static int lo_req_flush(struct loop_device *lo, struct request *rq)
return ret;
}

-static inline void handle_partial_read(struct loop_cmd *cmd, long bytes)
+static void lo_complete_rq(struct request *rq)
{
- if (bytes < 0 || op_is_write(req_op(cmd->rq)))
- return;
+ struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);

- if (unlikely(bytes < blk_rq_bytes(cmd->rq))) {
+ if (unlikely(req_op(cmd->rq) == REQ_OP_READ && cmd->use_aio &&
+ cmd->ret >= 0 && cmd->ret < blk_rq_bytes(cmd->rq))) {
struct bio *bio = cmd->rq->bio;

- bio_advance(bio, bytes);
+ bio_advance(bio, cmd->ret);
zero_fill_bio(bio);
}
+
+ blk_mq_end_request(rq, cmd->ret < 0 ? -EIO : 0);
}

static void lo_rw_aio_complete(struct kiocb *iocb, long ret, long ret2)
{
struct loop_cmd *cmd = container_of(iocb, struct loop_cmd, iocb);
- struct request *rq = cmd->rq;
-
- handle_partial_read(cmd, ret);

- if (ret > 0)
- ret = 0;
- else if (ret < 0)
- ret = -EIO;
-
- blk_mq_complete_request(rq, ret);
+ cmd->ret = ret;
+ blk_mq_complete_request(cmd->rq, 0);
}

static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
@@ -1688,8 +1683,10 @@ static void loop_handle_cmd(struct loop_cmd *cmd)
ret = do_req_filebacked(lo, cmd->rq);
failed:
/* complete non-aio request */
- if (!cmd->use_aio || ret)
- blk_mq_complete_request(cmd->rq, ret ? -EIO : 0);
+ if (!cmd->use_aio || ret) {
+ cmd->ret = ret ? -EIO : 0;
+ blk_mq_complete_request(cmd->rq, 0);
+ }
}

static void loop_queue_work(struct kthread_work *work)
@@ -1715,6 +1712,7 @@ static int loop_init_request(void *data, struct request *rq,
static const struct blk_mq_ops loop_mq_ops = {
.queue_rq = loop_queue_rq,
.init_request = loop_init_request,
+ .complete = lo_complete_rq,
};

static int loop_add(struct loop_device **l, int i)
diff --git a/drivers/block/loop.h b/drivers/block/loop.h
index fb2237c73e61..fecd3f97ef8c 100644
--- a/drivers/block/loop.h
+++ b/drivers/block/loop.h
@@ -70,6 +70,7 @@ struct loop_cmd {
struct request *rq;
struct list_head list;
bool use_aio; /* use AIO interface to handle I/O */
+ long ret;
struct kiocb iocb;
};

--
2.11.0