Re: [PATCH 10/25] loop: zero-fill bio on the submitting cpu

[Ming Lei]

On Thu, Apr 06, 2017 at 05:39:29PM +0200, Christoph Hellwig wrote:
> 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 
> ---
>  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 cc981f34e017..6924ec611a49 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,
> @@ -1686,8 +1681,10 @@ 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)
> @@ -1713,6 +1710,7 @@ 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;
>  };

Reviewed-by: Ming Lei 

Thanks,
Ming

[PATCH 10/25] loop: zero-fill bio on the submitting cpu

[Christoph Hellwig]

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 
---
 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 cc981f34e017..6924ec611a49 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,
@@ -1686,8 +1681,10 @@ 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)
@@ -1713,6 +1710,7 @@ 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