On 5/20/24 05:41, Christoph Hellwig wrote:
On Fri, May 10, 2024 at 01:23:13PM -0700, Bart Van Assche wrote:
Both nbd_send_cmd() and nbd_handle_cmd() return either a negative error
number or a positive blk_status_t value.
Eww. Please split these into separate values instead. There is a reason
why blk_status_t is a separate type with sparse checks, and drivers
really shouldn't do avoid with that for a tiny micro-optimization of
the calling convention (if this even is one and not just the driver
being sloppy).
How about the (untested) patch below?
Thanks,
Bart.
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 22a79a62cc4e..4ee76c39e3a5 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -588,11 +588,17 @@ static inline int was_interrupted(int result)
return result == -ERESTARTSYS || result == -EINTR;
}
+struct send_res {
+ int result;
+ blk_status_t status;
+};
+
/*
* Returns BLK_STS_RESOURCE if the caller should retry after a delay. Returns
* -EAGAIN if the caller should requeue @cmd. Returns -EIO if sending failed.
*/
-static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
+static struct send_res nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd,
+ int index)
{
struct request *req = blk_mq_rq_from_pdu(cmd);
struct nbd_config *config = nbd->config;
@@ -614,13 +620,13 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
type = req_to_nbd_cmd_type(req);
if (type == U32_MAX)
- return -EIO;
+ return (struct send_res){ .result = -EIO };
if (rq_data_dir(req) == WRITE &&
(config->flags & NBD_FLAG_READ_ONLY)) {
dev_err_ratelimited(disk_to_dev(nbd->disk),
"Write on read-only\n");
- return -EIO;
+ return (struct send_res){ .result = -EIO };
}
if (req->cmd_flags & REQ_FUA)
@@ -674,11 +680,11 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
nsock->sent = sent;
}
set_bit(NBD_CMD_REQUEUED, &cmd->flags);
- return (__force int)BLK_STS_RESOURCE;
+ return (struct send_res){ .status = BLK_STS_RESOURCE };
}
dev_err_ratelimited(disk_to_dev(nbd->disk),
"Send control failed (result %d)\n", result);
- return -EAGAIN;
+ return (struct send_res){ .result = -EAGAIN };
}
send_pages:
if (type != NBD_CMD_WRITE)
@@ -715,12 +721,14 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
nsock->pending = req;
nsock->sent = sent;
set_bit(NBD_CMD_REQUEUED, &cmd->flags);
- return (__force int)BLK_STS_RESOURCE;
+ return (struct send_res){
+ .status = BLK_STS_RESOURCE
+ };
}
dev_err(disk_to_dev(nbd->disk),
"Send data failed (result %d)\n",
result);
- return -EAGAIN;
+ return (struct send_res){ .result = -EAGAIN };
}
/*
* The completion might already have come in,
@@ -737,7 +745,7 @@ static int nbd_send_cmd(struct nbd_device *nbd, struct nbd_cmd *cmd, int index)
trace_nbd_payload_sent(req, handle);
nsock->pending = NULL;
nsock->sent = 0;
- return 0;
+ return (struct send_res){};
}
static int nbd_read_reply(struct nbd_device *nbd, struct socket *sock,
@@ -1018,7 +1026,8 @@ static blk_status_t nbd_handle_cmd(struct nbd_cmd *cmd, int index)
struct nbd_device *nbd = cmd->nbd;
struct nbd_config *config;
struct nbd_sock *nsock;
- int ret;
+ struct send_res send_res;
+ blk_status_t ret;
lockdep_assert_held(&cmd->lock);
@@ -1076,14 +1085,15 @@ static blk_status_t nbd_handle_cmd(struct nbd_cmd *cmd, int index)
* Some failures are related to the link going down, so anything that
* returns EAGAIN can be retried on a different socket.
*/
- ret = nbd_send_cmd(nbd, cmd, index);
- /*
- * Access to this flag is protected by cmd->lock, thus it's safe to set
- * the flag after nbd_send_cmd() succeed to send request to server.
- */
- if (!ret)
+ send_res = nbd_send_cmd(nbd, cmd, index);
+ ret = send_res.result < 0 ? BLK_STS_IOERR : send_res.status;
+ if (ret == BLK_STS_OK) {
+ /*
+ * cmd->lock is held. Hence, it's safe to set this flag after
+ * nbd_send_cmd() succeeded sending the request to the server.
+ */
__set_bit(NBD_CMD_INFLIGHT, &cmd->flags);
- else if (ret == -EAGAIN) {
+ } else if (send_res.result == -EAGAIN) {
dev_err_ratelimited(disk_to_dev(nbd->disk),
"Request send failed, requeueing\n");
nbd_mark_nsock_dead(nbd, nsock, 1);
@@ -1093,7 +1103,7 @@ static blk_status_t nbd_handle_cmd(struct nbd_cmd *cmd, int index)
out:
mutex_unlock(&nsock->tx_lock);
nbd_config_put(nbd);
- return ret < 0 ? BLK_STS_IOERR : (__force blk_status_t)ret;
+ return ret;
}
static blk_status_t nbd_queue_rq(struct blk_mq_hw_ctx *hctx,
