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,