block: introduce new block status code type

Currently we use nornal Linux errno values in the block layer, and while
we accept any error a few have overloaded magic meanings.  This patch
instead introduces a new  blk_status_t value that holds block layer specific
status codes and explicitly explains their meaning.  Helpers to convert from
and to the previous special meanings are provided for now, but I suspect
we want to get rid of them in the long run - those drivers that have a
errno input (e.g. networking) usually get errnos that don't know about
the special block layer overloads, and similarly returning them to userspace
will usually return somethings that strictly speaking isn't correct
for file system operations, but that's left as an exercise for later.

For now the set of errors is a very limited set that closely corresponds
to the previous overloaded errno values, but there is some low hanging
fruite to improve it.

blk_status_t (ab)uses the sparse __bitwise annotations to allow for sparse
typechecking, so that we can easily catch places passing the wrong values.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 7 insertions, 7 deletions

diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c
index 6de9f9943a0e..978d2d2d08d6 100644
--- a/drivers/block/nbd.c
+++ b/drivers/block/nbd.c
@@ -116,7 +116,7 @@ struct nbd_cmd {
 	int index;
 	int cookie;
 	struct completion send_complete;
-	int status;
+	blk_status_t status;
 };
 
 #if IS_ENABLED(CONFIG_DEBUG_FS)
@@ -286,7 +286,7 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
 	struct nbd_config *config;
 
 	if (!refcount_inc_not_zero(&nbd->config_refs)) {
-		cmd->status = -EIO;
+		cmd->status = BLK_STS_TIMEOUT;
 		return BLK_EH_HANDLED;
 	}
 
@@ -331,7 +331,7 @@ static enum blk_eh_timer_return nbd_xmit_timeout(struct request *req,
 				    "Connection timed out\n");
 	}
 	set_bit(NBD_TIMEDOUT, &config->runtime_flags);
-	cmd->status = -EIO;
+	cmd->status = BLK_STS_IOERR;
 	sock_shutdown(nbd);
 	nbd_config_put(nbd);
 
@@ -578,7 +578,7 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
 	if (ntohl(reply.error)) {
 		dev_err(disk_to_dev(nbd->disk), "Other side returned error (%d)\n",
 			ntohl(reply.error));
-		cmd->status = -EIO;
+		cmd->status = BLK_STS_IOERR;
 		return cmd;
 	}
 
@@ -603,7 +603,7 @@ static struct nbd_cmd *nbd_read_stat(struct nbd_device *nbd, int index)
 				 */
 				if (nbd_disconnected(config) ||
 				    config->num_connections <= 1) {
-					cmd->status = -EIO;
+					cmd->status = BLK_STS_IOERR;
 					return cmd;
 				}
 				return ERR_PTR(-EIO);
@@ -655,7 +655,7 @@ static void nbd_clear_req(struct request *req, void *data, bool reserved)
 	if (!blk_mq_request_started(req))
 		return;
 	cmd = blk_mq_rq_to_pdu(req);
-	cmd->status = -EIO;
+	cmd->status = BLK_STS_IOERR;
 	blk_mq_complete_request(req);
 }
 
@@ -744,7 +744,7 @@ static int nbd_handle_cmd(struct nbd_cmd *cmd, int index)
 		nbd_config_put(nbd);
 		return -EINVAL;
 	}
-	cmd->status = 0;
+	cmd->status = BLK_STS_OK;
 again:
 	nsock = config->socks[index];
 	mutex_lock(&nsock->tx_lock);