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, 5 insertions, 4 deletions

diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index d946e1eeac8e..e6b81d370882 100644
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -229,11 +229,11 @@ static void end_cmd(struct nullb_cmd *cmd)
 
 	switch (queue_mode)  {
 	case NULL_Q_MQ:
-		blk_mq_end_request(cmd->rq, 0);
+		blk_mq_end_request(cmd->rq, BLK_STS_OK);
 		return;
 	case NULL_Q_RQ:
 		INIT_LIST_HEAD(&cmd->rq->queuelist);
-		blk_end_request_all(cmd->rq, 0);
+		blk_end_request_all(cmd->rq, BLK_STS_OK);
 		break;
 	case NULL_Q_BIO:
 		bio_endio(cmd->bio);
@@ -422,11 +422,12 @@ static void cleanup_queues(struct nullb *nullb)
 
 #ifdef CONFIG_NVM
 
-static void null_lnvm_end_io(struct request *rq, int error)
+static void null_lnvm_end_io(struct request *rq, blk_status_t status)
 {
 	struct nvm_rq *rqd = rq->end_io_data;
 
-	rqd->error = error;
+	/* XXX: lighnvm core seems to expect NVM_RSP_* values here.. */
+	rqd->error = status ? -EIO : 0;
 	nvm_end_io(rqd);
 
 	blk_put_request(rq);