block/sd: Return -EREMOTEIO when WRITE SAME and DISCARD are disabled

When a storage device rejects a WRITE SAME command we will disable write
same functionality for the device and return -EREMOTEIO to the block
layer. -EREMOTEIO will in turn prevent DM from retrying the I/O and/or
failing the path.

Yiwen Jiang discovered a small race where WRITE SAME requests issued
simultaneously would cause -EIO to be returned. This happened because
any requests being prepared after WRITE SAME had been disabled for the
device caused us to return BLKPREP_KILL. The latter caused the block
layer to return -EIO upon completion.

To overcome this we introduce BLKPREP_INVALID which indicates that this
is an invalid request for the device. blk_peek_request() is modified to
return -EREMOTEIO in that case.

Reported-by: Yiwen Jiang <jiangyiwen@huawei.com>
Suggested-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Hannes Reinicke <hare@suse.de>
Reviewed-by: Ewan Milne <emilne@redhat.com>
Reviewed-by: Yiwen Jiang <jiangyiwen@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 476244d59309..35607dd0223b 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2447,14 +2447,16 @@ struct request *blk_peek_request(struct request_queue *q)
 
                         rq = NULL;
                         break;
-                } else if (ret == BLKPREP_KILL) {
+                } else if (ret == BLKPREP_KILL || ret == BLKPREP_INVALID) {
+                        int err = (ret == BLKPREP_INVALID) ? -EREMOTEIO : -EIO;
+
                         rq->cmd_flags |= REQ_QUIET;
                         /*
                          * Mark this request as started so we don't trigger
                          * any debug logic in the end I/O path.
                          */
                         blk_start_request(rq);
-                        __blk_end_request_all(rq, -EIO);
+                        __blk_end_request_all(rq, err);
                 } else {
                         printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
                         break;