Jianchao, > Discard command supports multiple ranges of blocks, so needn't > checking position contiguity when merging. Let's do the same thing > in attempt_merge as the blk_try_merge. Discards need to be contiguous unless queue->limits.max_discard_segments is bigger than 1. So if you remove this I think you need to add a contiguity check in req_attempt_discard_merge(). -- Martin K. Petersen Oracle Linux Engineering