NVMe: Reduce maximum queue depth by 1

The spec says we're not allowed to completely fill the submission queue.
Solve this by reducing the number of allocatable cmdids by 1.

Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>

diff --git a/drivers/block/nvme.c b/drivers/block/nvme.c
index 562d75a..45bfae1 100644 (file)
--- a/drivers/block/nvme.c
+++ b/drivers/block/nvme.c
@@ -156,7 +156,7 @@ static struct nvme_cmd_info *nvme_cmd_info(struct nvme_queue *nvmeq)
 static int alloc_cmdid(struct nvme_queue *nvmeq, void *ctx, int handler,
                                                        unsigned timeout)
 {
-       int depth = nvmeq->q_depth;
+       int depth = nvmeq->q_depth - 1;
        struct nvme_cmd_info *info = nvme_cmd_info(nvmeq);
        int cmdid;