Re: [PATCH v4] nvmet: add missing lock around nvmet_ns_changed in nvmet_ns_revalidate

[Christoph Hellwig <hch@lst.de>]

On Mon, Mar 14, 2022 at 12:41:15AM +0100, Niels Dossche wrote:
> -	mutex_lock(&ns->subsys->lock);
>  	if (!ns->enabled) {
>  		pr_err("enable ns before revalidate.\n");
> -		mutex_unlock(&ns->subsys->lock);
>  		return -EINVAL;
>  	}
>  	nvmet_ns_revalidate(ns);
> -	mutex_unlock(&ns->subsys->lock);
>  	return count;
>  }

And now we lose the atomicy vs the enabled check.  I think we'll need
something like:


diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index 6fb24746de069..46d0dab686dd6 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -511,7 +511,11 @@ static void nvmet_execute_identify_ns(struct nvmet_req *req)
 		goto done;
 	}
 
-	nvmet_ns_revalidate(req->ns);
+	if (nvmet_ns_revalidate(req->ns)) {
+		mutex_lock(&req->ns->subsys->lock);
+		nvmet_ns_changed(req->ns->subsys, req->ns->nsid);
+		mutex_unlock(&req->ns->subsys->lock);
+	}
 
 	/*
 	 * nuse = ncap = nsze isn't always true, but we have no way to find
diff --git a/drivers/nvme/target/configfs.c b/drivers/nvme/target/configfs.c
index 091a0ca16361c..06ba477fbf771 100644
--- a/drivers/nvme/target/configfs.c
+++ b/drivers/nvme/target/configfs.c
@@ -586,7 +586,8 @@ static ssize_t nvmet_ns_revalidate_size_store(struct config_item *item,
 		mutex_unlock(&ns->subsys->lock);
 		return -EINVAL;
 	}
-	nvmet_ns_revalidate(ns);
+	if (nvmet_ns_revalidate(ns))
+		nvmet_ns_changed(ns->subsys, ns->nsid);
 	mutex_unlock(&ns->subsys->lock);
 	return count;
 }
diff --git a/drivers/nvme/target/core.c b/drivers/nvme/target/core.c
index 5119c687de683..17cc1cda836cc 100644
--- a/drivers/nvme/target/core.c
+++ b/drivers/nvme/target/core.c
@@ -531,7 +531,7 @@ static void nvmet_p2pmem_ns_add_p2p(struct nvmet_ctrl *ctrl,
 		ns->nsid);
 }
 
-void nvmet_ns_revalidate(struct nvmet_ns *ns)
+bool nvmet_ns_revalidate(struct nvmet_ns *ns)
 {
 	loff_t oldsize = ns->size;
 
@@ -540,8 +540,7 @@ void nvmet_ns_revalidate(struct nvmet_ns *ns)
 	else
 		nvmet_file_ns_revalidate(ns);
 
-	if (oldsize != ns->size)
-		nvmet_ns_changed(ns->subsys, ns->nsid);
+	return oldsize != ns->size;
 }
 
 int nvmet_ns_enable(struct nvmet_ns *ns)
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index af193423c10bb..731f529e11a51 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -542,7 +542,7 @@ u16 nvmet_file_flush(struct nvmet_req *req);
 void nvmet_ns_changed(struct nvmet_subsys *subsys, u32 nsid);
 void nvmet_bdev_ns_revalidate(struct nvmet_ns *ns);
 int nvmet_file_ns_revalidate(struct nvmet_ns *ns);
-void nvmet_ns_revalidate(struct nvmet_ns *ns);
+bool nvmet_ns_revalidate(struct nvmet_ns *ns);
 u16 blk_to_nvme_status(struct nvmet_req *req, blk_status_t blk_sts);
 
 bool nvmet_bdev_zns_enable(struct nvmet_ns *ns);
diff --git a/drivers/nvme/target/zns.c b/drivers/nvme/target/zns.c
index 46bc30fe85d2b..56c20502b7ef3 100644
--- a/drivers/nvme/target/zns.c
+++ b/drivers/nvme/target/zns.c
@@ -123,7 +123,11 @@ void nvmet_execute_identify_cns_cs_ns(struct nvmet_req *req)
 		goto done;
 	}
 
-	nvmet_ns_revalidate(req->ns);
+	if (nvmet_ns_revalidate(req->ns)) {
+		mutex_lock(&req->ns->subsys->lock);
+		nvmet_ns_changed(req->ns->subsys, req->ns->nsid);
+		mutex_unlock(&req->ns->subsys->lock);
+	}
 	zsze = (bdev_zone_sectors(req->ns->bdev) << 9) >>
 					req->ns->blksize_shift;
 	id_zns->lbafe[0].zsze = cpu_to_le64(zsze);