[PATCH V3 2/2] nvmet: allow bdev in buffered_io mode

[Chaitanya Kulkarni]

From: Chaitanya Kulkarni <kch at nvidia.com>

Allow block device to be configured in the buffered I/O mode by using
the file backend. In this way now we can use cache for the block
device namespace which shows significant performance improvement.

We update the block device ns enable function and return early when
buffered_io flag is set.

Signed-off-by: Chaitanya Kulkarni <kch at nvidia.com>
---
 drivers/nvme/target/io-cmd-bdev.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/nvme/target/io-cmd-bdev.c b/drivers/nvme/target/io-cmd-bdev.c
index 70ca9dfc1771..8b2cfde7ad63 100644
--- a/drivers/nvme/target/io-cmd-bdev.c
+++ b/drivers/nvme/target/io-cmd-bdev.c
@@ -76,6 +76,14 @@ int nvmet_bdev_ns_enable(struct nvmet_ns *ns)
 {
 	int ret;
 
+	/*
+	 * When buffered_io namespace attribute is enabled that means user want
+	 * this block device to be used as a file, so block device can take
+	 * an advantage of cache.
+	 */
+	if (ns->buffered_io)
+		return -ENOTBLK;
+
 	ns->bdev = blkdev_get_by_path(ns->device_path,
 			FMODE_READ | FMODE_WRITE, NULL);
 	if (IS_ERR(ns->bdev)) {
-- 
2.29.0