[RFC PATCH] nvme: replace lazy sgl warn with informational message

[Keith Busch <kbusch@meta.com>]

From: Keith Busch <kbusch@kernel.org>

Instead of warning about the device's SGL capabilities the first time we
consider using them with a passthrough command, print out what the
device is capable of during initialization. While we're at it, print
other interesting capabilities that may be useful to know when you just
have a dmesg. The ouput format was inspired by other existing subsystems
like pci.

And example of the new message when used with a default qemu nvme
emulated device:

  nvme nvme0: sgl+ meta-sgl+ sed- vwc+ apst- dsm+ wz+

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 drivers/nvme/host/core.c  | 20 ++++++++++++++++++++
 drivers/nvme/host/ioctl.c | 11 ++---------
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 2bcd9f710cb65..7535a9b9d2afa 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3440,6 +3440,22 @@ static int nvme_init_identify(struct nvme_ctrl *ctrl)
 	return ret;
 }
 
+#define ENABLED(cond) ((cond) ? '+' : '-')
+
+static void nvme_ctrl_caps(struct nvme_ctrl *ctrl)
+{
+	dev_info(ctrl->device,
+		"sgl%c meta-sgl%c sed%c vwc%c apst%c dsm%c wz%c\n",
+		ENABLED(nvme_ctrl_sgl_supported(ctrl)),
+		ENABLED(nvme_ctrl_meta_sgl_supported(ctrl)),
+		ENABLED(!!ctrl->opal_dev),
+		ENABLED(ctrl->vwc & NVME_CTRL_VWC_PRESENT),
+		ENABLED(ctrl->apst_enabled),
+		ENABLED(ctrl->oncs & NVME_CTRL_ONCS_DSM),
+		ENABLED(ctrl->oncs & NVME_CTRL_ONCS_WRITE_ZEROES)
+	);
+}
+
 /*
  * Initialize the cached copies of the Identify data and various controller
  * register in our nvme_ctrl structure.  This should be called as soon as
@@ -3489,6 +3505,10 @@ int nvme_init_ctrl_finish(struct nvme_ctrl *ctrl, bool was_suspended)
 	}
 
 	clear_bit(NVME_CTRL_DIRTY_CAPABILITY, &ctrl->flags);
+
+	if (!ctrl->identified)
+		nvme_ctrl_caps(ctrl);
+
 	ctrl->identified = true;
 
 	nvme_start_keep_alive(ctrl);
diff --git a/drivers/nvme/host/ioctl.c b/drivers/nvme/host/ioctl.c
index e8930146847af..2b5b650443229 100644
--- a/drivers/nvme/host/ioctl.c
+++ b/drivers/nvme/host/ioctl.c
@@ -125,15 +125,8 @@ static int nvme_map_user_request(struct request *req, u64 ubuffer,
 	struct bio *bio = NULL;
 	int ret;
 
-	if (!nvme_ctrl_sgl_supported(ctrl))
-		dev_warn_once(ctrl->device, "using unchecked data buffer\n");
-	if (has_metadata) {
-		if (!supports_metadata)
-			return -EINVAL;
-		if (!nvme_ctrl_meta_sgl_supported(ctrl))
-			dev_warn_once(ctrl->device,
-				      "using unchecked metadata buffer\n");
-	}
+	if (has_metadata && !supports_metadata)
+		return -EINVAL;
 
 	if (ioucmd && (ioucmd->flags & IORING_URING_CMD_FIXED)) {
 		struct iov_iter iter;
-- 
2.43.5