[PATCH RFC 1/3] nvme: check ns's volatile write cache not present

[Guixin Liu <kanie@linux.alibaba.com>]

When the VWC of a namespace does not exist, the BLK_FEAT_WRITE_CACHE
flag should not be set when registering the block device, regardless
of whether the controller supports VWC.

Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
---
 drivers/nvme/host/core.c | 4 +++-
 include/linux/nvme.h     | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index b149b638453f..eed41d4d2599 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -42,6 +42,7 @@ struct nvme_ns_info {
 	bool is_readonly;
 	bool is_ready;
 	bool is_removed;
+	bool no_vwc;
 };
 
 unsigned int admin_timeout = 60;
@@ -1639,6 +1640,7 @@ static int nvme_ns_info_from_id_cs_indep(struct nvme_ctrl *ctrl,
 		info->is_shared = id->nmic & NVME_NS_NMIC_SHARED;
 		info->is_readonly = id->nsattr & NVME_NS_ATTR_RO;
 		info->is_ready = id->nstat & NVME_NSTAT_NRDY;
+		info->no_vwc = id->nsfeat & NVME_NS_VWC_NOT_PRESENT;
 	}
 	kfree(id);
 	return ret;
@@ -2185,7 +2187,7 @@ static int nvme_update_ns_info_block(struct nvme_ns *ns,
 	    ns->head->ids.csi == NVME_CSI_ZNS)
 		nvme_update_zone_info(ns, &lim, &zi);
 
-	if (ns->ctrl->vwc & NVME_CTRL_VWC_PRESENT)
+	if ((ns->ctrl->vwc & NVME_CTRL_VWC_PRESENT) && !info->no_vwc)
 		lim.features |= BLK_FEAT_WRITE_CACHE | BLK_FEAT_FUA;
 	else
 		lim.features &= ~(BLK_FEAT_WRITE_CACHE | BLK_FEAT_FUA);
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index b58d9405d65e..6ce2533cf9b4 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -560,6 +560,7 @@ enum {
 	NVME_NS_FLBAS_LBA_SHIFT	= 1,
 	NVME_NS_FLBAS_META_EXT	= 0x10,
 	NVME_NS_NMIC_SHARED	= 1 << 0,
+	NVME_NS_VWC_NOT_PRESENT = 1 << 5,
 	NVME_LBAF_RP_BEST	= 0,
 	NVME_LBAF_RP_BETTER	= 1,
 	NVME_LBAF_RP_GOOD	= 2,
-- 
2.43.0