[PATCH] nvme: improve check for attached metadata buffers

[Christoph Hellwig]

On Mon, Nov 06, 2017 at 12:55:53PM -0700, Keith Busch wrote:
> Sorry for missing this case earlier: this will break namespace usage
> when CONFIG_BLK_DEV_INTEGRITY is not set, and the format allows PRACT=1
> to strip/generate.

Indeed, I completely forgot about the CONFIG_BLK_DEV_INTEGRITY=n case.

How about something like this should do the right thing.  But while
looking over that I'm not sure our !CONFIG_BLK_DEV_INTEGRITY case
for inserting/stripping PI really works - as far as I can tell we
should never set NVME_RW_PRINFO_PRCHK_GUARD in that case, or am I
missing something?

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 66211617e7e8..3a58a07d2a53 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -137,6 +137,11 @@ int nvme_delete_ctrl_sync(struct nvme_ctrl *ctrl)
 }
 EXPORT_SYMBOL_GPL(nvme_delete_ctrl_sync);
 
+static inline bool nvme_ns_has_pi(struct nvme_ns *ns)
+{
+	return ns->pi_type && ns->ms == sizeof(struct t10_pi_tuple);
+}
+
 static blk_status_t nvme_error_status(struct request *req)
 {
 	switch (nvme_req(req)->status & 0x7ff) {
@@ -472,16 +477,6 @@ static inline blk_status_t nvme_setup_rw(struct nvme_ns *ns,
 	u16 control = 0;
 	u32 dsmgmt = 0;
 
-	/*
-	 * If formated with metadata, require the block layer provide a buffer
-	 * unless this namespace is formated such that the metadata can be
-	 * stripped/generated by the controller with PRACT=1.
-	 */
-	if (ns && ns->ms &&
-	    (!ns->pi_type || ns->ms != sizeof(struct t10_pi_tuple)) &&
-	    !blk_integrity_rq(req) && !blk_rq_is_passthrough(req))
-		return BLK_STS_NOTSUPP;
-
 	if (req->cmd_flags & REQ_FUA)
 		control |= NVME_RW_FUA;
 	if (req->cmd_flags & (REQ_FAILFAST_DEV | REQ_RAHEAD))
@@ -500,6 +495,18 @@ static inline blk_status_t nvme_setup_rw(struct nvme_ns *ns,
 		nvme_assign_write_stream(ctrl, req, &control, &dsmgmt);
 
 	if (ns->ms) {
+		/*
+		 * If formated with metadata, the block layer always provides a
+		 * metadata buffer if CONFIG_BLK_DEV_INTEGRITY is enabled.  Else
+		 * we enable the PRACT bit for protection information or set the
+		 * namespace capacity to zero to prevent any I/O.
+		 */
+		if (!blk_integrity_rq(req)) {
+			if (WARN_ON_ONCE(!nvme_ns_has_pi(ns)))
+				return BLK_STS_NOTSUPP;
+			control |= NVME_RW_PRINFO_PRACT;
+		}
+
 		switch (ns->pi_type) {
 		case NVME_NS_DPS_PI_TYPE3:
 			control |= NVME_RW_PRINFO_PRCHK_GUARD;
@@ -512,8 +519,6 @@ static inline blk_status_t nvme_setup_rw(struct nvme_ns *ns,
 					nvme_block_nr(ns, blk_rq_pos(req)));
 			break;
 		}
-		if (!blk_integrity_rq(req))
-			control |= NVME_RW_PRINFO_PRACT;
 	}
 
 	cmnd->rw.control = cpu_to_le16(control);
@@ -1173,7 +1178,7 @@ static void nvme_update_disk_info(struct gendisk *disk,
 	if (ns->ms && !ns->ext &&
 	    (ns->ctrl->ops->flags & NVME_F_METADATA_SUPPORTED))
 		nvme_init_integrity(disk, ns->ms, ns->pi_type);
-	if (ns->ms && !(ns->ms == 8 && ns->pi_type) && !blk_get_integrity(disk))
+	if (ns->ms && !nvme_ns_has_pi(ns) && !blk_get_integrity(disk))
 		capacity = 0;
 	set_capacity(disk, capacity);