[PATCH v3] nvme: Check the PRINFO bit and the Metadata size before deciding the host buffer length

[Revanth Rajashekar <revanth.rajashekar@intel.com>]

According to NVMe spec v1.4, section 8.3.1, the PRINFO bit and
the metadata size play a vital role in deteriming the host buffer size.

If PRIFNO bit is set and MS==8, the host doesn't add the metadata buffer,
instead the controller adds it.

Changes from v2:
1. Use sizeof(struct t10_pi_tuple) to check against MS.
2. Use if-else statements to set the meta_len and metadata

Changes from v1:
1. Remove the definition 'NVME_PRINFO_CTRL_BIT'
2. Remove variable 'control'
3. Remove test_bit and check the bit with the CPU arch's native endianness

Signed-off-by: Revanth Rajashekar <revanth.rajashekar@intel.com>
---
 drivers/nvme/host/core.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index f320273fc672..ec9f8f686460 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1543,8 +1543,21 @@ static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
 	}

 	length = (io.nblocks + 1) << ns->lba_shift;
-	meta_len = (io.nblocks + 1) * ns->ms;
-	metadata = nvme_to_user_ptr(io.metadata);
+
+	if ((io.control & NVME_RW_PRINFO_PRACT) &&
+		ns->ms == sizeof(struct t10_pi_tuple)) {
+		/*
+		 * Protection information is stripped/inserted by the
+		 * controller.
+		 */
+		if (nvme_to_user_ptr(io.metadata))
+			return -EINVAL;
+		meta_len = 0;
+		metadata = NULL;
+	} else {
+		meta_len = (io.nblocks + 1) * ns->ms;
+		metadata = nvme_to_user_ptr(io.metadata);
+	}

 	if (ns->features & NVME_NS_EXT_LBAS) {
 		length += meta_len;
--
2.17.1


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