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

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

[Revanth Rajashekar]

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.

Signed-off-by: Revanth Rajashekar <revanth.rajashekar@intel.com>
---
 drivers/nvme/host/core.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 7a9642719..5efacd596 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1273,12 +1273,14 @@ static void __user *nvme_to_user_ptr(uintptr_t ptrval)
 	return (void __user *)ptrval;
 }

+#define NVME_PRINFO_CTRL_BIT (13)
 static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
 {
 	struct nvme_user_io io;
 	struct nvme_command c;
 	unsigned length, meta_len;
 	void __user *metadata;
+	unsigned long control;

 	if (copy_from_user(&io, uio, sizeof(io)))
 		return -EFAULT;
@@ -1297,6 +1299,12 @@ 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);
+	control = cpu_to_le16(io.control);
+
+	if (test_bit(NVME_PRINFO_CTRL_BIT, &control) && ns->ms == 8) {
+		meta_len = 0;
+		metadata = NULL;
+	}

 	if (ns->ext) {
 		length += meta_len;
--
2.17.1


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

[Keith Busch]

On Mon, Jan 11, 2021 at 09:26:02AM -0700, Revanth Rajashekar wrote:
> +#define NVME_PRINFO_CTRL_BIT (13)

This bit already defined as 'NVME_RW_PRINFO_PRACT'.

>  static int nvme_submit_io(struct nvme_ns *ns, struct nvme_user_io __user *uio)
>  {
>  	struct nvme_user_io io;
>  	struct nvme_command c;
>  	unsigned length, meta_len;
>  	void __user *metadata;
> +	unsigned long control;

You can remove this variable.

> 
>  	if (copy_from_user(&io, uio, sizeof(io)))
>  		return -EFAULT;
> @@ -1297,6 +1299,12 @@ 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);
> +	control = cpu_to_le16(io.control);

You're checking the bit with the CPU arch's native endianness, so you
shouldn't be byte swapping here for BE archs.

> +	if (test_bit(NVME_PRINFO_CTRL_BIT, &control) && ns->ms == 8) {

No need for the "test_bit()" here, you can just do:

	if (io.control & NVME_RW_PRINFO_PRACT && ms == 8)) 

> +		meta_len = 0;
> +		metadata = NULL;
> +	}

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