[PATCH 0/6] nvme: improve discard_granularity spec compliance

[PATCH 0/6] nvme: improve discard_granularity spec compliance

[Caleb Sander Mateos]

NVMe block devices always report the logical block size for the
discard_granularity queue limit. However, more accurate values may be
available in the NPDG/NPDA fields of the Identify Namespace structure or
the NPDGL/NPDAL fields of the NVM Command Set Specific Identify
Namespace structure. So use these values to compute discard_granularity.

Also fix the use of the OPTPERF field to better comply with version 2.1
of the NVMe spec.

Update the target side to report NPDGL and NPDAL as wel, in case the
discard granularity doesn't fit in the 16-bit NPDG and NPDA fields.

Caleb Sander Mateos (6):
  nvme: add preferred I/O size fields to struct nvme_id_ns_nvm
  nvme: update nvme_id_ns OPTPERF constants
  nvme: always issue I/O Command Set specific Identify Namespace
  nvme: set discard_granularity from NPDG/NPDA
  nvmet: use NVME_NS_FEAT_OPTPERF_SHIFT
  nvmet: report NPDGL and NPDAL

 drivers/nvme/host/core.c          | 21 ++++++++++++++++-----
 drivers/nvme/target/admin-cmd.c   |  2 ++
 drivers/nvme/target/io-cmd-bdev.c | 19 +++++++++++++++----
 drivers/nvme/target/nvmet.h       |  2 ++
 include/linux/nvme.h              | 10 ++++++++--
 5 files changed, 43 insertions(+), 11 deletions(-)

-- 
2.45.2

[PATCH 1/6] nvme: add preferred I/O size fields to struct nvme_id_ns_nvm

[Caleb Sander Mateos]

A subsequent change will use the NPDGL and NPDAL fields of the NVM
Command Set Specific Identify Namespace structure, so add them (and the
handful of intervening fields) to struct nvme_id_ns_nvm.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
---
 include/linux/nvme.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index 655d194f8e72..bc991d4ae89d 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -511,11 +511,16 @@ struct nvme_id_ctrl_zns {
 struct nvme_id_ns_nvm {
 	__le64	lbstm;
 	__u8	pic;
 	__u8	rsvd9[3];
 	__le32	elbaf[64];
-	__u8	rsvd268[3828];
+	__le32	npdgl;
+	__le32	nprg;
+	__le32	npra;
+	__le32	nors;
+	__le32	npdal;
+	__u8	rsvd288[3808];
 };
 
 enum {
 	NVME_ID_NS_NVM_STS_MASK		= 0x7f,
 	NVME_ID_NS_NVM_GUARD_SHIFT	= 7,
-- 
2.45.2

[PATCH 2/6] nvme: update nvme_id_ns OPTPERF constants

[Caleb Sander Mateos]

Since NVM Command Spec 1.1, OPTPERF comprises both bits 4 and 5 of
NSFEAT in the Identify Namespace structure. Replace NVME_NS_FEAT_IO_OPT,
which represented only bit 4, with NVME_NS_FEAT_OPTPERF_SHIFT and
NVME_NS_FEAT_OPTPERF_MASK.

Update nvme_update_disk_info() to check both OPTPERF bits, as NPWG and
NOWS are supported even if only bit 5 is set.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
---
 drivers/nvme/host/core.c | 3 ++-
 include/linux/nvme.h     | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 3a2126584a23..674dd823b209 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2095,11 +2095,12 @@ static bool nvme_update_disk_info(struct nvme_ns *ns, struct nvme_id_ns *id,
 	}
 
 	phys_bs = bs;
 	atomic_bs = nvme_configure_atomic_write(ns, id, lim, bs);
 
-	if (id->nsfeat & NVME_NS_FEAT_IO_OPT) {
+	if (id->nsfeat >> NVME_NS_FEAT_OPTPERF_SHIFT &
+	    NVME_NS_FEAT_OPTPERF_MASK) {
 		/* NPWG = Namespace Preferred Write Granularity */
 		phys_bs = bs * (1 + le16_to_cpu(id->npwg));
 		/* NOWS = Namespace Optimal Write Size */
 		if (id->nows)
 			io_opt = bs * (1 + le16_to_cpu(id->nows));
diff --git a/include/linux/nvme.h b/include/linux/nvme.h
index bc991d4ae89d..f279e5d72e2d 100644
--- a/include/linux/nvme.h
+++ b/include/linux/nvme.h
@@ -593,11 +593,12 @@ enum {
 };
 
 enum {
 	NVME_NS_FEAT_THIN	= 1 << 0,
 	NVME_NS_FEAT_ATOMICS	= 1 << 1,
-	NVME_NS_FEAT_IO_OPT	= 1 << 4,
+	NVME_NS_FEAT_OPTPERF_SHIFT = 4,
+	NVME_NS_FEAT_OPTPERF_MASK = 0x3,
 	NVME_NS_ATTR_RO		= 1 << 0,
 	NVME_NS_FLBAS_LBA_MASK	= 0xf,
 	NVME_NS_FLBAS_LBA_UMASK	= 0x60,
 	NVME_NS_FLBAS_LBA_SHIFT	= 1,
 	NVME_NS_FLBAS_META_EXT	= 0x10,
-- 
2.45.2

[PATCH 3/6] nvme: always issue I/O Command Set specific Identify Namespace

[Caleb Sander Mateos]

Currently, the I/O Command Set specific Identify Namespace structure is
only fetched for controllers that support extended LBA formats. This is
because struct nvme_id_ns_nvm is only used by nvme_configure_pi_elbas(),
which is only called when the ELBAS bit is set in the CTRATT field of
the Identify Controller structure.

However, the I/O Command Set specific Identify Namespace structure will
soon be used in nvme_config_discard(), so always try to obtain it in
nvme_update_ns_info_block() if the controller supports NVMe version 2.0
or later.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
---
 drivers/nvme/host/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 674dd823b209..70ff14a56a01 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -2351,11 +2351,11 @@ static int nvme_update_ns_info_block(struct nvme_ns *ns,
 		ret = -ENXIO;
 		goto out;
 	}
 	lbaf = nvme_lbaf_index(id->flbas);
 
-	if (ns->ctrl->ctratt & NVME_CTRL_ATTR_ELBAS) {
+	if (ns->ctrl->vs >= NVME_VS(2, 0, 0)) {
 		ret = nvme_identify_ns_nvm(ns->ctrl, info->nsid, &nvm);
 		if (ret < 0)
 			goto out;
 	}
 
-- 
2.45.2

[PATCH 4/6] nvme: set discard_granularity from NPDG/NPDA

[Caleb Sander Mateos]

Currently, nvme_config_discard() always sets the discard_granularity
queue limit to the logical block size. However, NVMe namespaces can
advertise a larger preferred discard granularity in the NPDG or NPDA
field of the Identify Namespace structure or the NPDGL or NPDAL fields
of the I/O Command Set Specific Identify Namespace structure.

Use these fields to compute the discard_granularity limit. The logic is
somewhat involved. First, the fields are optional. NPDG is only reported
if the low bit of OPTPERF is set in NSFEAT. NPDA is reported if any bit
of OPTPERF is set. And NPDGL and NPDAL are reported if the high bit of
OPTPERF is set. NPDGL and NPDAL can also each be set to 0 to opt out of
reporting a limit. I/O Command Set Specific Identify Namespace may also
not be supported by older NVMe controllers. Another complication is that
multiple values may be reported among NPDG, NPDGL, NPDA, and NPDAL. The
spec says to prefer the values reported in the L variants. The spec says
NPDG should be a multiple of NPDA and NPDGL should be a multiple of
NPDAL, but it doesn't specify a relationship between NPDG and NPDAL or
NPDGL and NPDA. So use the maximum of the reported NPDG(L) and NPDA(L)
values as the discard_granularity.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
---
 drivers/nvme/host/core.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 70ff14a56a01..7ac11c40ca9f 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1880,23 +1880,33 @@ static bool nvme_init_integrity(struct nvme_ns_head *head,
 		bi->pi_offset = info->pi_offset;
 	}
 	return true;
 }
 
-static void nvme_config_discard(struct nvme_ns *ns, struct queue_limits *lim)
+static void nvme_config_discard(struct nvme_ns *ns, struct nvme_id_ns *id,
+				struct nvme_id_ns_nvm *nvm,
+				struct queue_limits *lim)
 {
 	struct nvme_ctrl *ctrl = ns->ctrl;
+	u32 npdg, npda;
+	u8 optperf;
 
 	if (ctrl->dmrsl && ctrl->dmrsl <= nvme_sect_to_lba(ns->head, UINT_MAX))
 		lim->max_hw_discard_sectors =
 			nvme_lba_to_sect(ns->head, ctrl->dmrsl);
 	else if (ctrl->oncs & NVME_CTRL_ONCS_DSM)
 		lim->max_hw_discard_sectors = UINT_MAX;
 	else
 		lim->max_hw_discard_sectors = 0;
 
-	lim->discard_granularity = lim->logical_block_size;
+	optperf = id->nsfeat >> NVME_NS_FEAT_OPTPERF_SHIFT &
+		  NVME_NS_FEAT_OPTPERF_MASK;
+	npdg = optperf & 0x2 && nvm && nvm->npdgl ? le32_to_cpu(nvm->npdgl) :
+	       optperf & 0x1 ? le16_to_cpu(id->npdg) + 1 : 1;
+	npda = optperf & 0x2 && nvm && nvm->npdal ? le32_to_cpu(nvm->npdal) :
+	       optperf ? le16_to_cpu(id->npda) + 1 : 1;
+	lim->discard_granularity = max(npdg, npda) * lim->logical_block_size;
 
 	if (ctrl->dmrl)
 		lim->max_discard_segments = ctrl->dmrl;
 	else
 		lim->max_discard_segments = NVME_DSM_MAX_RANGES;
@@ -2382,11 +2392,11 @@ static int nvme_update_ns_info_block(struct nvme_ns *ns,
 	nvme_configure_metadata(ns->ctrl, ns->head, id, nvm, info);
 	nvme_set_chunk_sectors(ns, id, &lim);
 	if (!nvme_update_disk_info(ns, id, &lim))
 		capacity = 0;
 
-	nvme_config_discard(ns, &lim);
+	nvme_config_discard(ns, id, nvm, &lim);
 	if (IS_ENABLED(CONFIG_BLK_DEV_ZONED) &&
 	    ns->head->ids.csi == NVME_CSI_ZNS)
 		nvme_update_zone_info(ns, &lim, &zi);
 
 	if ((ns->ctrl->vwc & NVME_CTRL_VWC_PRESENT) && !info->no_vwc)
-- 
2.45.2

[PATCH 5/6] nvmet: use NVME_NS_FEAT_OPTPERF_SHIFT

[Caleb Sander Mateos]

Use the NVME_NS_FEAT_OPTPERF_SHIFT constant in nvmet_bdev_set_limits()
to set the OPTPERF bits of the nvme_id_ns NSFEAT field instead of the
magic number 4.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
---
 drivers/nvme/target/io-cmd-bdev.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/io-cmd-bdev.c b/drivers/nvme/target/io-cmd-bdev.c
index 8d246b8ca604..d94f885a56d9 100644
--- a/drivers/nvme/target/io-cmd-bdev.c
+++ b/drivers/nvme/target/io-cmd-bdev.c
@@ -28,15 +28,15 @@ void nvmet_bdev_set_limits(struct block_device *bdev, struct nvme_id_ns *id)
 	id->nawun = lpp0b;
 	id->nawupf = lpp0b;
 	id->nacwu = lpp0b;
 
 	/*
-	 * Bit 4 indicates that the fields NPWG, NPWA, NPDG, NPDA, and
+	 * OPTPERF = 01b indicates that the fields NPWG, NPWA, NPDG, NPDA, and
 	 * NOWS are defined for this namespace and should be used by
 	 * the host for I/O optimization.
 	 */
-	id->nsfeat |= 1 << 4;
+	id->nsfeat |= 0x1 << NVME_NS_FEAT_OPTPERF_SHIFT;
 	/* NPWG = Namespace Preferred Write Granularity. 0's based */
 	id->npwg = to0based(bdev_io_min(bdev) / bdev_logical_block_size(bdev));
 	/* NPWA = Namespace Preferred Write Alignment. 0's based */
 	id->npwa = id->npwg;
 	/* NPDG = Namespace Preferred Deallocate Granularity. 0's based */
-- 
2.45.2

[PATCH 6/6] nvmet: report NPDGL and NPDAL

[Caleb Sander Mateos]

A block device with a very large discard_granularity queue limit may not
be able to report it in the 16-bit NPDG and NPDA fields in the Identify
Namespace data structure. For this reason, version 2.1 of the NVMe specs
added 32-bit fields NPDGL and NPDAL to the NVM Command Set Specific
Identify Namespace structure. So report the discard_granularity there
too and set OPTPERF to 11b to indicate those fields are supported.

Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
---
 drivers/nvme/target/admin-cmd.c   |  2 ++
 drivers/nvme/target/io-cmd-bdev.c | 19 +++++++++++++++----
 drivers/nvme/target/nvmet.h       |  2 ++
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/target/admin-cmd.c b/drivers/nvme/target/admin-cmd.c
index 3da31bb1183e..72e733b62a2c 100644
--- a/drivers/nvme/target/admin-cmd.c
+++ b/drivers/nvme/target/admin-cmd.c
@@ -1056,10 +1056,12 @@ static void nvme_execute_identify_ns_nvm(struct nvmet_req *req)
 	id = kzalloc(sizeof(*id), GFP_KERNEL);
 	if (!id) {
 		status = NVME_SC_INTERNAL;
 		goto out;
 	}
+	if (req->ns->bdev)
+		nvmet_bdev_set_nvm_limits(req->ns->bdev, id);
 	status = nvmet_copy_to_sgl(req, 0, id, sizeof(*id));
 	kfree(id);
 out:
 	nvmet_req_complete(req, status);
 }
diff --git a/drivers/nvme/target/io-cmd-bdev.c b/drivers/nvme/target/io-cmd-bdev.c
index d94f885a56d9..485b5cd42e4f 100644
--- a/drivers/nvme/target/io-cmd-bdev.c
+++ b/drivers/nvme/target/io-cmd-bdev.c
@@ -28,15 +28,15 @@ void nvmet_bdev_set_limits(struct block_device *bdev, struct nvme_id_ns *id)
 	id->nawun = lpp0b;
 	id->nawupf = lpp0b;
 	id->nacwu = lpp0b;
 
 	/*
-	 * OPTPERF = 01b indicates that the fields NPWG, NPWA, NPDG, NPDA, and
-	 * NOWS are defined for this namespace and should be used by
-	 * the host for I/O optimization.
+	 * OPTPERF = 11b indicates that the fields NPWG, NPWA, NPDG, NPDA,
+	 * NPDGL, NPDAL, and NOWS are defined for this namespace and should be
+	 * used by the host for I/O optimization.
 	 */
-	id->nsfeat |= 0x1 << NVME_NS_FEAT_OPTPERF_SHIFT;
+	id->nsfeat |= 0x3 << NVME_NS_FEAT_OPTPERF_SHIFT;
 	/* NPWG = Namespace Preferred Write Granularity. 0's based */
 	id->npwg = to0based(bdev_io_min(bdev) / bdev_logical_block_size(bdev));
 	/* NPWA = Namespace Preferred Write Alignment. 0's based */
 	id->npwa = id->npwg;
 	/* NPDG = Namespace Preferred Deallocate Granularity. 0's based */
@@ -50,10 +50,21 @@ void nvmet_bdev_set_limits(struct block_device *bdev, struct nvme_id_ns *id)
 	/* Set WZDS and DRB if device supports unmapped write zeroes */
 	if (bdev_write_zeroes_unmap_sectors(bdev))
 		id->dlfeat = (1 << 3) | 0x1;
 }
 
+void nvmet_bdev_set_nvm_limits(struct block_device *bdev,
+			       struct nvme_id_ns_nvm *id)
+{
+	/*
+	 * NPDGL = Namespace Preferred Deallocate Granularity Large
+	 * NPDAL = Namespace Preferred Deallocate Alignment Large
+	 */
+	id->npdgl = id->npdal = cpu_to_le32(bdev_discard_granularity(bdev) /
+					    bdev_logical_block_size(bdev));
+}
+
 void nvmet_bdev_ns_disable(struct nvmet_ns *ns)
 {
 	if (ns->bdev_file) {
 		fput(ns->bdev_file);
 		ns->bdev = NULL;
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index b664b584fdc8..3a7efd9cb81a 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -547,10 +547,12 @@ void nvmet_start_keep_alive_timer(struct nvmet_ctrl *ctrl);
 void nvmet_stop_keep_alive_timer(struct nvmet_ctrl *ctrl);
 
 u16 nvmet_parse_connect_cmd(struct nvmet_req *req);
 u32 nvmet_connect_cmd_data_len(struct nvmet_req *req);
 void nvmet_bdev_set_limits(struct block_device *bdev, struct nvme_id_ns *id);
+void nvmet_bdev_set_nvm_limits(struct block_device *bdev,
+			       struct nvme_id_ns_nvm *id);
 u16 nvmet_bdev_parse_io_cmd(struct nvmet_req *req);
 u16 nvmet_file_parse_io_cmd(struct nvmet_req *req);
 u16 nvmet_bdev_zns_parse_io_cmd(struct nvmet_req *req);
 u32 nvmet_admin_cmd_data_len(struct nvmet_req *req);
 u16 nvmet_parse_admin_cmd(struct nvmet_req *req);
-- 
2.45.2

Re: [PATCH 0/6] nvme: improve discard_granularity spec compliance

[Christoph Hellwig]

"Improving spec compliance" sounds a bit harsh for just adding support
for new optional fields / field extension.

Re: [PATCH 1/6] nvme: add preferred I/O size fields to struct nvme_id_ns_nvm

[Christoph Hellwig]

On Thu, Feb 19, 2026 at 08:28:04PM -0700, Caleb Sander Mateos wrote:
> A subsequent change will use the NPDGL and NPDAL fields of the NVM
> Command Set Specific Identify Namespace structure, so add them (and the
> handful of intervening fields) to struct nvme_id_ns_nvm.

Looks good.  Btw, as the kernel now has a the global scope static_assert,
can you add that too any on the wire format struct you touch to ensure
our modifications aren't changing the sizses?

Signed-off-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 2/6] nvme: update nvme_id_ns OPTPERF constants

[Christoph Hellwig]

On Thu, Feb 19, 2026 at 08:28:05PM -0700, Caleb Sander Mateos wrote:
> Since NVM Command Spec 1.1, OPTPERF comprises both bits 4 and 5 of
> NSFEAT in the Identify Namespace structure. Replace NVME_NS_FEAT_IO_OPT,
> which represented only bit 4, with NVME_NS_FEAT_OPTPERF_SHIFT and
> NVME_NS_FEAT_OPTPERF_MASK.

As you're deeper in this than me:  do the older specs require the
other bit to be cleared to zero and this is all compatible?  Or do
we need to guard it somehow?

Otherwise looks good.

Re: [PATCH 3/6] nvme: always issue I/O Command Set specific Identify Namespace

[Christoph Hellwig]

On Thu, Feb 19, 2026 at 08:28:06PM -0700, Caleb Sander Mateos wrote:
> Currently, the I/O Command Set specific Identify Namespace structure is
> only fetched for controllers that support extended LBA formats. This is
> because struct nvme_id_ns_nvm is only used by nvme_configure_pi_elbas(),
> which is only called when the ELBAS bit is set in the CTRATT field of
> the Identify Controller structure.
> 
> However, the I/O Command Set specific Identify Namespace structure will
> soon be used in nvme_config_discard(), so always try to obtain it in
> nvme_update_ns_info_block() if the controller supports NVMe version 2.0
> or later.

This was done kinda intentionally to avoid extra roundtrips and
tripping over buggy implementations.  But I think you have a good
use case to extent this, so:

Reviewed-by: Christoph Hellwig <hch@lst.de>

>  			goto out;
>  	}
>  
> -- 
> 2.45.2
---end quoted text---

Re: [PATCH 4/6] nvme: set discard_granularity from NPDG/NPDA

[Christoph Hellwig]

On Thu, Feb 19, 2026 at 08:28:07PM -0700, Caleb Sander Mateos wrote:
> -static void nvme_config_discard(struct nvme_ns *ns, struct queue_limits *lim)
> +static void nvme_config_discard(struct nvme_ns *ns, struct nvme_id_ns *id,
> +				struct nvme_id_ns_nvm *nvm,
> +				struct queue_limits *lim)

The indentation here looks weird, this should be just two tabs.

> -	lim->discard_granularity = lim->logical_block_size;
> +	optperf = id->nsfeat >> NVME_NS_FEAT_OPTPERF_SHIFT &
> +		  NVME_NS_FEAT_OPTPERF_MASK;
> +	npdg = optperf & 0x2 && nvm && nvm->npdgl ? le32_to_cpu(nvm->npdgl) :
> +	       optperf & 0x1 ? le16_to_cpu(id->npdg) + 1 : 1;
> +	npda = optperf & 0x2 && nvm && nvm->npdal ? le32_to_cpu(nvm->npdal) :
> +	       optperf ? le16_to_cpu(id->npda) + 1 : 1;

Please undinw this into a few if statemens.  (And I really
with the spec would given the bits names..)

Re: [PATCH 5/6] nvmet: use NVME_NS_FEAT_OPTPERF_SHIFT

[Christoph Hellwig]

On Thu, Feb 19, 2026 at 08:28:08PM -0700, Caleb Sander Mateos wrote:
> Use the NVME_NS_FEAT_OPTPERF_SHIFT constant in nvmet_bdev_set_limits()
> to set the OPTPERF bits of the nvme_id_ns NSFEAT field instead of the
> magic number 4.

Looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH 6/6] nvmet: report NPDGL and NPDAL

[Christoph Hellwig]

On Thu, Feb 19, 2026 at 08:28:09PM -0700, Caleb Sander Mateos wrote:
> A block device with a very large discard_granularity queue limit may not
> be able to report it in the 16-bit NPDG and NPDA fields in the Identify
> Namespace data structure. For this reason, version 2.1 of the NVMe specs
> added 32-bit fields NPDGL and NPDAL to the NVM Command Set Specific
> Identify Namespace structure. So report the discard_granularity there
> too and set OPTPERF to 11b to indicate those fields are supported.

From a pure mechanics point of view this looks fine.  I'll not that
actually aligning the discard to these granularities probably won't
really work for most file systems, though.

Re: [PATCH 2/6] nvme: update nvme_id_ns OPTPERF constants

[Caleb Sander Mateos]

On Fri, Feb 20, 2026 at 8:07 AM Christoph Hellwig <hch@lst.de> wrote:
>
> On Thu, Feb 19, 2026 at 08:28:05PM -0700, Caleb Sander Mateos wrote:
> > Since NVM Command Spec 1.1, OPTPERF comprises both bits 4 and 5 of
> > NSFEAT in the Identify Namespace structure. Replace NVME_NS_FEAT_IO_OPT,
> > which represented only bit 4, with NVME_NS_FEAT_OPTPERF_SHIFT and
> > NVME_NS_FEAT_OPTPERF_MASK.
>
> As you're deeper in this than me:  do the older specs require the
> other bit to be cleared to zero and this is all compatible?  Or do
> we need to guard it somehow?

In NVM Command Set spec 1.0 (NVMe version 2.0), OPTPERF is only bit 4
of NSFEAT and the higher bits are reserved. I think it seems
relatively safe to assume bit 5 will be reported as 0 on controllers
advertising older NVMe versions, but you're correct that the host
should technically check for version >= 2.1 before using bit 5. Let me
know which approach you'd prefer.

Thanks,
Caleb

Re: [PATCH 2/6] nvme: update nvme_id_ns OPTPERF constants

[Christoph Hellwig]

On Fri, Feb 20, 2026 at 08:17:29AM -0800, Caleb Sander Mateos wrote:
> On Fri, Feb 20, 2026 at 8:07 AM Christoph Hellwig <hch@lst.de> wrote:
> >
> > On Thu, Feb 19, 2026 at 08:28:05PM -0700, Caleb Sander Mateos wrote:
> > > Since NVM Command Spec 1.1, OPTPERF comprises both bits 4 and 5 of
> > > NSFEAT in the Identify Namespace structure. Replace NVME_NS_FEAT_IO_OPT,
> > > which represented only bit 4, with NVME_NS_FEAT_OPTPERF_SHIFT and
> > > NVME_NS_FEAT_OPTPERF_MASK.
> >
> > As you're deeper in this than me:  do the older specs require the
> > other bit to be cleared to zero and this is all compatible?  Or do
> > we need to guard it somehow?
> 
> In NVM Command Set spec 1.0 (NVMe version 2.0), OPTPERF is only bit 4
> of NSFEAT and the higher bits are reserved. I think it seems
> relatively safe to assume bit 5 will be reported as 0 on controllers
> advertising older NVMe versions, but you're correct that the host
> should technically check for version >= 2.1 before using bit 5. Let me
> know which approach you'd prefer.

Not entirely sure, but either way the code should have a big fat
comment about this.

Re: [PATCH 1/6] nvme: add preferred I/O size fields to struct nvme_id_ns_nvm

[Caleb Sander Mateos]

On Fri, Feb 20, 2026 at 8:06 AM Christoph Hellwig <hch@lst.de> wrote:
>
> On Thu, Feb 19, 2026 at 08:28:04PM -0700, Caleb Sander Mateos wrote:
> > A subsequent change will use the NPDGL and NPDAL fields of the NVM
> > Command Set Specific Identify Namespace structure, so add them (and the
> > handful of intervening fields) to struct nvme_id_ns_nvm.
>
> Looks good.  Btw, as the kernel now has a the global scope static_assert,
> can you add that too any on the wire format struct you touch to ensure
> our modifications aren't changing the sizses?

Looks like static_assert() was added 3 years before struct nvme_id_ns_nvm :)
Definitely agree it's good to assert on these struct sizes.

>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Assuming you meant "Reviewed-by". Let me know if you meant something else.

Thanks,
Caleb

Re: [PATCH 1/6] nvme: add preferred I/O size fields to struct nvme_id_ns_nvm

[Christoph Hellwig]

On Fri, Feb 20, 2026 at 06:55:25PM -0800, Caleb Sander Mateos wrote:
> Looks like static_assert() was added 3 years before struct nvme_id_ns_nvm :)
> Definitely agree it's good to assert on these struct sizes.
> 
> >
> > Signed-off-by: Christoph Hellwig <hch@lst.de>
> 
> Assuming you meant "Reviewed-by". Let me know if you meant something else.

Yes, sorry.