[ndctl,v2] Documentation/namespace-description: Clarify label-less restrictions
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Message ID 20190808175707.9089-1-vishal.l.verma@intel.com
State New
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  • [ndctl,v2] Documentation/namespace-description: Clarify label-less restrictions
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Commit Message

Verma, Vishal L Aug. 8, 2019, 5:57 p.m. UTC
In the ndctl-create-namespace (and related) man pages, add a
clarification note regarding some of the restrictions a user may see
when operating on label-less namespaces.

Link: https://github.com/pmem/ndctl/issues/52
Reported-by: Jane Chu <jane.chu@oracle.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---

v2:
- Remove the part about an address abstraction mechanism; It didn't add
  any value (Jeff)
- Add an additional sentence about space reclamation semantics (Dan)

 Documentation/ndctl/namespace-description.txt | 9 +++++++++
 1 file changed, 9 insertions(+)

Comments

Jeff Moyer Aug. 8, 2019, 6:13 p.m. UTC | #1
Vishal Verma <vishal.l.verma@intel.com> writes:

> In the ndctl-create-namespace (and related) man pages, add a
> clarification note regarding some of the restrictions a user may see
> when operating on label-less namespaces.
>
> Link: https://github.com/pmem/ndctl/issues/52
> Reported-by: Jane Chu <jane.chu@oracle.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> ---
>
> v2:
> - Remove the part about an address abstraction mechanism; It didn't add
>   any value (Jeff)
> - Add an additional sentence about space reclamation semantics (Dan)

LGTM

Reviewed-by: Jeff Moyer <jmoyer@redhat.com>

-Jeff

>
>  Documentation/ndctl/namespace-description.txt | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/Documentation/ndctl/namespace-description.txt b/Documentation/ndctl/namespace-description.txt
> index 94999e5..c59fbef 100644
> --- a/Documentation/ndctl/namespace-description.txt
> +++ b/Documentation/ndctl/namespace-description.txt
> @@ -18,6 +18,15 @@ the kernel's 'memmap=ss!nn' command line option (see the nvdimm wiki on
>  kernel.org), or NVDIMMs without a valid 'namespace index' in their label
>  area.
>  
> +NOTE: Label-less namespaces lack many of the features of their label-rich
> +cousins. For example, their size cannot be modified, or they cannot be
> +fully 'destroyed' (i.e. the space reclaimed). A destroy operation will
> +zero any mode-specific metadata. Finally, for create-namespace operations
> +on label-less namespaces, ndctl bypasses the region capacity availability
> +checks, and always satisfies the request using the full region capacity.
> +The only reconfiguration operation supported on a label-less namespace
> +is changing its 'mode'.
> +
>  A namespace can be provisioned to operate in one of 4 modes, 'fsdax',
>  'devdax', 'sector', and 'raw'. Here are the expected usage models for
>  these modes:

Patch
diff mbox series

diff --git a/Documentation/ndctl/namespace-description.txt b/Documentation/ndctl/namespace-description.txt
index 94999e5..c59fbef 100644
--- a/Documentation/ndctl/namespace-description.txt
+++ b/Documentation/ndctl/namespace-description.txt
@@ -18,6 +18,15 @@  the kernel's 'memmap=ss!nn' command line option (see the nvdimm wiki on
 kernel.org), or NVDIMMs without a valid 'namespace index' in their label
 area.
 
+NOTE: Label-less namespaces lack many of the features of their label-rich
+cousins. For example, their size cannot be modified, or they cannot be
+fully 'destroyed' (i.e. the space reclaimed). A destroy operation will
+zero any mode-specific metadata. Finally, for create-namespace operations
+on label-less namespaces, ndctl bypasses the region capacity availability
+checks, and always satisfies the request using the full region capacity.
+The only reconfiguration operation supported on a label-less namespace
+is changing its 'mode'.
+
 A namespace can be provisioned to operate in one of 4 modes, 'fsdax',
 'devdax', 'sector', and 'raw'. Here are the expected usage models for
 these modes: