Re: [PATCH v2 3/3] zonefs: document the explicit-open mount option

[Damien Le Moal <Damien.LeMoal@wdc.com>]

On 2020/09/09 19:26, Johannes Thumshirn wrote:
> Document the newly introduced explicit-open mount option.
> 
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
> 
> ---
> Changes to v1:
> - Address Randy's comments
> ---
>  Documentation/filesystems/zonefs.rst | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/Documentation/filesystems/zonefs.rst b/Documentation/filesystems/zonefs.rst
> index 6c18bc8ce332..6b213fe9a33e 100644
> --- a/Documentation/filesystems/zonefs.rst
> +++ b/Documentation/filesystems/zonefs.rst
> @@ -326,6 +326,21 @@ discover the amount of data that has been written to the zone. In the case of a
>  read-only zone discovered at run-time, as indicated in the previous section.
>  The size of the zone file is left unchanged from its last updated value.
>  
> +A zoned block device (e.g. an NVMe Zoned Namespace device) may have limits on
> +the number of zones that can be active, that is, zones that are in the
> +implicit open, explicit open or closed conditions.  This potential limitation
> +translates into a risk for applications to see write IO errors due to this
> +limit being exceeded if the zone of a file is not already active when a write
> +request is issued by the user.
> +
> +To avoid these potential errors, the "explicit-open" mount option forces zones
> +to be made active using an open zone command when a file is opened for writing
> +for the first time. If the zone open command succeeds, the application is then
> +guaranteed that write requests can be processed. Conversely, the
> +"explicit-open" mount option will result in a zone close command being issued
> +to the device on the last close() of a zone file if the zone is not full nor
> +empty.
> +
>  Zonefs User Space Tools
>  =======================
>  
> 

Looks good.

Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>

-- 
Damien Le Moal
Western Digital Research