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[v5,4/4] zonefs: document the explicit-open mount option

Message ID 20200911085651.23526-5-johannes.thumshirn@wdc.com (mailing list archive)
State New
Headers show
Series zonefs: introduce helper for zone management | expand

Commit Message

Johannes Thumshirn Sept. 11, 2020, 8:56 a.m. UTC
Document the newly introduced explicit-open mount option.

Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
 Documentation/filesystems/zonefs.rst | 15 +++++++++++++++
 1 file changed, 15 insertions(+)
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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
 Zonefs User Space Tools