xfs: document zoned rt specifics in admin-guide

Document the lifetime, nolifetime and max_open_zones mount options
added for zoned rt file systems.

Also add documentation describing the max_open_zones sysfs attribute
exposed in /sys/fs/xfs/<dev>/zoned/

Fixes: 4e4d52075577 ("xfs: add the zoned space allocator")
Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

diff --git a/Documentation/admin-guide/xfs.rst b/Documentation/admin-guide/xfs.rst
index 7b0811d650f919aa52fb0d9a324e1c9609ecabe0..3e76276bd488b22dc02c8b33dbd4c7960bb1575c 100644 (file)
--- a/Documentation/admin-guide/xfs.rst
+++ b/Documentation/admin-guide/xfs.rst
@@ -124,6 +124,14 @@ When mounting an XFS filesystem, the following options are accepted.
        controls the size of each buffer and so is also relevant to
        this case.
 
+  lifetime (default) or nolifetime
+       Enable data placement based on write life time hints provided
+       by the user. This turns on co-allocation of data of similar
+       life times when statistically favorable to reduce garbage
+       collection cost.
+
+       These options are only available for zoned rt file systems.
+
   logbsize=value
        Set the size of each in-memory log buffer.  The size may be
        specified in bytes, or in kilobytes with a "k" suffix.
@@ -143,6 +151,14 @@ When mounting an XFS filesystem, the following options are accepted.
        optional, and the log section can be separate from the data
        section or contained within it.
 
+  max_open_zones=value
+       Specify the max number of zones to keep open for writing on a
+       zoned rt device. Many open zones aids file data separation
+       but may impact performance on HDDs.
+
+       If ``max_open_zones`` is not specified, the value is determined
+       by the capabilities and the size of the zoned rt device.
+
   noalign
        Data allocations will not be aligned at stripe unit
        boundaries. This is only relevant to filesystems created
@@ -546,6 +562,19 @@ The interesting knobs for XFS workqueues are as follows:
 Zoned Filesystems
 =================
 
+For zoned file systems, the following attribute is exposed in:
+
+  /sys/fs/xfs/<dev>/zoned/
+
+  max_open_zones               (Min:  1  Default:  Varies  Max:  UINTMAX)
+       This read-only attribute exposes the maximum number of open zones
+       available for data placement. The value is determined at mount time and
+       is limited by the capabilities of the backing zoned device, file system
+       size and the max_open_zones mount option.
+
+Zoned Filesystems
+=================
+
 For zoned file systems, the following attributes are exposed in:
 
  /sys/fs/xfs/<dev>/zoned/