add doc for storage.linux-io_uring volume option.

Signed-off-by: Ravishankar N <ravishankar@redhat.com>

docs/Administrator-Guide/Managing-Volumes.md

@@ -89,6 +89,7 @@ performance.cache-size | Size of the read cache. | 32 MB |  size in bytes
 server.allow-insecure | Allow client connections from unprivileged ports. By default only privileged ports are allowed. This is a global setting in case insecure ports are to be enabled for all exports using a single option. | On | On/Off
 server.statedump-path | Location of the state dump file. | tmp directory of the brick |  New directory path
 storage.health-check-interval | Number of seconds between health-checks done on the filesystem that is used for the brick(s). Defaults to 30 seconds, set to 0 to disable. | tmp directory of the brick |  New directory path
+storage.linux-io_uring | Enable/Disable io_uring based I/O at the posix xlator on the bricks. | Off | On/Off
 
 You can view the changed volume options using command:
 

docs/Administrator-Guide/index.md

@@ -28,6 +28,7 @@
 	*  [Quotas](./Directory-Quota.md)
 	*  [Snapshots](./Managing-Snapshots.md)
 	*  [Trash](./Trash.md)
+	*  [io_uring](./io_uring.md)
 
 
 7. Data Access With Other Interfaces

docs/Administrator-Guide/io_uring.md

@@ -0,0 +1,17 @@
+# io_uring support in gluster
+
+io_uring is an asynchronous I/O interface similar to linux-aio, but aims to be more performant.
+Refer https://kernel.dk/io_uring.pdf and https://kernel-recipes.org/en/2019/talks/faster-io-through-io_uring/ for more details.
+
+Incorporating io_uring in various layers of gluster is an ongoing activity but beginning with glusterfs-9.0, support has been added to the posix translator via the ```storage.linux-io_uring``` volume option. When this option is enabled, the posix translator in the glusterfs brick process (at the server side) will use io_uring calls for reads, writes and fsyncs as opposed to the normal pread/pwrite based syscalls.
+
+#### Example:
+    [server~]# gluster volume set testvol storage.linux-io_uring on
+    volume set: success
+    [server~]#
+    [server~]# gluster volume set testvol storage.linux-io_uring off
+    volume set: success
+
+
+This option can be enabled/disabled only when the volume is not running.
+i.e. you can toggle the option when the volume is `Created` or is `Stopped` as indicated in ```gluster volume status $VOLNAME```

mkdocs.yml

@@ -43,6 +43,7 @@ nav:
      - Quotas: Administrator-Guide/Directory-Quota.md
      - Snapshots: Administrator-Guide/Managing-Snapshots.md
      - Trash: Administrator-Guide/Trash.md
+     - io_uring: Administrator-Guide/io_uring.md
   - Monitoring Workload: Administrator-Guide/Monitoring-Workload.md
   - Object Storage: Administrator-Guide/Object-Storage.md
   - GlusterFS Cinder: Administrator-Guide/GlusterFS-Cinder.md