docs: Mark "gluster" support in QEMU as deprecated

According to https://marc.info/?l=fedora-devel-list&m=171934833215726
the GlusterFS development effectively ended. Thus mark it as deprecated
in QEMU, so we can remove it in a future release if the project does
not gain momentum again.

Acked-by: Niels de Vos <ndevos@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-ID: <20241002082033.129022-1-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

block/gluster.c

@@ -809,6 +809,8 @@ static int qemu_gluster_open(BlockDriverState *bs,  QDict *options,
         goto out;
     }
 
+    warn_report_once("'gluster' is deprecated");
+
     filename = qemu_opt_get(opts, GLUSTER_OPT_FILENAME);
 
     s->debug = qemu_opt_get_number(opts, GLUSTER_OPT_DEBUG,

docs/about/deprecated.rst

@@ -377,6 +377,15 @@ Specifying the iSCSI password in plain text on the command line using the
 used instead, to refer to a ``--object secret...`` instance that provides
 a password via a file, or encrypted.
 
+``gluster`` backend (since 9.2)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+According to https://marc.info/?l=fedora-devel-list&m=171934833215726
+the GlusterFS development effectively ended. Unless the development
+gains momentum again, the QEMU project will remove the gluster backend
+in a future release.
+
+
 Character device options
 ''''''''''''''''''''''''
 

qapi/block-core.json

@@ -3190,12 +3190,18 @@
 #
 # @snapshot-access: Since 7.0
 #
+# Features:
+#
+# @deprecated: Member @gluster is deprecated because GlusterFS
+#     development ceased.
+#
 # Since: 2.9
 ##
 { 'enum': 'BlockdevDriver',
   'data': [ 'blkdebug', 'blklogwrites', 'blkreplay', 'blkverify', 'bochs',
             'cloop', 'compress', 'copy-before-write', 'copy-on-read', 'dmg',
-            'file', 'snapshot-access', 'ftp', 'ftps', 'gluster',
+            'file', 'snapshot-access', 'ftp', 'ftps',
+            {'name': 'gluster', 'features': [ 'deprecated' ] },
             {'name': 'host_cdrom', 'if': 'HAVE_HOST_BLOCK_DEVICE' },
             {'name': 'host_device', 'if': 'HAVE_HOST_BLOCK_DEVICE' },
             'http', 'https',