classification: provide infra to start labelling features/components

`doc/xlator-classification.md` talks about the reasoning and expectations

Reviewers are expected to check the 'category' of new
option / translator added in the codebase, and make sure the flag
is always properly set. It helps to keep the 'expectation' proper
on the codebase.

updates: #430
Change-Id: I2bfc9934a5f6eed77fcc3e20364046242decc82c
Signed-off-by: Amar Tumballi <amarts@redhat.com>

doc/developer-guide/xlator-classification.md

@@ -130,7 +130,50 @@ These xlators and their corresponding code and test health will not be executed.
 
 ### How to specify an xlators category
 
-(TBD)
+While defining 'xlator_api_t' structure for the corresponding xlator, add a
+flag like below:
+
+```
+diff --git a/xlators/performance/nl-cache/src/nl-cache.c b/xlators/performance/nl-cache/src/nl-cache.c
+index 0f0e53bac2..8267d6897c 100644
+--- a/xlators/performance/nl-cache/src/nl-cache.c
++++ b/xlators/performance/nl-cache/src/nl-cache.c
+@@ -869,4 +869,5 @@ xlator_api_t xlator_api = {
+         .cbks          = &nlc_cbks,
+         .options       = nlc_options,
+         .identifier    = "nl-cache",
++        .category      = GF_TECH_PREVIEW,
+ };
+diff --git a/xlators/performance/quick-read/src/quick-read.c b/xlators/performance/quick-read/src/quick-read.c
+index 8d39720e7f..235de27c19 100644
+--- a/xlators/performance/quick-read/src/quick-read.c
++++ b/xlators/performance/quick-read/src/quick-read.c
+@@ -1702,4 +1702,5 @@ xlator_api_t xlator_api = {
+         .cbks          = &qr_cbks,
+         .options       = qr_options,
+         .identifier    = "quick-read",
++        .category      = GF_MAINTAINED,
+ };
+```
+
+Similarly, if a particular option is in different state other than
+the xlator state, one can add the same flag in options structure too.
+
+```
+diff --git a/xlators/cluster/afr/src/afr.c b/xlators/cluster/afr/src/afr.c
+index 0e86e33d03..81996743d1 100644
+--- a/xlators/cluster/afr/src/afr.c
++++ b/xlators/cluster/afr/src/afr.c
+@@ -772,6 +772,7 @@ struct volume_options options[] = {
+           .description = "Maximum latency for shd halo replication in msec."
+         },
+         { .key   = {"halo-enabled"},
++          .category = GF_TECH_PREVIEW,
+           .type  = GF_OPTION_TYPE_BOOL,
+           .default_value = "False",
+
+```
+
 
 ### User experience using the categories
 

extras/create_new_xlator/new-xlator-tmpl.c

@@ -96,7 +96,8 @@ struct volume_options @FOP_PREFIX@_options[] = {
           .op_version = {GD_OP_VERSION_},
           .flags = OPT_FLAG_SETTABLE | OPT_FLAG_DOC | OPT_FLAG_CLIENT_OPT,
           .tags = {""},
-          .description = ""
+          .description = "",
+          .category = GF_EXPERIMENTAL,
         },
         { .key = {NULL} },
         */
@@ -115,6 +116,7 @@ xlator_api_t xlator_api = {
         .cbks          = &@FOP_PREFIX@_cbks,
         .options       = @FOP_PREFIX@_options,
         .identifier    = "@XL_NAME@",
+        .category      = GF_EXPERIMENTAL,
 };
 #pragma fragment HEADER_FMT
 #ifndef __@HFL_NAME@_H__

libglusterfs/src/glusterfs.h

@@ -390,6 +390,35 @@ typedef enum {
         GF_FOP_PRI_MAX,                 /* Highest */
 } gf_fop_pri_t;
 
+typedef enum {
+        /* The 'component' (xlator / option) is not yet setting the flag */
+        GF_UNCLASSIFIED = 0,
+        /* The 'component' is experimental, should not be recommened
+           in production mode */
+        GF_EXPERIMENTAL,
+        /* The 'component' is tech preview, ie, it is 'mostly' working as
+           expected, but can have some of the corner cases, which is not
+           handled. */
+        GF_TECH_PREVIEW,
+        /* The 'component' is good to run. Has good enough test and
+           documentation coverage. */
+        GF_MAINTAINED,
+        /* The component is:
+           - no more a focus
+           - no more solving a valid use case
+           - no more maintained, no volunteers to maintain
+           - there is 'maintained' or 'tech-preview' feature,
+           which does the same thing, better.
+        */
+        GF_DEPRECATED,
+        /* The 'component' is no more 'built'. */
+        GF_OBSOLETE,
+        /* The 'component' exist for Documentation purposes.
+           No real usecase */
+        GF_DOCUMENT_PURPOSE,
+} gf_category_t;
+
+
 static const char * const FOP_PRI_STRINGS[] = {
         "HIGH",
         "NORMAL",

libglusterfs/src/options.h

@@ -134,9 +134,15 @@ typedef struct volume_options {
          */
         char *setkey;
 
-        /* The level at which the option is classified
-         */
-        opt_level_t             level;
+        /* A 'level' is about the technical depth / understanding one
+           needs to handle the option. 'category' is based on
+           quality (ie, tests, people behind it, documentation available) */
+
+        /* The level at which the option is classified */
+        opt_level_t level;
+
+        /* Flag to understand how this option is categorized */
+        gf_category_t category;
 } volume_option_t;
 
 

libglusterfs/src/xlator.c

@@ -417,6 +417,8 @@ int xlator_dynload_newway (xlator_t *xl)
         xl->id         = xlapi->xlator_id;
         xl->flags      = xlapi->flags;
         xl->identifier = xlapi->identifier;
+        xl->category   = xlapi->category;
+
         memcpy (xl->op_version, xlapi->op_version,
                 sizeof (uint32_t) * GF_MAX_RELEASES);
 

libglusterfs/src/xlator.h

@@ -1051,7 +1051,8 @@ struct _xlator {
         /* flag to avoid recall of xlator_mem_cleanup for xame xlator */
         uint32_t call_cleanup;
 
-
+        /* Flag to understand how this xlator is categorized */
+        gf_category_t category;
 };
 
 typedef struct {
@@ -1092,6 +1093,9 @@ typedef struct {
            volume file, then that should be defined here. optional. */
         volume_option_t *options;
 
+        /* Flag to understand how this xlator is categorized */
+        gf_category_t category;
+
         /* XXX: GD2MARKER
          * If a new member that needs to be visible to GD2 is introduced,
          * add it above this comment.