CORTX-33537: disable alternative pvers by default

In case of some failure, we want the I/O to be done in the
base pool version in the degraded mode always without switching
to the alternative pool version. Later, when we introduce the
side pool versions, we will do the degraded I/O in them and use
them for faster SNS-recovery, which will try to recover only the
objects which have the side pool versions instead of traversing
all objects in the cluster.

Closes #1958.

Signed-off-by: Andriy Tkachuk <andriy.tkachuk@seagate.com>

conf/pvers.c

@@ -63,8 +63,10 @@ struct arr_int_pos {
 	uint32_t       ap_pos;
 };
 
+#ifdef ENABLE_ALT_PVERS
 static int conf_pver_formulate(const struct m0_conf_pver *fpver,
 			       struct m0_conf_pver **out);
+#endif
 static int conf_pver_formulaic_base(const struct m0_conf_pver *fpver,
 				    struct m0_conf_pver **out);
 static int conf_pver_objvs_count(struct m0_conf_pver *base, uint32_t *out);
@@ -73,7 +75,9 @@ static int conf_pver_virtual_create(const struct m0_fid *fid,
 				    const uint32_t *allowance,
 				    struct arr_int *failed,
 				    struct m0_conf_pver **out);
+#ifdef ENABLE_ALT_PVERS
 static int conf_pver_failures_cid(struct m0_conf_pver *base, uint64_t *out);
+#endif
 static void conf_pver_subtree_delete(struct m0_conf_obj *obj);
 static int conf_pver_recd_build(struct m0_conf_obj *obj, void *args);
 
@@ -145,13 +149,17 @@ static int conf_pver_find_locked(const struct m0_conf_pool *pool,
 			M0_LOG(M0_INFO, "Skipping "FID_F, FID_P(pver_to_skip));
 			continue;
 		}
+#ifdef ENABLE_ALT_PVERS
 		if (!m0_conf_pver_is_clean(pver))
 			continue;
+#endif
 		if (pver->pv_kind == M0_CONF_PVER_ACTUAL) {
 			*out = pver;
 			return M0_RC(0);
 		}
+#ifdef ENABLE_ALT_PVERS
 		return M0_RC(conf_pver_formulate(pver, out));
+#endif
 	} m0_tl_endfor;
 	return M0_ERR_INFO(-ENOENT, "No suitable pver is found at pool "FID_F,
 			   FID_P(&pool->pl_obj.co_id));
@@ -278,6 +286,7 @@ static int conf_pver_formulaic_base(const struct m0_conf_pver *fpver,
 	return M0_RC(0);
 }
 
+#ifdef ENABLE_ALT_PVERS
 M0_INTERNAL bool m0_conf_pver_is_clean(const struct m0_conf_pver *pver)
 {
 	struct m0_conf_pver *base = NULL;
@@ -302,6 +311,7 @@ M0_INTERNAL bool m0_conf_pver_is_clean(const struct m0_conf_pver *pver)
 	return M0_RC(m0_forall(i, M0_CONF_PVER_HEIGHT,
 			       recd[i] == allowance[i]));
 }
+#endif
 
 enum { CONF_PVER_FID_MASK = 0x003fffffffffffffULL };
 
@@ -414,6 +424,7 @@ M0_INTERNAL unsigned m0_conf_pver_level(const struct m0_conf_obj *obj)
 }
  /* page break */
 
+#ifdef ENABLE_ALT_PVERS
 /** Finds or creates virtual pool version, described by a formulaic one. */
 static int
 conf_pver_formulate(const struct m0_conf_pver *fpver, struct m0_conf_pver **out)
@@ -441,6 +452,7 @@ conf_pver_formulate(const struct m0_conf_pver *fpver, struct m0_conf_pver **out)
 			     &virt_fid, base,
 			     fpver->pv_u.formulaic.pvf_allowance, NULL, out));
 }
+#endif
 
 struct conf_pver_enumerate_st {
 	int  est_counter;
@@ -534,6 +546,7 @@ static int conf_pver_recd_build(struct m0_conf_obj *obj, void *args)
 	return M0_CW_CONTINUE;
 }
 
+#ifdef ENABLE_ALT_PVERS
 static int conf_objv_failed_fill(struct m0_conf_obj *obj, void *args)
 {
 	struct arr_int_pos        *a = args;
@@ -591,6 +604,7 @@ static int conf_pver_failures_cid(struct m0_conf_pver *base, uint64_t *out)
 	m0_free(a.ap_arr.ai_elems);
 	return M0_RC(0);
 }
+#endif
 
 struct conf_pver_base_walk_st {
 	uint32_t              bws_allowance[M0_CONF_PVER_HEIGHT];

conf/pvers.h

@@ -182,13 +182,15 @@ m0_conf_pver_formulaic_from_virtual(const struct m0_conf_pver *virtual,
 				    const struct m0_conf_root *root,
 				    const struct m0_conf_pver **out);
 
+#ifdef ENABLE_ALT_PVERS
 /**
  * Returns true iff pver consists of online elements only or can be
  * used to generate such a pver.
  *
  * @pre  pver is not virtual
  */
 M0_INTERNAL bool m0_conf_pver_is_clean(const struct m0_conf_pver *pver);
+#endif
 
 /**
  * Returns m0_conf_pver fid.

configure.ac

@@ -200,6 +200,7 @@ AH_TEMPLATE([M0_TRACE_HIGHEST_ALLOWED_LEVEL],[Highest trace level that is allowe
 AH_TEMPLATE([M0_DEFAULT_NETWORK],     [Default network transport type.])
 AH_TEMPLATE([M0_LUSTRE_VERSION],      [Autodetected Lustre version represented as integer])
 AH_TEMPLATE([ENABLE_USER_MODE_ONLY],  [Enabling user mode shall avoid kernel deps])
+AH_TEMPLATE([ENABLE_ALT_PVERS],       [Enable alternative pool versions.])
 AH_TEMPLATE([HAVE_JOURNAL_ABORT],     [Have journal_abort() function])
 AH_TEMPLATE([HAVE_FILE_READV],        [Have fops->readv function])
 AH_TEMPLATE([HAVE_FILE_AIO_READ],     [Have fops->aio_read function])
@@ -544,7 +545,13 @@ AC_ARG_WITH([user-mode-only],
 AS_IF([test "x$with_user_mode_only" = xyes],
       [AC_DEFINE([ENABLE_USER_MODE_ONLY])])
 
-
+# alternative-pvers {{{3
+AC_ARG_ENABLE([alternative_pvers],
+        AS_HELP_STRING([--enable-alternative-pvers], [enable alternative pvers]),
+        [], [enable_alternative_pvers=no]
+)
+AS_IF([test x$enable_alternative_pvers = xyes],
+      AC_DEFINE([ENABLE_ALT_PVERS], 1))
 
 # linux {{{3
 AC_ARG_WITH([linux],