cache: LV supports cache segs with metadata format

Cache pool read/writes metadata_format within its segment type..

For CachePoolLV unselected metadata format is NOT stored in metadata.

For CacheLV when metadata format is not present/selected in lvm2 metadata,
it's automatically assumed to be the version 1 (backward compatible).

To ensure older lvm2 will not 'miss-read' metadata with new version 2,
such LV is marked with METADATA_FORMAT status flag (segment is
specifying metadata format). So when cache uses metadata format 2,
it will become inaccesible on older system without such support.
(kernel dm cache < 1.10,  lvm2 < 2.02.169).

diff --git a/WHATS_NEW b/WHATS_NEW
index d1efed0ebbbc7620fcc56123882e900be7450b6c..4a5b0f6edc2612ba0ddbbcb70d91b10e94e0325e 100644 (file)
--- a/WHATS_NEW
+++ b/WHATS_NEW
@@ -1,5 +1,6 @@
 Version 2.02.169 - 
 =====================================
+  Support cache segment with configurable metadata format.
   Add allocation/cache_metadata_format profilable setttings.
   Use function cache_set_params() for both lvcreate and lvconvert.
   Skip rounding on cache chunk size boudary when create cache LV.

diff --git a/lib/cache_segtype/cache.c b/lib/cache_segtype/cache.c
index c378edafbdfb5a0bbf728da4125eeb041a3a445e..985af6856e8604d8e1ff21083fb8b2c7a1d0ae80 100644 (file)
--- a/lib/cache_segtype/cache.c
+++ b/lib/cache_segtype/cache.c
@@ -52,6 +52,12 @@ static void _fix_missing_defaults(struct lv_segment *cpool_seg)
                            cpool_seg->policy_name);
        }
 
+       if (cpool_seg->cache_metadata_format == CACHE_METADATA_FORMAT_UNSELECTED) {
+               cpool_seg->cache_metadata_format = CACHE_METADATA_FORMAT_1;
+               log_verbose("Cache pool %s uses implicit metadata format %u.",
+                           display_lvname(cpool_seg->lv), cpool_seg->cache_metadata_format);
+       }
+
        if (cpool_seg->cache_mode == CACHE_MODE_UNSELECTED) {
                cpool_seg->cache_mode = CACHE_MODE_WHEN_MISSING;
                log_verbose("Cache pool %s is missing cache mode, using %s.",
@@ -107,6 +113,16 @@ static int _cache_pool_text_import(struct lv_segment *seg,
                        return SEG_LOG_ERROR("Failed to duplicate policy in");
        }
 
+       if (dm_config_has_node(sn, "metadata_format")) {
+               if (!dm_config_get_uint32(sn, "metadata_format", &seg->cache_metadata_format) ||
+                   ((seg->cache_metadata_format != CACHE_METADATA_FORMAT_1) &&
+                    (seg->cache_metadata_format != CACHE_METADATA_FORMAT_2)))
+                       return SEG_LOG_ERROR("Unknown cache metadata format %u number in",
+                                            seg->cache_metadata_format);
+               if (seg->cache_metadata_format == CACHE_METADATA_FORMAT_2)
+                       seg->lv->status |= LV_METADATA_FORMAT;
+       }
+
        /*
         * Read in policy args:
         *   policy_settings {
@@ -164,6 +180,25 @@ static int _cache_pool_text_export(const struct lv_segment *seg,
        outf(f, "metadata = \"%s\"", seg->metadata_lv->name);
        outf(f, "chunk_size = %" PRIu32, seg->chunk_size);
 
+       switch (seg->cache_metadata_format) {
+       case CACHE_METADATA_FORMAT_UNSELECTED:
+               /* Unselected format is not printed */
+               break;
+       case CACHE_METADATA_FORMAT_1:
+               /* If format 1 was already specified with cache pool, store it,
+                * otherwise format gets stored when LV is cached.
+                * NB: format 1 could be lost anytime, it's a default format.
+                * Older lvm2 tool can easily drop it.
+                */
+       case CACHE_METADATA_FORMAT_2: /* more in future ? */
+               outf(f, "metadata_format = " FMTu32, seg->cache_metadata_format);
+               break;
+       default:
+               log_error(INTERNAL_ERROR "LV %s is using unknown cache metadada format %u.",
+                         display_lvname(seg->lv), seg->cache_metadata_format);
+               return 0;
+       }
+
        /*
         * Cache pool used by a cache LV holds data. Not ideal,
         * but not worth to break backward compatibility, by shifting

diff --git a/lib/format_text/flags.c b/lib/format_text/flags.c
index 716e6320199d2dd7c6cbd86eb2066b20bf6a79b6..a9f81f516cf28e75e4060c96d0f21d882dc3650c 100644 (file)
--- a/lib/format_text/flags.c
+++ b/lib/format_text/flags.c
@@ -67,6 +67,7 @@ static const struct flag _lv_flags[] = {
        {LV_WRITEMOSTLY, "WRITEMOSTLY", STATUS_FLAG},
        {LV_ACTIVATION_SKIP, "ACTIVATION_SKIP", COMPATIBLE_FLAG},
        {LV_ERROR_WHEN_FULL, "ERROR_WHEN_FULL", COMPATIBLE_FLAG},
+       {LV_METADATA_FORMAT, "METADATA_FORMAT", STATUS_FLAG},
        {LV_NOSCAN, NULL, 0},
        {LV_TEMPORARY, NULL, 0},
        {POOL_METADATA_SPARE, NULL, 0},

diff --git a/lib/metadata/metadata-exported.h b/lib/metadata/metadata-exported.h
index 5c84bdfd52f9e0f3d7d750029aa13580f260b620..c11899dac1e4fb30b7964ba2e36d2dc6b240d804 100644 (file)
--- a/lib/metadata/metadata-exported.h
+++ b/lib/metadata/metadata-exported.h
@@ -141,7 +141,8 @@
 #define LV_RESHAPE_DELTA_DISKS_MINUS           UINT64_C(0x0200000000000000)    /* LV reshape flag delta disks minus image(s) */
 
 #define LV_REMOVE_AFTER_RESHAPE        UINT64_C(0x0400000000000000)    /* LV needs to be removed after a shrinking reshape */
-/* Next unused flag:           UINT64_C(0x0800000000000000)    */
+#define LV_METADATA_FORMAT     UINT64_C(0x0800000000000000)    /* LV has segments with metadata format */
+/* Next unused flag:           UINT64_C(0x1000000000000000)    */
 
 /* Format features flags */
 #define FMT_SEGMENTS           0x00000001U     /* Arbitrary segment params? */
@@ -503,6 +504,7 @@ struct lv_segment {
        struct logical_volume *pool_lv;         /* For thin, cache */
        uint32_t device_id;                     /* For thin, 24bit */
 
+       cache_metadata_format_t cache_metadata_format;/* For cache_pool */
        cache_mode_t cache_mode;                /* For cache_pool */
        const char *policy_name;                /* For cache_pool */
        struct dm_config_node *policy_settings; /* For cache_pool */
@@ -964,6 +966,7 @@ struct lvcreate_params {
        uint32_t min_recovery_rate; /* RAID */
        uint32_t max_recovery_rate; /* RAID */
 
+       cache_metadata_format_t cache_metadata_format; /* cache */
        cache_mode_t cache_mode; /* cache */
        const char *policy_name; /* cache */
        struct dm_config_tree *policy_settings; /* cache */